Ultrasonic transducer array

Information

  • Patent Grant
  • 6821253
  • Patent Number
    6,821,253
  • Date Filed
    Monday, March 17, 2003
    21 years ago
  • Date Issued
    Tuesday, November 23, 2004
    20 years ago
Abstract
By bonding a conductive first matching layer 14 to the acoustic radiation surface side, which is the bottom side, of a belt-shape piezoelectric element on both faces with electrodes provided, and using a dicing machine to form divided grooves 16, an array of piezoelectric elements 6, 6, . . . , 6 is formed in the element array direction. By deepening the divided grooves 16, generation of cross talk can be prevented, and by filling the portions of the divided grooves 16 not in contact with the piezoelectric elements 6 with a conductive adhesive 17, a reduction in strength due to formation of the divided grooves 16 can be prevented, and a common connection between the ground electrode 13b on the bottom surface of each piezoelectric element 6 and the conductive first matching layer 14 can be reliably secured.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




This invention relates to an ultrasound transducer array, used in ultrasound diagnosis for medical use or for non-destructive inspection.




2. Description of the Related Art




In recent years, ultrasound diagnostic equipment using ultrasound transducers has come into widespread use in medical diagnostics and other fields. In addition to mechanical scanning-type ultrasound transducers which rotate a single ultrasound transducer or similar to mechanically scan with ultrasound, electronic scanning-type ultrasound transducers have also been adopted.




Such electronic scanning-type ultrasound transducers are formed using ultrasound transducer arrays, in which ultrasound transducers are formed in an array shape.




Conventional electronic scanning-type ultrasound transducers (ultrasound transducer arrays) provide signal electrodes and ground electrodes on each side of a piezoelectric element, and one or more grooves, extending to a depth partway through a provided matching layer, to divide the element and form a plurality of elements. Here, the ground electrodes must be connected to a common line.




As a method of connecting the ground electrodes to a common line, the matching layer adjacent to the piezoelectric element may be made of a conductive resin, and grooves are provided being extended to a depth midway through the matching layer, as in Japanese Unexamined Patent Application Publication No.


61-253999.






However, if the thickness of the remaining matching layer is small, the strength of the matching layer is relatively weakened, so that when a force is applied, cracks may appear in the matching layer, or conduction faults may occur.




On the other hand, if the thickness of the remaining matching layer is large (if the groove cut into the matching layer is shallow), cross talk may occur, and the image quality may worsen.




SUMMARY OF THE INVENTION




An object of this invention is to provide a progressive ultrasound transducer array, which prevents the occurrence of cross talk and in which a common connection of the ground electrodes of piezoelectric elements can be reliably secured.




In this invention, an ultrasound transducer array, in which are arranged a plurality of piezoelectric elements, which can be electrically operated independently, comprises one or a plurality of matching layers, provided on the acoustic radiating surface side of the above piezoelectric elements; a conductive material layer, provided on the side of the above matching layers joined with the above piezoelectric elements, in the direction along the array direction, part of which is in contact with and electrically connected to the above piezoelectric elements along the above array direction, and part of which is not in contact with the above piezoelectric elements along the above array direction; a plurality of grooves, which mechanically and electrically insulate at least part of the above piezoelectric elements and the above matching layer for each element which can be electrically operated independently; and, conductive material which fills at least a part of the portions of the above grooves which are formed where the above piezoelectric elements and the above conductive material layer are not in contact.




The above and other objects, features and advantages of the invention will become more clearly understood from the following description, referring to the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS




FIG.


1


through

FIG. 4

relate to a first aspect of the invention;





FIG. 1

is a perspective view showing the entirety of an ultrasound transducer array;





FIG. 2

is a cross-sectional view showing the cross-sectional structure in the array direction;





FIG. 3

is a cross-sectional view showing the internal structure in the elevation direction;





FIG. 4

is an explanatory diagram showing the internal structure before filling with backing material in

FIG. 3

;





FIG. 5

is an explanatory diagram showing the internal structure of the ultrasound transducer array of a second aspect of the invention;





FIG. 6

is an explanatory diagram showing the internal structure of an ultrasound transducer array of a modification of the second aspect;





FIG. 7

is an explanatory diagram showing the internal structure of an ultrasound transducer array of a third aspect of the invention;





FIG. 8

is an explanatory diagram showing the internal structure of an ultrasound transducer array of a modification of the third aspect;





FIG. 9

is an explanatory diagram showing the internal structure of an ultrasound transducer array of a fourth aspect of the invention;





FIG. 10

is a cross-sectional view showing the structure of an ultrasound transducer array of a fifth aspect of the invention;




FIG.


11


through

FIG. 13

relate to a sixth aspect of the invention;





FIG. 11

is a perspective view showing the appearance of an ultrasound transducer array;





FIG. 12

is a cross-sectional view showing the structure of the element array;





FIG. 13

is a cross-sectional view showing the structure in the elevation direction;




FIG.


14


through

FIG. 17

relate to a seventh aspect of the invention;





FIG. 14

is a side view of an ultrasound transducer array;





FIG. 15

is a cross-sectional view along line C


1


—C


1


in

FIG. 14

;





FIG. 16

is a cross sectional view of the layered member of an ultrasound transducer array manufactured using a first manufacturing method;





FIG. 17

is a perspective view of the parent layered member of an ultrasound transducer array manufactured using a second manufacturing method;





FIG. 18

is a cross-sectional view of an ultrasound transducer array of an eighth aspect of the invention;





FIG. 19

is a cross-sectional view of an ultrasound transducer array of a ninth aspect of the invention;





FIG. 20

is a side view of the layered member of an ultrasound transducer array of a tenth aspect of the invention;





FIG. 21

is a cross-sectional view, showing a section parallel to the front plane, of an ultrasound transducer array of an eleventh aspect of the invention;





FIG. 22

is a cross-sectional view, showing a section parallel to the front plane, of an ultrasound transducer array of a twelfth aspect of the invention;





FIG. 23

relates to a thirteenth aspect of the invention;





FIG. 23A

is a cross-sectional view, showing a section parallel to the front plane, of an ultrasound transducer array;





FIG. 23B

is an explanatory diagram showing in enlargement the wiring area and groove of the ultrasound transducer array of

FIG. 23A

;




FIG.


24


through

FIG. 27

relate to a fourteenth aspect of the invention;





FIG. 24A

is a summary perspective view showing the configuration of an ultrasound transducer array;





FIG. 24B

is a cross-sectional view of

FIG. 24A

;





FIG. 24C

is a perspective view showing only a piezoelectric element of

FIG. 24A

;





FIG. 25

are first graphs showing the impedance curve with the ratio w/t of the thickness t to the width w of a piezoelectric element varied;





FIG. 25A

is a graph showing the impedance curve when w/t=0.2;





FIG. 25B

is a graph showing the impedance curve when w/t=0.3;





FIG. 25C

is a graph showing the impedance curve when w/t=0.5;





FIG. 25D

is a graph showing the impedance curve when w/t=0.6;





FIG. 26

are second graphs showing the impedance curve with the ratio w/t of the thickness t to the width w of a piezoelectric element varied;





FIG. 26A

is a graph showing the impedance curve near the fundamental resonance point when w/t=0.5;





FIG. 26B

is a graph showing the impedance curve near the fundamental resonance point when w/t=0.6;





FIG. 26C

is a graph showing the impedance curve near the fundamental resonance point when w/t=0.8;





FIG. 27

are third graphs showing the echo waveform and spectrum of an ultrasound transducer array with the ratio w/t of the thickness t to the width w of a piezoelectric element varied;





FIG. 27A

is a graph showing the echo waveform and spectrum of an ultrasound transducer array for which w/t=0.2;





FIG. 27B

is a graph showing the echo waveform and spectrum of an ultrasound transducer array for which w/t=0.25;





FIG. 27C

is a graph showing the echo waveform and spectrum of an ultrasound transducer array for which w/t=0.3;





FIG. 27D

is a graph showing the echo waveform and spectrum of an ultrasound transducer array for which w/t=0.5;





FIG. 28

is a summary cross-sectional view showing an ultrasound transducer array of a fifteenth aspect of the invention;





FIG. 29

is a summary cross-sectional view showing an ultrasound transducer array of a sixteenth aspect of the invention;





FIG. 30

are configuration diagrams showing a conventional ultrasound transducer array;





FIG. 30A

is a summary perspective view showing the configuration of an ultrasound transducer array;





FIG. 30B

is a side cross-sectional view of

FIG. 30A

; and,





FIG. 31

is a perspective view showing only a piezoelectric element of FIG.


30


A.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Below, first through sixth aspects of this invention are explained, based on FIG.


1


through FIG.


13


.




FIG.


1


through

FIG. 4

show a first aspect of the invention. The ultrasound transducer array


1


shown in

FIG. 1

has a backing material framework


3


positioned on the inside of the acoustic lens


2


; a cable wiring board


4


is provided vertically on the inside of this backing material framework


3


, and the vicinity of the cable wiring board


4


is filled with backing material


5


.




Signal wiring lands


8


,


8


, . . . ,


8


, connected by a signal wires


7


to numerous piezoelectric elements


6


,


6


, . . . ,


6


formed in an array shape as shown in

FIG. 2

, are provided in the length direction on both sides of the cable wiring board


4


.




On both surfaces of the cable wiring board


4


, near the top, GND wiring lands


9


are formed in a strip shape in the length direction, and are electrically connected, for example, by a connection wire


10


at both end positions by a conducting film


11


provided on the inner face of the backing material framework


3


and by solder


12


or the like.




As shown in

FIG. 2

, FIG.


3


and

FIG. 4

, signal electrodes


13




a


and ground electrodes


13




b


are formed on the upper and lower surfaces of each piezoelectric element


6


by evaporation deposition of gold, silver or some other metal, or by some other means; on the lower side (the acoustic radiation side), at which transmission and reception of ultrasound waves is performed, a first matching layer


14


and second matching layer


15


for matching, and an acoustic lens


2


to concentrate the emitted ultrasound waves, are formed in layers.




In this aspect, the first matching layer


14


is formed from a conductive resin (for example, an epoxy resin with carbon or a carbon composite material added) or similar. That is, the first matching layer


14


is conducted to a line common with each electrode


13


serving as the ground electrode on the lower side of each piezoelectric element


6


, provided on the side of the first matching layer


14


.




The numerous piezoelectric elements formed in an array shape (as an array-shape transducer)


6


,


6


, . . . ,


6


have, for example, a width in the elevation direction (width direction) of w, as shown in

FIG. 4. A

belt-shaped piezoelectric element board is cut to form divided grooves


16


at a prescribed pitch in the element array direction, and long in the element array direction perpendicular to the width direction. At this time, the dicing machine on both cuts the piezoelectric element board, adhered to the first matching layer


14


, on which full-coverage electrodes on both faces are provided by evaporation deposition.




In this case, the depth of the divided grooves


16


is greater than the thickness of the piezoelectric elements


6


, and the grooves are formed so as to penetrate partway in the thickness direction of the first matching layer


14


connected to the ground electrodes


13




b


on the lower faces of the piezoelectric elements


6


. More specifically, if as in

FIG. 2

the thickness of the first matching layer


14


is T, then divided grooves


16


are formed at a thickness t (thickness t is measured from the lower face of the piezoelectric elements


6


) equal to approximately 60 to 100% of the thickness T of the first matching layer


14


.




In this way, divided grooves


16


are formed to a depth sufficient to reach the first matching layer


14


, and to extend to approximately ⅔ or more of the thickness T of this layer


14


; hence the occurrence of cross talk between neighboring piezoelectric elements


6


,


6


, . . . ,


6


can be adequately suppressed by the dividing groove


16


between them.




By increasing the depth of the divided grooves


16


, the strength of the first matching layer


14


is relatively decreased (compared with the case in which the depth of the divided grooves


16


is small); but in this aspect, the divided grooves


16


are filled with a conductive adhesive


17


as a filler material (reinforcing material), to prevent a relative decrease in strength of the first matching layer


14


.




In this aspect, as this conductive adhesive


17


, the same conductive member as the member used to form the first matching layer


14


is impregnated and reinforced. Even if cracks appear in the first matching layer


14


, the occurrence of conduction faults can be reliably prevented by this conductive adhesive


17


.




This conductive adhesive


17


fills the portion of the divided grooves


16


in the first matching layer


14


other than the portion in contact with the piezoelectric elements


6


, as shown in FIG.


4


. The ground electrode


13


b of each piezoelectric element


6


is electrically connected with the first matching layer


14


, and as shown in

FIG. 2

, the first matching layer


14


is electrically connected, by a conducting material (solder), with the conductive film


11


provided on the inner face of the backing material framework


3


near both ends in the array direction.




The backing material framework


3


is formed from, for example, glass-epoxy resin, with copper foil applied to the inner surface to form a conductive film


11


. The conductive film


11


is electrically connected at the upper edge to the GND wiring land


9


by a connecting wire


10


.




Each signal electrode


13




a


on the upper-face side of each piezoelectric element


6


is electrically connected (by solder or similar) using a signal wire


7


to a signal wiring lands


8


formed in a short strip shape opposite the upper side of each signal electrode


13




a


on the cable wiring board


4


, provided vertically such that the lower edge is not in contact with the upper face of each piezoelectric element


6


.




In this case, as shown in FIG.


2


and

FIG. 4

, signal wiring lands


8


are formed, in alternation on both faces of the cable wiring board


4


, along the length direction at the same intervals as the array of piezoelectric elements


6


. That is, the array pitch on one face is double the array pitch for the piezoelectric elements


6


, and on each face, each signal electrode


13




a


is connected to a signal wiring land


8


by a signal wire


7


at every other piezoelectric element


6


. In this way, signal wiring lands


8


are provided on each face, and by using a signal wire


7


to connect each signal electrode


13




a


to a signal wiring land


8


at every other piezoelectric element


6


, signal electrodes can easily be connected to signal wiring lands


8


even when the array-shape piezoelectric elements


6


are formed with a small pitch.




After connecting each signal electrode


13




a


to a signal wiring land


8


by a signal wire


7


, the vicinity of the piezoelectric elements


6


is covered by backing material


5


which absorbs or attenuates ultrasound, as shown in FIG.


3


.




Each of the signal wiring lands


8


and the GND wiring land


9


of the cable wiring board


4


are connected, by solder or other means, to one end of an ultrasound cable (not shown). The connector at the other end of the ultrasound cable is connected to ultrasound system.




As shown in

FIG. 3

, the ultrasound transducer array


1


is mounted such that the portion of the acoustic lens


2


is exposed in an opening provided in a case


19


.




An ultrasound transducer array


1


configured in this way may be manufactured as follows.




An unhardened resin in liquid form which forms a second matching layer


15


, is poured into a frame member, not shown, and hardened, and the surface is machined to form the second matching layer


15


of prescribed thickness on top of this the first matching layer


14


is similarly formed, and on top of this, the piezoelectric element board, provided with electrodes on both faces, is bonded. After formation of the second matching layer


15


, the frame member is removed.




The piezoelectric element board (and first matching layer


14


) is divided at a prescribed pitch in the length direction using a dicing machine, such that the elements of the piezoelectric element board are completely separated, and divided grooves


16


are formed extending to a depth T which is approximately 60 to 100% of the thickness T of the first matching layer


14


beneath, to form separated array-shape piezoelectric elements


6


,


6


, . . . ,


6


.




Next, each dividing groove


16


, except for portions neighboring each piezoelectric element


6


, is filled with a conductive material, for example the same material as the conductive adhesive


17


used to form the first matching layer


14


, and this material is hardened to reinforce the first matching layer


14


.




Next, the cable wiring board


4


, having signal wiring lands


8


and GND wiring lands


9


on its both faces, is positioned using a jig upward the signal electrodes


13




a


on the upper faces of the piezoelectric elements


6


, at for example the center of the effective width w in the elevation direction. Each of the signal electrodes


13




a


on the upper face of the piezoelectric elements


6


,


6


, . . . ,


6


is connected to respective signal wiring lands


8


with signal wires


7


.




A rectangular-shape backing material framework


3


, with the top and bottom sides open, is mounted so as to surround the array-shape piezoelectric elements


6


,


6


, . . . ,


6


and cable wiring board


4


. Copper foil or other conductive film


11


is formed on the inner walls of this backing material framework


3


, and as shown in

FIG. 2

, the bottom-side opening is fixed in place and connected for electrical connection with the first matching layer


14


by means of conductive adhesive. This backing material framework


3


is smaller in size than the inner dimensions of the above frame member.




Thereafter, unhardened backing material


5


is poured up to a prescribed height from the top-side aperture of the backing material framework


3


, and hardened. Then, the jig which had held the cable wiring board in place is removed, and the conductive film


11


of the backing material framework


3


is electrically connected to the GND wiring lands


9


of the cable wiring board using connecting wire


10


. An assembly fabricated in this way is housed in an acoustic lens


2


(not shown) formed in advance using a frame member, and joined such that the second matching layer


15


on the bottom is in contact with the top surface of the acoustic lens


2


.




An ultrasound cable, not shown, is connected to the cable wiring board


4


, and the connection portion is covered. The ultrasound transducer array


1


manufactured in this manner is mounted in the case


19


such that the bottom side of the acoustic lens


2


is exposed, as shown in FIG.


3


.




The operation of an ultrasound transducer array


1


manufactured in this manner is next explained.




The connector at the other end of the ultrasound cable is connected to ultrasound system, the power to the ultrasound system is turned on, and on applying the bottom face of the acoustic lens


2


to the site for inspection of the patient or similar, transmission pulses which perform electric scanning are applied to this ultrasound transducer array


1


.




Transmission pulses are applied in order across the signal electrodes


13




a


and ground electrodes


13




b


for each piezoelectric element in the element array direction of the ultrasound transducer array


1


, and as a result of application of these transmission pulses, the electro-acoustic transduction function of the piezoelectric elements


6


causes ultrasound excitation, so that ultrasound is emitted toward the bottom face (acoustic radiation face) and the top face. On the top-face side, the ultrasound is attenuated by the backing material


5


. On the other hand, the ultrasound emitted from the bottom-face side passes through the first matching layer


14


and second matching layer


15


, is focused by the acoustic lens


2


, and is sent toward the site for inspection in contact with this acoustic lens


2


; at this time, linear scanning is performed in the element array direction.




Reflected ultrasound, reflected by the portion of the inspection site at which the acoustic impedance changes, is received by the same piezoelectric elements


6


, converted into electrical signals, subjected to signal processing by the signal processing system within the ultrasound system, and converted into image signals, and an ultrasound cross-sectional image is displayed on a monitor display screen for the case of linear scanning.




When a transmission pulse is applied across the signal electrode


13




a


and ground electrode


13




b


of a piezoelectric element


6


, the transmission pulse is applied over a route as follows: signal wiring land


8


of cable wiring board


4


→signal wire


7


→signal electrode


13




a


of piezoelectric element


6


→ground electrode


13




b


→first matching layer (conductive adhesive


17


in dividing groove


16


)→conductive film


11


on inner face of backing material framework


3


→connecting wire


10


→ground wiring land


9


of cable wiring board


4


.




By means of this ultrasound transducer array


1


, by forming deep divided grooves


16


extending to, for example, approximately ⅔ the thickness T of the first matching layer


14


, cross talk between neighboring piezoelectric elements


6


in particular can be kept small. Hence cross-sectional images with high resolution in the element array direction can be obtained.




By forming deep divided grooves


16


, the strength is reduced compared with the case of shallow grooves; but by filling the divided grooves


16


with a reinforcing conductive adhesive


17


, this reduction in strength can be prevented.




When deep divided grooves


16


are formed, even if cracks appear in the first matching layer


14


formed from conductive material, the strength is reinforced as a result of filling the divided grooves


16


with the conductive adhesive


17


, and in addition conductive properties are more reliably secured, so that the connection of the ground electrodes


13




b


to a common line can be maintained adequately.




The advantageous results of this aspect are as follows.




By forming deep divided grooves


16


, extending to for example approximately 60 to 100% of the thickness T of the first matching layer


14


, cross talk can be reduced sufficiently. And, by filling the divided grooves


16


with a conductive adhesive


17


, a reduction in strength can be prevented. Also, a common connection of the ground electrodes


13




b


of the piezoelectric elements


6


can be reliably secured.




Next, the structure of an ultrasound transducer array of a second aspect of this invention is explained, referring to FIG.


5


.




In this ultrasound transducer array


21


, the first matching layer


14


made from conductive material in the ultrasound transducer array shown in

FIG. 4

is replaced by a first matching layer


14


′ not having conductivity; groove portions


22


,


22


are formed in this first matching layer


14


′ along the element array direction in two places where both ends of piezoelectric elements


6


make contact in the elevation direction, and conductive layers


23


are provided in each of these groove portions


22


.




Because the conductor which forms the conductive layer


23


is fabricated by mixing a resin and metal powder or similar, it tends to swell on contact with water or other substances. Hence in this aspect, the conductive layer


23


is made 60 to 100% of the thickness of the first matching layer, and at least the second matching layer is reserved, in order to ensure the necessary durability.




In this aspect, when forming the divided grooves


16


, the divided grooves


16


are formed more shallow than the thickness of the conductive layer


23


, so that formation of the divided grooves


16


does not cause the conductive layer


23


to be separated.




Polishing or other machining is performed in order that the upper face of the first matching layer


14


′ and the upper face of the conductive layer


23


are in a single plane, and by bonding the piezoelectric element board with electrodes provided on both faces onto the first matching layer


14


and onto the conductive layer


23


formed in the groove portions


22


, and using a dicing machine to form the divided grooves


16


similarly to the first aspect, a piezoelectric element array


6


,


6


, . . . ,


6


is formed in which signal electrodes


13




a


and ground electrodes


13




b


are formed on the upper and lower faces respectively.




Here, the upper surface of the first matching layer


14


′ makes contact with the central portion of the ground electrodes


13




b


on the bottom face of each piezoelectric element


6


, and the ground electrodes


13




b


on both ends in the elevation direction make contact with the conductive layer


23


.




In this aspect, the portion of the divided grooves


16


which, for example, is not in contact with the piezoelectric elements


6


, but which is formed in the conductive layer


23


, is filled with a conductive adhesive


24


as a filler material.




As the conductive layer


23


and conductive adhesive


24


, an epoxy resin with additive like carbon or a carbon composite material or similar may be adopted, for example, to impart electrical conductivity, as the case in forming the first matching layer


14


explained in the first aspect.




Further, a thermosetting resin may be adopted as the conductive layer


23


and conductive adhesive


24


. In this case, the same thermosetting resin material may be adopted in both the conductive layer


23


and conductive adhesive


24


. These thermosetting resins include resins which harden at room temperature.




The configuration is otherwise similar to that of the first aspect.




As one effect of this aspect, the central portion of each piezoelectric element


6


makes contact with the first matching layer


14


′, and both ends make contact only with the conductive layer


23


, so that there are fewer constraints on the conductive material properties of the material of the first matching layer


14


′ compared with the first matching layer


14


; hence matching is possible at more appropriate values, and more inexpensive material can be used in manufacture.




In this aspect, part of the ultrasound transmitted from the acoustic radiation surface side of the piezoelectric elements


6


which is formed by the first matching layer


14


′ is mainly used in formation of ultrasound images.




Other effects are similar to those of the first aspect.




The advantageous results of this aspect are as follows.




Compared with the constraint of conductive properties imposed on the first matching layer


14


, there are fewer material constraints, so that matching can be performed at more appropriate values, and more inexpensive materials can be used in manufacturing. Otherwise, the advantageous results are substantially the same as for the first aspect.




As a variant of the second aspect, a structure such as that shown in

FIG. 6

may be adopted. In the ultrasound transducer array


21


′ shown in

FIG. 6

, the width of the groove portion


22


in

FIG. 5

is effectively broadened (made larger) to extend to the edge of the first matching layer


14


′. In other words, the central portion in the elevation direction of the first matching layer


14


′ is reserved, and both ends are cut away to form cut-out grooves


22


′,


22


′; each cut-out groove


22


′ is filled with a conductive material to form the conductive layer


23


.




Except near the portions in contact with the piezoelectric elements


6


, each of the cut-out grooves


22


′ of the divided grooves


16


is filled with conductive adhesive


24


. Otherwise the configuration is similar to that of

FIG. 5

, and the action and advantageous results are also similar.




In this aspect (including the variant), two conductive layers


23


are provided; however, either may be provided as the sole such layer instead.




Next, the structure of the ultrasound transducer array of a third aspect of this invention is explained, referring to FIG.


7


.




The ultrasound transducer array


31


of this aspect has a structure in which, after formation of the divided grooves


16


in the ultrasound transducer array


21


of

FIG. 5

, conductive wires


32


, having common connection and reinforcement functions, are fixed with conductive adhesive


33


on the upper face of the portion of the conductive layer


23


not in contact with the piezoelectric elements


6


, along the element array direction. The conductive wire


32


is formed of metal, for example silver.




The part of the divided grooves


16


near the lower side of the conductive wire


32


is filled with the conductive adhesive


33


.




The effect and advantageous results of this aspect are substantially the same as in the case of

FIG. 5

; but by adopting the conductive wires


32


, both the effect of common connection of the ground electrodes


13




b


, and the effect of reinforcement, can be enhanced.




Also, upon sterilizing the ultrasound transducer array


31


of this aspect in an autoclave, the resin part of the conductive layer


23


absorbs moisture and swells, and the electrical conductivity declines; but because the conductive wires


32


are metal wires, they are not affected by moisture and there is no decline in conductivity, so that durability with respect to sterilization can be improved.




As a variant of this aspect, a structure such as that in

FIG. 8

may be adopted. The ultrasound transducer array


31


′ shown in

FIG. 8

has a structure in which, in the ultrasound transducer array


21


′ shown in

FIG. 6

, after forming the divided grooves


16


a flat wire


32


′ with rectangular cross-section for making a common connection is fixed with conductive adhesive


33


to the upper face of the portion of the conductive layer


23


not in contact with the piezoelectric elements


6


, along the element array direction.




Of the divided grooves


16


, the part near the lower part of this flat wire


32


′ is filled with conductive adhesive


33


.




In this case also, the effect and advantageous results are similar to those of the above case.




In this aspect, including the variant, two wires


32


or flat wires


32


′ are provided; but a single wire only may be provided instead.




Next, the structure of the ultrasound transducer array


41


of a fourth aspect of this invention is explained, referring to FIG.


9


.




This ultrasound transducer array


41


has a structure in which, in the ultrasound transducer array


1


of

FIG. 4

, after forming the divided grooves


16


, conductive tape


42


for common connection is fixed with conductive adhesive


47


to the upper face of the portion of the first matching layer


14


not in contact with each piezoelectric element


6


, along the element array direction. This conductive tape


42


is, for example, silver tape, on one face of which is provided an adhesive portion employing conductive adhesive


47


.




Of the divided grooves


16


, the portions near the bottom of this conductive tape


42


are filled with the conductive adhesive


47


, to ensure more reliable conduction, and to provide a reinforcement function.




The effect and advantageous results of this aspect are substantially the same as in the cases of the aspects shown in FIG.


7


and FIG.


8


.




Further, by employing conductive tape


42


as the conductive member for a common connection, mounting is simplified, and a larger contact area can be secured, so that a common connection of the ground electrodes can be made reliably, and manufacture of the ultrasound transducer array


41


becomes easier.




In this aspect, two conductive tape members


42


are provided, but a single tape member may be provided instead.




Next, a fifth aspect is explained, referring to FIG.


10


. This figure shows a cross-section, along a dividing groove, of the structure of an ultrasound transducer array


51


.




In this ultrasound transducer array


51


, a dicing machine is used to form the divided grooves


16


, similarly for example to the case of the ultrasound transducer array of the first aspect; but the divided grooves


16


are not formed extending to both ends of the first matching layer


14


, but only in a portion which is extends slightly beyond both ends of the piezoelectric elements


6


(in the elevation direction).




That is, as shown in

FIG. 10

, divided grooves


16


are formed to separate the piezoelectric elements


6


, and in addition the grooves are formed sufficiently deeply in the underlying first matching layer


14


, in the portion opposed to the piezoelectric elements


6


, to adequately suppress cross talk.




However, divided grooves


16


are not formed near both edges of the first matching layer


14


, apart from the two edges, in the elevation direction, of the piezoelectric elements


6


, and so the strength of the first matching layer


14


is increased compared with the case in which divided grooves


16


are formed in these portions as well; moreover, the occurrence of cracks during machining to form the divided grooves


16


can also be prevented.




In this aspect, divided grooves


16


are not formed in the portion (at both ends) of the first matching layer


14


apart from both ends in the elevation direction of the piezoelectric elements


6


, and so this portion is not reinforced with filler material. Otherwise, the configuration is similar to that of the first aspect.




This aspect has substantially the same effect and advantageous results as the first aspect, even if the portion of the divided grooves


16


which is formed is not reinforced with conductive adhesive


17


.




In

FIG. 10

, divided grooves


16


are formed in the vicinity adjacent to the piezoelectric elements


6


, and divided grooves


16


are not formed at the two ends, thereby increasing the strength of the first matching layer


14


; however, this aspect also includes a method in which the groove depth is reduced at both ends, to prevent reductions in strength.




This aspect has been explained as a variant of the first aspect with changes to the formed portions of the divided grooves


16


; however, the changes can also be applied to the other aspects. That is, in the other aspects also, the divided grooves


16


may likewise be formed only in portions which are slightly longer than the piezoelectric elements


6


.




Next, a sixth aspect of this invention is explained, referring to FIG.


11


through FIG.


13


.

FIG. 11

shows the outer appearance of a curved linear-type ultrasound transducer array;

FIG. 12

shows the cross-sectional structure in the element array direction; and

FIG. 13

shows the cross-sectional structure in the elevation direction.




In this ultrasound transducer array, the backing material framework


63


is positioned inside the semicircular acoustic lens


62


, the cable wiring board


64


is provided vertically inside this backing material framework


63


, and the vicinity is filled with backing material


65


.




On the cable wiring board


64


are provided signal wiring lands


68


,


68


, . . . ,


68


almost radially in the length direction, being connected by signal wires


67


to a plurality of piezoelectric elements


66


,


66


, . . . ,


66


formed in an array along, for example, a circular arc.




Near the upper portion of the cable wiring board


64


, a GND wiring land


69


is formed in a strip shape in the length direction, and extends to ground wiring lands provided on both sides of the signal wiring lands


68


,


68


, . . . ,


68


. The ground electrodes


71




b


on the bottom side of the piezoelectric elements


66


,


66


, . . . ,


66


are electrically connected, by means of solder or similar, to a conductive layer


72


using connecting wires


70


.




As shown in FIG.


12


and

FIG. 13

, signal electrodes


71




a


and ground electrodes


71




b


are formed, by evaporation of metal or similar means, on the upper and lower faces of each piezoelectric element


66


. On the bottom face, which performs transmission and reception of ultrasound, a first matching layer


74


and second matching layer


75


for matching, and an acoustic lens


62


for concentration of the emitted ultrasound, are formed in layers.




As shown in

FIG. 13

, grooves are formed on the upper face of the first matching layer


74


opposite both ends in the elevation direction of the piezoelectric element


66


, and conductive layers


72


are formed in the grooves.




In this aspect, the first matching layer


14


is formed from, for example, epoxy resin.




The numerous piezoelectric elements


66


,


66


, . . . ,


66


formed in an array are formed by providing full-coverage electrodes by evaporation deposition or similar on both faces of a belt-shape piezoelectric element board formed along a cylinder surface, bonding to this a first matching layer


74


, and, by using a dicing machine to form divided grooves


76


so as to separate elements, forming an array of elements separated in the array direction along the cylinder surface.




Except for the portion adjacent to the piezoelectric elements


66


, the portion of each dividing groove


76


in which is formed a conductive layer


72


is filled with a conductive filler material


77


, for common connection to the ground electrodes


71




b


and for reinforcement.




Except for the fact that ultrasound is transmitted and received radially, this aspect has substantially the same effect and advantageous results as the first aspect.




In each of the above-described aspects, it is preferable that the divided grooves be deep rather than shallow, in consideration of the effect of cross talk. Also, in the above-described aspects a matching layer is formed from a first matching layer and a second matching layer; however, a single matching layer may be used, or, three or more matching layers may be used.




Aspects which are configured by partial combination of the above-described aspects or similar, also, fall within the scope of this invention.




The above has mainly explained the structure of ultrasound transducers. The following explanation places emphasis on selection of materials.




Japanese Unexamined Patent Application Publication No. 9-139998 discloses an ultrasound transducer array having a back load member, piezoelectric elements, matching layer comprising carbon as a conductive material, and acoustic lens, with these layered in order similarly to the ultrasound transducer array


1001


shown in FIG.


30


A and FIG.


30


B. The matching layer is joined, with electrical conductivity ensured, to electrodes formed on the upper faces of the piezoelectric elements. The matching layer also serves as a grounding electrode.




Japanese Patent Publication No. 1-61062 discloses an ultrasound transducer array having a back load member, piezoelectric elements, and matching layer comprising conductive resin as a conductive material, with these layered in order. The conductive resin is formed by intermixing metal powder as a filler into a resin material as a matrix. Similarly to Japanese Unexamined Patent Application Publication No. 9-139998, the matching layer is used as a ground electrode.




However, in the ultrasound transducer array of Japanese Unexamined Patent Application Publication No. 9-139998 using carbon in the matching layer, whereas the matching layer has electrical conductivity and good cutting properties, while when the thickness typically used for the matching layer is (¼)λ, mechanical strength is reduced, and cracks and chips appear during machining into thin sheets.




In cases where uncombined carbon is used to form the matching layer, when the ultrasound transducer array is used with the human body, the acoustic impedance of the acoustic impedance-matching layer deviates from the optimal value. As a result, ultrasound is not propagated efficiently, sensitivity declines, and image definition deteriorates.




In the ultrasound transducer array of Japanese Patent Publication No. 1-61062, using conductive resin for the matching layer, by appropriately choosing the filler material and the resin material as the matrix, electrical conductivity can be obtained; but in addition to aging, during such processes as disinfecting and sterilization, the disinfectant and sterilizing fluids may penetrate into the resin and cause degradation or swelling of the resin, or oxidation or other changes to the metal filler, worsening electrical conductivity and increasing the resistance value. As a result the S/N ratio decreases, and conduction faults and image quality deterioration occur. Also, the conductive resin is a material with large ultrasound attenuation factor, so that transmission and reception sensitivity and image quality are reduced.




Hence there is a need for an ultrasound transducer array comprising a matching layer which is conductive, not prone to cracking or chipping during machining, which is easy to machine, and has an optimal acoustic impedance.




Below, seventh to thirteenth aspects of this invention are explained, referring to FIG.


14


through FIG.


23


.




FIG.


14


through

FIG. 17

show the seventh aspect of this invention.

FIG. 14

is a side view of an ultrasound transducer array;

FIG. 15

is a cross-sectional view of a layered member, cut along line C


1


—C


1


in

FIG. 14

;

FIG. 16

is a side view of the layered member of an ultrasound transducer array manufactured by a first manufacturing method; and

FIG. 17

is a perspective view of the principal components of the parent layered member of an ultrasound transducer array manufactured by a second manufacturing method.




The ultrasound transducer array


81


of this aspect has a back load member


82


. The back load member


82


is formed from a flexible urethane resin, with alumina used as a filler. The urethane resin has a Shore hardness of approximately A90.




In

FIG. 14

, the front surface of the back load member


82


, which is one of the four surfaces, faces the plane of the paper. On the upper surface of the back load member


82


are layered, in the order of a piezoelectric element


84


, first matching layer


86


, and second matching layer


88


. The piezoelectric element


84


is formed from a piezoelectric ceramic manufactured by ordinary sintering processes or similar.




Electrodes are formed on the lower surface (the surface opposed to the upper surface of the back load member


82


) and the upper surface of the piezoelectric element


84


. The first matching layer


86


comprises a carbon composite material containing carbon, and is conductive.




A conductive layer (not shown) provided at the portion of this first matching layer


86


which is in contact with both ends in the elevation direction of the piezoelectric element


84


is formed by intermixing carbon powder with a thermosetting resin matrix. This carbon powder may be the same as the powder of the carbon composite material used to form the first matching layer


86


. The thermosetting resin may be a material which hardens at room temperature.




The thickness of the first matching layer


86


is 200 μm, and when using 5 MHz ultrasound, the ultrasound is propagated efficiently. The second matching layer


88


is formed from an epoxy resin, and is of thickness 100 μm. The piezoelectric element


84


, first matching layer


86


and second matching layer


88


form a layered member.




In

FIG. 16

, the front surface (the surface facing the plane of the paper in

FIG. 14

) of the layered member is facing the plane of the paper, and the top and bottom are reversed from their positions in FIG.


14


. The lower surface of the layered member is the lower surface of the piezoelectric element


84


. On the layered member are formed a plurality of array grooves


85


, extending along the lower surface of the layered member. These array grooves


85


extend substantially parallel to the front surface of the layered member and in substantially straight lines, and are positioned at prescribed intervals.




As shown in

FIG. 16

, the array grooves


85


are formed between the lower surface of the piezoelectric element


84


(the surface in contact with the back load member


82


) and a line


83


passing through the second matching layer


88


. Through formation of the array grooves


85


, the piezoelectric element


84


and first matching layer


86


are each divided into a plurality of portions. Focusing on the first matching layer


86


, the array grooves


85


extend along the surface of the first matching layer


86


, and the depth of each dividing groove


85


is, at all portions of the dividing groove


85


, equal to the thickness of the first matching layer


86


, such that the first matching layer


86


is divided. An acoustic lens


90


is provided on top of the second matching layer


88


(FIG.


14


). The acoustic lens


90


is formed from silicone resin. The upper surface of the acoustic lens


90


is formed in a convex shape.




In the back load member


82


, a substantially flat flexible printed board


92


extends in the vertical direction along a side surface adjacent to the front surface. The top end of the flexible printed board


92


is enclosed between the upper surface of the back load member


82


and the lower surface of the piezoelectric element


84


. The other hand is connected to a pulser and observation equipment, not shown, similarly to the conventional ultrasound transducer array


1001


shown in FIG.


30


A and FIG.


30


B.




A plurality of lead wires are positioned on the flexible printed board


92


. These lead wires are connected, via solder, to electrodes on the lower surface of corresponding portions of the divided piezoelectric elements


84


. The flexible printed board


92


is used as signal lines to transmit driving signals and received signals.




In the ultrasound transducer array


81


, a substantially flat flexible printed board


94


having a full-coverage electrode is bonded with conductive adhesive to the side surface opposite the side surface on which the flexible printed board


92


is provided. The piezoelectric element


84


and first matching layer


86


are electrically connected, and by bonding the flexible printed board


94


to the first matching layer


86


, the first matching layer


86


forms a common electrode for each of the portions of the divided piezoelectric element


84


.




A polyimide insulator is positioned on the portion of the flexible printed board


94


adjacent to the piezoelectric element


84


. By this means, the electrode on the lower surface of the piezoelectric element


84


is insulated from the flexible printed board


94


. The flexible printed board


94


is connected to ground, not shown, and used as a ground line.




As described above, the electrode on the upper surface of the piezoelectric element


84


is connected to the first matching layer


86


and to ground via a ground line. The action of the ultrasound transducer array


81


is similar to that of the ultrasound transducer array


1001


of FIG.


30


A and

FIG. 30B

, and an explanation is here omitted.




Next, the material forming the first matching layer


86


is explained. As described above, the first matching layer


86


is formed from a carbon composite material. This carbon composite material contains carbon and carbides. These carbides contain silicon carbide (SiC) and boron carbide (B


4


C). The above carbon composite material contains fine ceramic powder of these carbides, and fine ceramic powder of borides. The carbon composite material is formed into sintered members.




The strength of the first matching layer


86


comprising this carbon composite material is higher compared with a layer comprising carbon alone. This is thought to arise by the following reasons.




The carbon composite material is formed primarily from granular carbon and from fine ceramic particles existing between the carbon grains. The fine ceramic particles are embedded like wedges between adjacent carbon grains. By this means, adjacent carbon grains are not easily separated by fine ceramic particles, so that the growth of microcracks is believed to be suppressed. In particular, when the shape of the fine ceramic particles is polygonal having protrusions and depressions (a combination of polygons) rather than spherical, there is a strong action binding carbon grains in place, and strength can be expected to be improved.




In this way, there is little occurrence of cracking and chipping during machining of the carbon composite material, so that machining is relatively easy. Particularly when used with high-frequency ultrasound at 10 MHz or more, the matching layer must be machined to a thickness of 100 μm or less, but this machining to a thin shape can also be performed easily.




The carbon composite material is formed by intermixing carbon with silicon carbide (SiC) having an average particle diameter of 0.5 μm and boron carbide (B


4


C) having an average particle diameter of 5 μm. The mass fractions of the silicon carbide (SiC) and of the boron carbide (B


4


C) are respectively 6 wt % (mass percentage) and 9 wt %. In addition to these, 4 wt % zirconium boride is also intermixed with the carbon. The acoustic impedance is approximately 8.5×10


6


kg/m


2


s (8.5 MRayl).




The carbon composite material contains fine ceramic particles of density higher than carbon, so that compared with uncombined carbon, the density is higher. Consequently the acoustic impedance of the carbon composite material is larger than that of uncombined carbon.




If the proportion of carbides intermixed in the carbon composite material (that is, the mass fraction) is changed, or the average grain diameter is varied, the acoustic impedance changes. Typically, acoustic impedances between approximately 7.5×10


6


kg/m


2


s (7.5 MRayl) and approximately 10×10


6


kg/m


2


s (10 MRayl) can be obtained. By this means, a matching layer which has optimal acoustic impedance can be prepared for the efficient propagation of ultrasound.




In the case of a resin formed with a filler intermixed in the resin material, if the intermixed filler is modified, the acoustic impedance also changes. However, such a resin has a large ultrasound attenuation factor, so that if a matching layer using such a resin is employed, the ultrasound is not propagated efficiently. In particular, a conductive resin such as that disclosed in Japanese Patent Publication No. 1-61062 contains a filler with a unique shape in order to secure conductivity, and for this reason has a still larger attenuation factor, so that this defect is more prominent. Compared with such a resin, a carbon composite material has a comparatively small ultrasound attenuation factor, and so ultrasound propagates comparatively efficiently. In this way, by using a matching layer consisting of a carbon composite material, a stronger driving signal can be guided to the object, and a stronger received signal can be made incident on the piezoelectric element. Hence the sensitivity of the ultrasound transducer array


81


can be improved.




In this aspect, the carbon composite material is formed by mixing silicon carbide (SiC), boron carbide (B


4


C) and zirconium boride into carbon; but a similar advantageous result to that of the carbon composite material of this aspect is obtained from a carbon composite material in which, in place of mixing the above compounds with carbon, aluminum carbide (Al


4


C


3


) and other carbides, and tungsten boride (WB) and similar, are mixed with carbon. Also, an advantageous result similar to that of the carbon composite material of this aspect is also obtained if at least one among silicon carbide (SiC), boron carbide (B


4


C), zirconium boride, aluminum carbide (Al


4


C


3


), and tungsten boride (WB), is intermixed.




In an ultrasound transducer array


81


with such a configuration, by varying the ratio of silicon carbide (SiC) and boron carbide (B


4


C), the acoustic impedance of the carbon composite material can be modified, and so an ultrasound transducer array


81


can be provided comprising a matching layer having an optimal acoustic impedance.




Further, because the carbon composite material does not swell due to moisture or water as resins do, this material can be durable even for transducers subjected to harsh washing or requiring sterilization for use within the body.




Of course various modifications and alterations of the configurations of this aspect are possible. When using 5 MHz ultrasound, the thickness of the first matching layer


86


is 200 μm; but this invention is not limited to this thickness. For example, in order to use 10 MHz ultrasound, the thickness may be made 100 μm. Also, in order to use ultrasound with an arbitrary frequency, it is of course possible that the thickness can correspond to the frequency.




In this aspect, by providing an insulator on the surface of the flexible printed board


94


facing the piezoelectric elements


84


, the flexible printed board


94


is insulated from the electrodes on the lower surface of the piezoelectric elements


84


; however, this invention is not limited to this configuration. For example, insulation may be effected by forming the electrodes on the lower surface of the piezoelectric elements


84


such that the electrodes on the lower surface of the piezoelectric elements


84


are not exposed to the outside from a crevice between a side surface of the piezoelectric elements


84


and a side surface of the first matching layer


86


. The portion of the electrodes on the lower surface of the piezoelectric elements


84


which are exposed to the outside may be insulated by sealing with resin.




In this aspect, the flexible printed board


92


is connected to the electrodes of the piezoelectric elements


84


via solder; but this invention is not thereby limited. For example, connection may be made by an anisotropic conductive film (ACF). In this case, depolarization of piezoelectric elements


84


arising from contact of the piezoelectric elements


84


with heated solder can be prevented.




The piezoelectric elements


84


may be curved in a convex shape in a direction intersecting the direction in which the array grooves


85


extend. Such an ultrasound transducer array


81


is called a convex-array probe.




Next, method of manufactures of the ultrasound transducer array


81


of this aspect is explained. Two methods of manufacture of the ultrasound transducer array


81


are conceivable.




Initially, a first manufacturing method is explained.




First Process: Carbon composite material containing prescribed carbides is prepared, and this carbon composite material is ground to shape a substantially flat first matching layer


86


.




As explained above, the thickness of the first matching layer


86


is 200 μm. In order to shape carbon composite material to a thickness of 200 μm, a two-sided lapping machine may be used, or wax or a water-soluble adhesive may be used to apply the carbon composite material to a base, and grinding and polishing performed to machine the carbon composite material.




Second Process (process of formation of the second matching layer): A framework is mounted so as to cover the side faces of the first matching layer


86


, forming a container, and tape or similar is used to mask one surface of the first matching layer


86


.




A water-soluble resin or resist may be used for masking. The bottom face of this container is the first matching layer


86


; the side faces constitutes the framework. The masked surface is the surface facing outside the container.




Next, epoxy resin is poured into the container, and the resin is hardened to form the second matching layer


88


. The amount of resin poured is adjusted such that the thickness of the second matching layer


88


is 100 μm. Then the framework and masking are removed.




Third Process (process to form a layered member): A piezoelectric element


84


which is substantially flat and with electrodes formed on the upper and lower surfaces is prepared. The upper surface of the piezoelectric element


84


is bonded with adhesive to the surface of the first matching layer


86


from which the masking was removed, to form a layered member comprising the piezoelectric element


84


, first matching layer


86


, and second matching layer


88


.




Fourth Process (process to connect signal lines): The flexible printed board


92


, serving as signal lines, is connected via solder to the electrode on the bottom surface of the piezoelectric element


84


(the reverse side surface of the surface in contact with the first matching layer


86


).




Fifth Process (process to form array grooves): As shown in

FIG. 16

, the blade


93


of a precision cutting machine is moved from one side surface adjacent to the front surface of the layered member to the other side surface, along a line


83


in the direction of the arrow in the figure. As explained above, the line


83


penetrates the second matching layer


88


. By repeating this movement, the array grooves


85


shown in

FIG. 15

are formed.




Sixth Process: Using a framework similar to that of the second process, the back load member


82


is formed using urethane resin on the bottom surface of the piezoelectric elements


84


.




Next, conductive adhesive is used to bond the flexible printed board


94


, serving as a ground line, to the side surface of the first matching layer


86


. Then, silicone resin is used to form an acoustic lens


90


on the upper surface (the reverse side surface of the surface in contact with the first matching layer


86


) of the second matching layer


88


.




As described in detail above, in the first method of manufacture of the ultrasound transducer array


81


, there is little occurrence of cracking or chipping during machining, and by using easily-machined carbon composite material as the first matching layer


86


, manufacturing can be performed easily.




In the first process of this first manufacturing method, in order to enable the use of 5 MHz ultrasound, the carbon composite material is ground to form a first matching layer


86


of thickness 200 μm. However, in order to use ultrasound at still higher frequencies, the carbon composite material may be machined to a thinner shape. In this case, because the carbon composite material is such that cracking and chipping do not readily occur during machining, machining can be performed more easily than the machining to a thin shape of uncombined carbon such as is used in the matching layer of Japanese Unexamined Patent Application Publication No. 9-139998.




It is preferable that the content of fine ceramic powder including carbides in the carbon composite material used as the matching layer of this invention be from 10 to 50 wt %. If 50 wt % or more is intermixed, electrical conductivity worsens, and because of the high hardness of the carbides such as SiC and B


4


C which are intermixed to suppress microcracks, the lifetime of grinding tools used in machining is shortened, and as a result it becomes difficult to reduce the cost of the probe. If the content is 10 wt % or less, the effect in suppressing microcracks is reduced. It is preferable that the carbon composite material be sintered and bake-hardened.




In order to manufacture a convex-array probe, the layered member may be curved in a convex shape. The second matching layer


88


is formed from epoxy resin, and is flexible. By using this to deform the vicinity of the array grooves


85


in the second matching layer


88


after forming the layered member of

FIG. 15

, a convex-array probe can be manufactured.




Next, a second method of manufacture of the ultrasound transducer array


81


is explained. The above-described first manufacturing method and the second manufacturing method are essentially the same.




Differences between the first manufacturing method and the second manufacturing method are the provision of a process to cut the layered member between the third process (process to form the layered member) and the fourth process (process for signal line connection) of the first manufacturing method.




The layered member (parent layered member) is formed according to the first through third processes (layered member formation processes) of the first manufacturing method, and in the next process, the blade


93


of a precision cutting machine is used to cut the unmachined layered member (parent layered member) along the lines


96


.




As in

FIG. 17

, lines


96


in a lattice shape show the portions of the parent layered member to be cut. The surface of the parent layered member is larger than four times the surface of the layered member formed according to the first manufacturing method.




The parent layered member has a piezoelectric element


84


′ which is effectively the same as the piezoelectric element, first matching layer and second matching layer formed in the first manufacturing method; a first matching layer


86


′; and a second matching layer


88


′. There exist four windows in the lines


96


in a lattice shape. When the parent layered member is cut along the lines


96


, four layered members (child layered members)


97


,


98


,


99


,


100


corresponding to the four windows of the lattice are obtained. The remaining portions of the parent layered member are discarded.




Then, by performing the fourth process (process to connect signal lines) and subsequent processes of the above first manufacturing method, the ultrasound transducer array


81


shown in

FIG. 14

is obtained.




In the above-described first manufacturing method, the side surfaces of the layered member formed in the third process (process to form the layered member) and previous processes may be smeared with epoxy resin leaked from the framework of the second process (process to form the second matching layer) or with the adhesive used in the third process (process to form the layered member).




However, in the second manufacturing method, the portions which had been in contact with the side surfaces of the parent layered member are discarded after cutting, so that the side surfaces of the child layered members are not smeared. Hence in the sixth process, the flexible printed board


94


can be bonded to the side surface of a child layered member free of smearing, and so there is no intervening adhesive or other insulator. Thus reliability is improved when securing electrical conductivity at the side surface of the carbon composite material. Also, the contact strength and bonding durability can be improved.




The time required to form four child layered members through this manufacturing method is approximately ¼ the time required to form four layered members through the above-described first manufacturing method. By means of this manufacturing method, ultrasound transducer arrays


81


can be manufactured rapidly and at low cost.




In this aspect, the layered member is cut along the lines


96


in a lattice shape having four windows; but this invention is not thus limited. The number of windows may be two or three, or may be five or more. Also, the window shape is not limited to a quadrilateral, but may for example be a hexagon. Also, the method for cutting the layered member is not limited to a lattice.





FIG. 18

shows a cross-sectional view of the ultrasound transducer array of an eighth aspect of this invention. The configuration of the ultrasound transducer array


81




a


of this aspect is basically the same as that of the ultrasound transducer array


81


of the seventh aspect, and the configuration as seen from the front of the ultrasound transducer array


81


is the same as in the seventh aspect; hence an explanation is given referring to

FIG. 14

as a side view of the ultrasound transducer array


81




a


of this aspect, and to

FIG. 16

as a side view of the layered member of this aspect.




Differences between the configuration of this aspect and the configuration of the seventh aspect; hence in FIG.


14


and

FIG. 16

, the first matching layer is indicated by the symbol


86




a


instead of the symbol


86


, and the second matching layer is indicated by the symbol


88




a


instead of the symbol


88


.





FIG. 18

is a cross-sectional view of the layered member, along the line C


1


—C


1


in FIG.


14


. In the layered member of the seventh aspect shown in

FIG. 15

, the array grooves


85


are formed from the lower surface of the piezoelectric elements


84


to the second matching layer


88


, but in the layered member shown in

FIG. 18

, the array grooves


85




a


are only formed up to the first matching layer


86




a.






Referring to FIG.


16


and

FIG. 18

, the array grooves


85




a


are formed between the lower surface of the piezoelectric elements


84


and the line


34


penetrating the first matching layer


86




a


. Concerning the first matching layer


86




a


, the depth of the array grooves


85




a


is, throughout the entirety of the array grooves


85




a


, less than the thickness of the first matching layer


86




a.






In the eighth aspect of an ultrasound transducer array


81




a


configured as described in detail above, the first matching layer


86




a


is not divided by the array grooves


85




a


, so that by connecting wires to a part of the conductive first matching layer


86




a


, an electrical connection is made entirely to the divided portions of the first matching layer


86




a


. Hence the flexible printed board


94


used as a ground line need not be bonded to all divided portions of the first matching layer


86




a


. Bonding to at least one portion of the first matching layer


86




a


is sufficient, and so a highly reliable ultrasound transducer array


81


with simple configuration can be provided.




The ultrasound transducer array


81




a


of this aspect can, in essence, be manufactured by either the first or the second method for manufacturing the ultrasound transducer array


81


of the above-described seventh aspect. However, in the fifth process (process to form array grooves), the blade


93


of the precision cutting machine is moved along the lines


34


rather than along the lines


83


.





FIG. 19

shows a cross-sectional view of the ultrasound transducer array of a ninth aspect of this invention. The configuration of the ultrasound transducer array


81




b


of this aspect is essentially the same as the configuration of the ultrasound transducer array


81


of the seventh aspect.




The configuration seen from the front of the ultrasound transducer array


81




b


of this aspect is the same as that of the seventh aspect, and so

FIG. 14

is again referenced as a side view of the ultrasound transducer array


81




b


of this aspect.




Differences in the configuration of this aspect and the configuration of the seventh aspect are the configurations of the first matching layer and the second matching layer; hence in

FIG. 14

, the first matching layer is indicated by the symbol


86




b


instead of the symbol


86


, and the second matching layer is indicated by the symbol


88




b


instead of the symbol


88


.

FIG. 19

is a cross-sectional view of the layered member along the line C


1


—C


1


in FIG.


14


.




The array grooves


85


of the seventh aspect shown in FIG.


15


and

FIG. 16

are formed up to the line


83


penetrating the second matching layer


88


. However, the array grooves


85




a


shown in FIG.


16


and

FIG. 18

are formed up to the line


34


passing through the first matching layer


86




a


. Different from the layered member of the seventh aspect, in the layered member of the ninth aspect there are regularly intermixed main dicing grooves


52


, which are grooves of depth similar to the array grooves


85


, and sub-dicing grooves


54


, which are grooves of depth similar to the array grooves


85




a


, as shown in FIG.


19


. If the main dicing grooves


52


are abbreviated “deep” and the sub-dicing grooves


54


are abbreviated “shallow”, then these grooves are arranged in the order “shallow”, “shallow”, “deep”, “shallow”, “shallow”, “deep”, “shallow”, “shallow”, with two sub-dicing grooves


54


isolated by main dicing grooves


52


.




As a result, the portions of the piezoelectric element


84


divided by the main dicing grooves


52


are further separated into three portions by the two sub-dicing grooves (for example, the portions


55


,


56


,


57


). On the other hand, in the portion


58


of the first matching layer


86




b


separated by main dicing grooves


52


, sub-dicing grooves


54


are formed, but this portion


58


is not divided, and remains continuous. The portions


55


,


56


,


57


of the piezoelectric element


84


are mutually electrically connected via the portion


58


of the first matching layer


86




b


. The portions


55


,


56


,


57


and the portion


58


form a single driving unit. The layered member has a plurality of such driving units.




In the seventh aspect, the flexible printed board


94


must be bonded to all portions of the divided first matching layer


86


. In an ultrasound transducer array


81




b


configured as described in detail above, the flexible printed board


94


need only be bonded to one portion of each driving unit, so that reliability with respect to electrical conduction faults can be improved. Further, the portions of the piezoelectric element


84


forming driving units are further divided by the sub-dicing grooves


54


, so that the sensitivity of the ultrasound transducer array


81




b


can be improved.




In this aspect, two sub-dicing grooves


54


are isolated by main dicing grooves


52


; however, the present invention is not thus limited. For example, single sub-dicing groove may be isolated by main dicing grooves; or, three or more sub-dicing grooves may be so isolated.




The piezoelectric elements


84


may be curved in a direction intersecting the direction in which the main dicing grooves


52


extend. Utilizing the fact that the second matching layer


88




b


is flexible, by deforming the second matching layer


88




b


near the main dicing grooves


52


, and arranging the driving units in a convex shape, a convex-array probe can be formed.




The ultrasound transducer array


81




b


of this aspect can in essence be manufactured by either the first or the second method of manufacturing the ultrasound transducer array


81


of the above-described seventh aspect. However, in the fifth process (the process to form the array grooves), the blade


93


of the precision cutting machine is moved along the line


83


or the line


34


in order to form the main dicing grooves


52


or the sub-dicing grooves


54


, respectively.





FIG. 20

is a side view of the layered member of the ultrasound transducer array of a tenth aspect of this invention. The configuration of the ultrasound transducer array


81




c


of this aspect is essentially the same as the configuration of the ultrasound transducer array


81


of the seventh aspect. The configuration as seen from the front of the ultrasound transducer array


81




c


of this aspect is the same as that of the seventh aspect, and so

FIG. 14

is again referenced as a side view of the ultrasound transducer array


81




c


of this aspect.




Also, the configuration of the layered member of this aspect as seen along the line C


1


—C


1


of

FIG. 14

is the same as that of the seventh aspect, and so

FIG. 15

is again referenced as a cross-sectional view of the layered member of this aspect.




Differences between the configuration of this aspect and that of the seventh aspect are the configurations of the first and the second matching layers; hence in FIG.


14


and

FIG. 15

, the first matching layer, second matching layer, and array grooves are indicated by the symbols


86




c


,


88




c


,


85




c


instead of the symbols


86


,


88


,


85


, respectively.




In

FIG. 20

, similarly to

FIG. 16

, the front surface of the layered member faces the plane of the paper, and the top and bottom are reversed relative to FIG.


14


. In the seventh aspect, the bottom surfaces of the array grooves


85


are along a line


83


which penetrates the second matching layer


88


, as shown in

FIG. 16

; but in this aspect, the bottom surfaces of the array grooves


85




c


are along the line


864


in FIG.


20


. That is, the bottom surfaces of the array grooves


85




c


extend in a straight line up to point B from one side surface of the second matching layer


88




c


through the interior of the second matching layer


88




c


, similarly to the line


83


, but from point B, extend to the side surface of the first matching layer


86




c


opposite the above side surface. Consequently, concerning the first matching layer


86




c


, the depth of the array grooves


85




c


near the above side surface of the first matching layer


86




c


is less than the thickness of the first matching layer


86




c.






In other portions, the thickness of the array grooves


85




c


is equal to the thickness of the matching layer


86




c


. The first matching layer


86




c


is continuous via the portions


862


of the first matching layer


86




c


, positioned between the bottom surface of the portion of the array grooves


85




c


at which the depth is less than the thickness of the first matching layer


86




c


and the second matching layer


88




c


. The piezoelectric element


84


is divided by the array grooves


85




c


. Each of the divided portions of the piezoelectric element


84


is electrically connected via the portions


862


of the conductive first matching layer


86




c.






Similarly to the eighth aspect explained using

FIG. 18

, in an ultrasound transducer array


81




c


configured as explained in detail above, the flexible printed board


94


used as a ground line need be bonded to only a portion of the first matching layer


86




c


, so that a highly reliable ultrasound transducer array


81




c


with simple configuration can be provided.




The ultrasound transducer array


81




c


of this aspect can in essence be manufactured by the first or the second method of manufacture of the ultrasound transducer array


81


of the above-described seventh aspect. However, in the fifth process (the process to form the array grooves), in order to form the array grooves


85




c


, the tip of the blade


93


of the precision cutting machine is for example moved along the line


864


from point A in the direction of the arrow in

FIG. 20

, stopped at point B, and from point B is removed by moving in the direction perpendicular to the line


864


.




An eleventh aspect of this invention is shown in FIG.


21


. The figure is a cross-sectional view of the ultrasound transducer array


81




d


, in the plane parallel to the front surface (similar to the surface facing the plane of the paper in FIG.


14


).




The configuration of the ultrasound transducer array


81




d


of this aspect is in essence the same as the configuration of the ultrasound transducer array


81


of the seventh aspect. In this aspect, constituent members which are effectively the same as constituent members explained referring to FIG.


14


through

FIG. 16

in explaining the seventh aspect are assigned the same reference symbols as those used for the corresponding members of the seventh aspect, and detailed explanations are omitted.




A difference between the configuration of this aspect and the configuration of the seventh aspect is the configuration of the piezoelectric element, signal lines, and ground lines. The lower surface


80


of the first matching layer


86


(the surface opposed to the piezoelectric element


84




d


) is larger than the upper surface of the piezoelectric element


84




d


(the surface opposed to the first matching layer


86


). The upper surface of the piezoelectric element


84




d


is an acoustic radiation surface which radiates ultrasound. The lower surface


80


of the first matching layer


86


is used as an opposed region


80


. The opposed region


80


comprises the junction region


80




a


joined to the acoustic radiation surface of the piezoelectric element


84




d


, and the regions


80




b


joined to the acoustic radiation surface. Copper wires


94




d


used as ground lines are positioned on the regions


80




b


. The regions


80




b


are used as wiring regions


80




b


. The wires


94




d


are connected to the wiring regions


80




b


using conductive resin


106


. The wiring regions


80




b


extend from the front surface of the ultrasound transducer array


81




d


to the back surface (the reverse surface of the front surface) along the side surfaces of the ultrasound transducer array


81




d


, together with the wires


94




d


, and are connected to all the portions of the first matching layer


86


divided by the array grooves


85


.




In this aspect, wires


94




d


are shown as one example of conductive members; but the conductive members need not be formed in wire shape, and may instead be formed in ribbon shape, rod shape, or foil shape.




The cross-sectional plane of the layered member along the line C


8


-C


8


is effectively the same as the layered member cross-section shown in FIG.


15


. Below the piezoelectric element


84




d


, the substantially flat glass-epoxy resin


108


extends from the front surface of the ultrasound transducer array


81




d


to the back surface (the reverse surface of the front surface) in the direction orthogonal to the direction in which the array grooves


85


extend (the direction perpendicular to the plane of the paper in FIG.


21


). A plurality of wires are connected to both ends of the glass-epoxy resin


108


. At both ends of the glass-epoxy resin


108


, electrodes corresponding to these wires are arranged in the length direction in portions close to the piezoelectric element


84




d.






These electrodes are connected to the electrodes on the lower surface of portions corresponding to the divided piezoelectric elements


84




d


, via wires


94




d


. The wires


94




d


are connected to the piezoelectric elements


84




d


using solder. The glass-epoxy resin


108


and wires


94




d


are used as signal lines


92




d


. A portion of the glass-epoxy resin


108


and the wires


94




d


are positioned within the back load member


82


.




In cases where high-frequency ultrasound is to be used, the first matching layer


86


is made thin. Hence if, as in the seventh aspect, a ground line is connected to a side surface of the first matching layer


86


, the area over which the first matching layer


86


is in contact with the ground line (the contact area) is small, and so it is difficult to ensure that conduction faults do not occur.




However, in an ultrasound transducer array


81




d


configured as described in detail above, by connecting a portion of the lower surface of the first matching layer


86


(the surface opposed to the piezoelectric element


84




d


) to the ground line, the contact area is not affected by the thickness of the first matching layer


86


, and so conduction faults can be reliably prevented regardless of the frequency of use.




The configuration of the layered member of this aspect is effectively the same as the configuration of the layered member of the seventh aspect shown in

FIG. 15

, but this invention is not thus limited. For example, the configuration may be effectively the same as the configuration of the eighth aspect shown in

FIG. 18

, or the ninth aspect shown in FIG.


19


. Or, the configuration may be effectively the same as the configuration of the tenth aspect shown in FIG.


20


.




Next, the method of manufacture of the ultrasound transducer array


81




d


of this aspect is explained. The ultrasound transducer array


81




d


of this aspect can in essence be manufactured by the first manufacturing method used to manufacture the ultrasound transducer array


81


of the above-described seventh aspect.




First, the layered member is formed according to the first through the third process (process to form the layered member). In the third process, a piezoelectric element


84




d


having an acoustic radiation surface smaller than the lower surface of the first matching layer


86


is prepared. When the piezoelectric element


84




d


is bonded to the first matching layer


86


, the piezoelectric element is positioned with respect to the first matching layer


86


such that wiring regions


80




b


are formed.




Next, the array grooves


85


are formed according to the fifth process (process to form array grooves). Then, the wires


94




d


and signal lines


92




d


are connected, and the back load member


82


and acoustic lens


90


are formed.




In cases where high-frequency ultrasound is to be used, as described above, if ground lines are connected to the side faces of the first matching layer


86


as in the seventh aspect, the area over which the first matching layer


86


makes contact with the ground lines (the contact area) is small, and so it is difficult to connect the ground lines to the first matching layer


86


.




In this respect, in the method for manufacture of the ultrasound transducer array


81




d


of this aspect, the ground lines are connected to a comparatively large contact area, so that the connection operation is easy. Also, the ground lines can be securely connected, so that manufacturing yields are improved.





FIG. 22

shows a twelfth aspect of the invention. This figure is a cross-sectional view in a plane parallel to the front plane (similar to the plane facing the plane of the paper in

FIG. 21

) of the ultrasound transducer array


81


e.




The configuration of the ultrasound transducer array


81




e


of this aspect is in essence the same as that of the ultrasound transducer array


81




d


shown in

FIG. 21. A

difference in the configuration of this aspect with that of the eleventh aspect is the configuration of the first matching layer.




In the first matching layer


86


shown in

FIG. 21

above, the junction region


80




a


and wiring regions


80




b


exist in the same plane. However, in the first matching layer


86




e


of this aspect, the wiring regions


80




b


are sunken with respect to the junction region


80




a


. Even configured in this way, advantageous results similar to those of the ultrasound transducer array,


81




d


of the eleventh aspect can be obtained.




Next, a method for manufacturing the ultrasound transducer array


81




e


of this aspect is explained. In essence, manufacture is possible using the second method of manufacture of the ultrasound transducer array


81


of the above-described seventh aspect.




First, the parent layered member shown in

FIG. 17

is formed. Then, grooves (hereafter “wiring grooves”) are formed along either the vertical lines, or the horizontal lines, of the lines


96


in a lattice shape in the lower surface (the reverse surface of the piezoelectric element


84


′ that is in contact with the first matching layer


86


′) of the parent layered member, in order to form the sunken wiring regions


80




b


. The width of the wiring grooves is larger than twice the width of the wiring regions


80




b


. The wiring grooves extend in the depth direction as far as the interior of the first matching layer


86




e.






Next, the process to cut the parent layered member of the second manufacturing method is performed. However, when cutting along the wiring grooves, cutting is performed through the center in the width direction of the wiring grooves, along the center line extending in the length direction of the wiring grooves. Then, the signal lines


92




d


and wires


94




d


are connected, and the back load member


82


and acoustic lens


90


are formed, similarly to the method for manufacturing the ultrasound transducer array


81




d


shown in FIG.


21


.




In the method of manufacture of the ultrasound transducer array


81




d


of the twelfth aspect, when the piezoelectric element


84




d


is bonded to the first matching layer


86


, the adhesive may adhere to the wiring regions


80




b


. If so, there is an increased possibility of the occurrence of conduction faults.




With respect to this, in the method of manufacture of the ultrasound transducer array


81




e


of this aspect, by forming the wiring grooves prior to the process of cutting the layered member, adhesive on the wiring regions


80




b


is removed, so that ultrasound transducer arrays


81




e


can be manufactured rapidly and at low cost, and reliability with respect to conduction faults can be improved.




In the eleventh aspect and this aspect, two wires


109


, each extending from respective surface of the glass-epoxy resin


108


, are used to improve reliability; of course a single wire extending from one surface can also be used to obtain a similar advantageous result.




FIG.


23


A and

FIG. 23B

show a thirteenth aspect of this invention.

FIG. 23A

is a cross-sectional view of the ultrasound transducer array


81




f


in a plane parallel to the front plane (similar to the plane facing the plane of the paper in FIG.


14


);

FIG. 23B

is an enlarged view of one of the wiring regions


80




f


and one of grooves


101


.




Grooves


101


are formed between the junction region


80




a


of the first matching layer


86




f


of this aspect, and the wiring regions


80




f


,


80




g


used for wiring. The configuration of the ultrasound transducer array


81




f


of this aspect is in essence the same as the configuration of the ultrasound transducer array


81




d


shown in FIG.


21


.




A difference between the configuration of this aspect and that of the eleventh aspect is the configuration of the matching layer, signal lines and ground lines. The wiring region


80




f


is formed in the portion in contact with the side surface


102


(a side surface adjacent to the front surface). The wiring region


80




f


is defined by the upper surface


104


of the wiring region orthogonal to the side surface


102


which is continuous with the side surface


102


and extends along the side surface


102


, and the wiring region side surface


105


which is continuous with the wiring region upper surface


102


and extends parallel to the side surface


102


.




A substantially flat glass-epoxy board


116


extends along the side surface (surface adjacent to the front surface) of the ultrasound transducer array


81




f


from the back load member


82


toward the first matching layer


86




f


. One end of the glass-epoxy board


116


is inserted into the wiring region


80




f.






On the glass-epoxy board


116


, a ground electrode is formed in the portion


107


opposed to the wiring region upper surface


104


and in the portion


108


opposed to the wiring region side surface


105


, extending along the wiring region


80




f


. That is, the first matching layer


86




f


is in contact on two surfaces with a ground electrode in the wiring region


80




f


. The contact area between the first matching layer


86




f


and the ground electrode is large, so that reliability against electrical conduction faults is high. This electrode is connected to a single wire


94




f


positioned on the surface of the glass-epoxy board


116


facing outside, and is used as a ground line.




The configuration of the wiring region


80




g


and the glass-epoxy board


116




f


which is connected to the wiring region


80




g


is effectively the same as the configuration of the wiring region


80




f


and the glass-epoxy board


116


respectively. A difference between the former and the latter is that an electrode is formed on the portion


108


of the glass-epoxy board


116


, but no electrode is formed on the portion of the glass-epoxy board


116




f


corresponding to the portion


108


. That is, the first matching layer


86




f


is in contact with a ground electrode at one surface in the wiring region


80




g.






A plurality of wires


92




f


are positioned as signal lines on the surfaces facing inward of the glass-epoxy boards


116


,


116




f


. These wires are connected using solder to the electrodes on the lower surfaces in portions corresponding to divided piezoelectric elements


84




d


via wires


119


.




If, as in the conventional ultrasound transducer array


1001


shown in FIG.


30


A and

FIG. 30B

, a ground line


1009


spans two neighboring portions among the plurality of portions of a divided first matching layer


1004


, vibrations propagate between these portions via this ground line


1009


, so that mechanical cross talk may occur. In this aspect, however, by forming the groove


101


, vibrations are not easily transmitted to the glass-epoxy boards


116


,


116




f


, so that mechanical cross talk can be prevented.




In this aspect, wires


92




f


used as signal lines are connected using solder to electrodes on the bottom surface of the piezoelectric element


84




d


via wires


119


; but this invention is not thus limited. For example, wire bonding may also be used. When using solder, there may be variations in the amount of solder for each of the wires


119


, so that differences in loads for different wires


119


may occur. If wire bonding is used, differences in loads can be reduced, and so the characteristics of the ultrasound transducer array


81




f


can be stabilized. Also, solder may be used to make connections via conductors other than wire.




Next, a method of manufacture of the ultrasound transducer array


81




f


of this aspect is explained.




The ultrasound transducer array


81




f


can, in essence, be manufactured by the method of manufacture of the ultrasound transducer array


81




d


of the eleventh aspect shown in FIG.


21


.




First, similarly to the eleventh aspect, a layered member having a small piezoelectric element


84




d


is formed. Then, the array grooves


85


, wiring regions


80




f


,


80




g


, and grooves


101


are formed. Following this, the glass-epoxy boards


116


,


116




f


and wires


119


are mounted, and the back load member


82


and acoustic lens


90


are formed.




In this aspect, a ground electrode to which is connected a wire


94




f


used as a ground line is directly bonded to the first matching layer


86




f


using conductive adhesive; but this invention is not thus limited. For example, wire bonding may be used, similarly to the wires


92




f


used as signal lines. In this case, sputtering or another method is used to provide gold, aluminum, or some other metal on the portion of the first matching layer


86




f


to be wire-bonded. By using wire bonding, the time required for manufacture can be shortened compared with cases in which conductive adhesive is used, so that wire bonding is suited to mass production.




In this aspect, the electrode of the piezoelectric element


84




d


on the side of the first matching layer


86




f


is used as a ground electrode, but if a sufficiently high breakdown voltage is secured for the acoustic lens


90


and second matching layer


88


and similar, the patterning of the glass-epoxy boards


116


,


116




f


may be modified, and the signal line and ground line interchanged.




In each of the aspects described above, a piezoelectric ceramic obtained by ordinary sintering is used as the piezoelectric element; but a piezoelectric single crystal may be used instead.




In each of the above-described aspects, the ultrasound transducer arrays


81


and


81




a


to


81




e


have been described in detail as having divided piezoelectric element portions arranged in a one-dimensional array. Of course, a carbon composite material containing carbides, of which material itself has small ultrasound attenuation and an optimal acoustic impedance, is easily machined and can be formed into thin shapes, can be applied to an ultrasound transducer array using a piezoelectric element not divided by array grooves or to an ultrasound transducer array in which divided piezoelectric element portions are arranged in two dimensions.




Below, the dimensions of elements in the configuration of the ultrasound transducer arrays described thus far are explained.




In Japanese Patent Publication No. 62-2813, for example, an embodiment is proposed in which an ultrasound transducer array


1001


has a ratio w/t of the width w in the array direction of a single piezoelectric element


1003


, shown in

FIG. 31

, to the thickness t in the acoustic radiation axis direction, being equal or less than 0.8, and in particular being w/t=0.66 (w=0.4 mm, t=0.6 mm).




However, if in the ultrasound transducer array of the above Japanese Patent Publication No. 62-2813 the ratio w/t of the width in the array direction of a single piezoelectric element


1003


to the thickness t in the acoustic radiation axis direction of the above piezoelectric element


1003


is made much smaller than 0.8, the problem described below occurs.




If the ratio w/t of the width w to the thickness t of the above piezoelectric element


1003


is set such that w/t<0.3, vibration modes in the transverse direction are small, but higher-order vibrations in the thickness direction become large. In an ultrasound transducer array


1001


configured with at least one row of such piezoelectric elements


1003


, high-harmonic vibrations will occur (see

FIG. 25A

, FIG.


25


B).




Due to this occurrence of high harmonics, energy in the ultrasound transducer array


1001


is also distributed to high harmonic components, so that there is energy loss in the fundamental frequency component, and the sensitivity declines. Also, because of the presence of these high harmonic components in the ultrasound transducer array


1001


, disorder appears in the transmitted sound field formed by electronic focusing in order to electronically focus the ultrasound, so that artifacts occur, and the accuracy of the result of ultrasound beam synthesis upon reception is reduced. Consequently the resolution of the resulting ultrasound diagnostic image is degraded.




On the other hand, if the ratio w/t of the width w to the thickness t of the above piezoelectric elements


1003


is set to 0.6 to 0.8, the electromechanical transduction efficiency is improved, but transverse-direction vibration modes appear. Consequently problems similar to the above-described high harmonic components arise, cross talk and increases in pulse width occur due to radial-direction vibrations, and there is degradation of the resolution of ultrasound diagnostic images resulting from imaging.




Hence the piezoelectric element


1003


must have a high electromechanical transduction efficiency and must be of a shape which suppresses the occurrence of unnecessary vibration modes.




Therefore, the provision of an ultrasound transducer array having piezoelectric elements with a high electromechanical transduction efficiency, of an optimal shape for suppressing the occurrence of unnecessary vibration modes, and enabling the enhancement of image resolution, is desired.




Below, fourteenth through sixteenth aspects of this invention are explained, referring to FIG.


24


through FIG.


29


.




FIG.


24


through

FIG. 27

show a fourteenth aspect of this invention. As shown in FIG.


24


A through

FIG. 24C

, the ultrasound transducer array


121


of this aspect comprises a plurality of piezoelectric elements


122


which generate ultrasound and which transmit and receive this ultrasound; a piezoelectric element, positioned on the acoustic radiation surface side of the above plurality of piezoelectric elements


122


, which radiates the ultrasound generated by the above plurality of piezoelectric elements


122


; an acoustic lens


124


, positioned further on the acoustic radiation surface side than the above piezoelectric element


123


; and a backing member


125


, positioned on the back side of the above plurality of piezoelectric elements


122


, as a back load member to absorb unnecessary ultrasound. In this ultrasound transducer array


121


, the above plurality of piezoelectric elements


122


are configured to form at least a one-dimensional array.




The above piezoelectric elements


122


are formed from, for example, soft lead zirconate titanate, Pb(Zr,Ti)O


3


, or other PZT-system piezoelectric ceramic material, with electrodes formed on both surfaces. The above acoustic lens


124


is formed from silicone resin. The above piezoelectric element


123


is configured from, for example, a first piezoelectric element


123




a


formed from an epoxy resin with alumina as a filler on the acoustic radiation surface side of the piezoelectric elements


122


, and a second piezoelectric element


123




b


formed from an uncombined epoxy resin, further on the acoustic radiation surface side further than the first piezoelectric element


123




a.






The above backing member


125


is formed from urethane with alumina as a filler. The above piezoelectric elements


122


are connected on the signal line side by a flexible printed board


126


on which a pattern


126




a


is formed; the grounds on the sides of the above first and second piezoelectric elements


123




a


,


123




b


are connected by solder or conductive adhesive using a ground line


127


as a common connection, and covered by a protective resin


128


. As the ground line


127


, a conductive wire or foil is used.




The 3 MHz ultrasound transducer array


121


of this aspect is manufactured by the following method.




First, a 250 μm thin sheet for the first piezoelectric element


123




a


(with acoustic impedance approximately 7.5 MRayl) is ground. Then, one surface of the first piezoelectric element


123




a


is masked with tape or similar, and the second piezoelectric element


123




b


is formed to a thickness of 190 μm on the unmasked surface.




Next, a piezoelectric element


122


approximately 500 μm thick is fixed with adhesive to the above first piezoelectric element


123




a


, and a flexible printed board


126


is joined with solder to the above piezoelectric elements


122


.




Following this, backing material


125


is poured onto and joined with the back side of the above plurality of piezoelectric elements


122


, and wax is used to fix the assembly onto a base, or tape is used to fix it in place. In this state, cutting is performed from the side of the above piezoelectric elements


122


, to form the ultrasound transducer array.




In performing cutting, a precision cutting machine is employed, using a 60 μm thick blade, and cutting at a pitch of 0.3 mm. At this time, the ratio w/t of the width in the array direction of the above piezoelectric elements


122


to the thickness t of a single piezoelectric element


122


in the acoustic radiation axis direction is w/t=0.48.




After cutting, lead wires and solder are used for joining to the surface electrodes on the piezoelectric element


123


side of the piezoelectric elements


122


to make a common GND electrode. Finally, the acoustic lens


124


is formed from silicone resin, to obtain the transducer.




Upon varying the ratio w/t of the width w in the array direction of the piezoelectric elements


122


to the thickness t of the above piezoelectric elements


122


in the acoustic radiation axis direction, impedance curve such as those shown in

FIG. 25A

to

FIG. 25D

, and in

FIG. 26A

to

FIG. 26C

, are obtained.





FIG. 25A

to

FIG. 25D

, and

FIG. 26A

to

FIG. 26C

, are graphs showing the impedance curve (acoustic impedance and phase versus frequency) when the ratio w/t of the width w to the thickness t of the piezoelectric elements


122


is varied.




Here,

FIG. 25A

is a graph showing the impedance curve when w/t=0.2;

FIG. 25B

is a graph showing the impedance curve when w/t=0.3;

FIG. 25C

is a graph showing the impedance curve when w/t=0.5; and

FIG. 25D

is a graph showing the impedance curve when w/t=0.6. Further,

FIG. 26A

is a graph showing the vicinity of the fundamental resonance for w/t=0.5;

FIG. 26B

is a graph showing the vicinity of the fundamental resonance for w/t=0.6; and

FIG. 26C

is a graph showing the vicinity of the fundamental resonance for w/t=0.8.




The phase is the phase difference between the current and the voltage of the driving signal driving the piezoelectric elements


122


. The magnitude of the acoustic impedance is minimum at the point where this phase difference is zero, at which all the electrical energy supplied to the piezoelectric elements


122


is being converted into vibrational energy.




When w/t<0.3, transverse-direction vibration modes are small, but thickness-direction higher-order vibrations are increased. More specifically, at w/t=0.2 third- and higher-order harmonics are larger, and as w/t is increased, higher-order mode vibrations diminish.




On the other hand, when w/t>0.6, a vibration component occurs in lateral directions perpendicular to the polarization axis of the piezoelectric elements


122


. Consequently when an ultrasound transducer array


121


is configured using piezoelectric elements


122


with w/t>0.6, unwanted vibration modes appear. Hence a problem similar to the above-described harmonic components arises, and cross talk and pulse widths are increased, so that image accuracy is worsened during imaging.




FIG.


27


A through

FIG. 27D

show graphs of the echo waveforms and spectrums of ultrasound transducer arrays


121


similarly fabricated using 5 MHz piezoelectric elements


122


, with the ratio w/t of the width w to the thickness t of the piezoelectric elements


122


varied, and measured using a flat stainless steel reflecting sheet.




Here,

FIG. 27A

shows the echo waveform and spectrum for w/t=0.2;

FIG. 27B

shows the echo waveform and spectrum for w/t=0.25;

FIG. 27C

shows the echo waveform and spectrum for w/t=0.3; and

FIG. 27D

shows the echo waveform and spectrum for w/t=0.5.




For example, when w/t<0.25 as shown in FIG.


27


A and

FIG. 27B

, large harmonic components appear in the echo waveform, and the waveform is disturbed. It is difficult to completely eliminate these harmonic components even when using a bandpass filter.




On the other hand, as shown in FIG.


27


C and

FIG. 27D

, when w/t=0.3 and w/t=0.5, the harmonic components appearing in the echo waveform are extremely small, and there is no disturbance of the waveform.




From these results it is found that in order to efficiently vibrate the piezoelectric elements


122


and suppress higher-order modes and transverse-direction vibrations, the ratio w/t of the width w in the array direction of the piezoelectric elements


122


to the thickness t of the above piezoelectric elements


122


in the acoustic radiation axis direction must be set within 0.3<w/t<0.5.




In this aspect, the ratio w/t of the width w of piezoelectric elements


122


in the array direction to the thickness t of the above piezoelectric elements in the acoustic radiation axis direction is set to 0.3 to 0.5, and, in the case of soft PZT-system materials, preferably to w/t=0.4 to 0.5 in order to more effectively suppress higher-order vibration modes.




By setting the w/t ratio of piezoelectric elements


122


to 0.3 to 0.5, and preferably to an optimal value of 0.4 to 0.5, higher-order vibration modes, transverse-direction vibration modes, and other unwanted vibration modes are suppressed, only a simple filter is necessary for imaging, energy losses are reduced, and high-sensitivity piezoelectric elements


122


can be realized inexpensively.




In this aspect, an ultrasound transducer array


121


arranged linearly was described; however, the plurality of piezoelectric elements


122


may be curved in a divided manner, to apply this invention to a convex-type ultrasound transducer array.





FIG. 28

shows a fifteenth aspect of this invention.




In the above-described fourteenth aspect, an ultrasound transducer array


121


is configured by forming a first piezoelectric element


123




a


from epoxy resin using alumina as a filler; in this aspect, the first piezoelectric element


123




a


is formed from carbon to configure the ultrasound transducer array


121


. Otherwise the configuration is substantially the same as that of the above fourteenth aspect, and an explanation is omitted; similar constituent components are assigned the same symbols in the explanation.




As shown in

FIG. 28

, the ultrasound transducer array


130


of this aspect is configured having a first matching layer


131


formed from a carbon composite containing ultra-fine particles of silicon carbide (SiC) and boron carbide (B


4


C) on the acoustic radiation surface side of the piezoelectric element


122


.




The 5 MHz ultrasound transducer array of this invention is manufactured by the following method.




First, the carbon composite material which is to become the first matching layer


131


, prepared containing ultra-fine particles of silicon carbide (SiC) and boron carbide (B


4


C), is ground to a thickness of 200 μm. Here the carbon composite material is graphite (carbon) containing fine particles of SiC and B


4


C. This carbon composite material has wedge-shape fine ceramic particles intermixed between grains of the above graphite (carbon) to suppress the growth of microcracks and greatly increase strength compared with graphite. Consequently, even when machined to a thin shape (under 100 μm) for use at still higher frequencies of 10 MHz or higher, this carbon composite material can be machined comparatively easily by using a two-sided lapping machine and using wax, water-soluble adhesive or similar to affix the material to a base for grinding and polishing.




The carbon composite material used in this aspect contains SiC with an average grain diameter 0.5 μm at a mass fraction of 6 wt %, B


4


C with an average grain diameter of 5 μm at a mass fraction of 9 wt %, and 4 wt % zirconium boride. The acoustic impedance of this carbon composite material is approximately 8.5 MRayl.




Next, one side of the first matching layer


131


formed from this carbon composite material is masked with tape or similar, and a resin layer 100 μm thick is formed from epoxy resin on the unmasked side to form the second piezoelectric element


123




b


. Then, a piezoelectric element


122


, approximately 300 μm thick, is fixed with adhesive to the above first matching layer


131


, and a flexible printed board


126


provided with a pattern is joined with solder to the piezoelectric element


122


.




Thereafter, wax is used to fix to a base, or tape is used to fix in place, the layered member. In this state, cutting is performed from the side of the above piezoelectric element


122


to midway through the second piezoelectric element


123




b


, to form the ultrasound transducer array.




In this cutting, a precision cutting machine is used, employing a 30 μm thick blade, cutting at a pitch of 130 μm. At this time, the ratio w/t of the width w in the array direction of one piezoelectric element


122


to the thickness t of the piezoelectric element


122


in the acoustic radiation axis direction is w/t=0.33. The ultrasound transducer array of this aspect has a so-called sub-diced configuration, in which two elements are connected in a single pattern.




Next, after a backing material


125


formed from epoxy resin with an alumina filler, used as a back load member, is poured onto and joined with the reverse side of the piezoelectric element


122


, the side surfaces of the above first matching layer


131


are cleaned.




Then, a flexible printed board


132


having a full-coverage electrode is joined to the surface electrode on the side of the piezoelectric element


123


of the piezoelectric element


122


using conductive adhesive, for use as a common GND electrode. Finally, an acoustic lens


124


is formed from silicone resin, to complete fabrication of the transducer.




Similarly to the above-described fourteenth aspect, if the configuration of the transducer of this ultrasound transducer array


130


configured in this way is varied, including the first and second matching layer


131


,


123




b


, the third- and higher-order harmonics are increased for w/t=0.25 or less, and as the w/t ratio is increased, higher-order vibration modes diminish.




If the fabricated ultrasound transducer array


130


has a w/t ratio-of 0.25 or less, large harmonic components appear in the echo waveform and cannot easily be eliminated completely even using a band-pass filter.




As shown in FIG.


25


A through FIG.


25


D and FIG.


26


A through

FIG. 26C

, when the w/t ratio is 0.6 or higher, vibration components in transverse directions perpendicular to the polarization axis appear, so that when used in an ultrasound transducer array


121


, unwanted vibration modes are present. Consequently a problem similar to that of the above-mentioned high harmonic components arises, and there are increases in cross talk and in pulse widths, so that the image accuracy upon imaging is degraded.




As a result, similarly to the above-described fourteenth aspect, in order that the piezoelectric element


122


vibrates efficiently, and in order to suppress higher-order modes and transverse-direction vibrations, the ratio w/t of the width w of the piezoelectric element


122


in the array direction to the thickness t of the above piezoelectric element


122


in the acoustic radiation axis direction must be set in the range 0.3<w/t<0.5.




In this aspect, similarly to the above-described fourteenth aspect, the ratio w/t of the width w of piezoelectric elements


122


in the array direction to the thickness t of the above piezoelectric elements in the acoustic radiation axis direction is set to 0.3 to 0.5, and, in the case of soft PZT-system materials, preferably to w/t=0.4 to 0.5 in order to more effectively suppress higher-order vibration modes.




By this means, advantageous results similar to those of the ultrasound transducer array


121


of the above-described fourteenth aspect can be obtained from the ultrasound transducer array


130


of this aspect.




Because the first matching layer


131


formed from the above carbon composite material is conductive, in addition to functioning as a matching layer, it can also be used as an electrode from the piezoelectric element


122


.




In this aspect, the piezoelectric element


122


and the first matching layer


131


are electrically connected via a thin adhesive layer, and by connecting wires to this first matching layer


131


, a common electrode for the piezoelectric elements


122


after cutting is formed. Also, the exposed side-surface electrode of the piezoelectric element


122


has more area available for wiring than the side surface of the above first matching layer


131


, so that wiring reliability is improved. Further, in a configuration in which wiring is performed from the side surface of the first matching layer


131


, the acoustic radiation area can be made large with respect to the size of the transducer, so that the device size can be easily reduced.




Though not shown in

FIG. 28

, the signal electrode side of the piezoelectric element


122


and the flexible printed board


132


which serves as the common GND electrode must be insulated. As the method of insulation, a method is used in which a polyimide insulator is positioned in the portion neighboring the piezoelectric element


122


of the flexible printed board


132


itself. Other possible insulation methods are available not by providing a full-surface electrode on the piezoelectric element


122


but by providing a portion without an electrode in the region neighboring the flexible printed board


132


, or by sealing the exposed signal electrode of the piezoelectric element


122


with resin or similar means.





FIG. 29

shows the ultrasound transducer array of a sixteenth aspect of the invention. This aspect is a modification of

FIG. 28

; in the ultrasound transducer array


140


shown in the figure, first and second matching layers


131


,


123




b


are layered as shown in

FIG. 28

, and are joined to a piezoelectric element


141


which is somewhat smaller than these first and second matching layers


131


,


123




b.






Then, wax is used to fix to a base, or tape is used to fix in place, the layered member. In this state, cutting is performed from the side of the above piezoelectric element


141


to midway through the second piezoelectric element


123




b


, to form the ultrasound transducer array in which the w/t ratio is 0.3 to 0.5, and preferably an optimal value of 0.4 to 0.5.




After cutting, the divided first matching layer


131


is connected using copper wires


129


and conductive resin


142


, and the signal-line is connected by solder to each piezoelectric element


141


using fine wires


144


from substantially the distal end of the glass-epoxy board


143


with patterns formed on both sides.




A framework, not shown, is provided on both ends of the above first matching layer


131


, and a groove portion formed is filled with backing material


125


to form the back load member, and in addition the acoustic lens


124


is formed from silicone resin to fabricate the transducer.




Advantageous results similar to those of the above-described fourteenth and fifteenth aspects are obtained from the ultrasound transducer array


140


configured in this way, and in cases where wiring is difficult from the side surface of the first matching layer


131


, which is made thin for operation at higher frequencies, wiring operations are made easy, and manufacturing yields are improved.




In this variant, the first and second matching layers


131


,


123




b


are layered, and are joined to a piezoelectric element


141


somewhat smaller than these first and second matching layers


131


,


123




b


to form a layered member, after which, by cutting to a depth such that a portion of the cut reaches the first matching layer


131


, a region for ground wiring is formed. Then, dicing is performed to form the array elements, and by connecting wires


129


using conductive resin


142


a common electrode is formed, to fabricate the ultrasound transducer array


140


. After bonding, wiring is performed in portions at the cut in the carbon material, so that there are no conduction faults due to adhesive, and manufacturing yields and reliability are improved.




In this aspect, the first matching layer


131


is cut completely through; however, by leaving a slight amount in the depth direction, or by providing a remaining portion at an edge, there is no need to connect a common ground to each piezoelectric element after cutting, so that an array can be fabricated inexpensively and with high reliability. Further, by cutting through 80% or more of the piezoelectric element


141


in the depth direction, piezoelectric elements


141


can be fabricated with a high electromechanical transduction efficiency, regardless of the presence of the first matching layer


131


.




Because after cutting the neighboring piezoelectric elements


141


are connected, the problem of cross talk arises. However, by leaving material on the common GND electrode side, the need for wiring is eliminated, and the transducer can be manufactured inexpensively. And by cutting into only the sub-diced portion to midway through the piezoelectric element


141


, or to midway through the first matching layer


131


, which is a conductive matching layer, cross talk can be suppressed and wiring reliability improved.




Similarly to the fourteenth aspect, by curving the array in a state in which a plurality of piezoelectric elements


141


are separated, a convex-shape ultrasound transducer array can be manufactured.




Various variants of each of the configurations of the above-described fourteenth through sixteenth aspects are conceivable; representative examples of these are indicated below.




In addition to PZT-system piezoelectric ceramics and other PMN-system piezoelectric ceramics obtained by ordinary sintering, similar advantageous results can be obtained by using materials such as piezoelectric single crystals as the piezoelectric element


141


.




The method of manufacture of transducers is not limited to only those of the above-described aspects; for example, a second piezoelectric element


123




b


using epoxy resin may be ground and shaped to a prescribed thickness, a first piezoelectric element


123




a


formed by pouring an epoxy resin with alumina filler, then grinding and shaping, and after fixing in place the piezoelectric element


141


using an adhesive, dicing is performed from the side of the piezoelectric element


141


to midway through the second piezoelectric element


123




b


, such that the w/t ratio is from 0.3 to 0.5.




Compared with such a backing member


125


as a back load member, by forming a hard piezoelectric element


123


and then cutting from the side of the piezoelectric element


141


, the precision in the depth direction is improved, there is little vibration in the piezoelectric element


141


during cutting, chipping and other problems tend not to occur, and groove widths are stable. Consequently the width of the piezoelectric elements


141


can be reduced for use at high frequencies, and sizes can be reduced, to manufacture transducers with good yields.




As explained using

FIG. 29

, a framework, not shown, is provided after wiring signal-side, and an epoxy resin, which remains flexible after hardening, intermixed with alumina, zirconia or similar insulating powder is poured into the framework to form the backing member


125


as a back load member; by this means, an adhesive layer is not necessary, scattering in reflections at interfaces is small, and stable transducers can be formed. Of course each of the configurations of the aspects here described can be variously modified and altered.




This invention is not limited only to the above aspects; if the width w in the array direction of the above piezoelectric element


141


is the width w perpendicular to the acoustic radiation axis of the above piezoelectric element


141


, an ultrasound transducer array


140


may also be configured in which the ratio of the width w perpendicular to the acoustic radiation axis of the above piezoelectric element


141


to the thickness t of the above piezoelectric element


141


in the acoustic radiation axis direction is from 0.3 to 0.5, and more preferably from 0.4 to 0.5.




Having described the preferred embodiments of the invention referring to the accompanying drawings, it should be understood that the present invention is not limited to those precise embodiments, and that various changes and modifications thereof could be made by one skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.




As explained above, in this invention divided grooves are formed to a depth such that piezoelectric elements are separated, reaching the matching layer, and the thickness of remaining material in the matching layer is made small, such that cross talk can be sufficiently suppressed, and filler material can be used to prevent a reduction in the strength.



Claims
  • 1. An ultrasound transducer array, in which a plurality of piezoelectric elements, which can be electrically operated independently, are arranged in an array, and comprising:one or a plurality of matching layers, provided on the acoustic radiation surface side of said piezoelectric elements; a conductive material layer, provided on the side of said matching layer joined with said piezoelectric elements, in the direction along the array direction, a portion of which is in contact with and electrically connected to said piezoelectric elements along said array direction, and a portion of which is not in contact with said piezoelectric elements along said array direction; a plurality of grooves, which mechanically and electrically insulate said piezoelectric elements and at least a portion of said matching layer for each electrically independently operable element; and, conductive material, which fills at least a part of the portions of said grooves formed where said piezoelectric elements and said conductive material layer are not in contact.
  • 2. The ultrasound transducer array according to claim 1, wherein said conductive material layer is formed from a first thermosetting base resin, and said conductive material used for filling is formed from a second thermosetting base resin.
  • 3. The ultrasound transducer array according to claim 2, wherein said first thermosetting base resin and said second thermosetting base resin are the same.
  • 4. The ultrasound transducer array according to claim 2, wherein, of said matching layer, the layer adjacent to said piezoelectric elements is formed from a carbon composite material containing carbides.
  • 5. The ultrasound transducer array according to claim 4, wherein said conductive material layer and said filler conductive material are formed from a thermosetting resin intermixed with carbon powder.
  • 6. The ultrasound transducer array according to claim 5, wherein said carbon powder is a powder of the carbon composite material of said matching layer.
  • 7. The ultrasound transducer array according to claim 2, having a conductive member which makes a common electrical connection to said plurality of electrically independently operable piezoelectric elements along said array direction, and wherein said conductive member is fixed to said conductive material layer by said filled conductive material.
  • 8. The ultrasound transducer array according to claim 2, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.3 to 0.5.
  • 9. The ultrasound transducer array according to claim 8, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.4 to 0.5.
  • 10. The ultrasound transducer array according to claim 1, wherein, of said matching layers, the layer adjacent to said plurality of piezoelectric elements is formed from a carbon composite material containing carbides, and also serves as said conductive material layer.
  • 11. The ultrasound transducer array according to claim 10, wherein said filled conductive material is formed from a thermosetting resin base intermixed with carbon powder.
  • 12. The ultrasound transducer array according to claim 10, wherein said carbon composite material containing carbides contains, as said carbides, fine powder of silicon carbide or of boron carbide.
  • 13. The ultrasound transducer array according to claim 10, wherein said carbon composite material containing carbides contains silicon carbide as said carbides, and also contains a fine powder of borides.
  • 14. The ultrasound transducer array according to claim 10, having a conductive member which makes a common electrical connection to said plurality of electrically independently operable piezoelectric elements along said array direction, and wherein said conductive member is fixed to said conductive material layer by said filled conductive material.
  • 15. The ultrasound transducer array according to claim 10, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.3 to 0.5.
  • 16. The ultrasound transducer array according to claim 15, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.4 to 0.5.
  • 17. The ultrasound transducer array according to claim 1, having a conductive member which makes a common electrical connection to said plurality of electrically independently operable piezoelectric elements along said array direction, and wherein said conductive member is fixed to said conductive material layer by said filled conductive material.
  • 18. The ultrasound transducer array according to claim 17, wherein said conductive member is a conductive material formed into any of those among a wire shape, ribbon shape, rod shape, or foil shape.
  • 19. The ultrasound transducer array according to claim 17, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.3 to 0.5.
  • 20. The ultrasound transducer array according to claim 19, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.4 to 0.5.
  • 21. The ultrasound transducer array according to claim 1, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.3 to 0.5.
  • 22. The ultrasound transducer array according to claim 21, wherein the ratio of the width w in the array direction to the thickness t in the ultrasound radiation direction of said plurality of piezoelectric elements is from 0.4 to 0.5.
Priority Claims (3)
Number Date Country Kind
2000-363641 Nov 2000 JP
2001-022202 Jan 2001 JP
2001-043785 Feb 2001 JP
CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No. 09/998,982 filed Nov. 30, 2001, now U.S. Pat. No. 6,558,323 entitled ULTRASOUND TRANSDUCER ARRAY which claims the benefit and priority of Japanese Application Nos. 2001-22202, filed in Japan on Jan. 30, 2001; 2001-43785, filed in Japan on Feb. 20, 2001; and 2000-363641, filed in Japan on Nov. 29, 2000, the contents of which are incorporated by this reference.

US Referenced Citations (2)
Number Name Date Kind
6043589 Hanafy Mar 2000 A
6558323 Wakabayashi et al. May 2003 B2
Continuations (1)
Number Date Country
Parent 09/998982 Nov 2001 US
Child 10/391037 US