Information
-
Patent Grant
-
6616269
-
Patent Number
6,616,269
-
Date Filed
Thursday, July 5, 200123 years ago
-
Date Issued
Tuesday, September 9, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Nguyen; Judy
- Brooke; Michael S
Agents
- Fitzpatrick, Cella, Harper & Scinto
-
CPC
-
US Classifications
Field of Search
US
- 347 50
- 347 58
- 347 59
- 347 63
-
International Classifications
-
Abstract
In the electrode pads in the ink jet print head substrate that uses ball bumps, bonding of the ball bumps is carried out in satisfactory condition despite reduced thickness of films in the substrate. In an ink jet print head substrate, which has a heater film constituting the heater portions, a second electric wire in electrical contact with the heater film to supply it with electric power, and a first electric wire constituting a common electrode of a matrix wire for selectively driving the heater portions, the first electric wire is used as the electrode pads to which the ball bump is joined. The first electric wire does not need to be reduced in thickness even when the thickness of the protective film is reduced. Thus, an ultrasonic wave can be transferred well to the electrode pad during ultrasonic bonding.
Description
This application is based on Patent Application No. 2000-209101 filed Jul. 10, 2000 in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a substrate for an ink jet print head, an ink jet print head and a manufacture method thereof, and more particularly to a structure of a bump electrode pad used for electrical connection between the substrate and electric wiring such as a TAB tape, both forming the ink jet print head.
2. Description of the Prior Art
The manufacture of an ink jet print head involves a process of connecting two components: a head chip (hereinafter simply referred to as a “chip” or “print element substrate”), which is composed of a substrate has formed therein heaters and a driver IC and matrix wires for driving the heaters and a nozzle forming member in which ink ejection ports are formed, and a TAB tape electrically connects the print head to a printer body. This connecting process is normally performed by using both heat and ultrasonic wave to connect the bumps provided on the electrode pad on the chip to inner leads of the TAB tape.
A commonly used bump is a so-called plated bump which is formed by forming and patterning a SiO
2
or SiN film as a passivation layer, forming one to three layers of barrier metal such as Ti, Cu and W as a contact improving layer on aluminum electrodes, forming a resist pattern over the barrier metal layer by photolithography, and finally growing gold by electrolytic plating.
The forming of the plated bump requires performing several cycles of a vacuum film forming process and an exposure/development process. Because in the case of the plated bump an entire wafer is subjected to the plating process, not only sound chips but also chips that become faulty in the subsequent steps are formed with gold-plated bumps. This leads to a possible increase in cost. Further, when the number of electrode pads per the wafer is small (i.e., when the number of bumps is small), the cost per bump increases.
For these reasons, an increasing number of a ball bumps are being used in recent years. The ball bump is formed by using the wire bonding method. In this forming process an arc discharge is applied to the front end of a wire passed through a ceramic tube called capillary to form a ball, which is then joined to a predetermined electrode pad on the substrate by using both heat and ultrasonic wave. Then, the capillary is lifted while at the same time the wire is held by a cut clamper, thus fracturing the wire by a tensile strength to cut off the ball portion and thereby form a bump. Another method of joining the balls to the electrode pad is known to use only heat, rather than using both heat and ultrasonic wave as in the above method.
As described above, the ball bump does not require the expensive vacuum film forming device and exposure device as do the plated bump. Further, because the passivation film and the barrier metal are not necessary, the ball bump is more advantageous than the plated bump in terms of cost when the number of pads per a piece of wafer is small.
In an ink jet print head that uses thermal energy produced by a heater to eject ink, films making up the heater or the like tend to decrease in thickness. The structure of this type of print head will be discussed as follows in terms of the thickness of the film tending to decrease.
An example substrate making such an ink jet print head is made by successively forming on a silicon base an IC film (made up of about six layers) for a driver IC or the like which consists of semiconductor devices to drive the heater in ejecting ink, a first interlayer insulating film (e.g., SiN film) forming a lowermost layer in contact with the base, a first electric wiring film (e.g., Al film) forming a common electrode for supplying an electric power to drive the heater by the driver IC in response to a drive signal or a common electrode for grounding, a second interlayer insulating film (e.g., SiO film) overlying the first electric wiring film, a heater film (e.g., TaN film) forming the heater, a second electric wiring film (e.g., Al film) directly connected to the heater to supply an electric power to the heater, and a wear resistant film (e.g., Ta film) overlying the second electric wiring film.
FIG. 16
is a plan view showing a conventional example of a heater and an electric wire for driving the heater corresponding to one ejection port in the substrate for the ink jet print head of the type described above.
FIG. 17
is a perspective view showing a head chip made by forming, on the substrate having the electric wiring film or the like, a nozzle forming member in which ink ejection ports or the like are formed.
In order to selectively drive a plurality of heaters to eject ink according to print data, the substrate for the print head is normally formed with a matrix electrode wire. In
FIG. 16
a first electric wire
202
represents a common electrode forming a part of the matrix wire and is connected in a through-hole portion
105
to a second electric wire
205
which in turn is connected to a heater film
204
forming a heater
101
. More specifically, as described later by referring to
FIG. 18
, the first electric wire
202
is formed as lower layer with respect to a direction of thickness of the substrate, and this wire
202
and the second electric wire
205
formed as an upper layer than the wire
202
are generally formed in separate steps in a substrate making process and thus are electrically interconnected via the through-holes. Further, as to the connections for supplying an electric power and a drive signal to the head chip and connections for grounding the substrate potential, the substrate is formed at its end portions with electrode pads
110
, as shown in
FIG. 17
, for electrical connection to a printer body.
FIG. 18
is a cross section showing a film structure of mainly the heater portion
101
, the through-hole portion
105
and the electrode pad portions
110
in the above substrate structure.
The film structure of the heater
101
and its vicinity is presented in
FIG. 18
as a cross section taken along the line
18
a
—
18
a
of FIG.
16
. On the silicon base
11
are laminated a first interlayer insulating film
201
, a second interlayer insulating film
203
, a heater film
204
, a part of the second electric wire film
205
, a protective film
206
, and a wear resistant film
207
.
In
FIG. 18
the film structure of the through-hole portion
105
that connects the first electric wire film
202
and the second electric wire film
205
is presented as a cross section taken along the line
18
b
—
18
b
of FIG.
16
. On the silicon base
11
are successively laminated the first interlayer insulating film
201
, the first electric wire film
202
, the second interlayer insulating film
203
, the heater film
204
, the second electric wire film
205
, the protective film
206
and the wear resistant film
207
. In this film structure, the second interlayer insulating film
203
is partly formed with through-holes to electrically connect the first electric wire film
202
to the second electric wire film
205
through the heater film
204
.
Further, in
FIG. 18
the film structure of the electrode pad is presented as a cross section taken along the line
18
c
—
18
c
of FIG.
17
. The first interlayer insulating film
201
, the first electric wire film
202
, the heater film
204
, and the second electric wire film
205
are successively laminated.
As described above, although the first electric wire film
202
and the second electric wire film
205
are electrically connected together, they are formed as separate films owing to different functions performed. That is, they are formed in separate manufacture processing steps. In more concrete terms, the first electric wire film
202
is formed under the heater film
204
. On the other hand, the second electric wire film
205
is formed over the heater film. For the sake of the film making process, the heater film
204
and the second electric wire film
205
are also formed in the electrode pad portion
110
along with the heater portion
101
and the through-hole portion
105
. The second electric wire film
205
in the electrode pad portion
110
forms a surface conductive film in contact with the ball bumps.
In the bubble jet type print head composed of the substrate with the above-described structure, the density of ink ejection ports and their associated structures in the print head are being increasingly enhanced in recent years to cope with the growing demands for faster printing and higher print quality. Such an increase in density may cause a problem of a heat generation or heat storage. For example, the heat generated by the heater in ejecting ink is mostly released outside together with the ejected ink droplet, with the remaining heat, which is small, accumulated in the head when the printing process continues. When the ink ejection ports are arranged in high density, the extent to which the heat is accumulated increases, causing the head temperature to rise, resulting in an ejection failure or a broken head.
To deal with this problem, it is important to minimize the amount of energy applied to the print head for ink ejection. In this respect, measures to improve the thermal efficiency of ink ejection include, for example, reducing the thickness of the protective film over the heater film to transfer heat to the ink with an increased efficiency. For example, reducing the thickness of the protective film from the conventional 8000 Å to 3000 Å can reduce the energy applied to the print head at time of ink ejection by about 40%.
Such a reduction in the thickness of the protective film, however, degrades a coverage by the protective film of stepped portions of the electric wires. To deal with this situation, the second electric wire film
205
such shown in
FIG. 18
, which is covered by the protective film and formed over the heater film, is reduced in thickness to minimize a vertical difference between levels at the stepped portion and thereby prevent the deterioration of step coverage. For example, the aluminum film of the electric wire is reduced in thickness from the conventional 4,000 Å to 2,000 Å.
However, the above-described reducing the thickness of the second electric wire causes reducing the thickness of the second electric wire film in the electrode pad portion, i.e., the surface conductive film in contact with the ball bumps. As a result, the ball bumps may result in a faulty joint and, in the worst case, may cause a bump loss, the phenomenon in which bumps come off the electrode pad. For example, when gold is used as a material of the ball bump and an aluminum electric wiring layer is used as a surface conductive film that comes into contact with the bumps on the electrode pad, the frequency of the bump loss generally increases as the thickness of the aluminum electric wiring layer decreases.
As described above, a trouble may occur in which the surface conductive film fails to adhere to the ball bumps or their joining strength is weak (generally evaluated by the strength measured by a shear tester). This is explained as follows. Because the second electric wire film of, for example, aluminum formed over the relatively hard heater film is thin, resulting in a reduced joining strength of an alloy of gold ball bump and aluminum joined by ultrasonic bonding. Increasing the intensity of the ultrasonic wave for solving this problem, however, may cause cracks in the pad portion in the substrate. Further, to minimize the energy necessary for ink ejection requires a further reduction in the thickness of the protective film and its associated second electric wire film, for example, down to 1,500 Å and 1,000 Å, respectively. This in turn makes the problem of poor junction of ball bumps more significant.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a substrate for an ink jet print head, an ink jet print head and a method of manufacture thereof, which assures a satisfactory joint between a ball bump and an electrode pad regardless of a reduction in the film thickness in the substrate for the ink jet print head.
In a first aspect of the present invention, there is provided a substrate for an ink jet print head that uses thermal energy to eject ink, the substrate comprising:
a film structure having a plurality of films laminated over the substrate, the plurality of films including a first electric wire film, a heater film and a second electric wire film formed one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;
wherein an electrode pad portion, which is formed at a part of the film structure to make electrical connection to other than the substrate through a ball bump, is formed by an exposed part of the first electric wire film, and a thickness of the first electric wire film is larger than that of the second electric wire film.
In a second aspect of the present invention, there is provided an ink jet print head which uses thermal energy to eject ink, comprising:
a substrate making the ink jet print head, the substrate including:
a film structure having a plurality of films laminated over the substrate, the plurality of films including a first electric wire film, a heater film and a second electric wire film formed one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;
wherein an electrode pad portion, which is formed at a part of the film structure to make electrical connection to other than the substrate through a ball bump, is formed by an exposed part of the first electric wire film, and a thickness of the first electric wire film is larger than that of the second electric wire film.
In a third aspect of the present invention, there is provided a method of manufacturing an ink jet print head which uses thermal energy to eject ink, the method comprising the steps of:
forming a substrate, the substrate constituting the ink jet print head and having a film structure, the film structure having at least a first electric wire film, an interlayer insulating film, a heater film, a second electric wire film and a protective film laminated one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;
wherein, in an electrode pad portion formed by a part of the step of forming the film structure of the substrate and adapted to make electrical connection to other than the substrate through a ball bump, the interlayer insulating film is removed to expose the first electric wire film and to make an exposed part of the surface first electric wire film be a part to which the ball bump are joined.
In a fourth aspect of the present invention, there is provided a method of manufacturing an ink jet print head which uses thermal energy to eject ink, the method comprising the steps of:
forming a substrate, the substrate constituting the ink jet print head and having a film structure, the film structure having at least a first electric wire film, an interlayer insulating film, a heater film, a second electric wire film and a protective film laminated one upon the other in that order over the substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated;
wherein, in an electrode pad portion formed by a part of the step of forming the film structure of the substrate and adapted to make electrical connection to other than the substrate through a ball bump, after the interlayer insulating film is patterned to form a window therein, the heater film and the second electric wire film are deposited one upon the other and then removed to expose the first electric wire film and to make an exposed part of the surface first electric wire film be a part to which the ball bump are joined.
With the above construction, because the exposed part of the first wire electrode underlying the heater forms the electrode pad, a film which does not need to be reduced in thickness to secure the heater protective film's step coverage even when the protective film is made thinner can be used for the electrode pad. Further, an inherently thick film can be used for the electrode pad. As a result, when the ball bump is joined by an ultrasonic bonding process bonding, the bonding strength can be increased.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view showing an external construction of an ink jet printer as one embodiment of the present invention;
FIG. 2
is a perspective view showing the printer of
FIG. 1
with an enclosure member removed;
FIG. 3
is a perspective view showing an assembled print head cartridge used in the printer of one embodiment of the present invention;
FIG. 4
is an exploded perspective view showing the print head cartridge of
FIG. 3
;
FIG. 5
is an exploded perspective view of the print head of
FIG. 4
as seen diagonally below;
FIGS. 6A and 6B
are perspective views showing a construction of a scanner cartridge upside down which can be mounted in the printer of one embodiment of the present invention instead of the print head cartridge of
FIG. 3
;
FIG. 7
is a block diagram schematically showing the overall configuration of an electric circuitry of the printer according to one embodiment of the present invention;
FIG. 8
is a diagram showing the relation between
FIGS. 8A and 8B
,
FIGS. 8A and 8B
being block diagrams representing an example inner configuration of a main printed circuit board (PCB) in the electric circuitry of
FIG. 7
;
FIG. 9
is a diagram showing the relation between
FIGS. 9A and 9B
,
FIGS. 9A and 9B
being block diagrams representing an example inner configuration of an application specific integrated circuit (ASIC) in the main PCB of
FIGS. 8A and 8B
;
FIG. 10
is a flow chart showing an example of operation of the printer as one embodiment of the present invention;
FIG. 11
is a perspective view showing a detailed construction of a print element substrate shown in
FIG. 5
;
FIG. 12
is a cross section showing a film structure of a print head substrate according to the one embodiment of the invention;
FIG. 13
is a cross section showing a ball bump formed on an electrode pad in the substrate shown in
FIG. 12
;
FIG. 14
is an explanatory diagram showing an example method of manufacturing the substrate shown in
FIG. 12
;
FIG. 15
is an explanatory diagram showing another example method of manufacturing the substrate shown in
FIG. 12
;
FIG. 16
is a plan view showing in particular an example of an electric wire in a conventional print head substrate;
FIG. 17
is a perspective view showing a head chip using the conventional substrate; and
FIG. 18
is a longitudinal cross section showing a film structure of the conventional head substrate.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described below in detail with reference to the drawings.
A general structure of an ink jet printer which uses a ink jet print head will be explained below by referring to
FIGS. 1-10
, before explaining a structure of an electrode pad in the ink jet print head according to one embodiment of the present invention.
A term “printing”, as used herein, refers to formation of images, patterns, or the like on a printing medium or processing of the printing medium whether meaningful information such as characters, graphics, or the like or meaningless information is to be formed or whether or not the information is embodied so as to be visually perceived by human beings.
A term “printing medium”, as used herein, refers not only to paper for use in general printing apparatuses but also to materials such as cloths, plastic films, metal plates, glass, ceramics, woods, and leathers which can receive inks.
Furthermore, a term “ink” (or “liquid”) should be broadly interpreted as in a definition of the above term “printing”, and refers to a liquid that is applied to the printing medium to form images, patterns, or the like, process the printing medium, or process the ink (for example, solidify or insolubilize a coloring material in the ink applied to the printing medium).
1. Apparatus Body
FIGS. 1 and 2
show an outline construction of a printer using an ink jet printing system. In
FIG. 1
, a housing of a printer body M
1000
of this embodiment has an enclosure member, including a lower case M
1001
, an upper case M
1002
, an access cover M
1003
and a discharge tray M
1004
, and a chassis M
3019
(see
FIG. 2
) accommodated in the enclosure member.
The chassis M
3019
is made of a plurality of plate-like metal members with a predetermined rigidity to form a skeleton of the printing apparatus and holds various printing operation mechanisms described later.
The lower case M
1001
forms roughly a lower half of the housing of the printer body M
1000
and the upper case M
1002
forms roughly an upper half of the printer body M
1000
. These upper and lower cases, when combined, form a hollow structure having an accommodation space therein to accommodate various mechanisms described later. The printer body M
1000
has an opening in its top portion and front portion.
The discharge tray M
1004
has one end portion thereof rotatably supported on the lower case M
1001
. The discharge tray M
1004
, when rotated, opens or closes an opening formed in the front portion of the lower case M
1001
. When the print operation is to be performed, the discharge tray M
1004
is rotated forwardly to open the opening so that printed sheets can be discharged and successively stacked. The discharge tray M
1004
accommodates two auxiliary trays M
1004
a
, M
1004
b
. These auxiliary trays can be drawn out forwardly as required to expand or reduce the paper support area in three steps.
The access cover M
1003
has one end portion thereof rotatably supported on the upper case M
1002
and opens or closes an opening formed in the upper surface of the upper case M
1002
. By opening the access cover M
1003
, a print head cartridge H
1000
or an ink tank H
1900
installed in the body can be replaced. When the access cover M
1003
is opened or closed, a projection formed at the back of the access cover, not shown here, pivots a cover open/close lever. Detecting the pivotal position of the lever as by a micro-switch and so on can determine whether the access cover is open or closed.
At the upper rear surface of the upper case M
1002
a power key E
0018
, a resume key E
0019
and an LED E
0020
are provided. When the power key E
0018
is pressed, the LED E
0020
lights up indicating to an operator that the apparatus is ready to print. The LED E
0020
has a variety of display functions, such as alerting the operator to printer troubles as by changing its blinking intervals and color. Further, a buzzer E
0021
(
FIG. 7
) may be sounded. When the trouble is eliminated, the resume key E
0019
is pressed to resume the printing.
2. Printing Operation Mechanism
Next, a printing operation mechanism installed and held in the printer body M
1000
according to this embodiment will be explained.
The printing operation mechanism in this embodiment comprises: an automatic sheet feed unit M
3022
to automatically feed a print sheet into the printer body; a sheet transport unit M
3029
to guide the print sheets, fed one at a time from the automatic sheet feed unit, to a predetermined print position and to guide the print sheet from the print position to a discharge unit M
3030
; a print unit to perform a desired printing on the print sheet carried to the print position; and an ejection performance recovery unit M
5000
to recover the ink ejection performance of the print unit.
Here, the print unit will be described. The print unit comprises a carriage M
4001
movably supported on a carriage shaft M
4021
and a print head cartridge H
1000
removably mounted on the carriage M
4001
.
2.1. Print Head Cartridge
First, the print head cartridge used in the print unit will be described with reference to
FIGS. 3
to
5
.
The print head cartridge H
1000
in this embodiment, as shown in
FIG. 3
, has an ink tank H
1900
containing inks and a print head H
1001
for ejecting ink supplied from the ink tank H
1900
out through nozzles according to print information. The print head H
1001
is of a so-called cartridge type in which it is removably mounted to the carriage M
4001
described later.
The ink tank for this print head cartridge H
1000
consists of separate ink tanks H
1900
of, for example, black, light cyan, light magenta, cyan, magenta and yellow to enable color printing with as high an image quality as photograph. As shown in
FIG. 4
, these individual ink tanks are removably mounted to the print head H
1001
.
Then, the print head H
1001
, as shown in the perspective view of
FIG. 5
, comprises a print element substrate H
1100
, a first plate H
1200
, an electric wiring board H
1300
, a second plate H
1400
, a tank holder H
1500
, a flow passage forming member H
1600
, a filter H
1700
and a seal rubber H
1800
.
The print element silicon substrate H
1100
has formed in one of its surfaces, by the film deposition technology, a plurality of print elements to produce energy for ejecting ink and electric wires, such as aluminum, for supplying electricity to individual print elements. A plurality of ink passages and a plurality of nozzles H
1100
T, both corresponding to the print elements, are also formed by the photolithography technology. In the back of the print element substrate H
1100
, there are formed ink supply ports for supplying ink to the plurality of ink passages. The print element substrate H
1100
is securely joined to the first plate H
1200
which is formed with ink supply ports H
1201
for supplying ink to the print element substrate H
1100
. The first plate H
1200
is securely joined with the second plate H
1400
having an opening. The second plate H
1400
holds the electric wiring board H
1300
to electrically connect the electric wiring board H
1300
with the print element substrate H
1100
. The electric wiring board H
1300
is to apply electric signals for ejecting ink to the print element substrate H
1100
, and has electric wires associated with the print element substrate H
1100
and external signal input terminals H
1301
situated at electric wires' ends for receiving electric signals from the printer body. The external signal input terminals H
1301
are positioned and fixed at the back of a tank holder H
1500
described later.
The tank holder H
1500
that removably holds the ink tank H
1900
is securely attached, as by ultrasonic fusing, with the flow passage forming member H
1600
to form an ink passage H
1501
from the ink tank H
1900
to the first plate H
1200
. At the ink tank side end of the ink passage H
1501
that engages with the ink tank H
1900
, a filter H
1700
is provided to prevent external dust from entering. A seal rubber H
1800
is provided at a portion where the filter H
1700
engages the ink tank H
1900
, to prevent evaporation of the ink from the engagement portion.
As described above, the tank holder unit, which includes the tank holder H
1500
, the flow passage forming member H
1600
, the filter H
1700
and the seal rubber H
1800
, and the print element unit, which includes the print element substrate H
1100
, the first plate H
1200
, the electric wiring board H
1300
and the second plate H
1400
, are combined as by adhesives to form the print head H
1001
.
2.2. Carriage
Next, by referring to
FIG. 2
, the carriage M
4001
carrying the print head cartridge H
1000
will be explained.
As shown in
FIG. 2
, the carriage M
4001
has a carriage cover M
4002
for guiding the print head H
1001
to a predetermined mounting position on the carriage M
4001
, and a head set lever M
4007
that engages and presses against the tank holder H
1500
of the print head H
1001
to set the print head H
1001
at a predetermined mounting position.
That is, the head set lever M
4007
is provided at the upper part of the carriage M
4001
so as to be pivotable about a head set lever shaft. There is a spring-loaded head set plate (not shown) at an engagement portion where the carriage M
4001
engages the print head H
1001
. With the spring force, the head set lever M
4007
presses against the print head H
1001
to mount it on the carriage M
4001
.
At another engagement portion of the carriage M
4001
with the print head H
1001
, there is provided a contact flexible printed cable (see FIG.
7
: simply referred to as a contact FPC hereinafter) E
0011
whose contact portion electrically contacts a contact portion (external signal input terminals) H
1301
provided in the print head H
1001
to transfer various information for printing and supply electricity to the print head H
1001
.
Between the contract portion of the contact FPC E
0011
and the carriage M
4001
there is an elastic member not shown, such as rubber. The elastic force of the elastic member and the pressing force of the head set lever spring combine to ensure a reliable contact between the contact portion of the contact FPC E
0011
and the carriage M
4001
. Further, the contact FPC E
0011
is connected to a carriage substrate E
0013
mounted at the back of the carriage M
4001
(see FIG.
7
).
3. Scanner
The printer of this embodiment can mount a scanner in the carriage M
4001
in place of the print head cartridge H
1000
and be used as a reading device.
The scanner moves together with the carriage M
4001
in the main scan direction, and reads an image on a document fed instead of the printing medium as the scanner moves in the main scan direction. Alternating the scanner reading operation in the main scan direction and the document feed in the subscan direction enables one page of document image information to be read.
FIGS. 6A and 6B
show the scanner M
6000
upside down to explain about its outline construction.
As shown in the figure, a scanner holder M
6001
is shaped like a box and contains an optical system and a processing circuit necessary for reading. A reading lens M
6006
is provided at a portion that faces the surface of a document when the scanner M
6000
is mounted on the carriage M
4001
. The lens M
6006
focuses light reflected from the document surface onto a reading unit inside the scanner to read the document image. An illumination lens M
6005
has a light source not shown inside the scanner. The light emitted from the light source is radiated onto the document through the lens M
6005
.
The scanner cover M
6003
secured to the bottom of the scanner holder M
6001
shields the interior of the scanner holder M
6001
from light. Louver-like grip portions are provided at the sides to improve the ease with which the scanner can be mounted to and dismounted from the carriage M
4001
. The external shape of the scanner holder M
6001
is almost similar to that of the print head H
1001
, and the scanner can be mounted to or dismounted from the carriage M
4001
in a manner similar to that of the print head H
1001
.
The scanner holder M
6001
accommodates a substrate having a reading circuit, and a scanner contact PCB M
6004
connected to this substrate is exposed outside. When the scanner M
6000
is mounted on the carriage M
4001
, the scanner contact PCB M
6004
contacts the contact FPC E
0011
of the carriage M
4001
to electrically connect the substrate to a control system on the printer body side through the carriage M
4001
.
4. Example Configuration of Printer Electric Circuit
Next, an electric circuit configuration in this embodiment of the invention will be explained.
FIG. 7
schematically shows the overall configuration of the electric circuit in this embodiment.
The electric circuit in this embodiment comprises mainly a carriage substrate (CRPCB) E
0013
, a main PCB (printed circuit board) E
0014
and a power supply unit E
0015
.
The power supply unit E
0015
is connected to the main PCB E
0014
to supply a variety of drive power.
The carriage substrate E
0013
is a printed circuit board unit mounted on the carriage M
4001
(
FIG. 2
) and functions as an interface for transferring signals to and from the print head through the contact FPC E
0011
. In addition, based on a pulse signal output from an encoder sensor E
0004
as the carriage M
4001
moves, the carriage substrate E
0013
detects a change in the positional relation between an encoder scale E
0005
and the encoder sensor E
0004
and sends its output signal to the main PCB E
0014
through a flexible flat cable (CRFFC) E
0012
.
Further, the main PCB E
0014
is a printed circuit board unit that controls the operation of various parts of the ink jet printing apparatus in this embodiment, and has I/O ports for a paper end sensor (PE sensor) E
0007
, an automatic sheet feeder (ASF) sensor E
0009
, a cover sensor E
0022
, a parallel interface (parallel I/F) E
0016
, a serial interface (Serial I/F) E
0017
, a resume key E
0019
, an LED E
0020
, a power key E
0018
and a buzzer E
0021
. The main PCB E
0014
is connected to and controls a motor (CR motor) E
0001
that constitutes a drive source for moving the carriage M
4001
in the main scan direction; a motor (LF motor) E
0002
that constitutes a drive source for transporting the printing medium; and a motor (PG motor) E
0003
that performs the functions of recovering the ejection performance of the print head and feeding the printing medium. The main PCB E
0014
also has connection interfaces with an ink empty sensor E
0006
, a gap sensor E
0008
, a PG sensor E
0010
, the CRFFC E
0012
and the power supply unit E
0015
.
FIG. 8
is a diagram showing the relation between
FIGS. 8A and 8B
, and
FIGS. 8A and 8B
are block diagrams showing an inner configuration of the main PCB E
0014
.
Reference number E
1001
represents a CPU, which has a clock generator (CG) E
1002
connected to an oscillation circuit E
1005
to generate a system clock based on an output signal E
1019
of the oscillation circuit E
1005
. The CPU E
1001
is connected to an ASIC (application specific integrated circuit) and a ROM E
1004
through a control bus E
1014
. According to a program stored in the ROM E
1004
, the CPU E
1001
controls the ASIC E
1006
, checks the status of an input signal E
1017
from the power key, an input signal E
1016
from the resume key, a cover detection signal E
1042
and a head detection signal (HSENS) E
1013
, drives the buzzer E
0021
according to a buzzer signal (BUZ) E
1018
, and checks the status of an ink empty detection signal (INKS) E
1011
connected to a built-in A/D converter E
1003
and of a temperature detection signal (TH) E
1012
from a thermistor. The CPU E
1001
also performs various other logic operations and makes conditional decisions to control the operation of the ink jet printing apparatus.
The head detection signal E
1013
is a head mount detection signal entered from the print head cartridge H
1000
through the flexible flat cable E
0012
, the carriage substrate E
0013
and the contact FPC E
0011
. The ink empty detection signal E
1011
is an analog signal output from the ink empty sensor E
0006
. The temperature detection signal E
1012
is an analog signal from the thermistor (not shown) provided on the carriage substrate E
0013
.
Designated E
1008
is a CR motor driver that uses a motor power supply (VM) E
1040
to generate a CR motor drive signal E
1037
according to a CR motor control signal E
1036
from the ASIC E
1006
to drive the CR motor E
0001
. E
1009
designates an LF/PG motor driver which uses the motor power supply E
1040
to generate an LF motor drive signal E
1035
according to a pulse motor control signal (PM control signal) E
1033
from the ASIC E
1006
to drive the LF motor. The LF/PG motor driver E
1009
also generates a PG motor drive signal E
1034
to drive the PG motor.
E
1010
is a power supply control circuit which controls the supply of electricity to respective sensors with light emitting elements according to a power supply control signal E
1024
from the ASIC E
1006
. The parallel I/F E
0016
transfers a parallel I/F signal E
1030
from the ASIC E
1006
to a parallel I/F cable E
1031
connected to external circuits and also transfers a signal of the parallel I/F cable E
1031
to the ASIC E
1006
. The serial I/F E
0017
transfers a serial I/F signal E
1028
from the ASIC E
1006
to a serial I/F cable E
1029
connected to external circuits, and also transfers a signal from the serial I/F cable E
1029
to the ASIC E
1006
.
The power supply unit E
0015
provides a head power signal (VH) E
1039
, a motor power signal (VM) E
1040
and a logic power signal (VDD) E
1041
. A head power ON signal (VHON) E
1022
and a motor power ON signal (VMON) E
1023
are sent from the ASIC E
1006
to the power supply unit E
0015
to perform the ON/OFF control of the head power signal E
1039
and the motor power signal E
1040
. The logic power signal (VDD) E
1041
supplied from the power supply unit E
0015
is voltage-converted as required and given to various parts inside or outside the main PCB E
0014
.
The head power signal E
1039
is smoothed by the main PCB E
0014
and then sent out to the flexible flat cable E
0011
to be used for driving the print head cartridge H
1000
. E
1007
denotes a reset circuit which detects a reduction in the logic power signal E
1041
and sends a reset signal (RESET) to the CPU E
1001
and the ASIC E
1006
to initialize them.
The ASIC E
1006
is a single-chip semiconductor integrated circuit and is controlled by the CPU E
1001
through the control bus E
1014
to output the CR motor control signal E
1036
, the PM control signal E
1033
, the power supply control signal E
1024
, the head power ON signal E
1022
and the motor power ON signal E
1023
. It also transfers signals to and from the parallel interface E
0016
and the serial interface E
0017
. In addition, the ASIC E
1006
detects the status of a PE detection signal (PES) E
1025
from the PE sensor E
0007
, an ASF detection signal (ASFS) E
1026
from the ASF sensor E
0009
, a gap detection signal (GAPS) E
1027
from the GAP sensor E
0008
for detecting a gap between the print head and the printing medium, and a PG detection signal (PGS) E
1032
from the PE sensor E
0007
, and sends data representing the statuses of these signals to the CPU E
1001
through the control bus E
1014
. Based on the data received, the CPU E
1001
controls the operation of an LED drive signal E
1038
to turn on or off the LED E
0020
.
Further, the ASIC E
1006
checks the status of an encoder signal (ENC) E
1020
, generates a timing signal, interfaces with the print head cartridge H
1000
and controls the print operation by a head control signal E
1021
. The encoder signal (ENC) E
1020
is an output signal of the CR encoder sensor E
0004
received through the flexible flat cable E
0012
. The head control signal E
1021
is sent to the print head H
1001
through the flexible flat cable E
0012
, carriage substrate E
0013
and contact FPC E
0011
.
FIG. 9
is a diagram showing the relation between
FIGS. 9A and 9B
, and
FIGS. 9A and 9B
are block diagrams showing an example internal configuration of the ASIC E
1006
.
In these figures, only the flow of data, such as print data and motor control data, associated with the control of the head and various mechanical components is shown between each block, and control signals and clock associated with the read/write operation of the registers incorporated in each block and control signals associated with the DMA control are omitted to simplify the drawing.
In the figures, reference number E
2002
represents a PLL controller which, based on a clock signal (CLK) E
2031
and a PLL control signal (PLLON) E
2033
output from the CPU E
1001
, generates a clock (not shown) to be supplied to the most part of the ASIC E
1006
.
Denoted E
2001
is a CPU interface (CPU I/F) E
2001
, which controls the read/write operation of register in each block, supplies a clock to some blocks and accepts an interrupt signal (none of these operations are shown) according to a reset signal E
1015
, a software reset signal (PDWN) E
2032
and a clock signal (CLK) E
2031
output from the CPU E
1001
, and control signals from the control bus E
1014
. The CPU I/F E
2001
then outputs an interrupt signal (INT) E
2034
to the CPU E
1001
to inform it of the occurrence of an interrupt within the ASIC E
1006
.
E
2005
denotes a DRAM which has various areas for storing print data, such as a reception buffer E
2010
, a work buffer E
2011
, a print buffer E
2014
and a development data buffer E
2016
. The DRAM E
2005
also has a motor control buffer E
2023
for motor control and, as buffers used instead of the above print data buffers during the scanner operation mode, a scanner input buffer E
2024
, a scanner data buffer E
2026
and an output buffer E
2028
.
The DRAM E
2005
is also used as a work area by the CPU E
1001
for its own operation. Designated E
2004
is a DRAM control unit E
2004
which performs read/write operations on the DRAM E
2005
by switching between the DRAM access from the CPU E
1001
through the control bus and the DRAM access from a DMA control unit E
2003
described later.
The DMA control unit E
2003
accepts request signals (not shown) from various blocks and outputs address signals and control signals (not shown) and, in the case of write operation, write data E
2038
, E
2041
, E
2044
, E
2053
, E
2055
, E
2057
etc. to the DRAM control unit to make DRAM accesses. In the case of read operation, the DMA control unit E
2003
transfers the read data E
2040
, E
2043
, E
2045
, E
2051
, E
2054
, E
2056
, E
2058
, E
2059
from the DRAM control unit E
2004
to the requesting blocks.
Denoted E
2006
is a IEEE 1284 I/F which functions as a bi-directional communication interface with external host devices, not shown, through the parallel I/F E
0016
and is controlled by the CPU E
1001
via CPU I/F E
2001
. During the printing operation, the IEEE 1284 I/F E
2006
transfers the receive data (PIF receive data E
2036
) from the parallel I/F E
0016
to a reception control unit E
2008
by the DMA processing. During the scanner reading operation, the 1284 I/F E
2006
sends the data (1284 transmit data (RDPIF) E
2059
) stored in the output buffer E
2028
in the DRAM E
2005
to the parallel I/F E
0016
by the DMA processing.
Designated E
2007
is a universal serial bus (USB) I/F which offers a bi-directional communication interface with external host devices, not shown, through the serial I/F E
0017
and is controlled by the CPU E
1001
through the CPU I/F E
2001
. During the printing operation, the universal serial bus (USB) I/F E
2007
transfers received data (USB receive data E
2037
) from the serial I/F E
0017
to the reception control unit E
2008
by the DMA processing. During the scanner reading, the universal serial bus (USB) I/F E
2007
sends data (USB transmit data (RDUSB) E
2058
) stored in the output buffer E
2028
in the DRAM E
2005
to the serial I/F E
0017
by the DMA processing. The reception control unit E
2008
writes data (WDIF E
2038
) received from the 1284 I/F E
2006
or universal serial bus (USB) I/F E
2007
, whichever is selected, into a reception buffer write address managed by a reception buffer control unit E
2039
.
Designated E
2009
is a compression/decompression DMA controller which is controlled by the CPU E
1001
through the CPU I/F E
2001
to read received data (raster data) stored in a reception buffer E
2010
from a reception buffer read address managed by the reception buffer control unit E
2039
, compress or decompress the data (RDWK) E
2040
according to a specified mode, and write the data as a print code string (WDWK) E
2041
into the work buffer area.
Designated E
2013
is a print buffer transfer DMA controller which is controlled by the CPU E
1001
through the CPU I/F E
2001
to read print codes (RDWP) E
2043
on the work buffer E
2011
and rearrange the print codes onto addresses on the print buffer E
2014
that match the sequence of data transfer to the print head cartridge H
1000
before transferring the codes (WDWP E
2044
). Reference number E
2012
denotes a work area DMA controller which is controlled by the CPU E
1001
through the CPU I/F E
2001
to repetitively write specified work fill data (WDWF) E
2042
into the area of the work buffer whose data transfer by the print buffer transfer DMA controller E
2013
has been completed.
Designated E
2015
is a print data development DMA controller E
2015
, which is controlled by the CPU E
1001
through the CPU I/F E
2001
. Triggered by a data development timing signal E
2050
from a head control unit E
2018
, the print data development DMA controller E
2015
reads the print code that was rearranged and written into the print buffer and the development data written into the development data buffer E
2016
and writes developed print data (RDHDG) E
2045
into the column buffer E
2017
as column buffer write data (WDHDG) E
2047
. The column buffer E
2017
is an SRAM that temporarily stores the transfer data (developed print data) to be sent to the print head cartridge H
1000
, and is shared and managed by both the print data development DMA CONTROLLER and the head control unit through a handshake signal (not shown).
Designated E
2018
is a head control unit E
2018
which is controlled by the CPU E
1001
through the CPU I/F E
2001
to interface with the print head cartridge H
1000
or the scanner through the head control signal. It also outputs a data development timing signal E
2050
to the print data development DMA controller according to a head drive timing signal E
2049
from the encoder signal processing unit E
2019
.
During the printing operation, the head control unit E
2018
, when it receives the head drive timing signal E
2049
, reads developed print data (RDHD) E
2048
from the column buffer and outputs the data to the print head cartridge H
1000
as the head control signal E
1021
.
In the scanner reading mode, the head control unit E
2018
DMA-transfers the input data (WDHD) E
2053
received as the head control signal E
1021
to the scanner input buffer E
2024
on the DRAM E
2005
. Designated E
2025
is a scanner data processing DMA controller E
2025
which is controlled by the CPU E
1001
through the CPU I/F E
2001
to read input buffer read data (RDAV) E
2054
stored in the scanner input buffer E
2024
and writes the averaged data (WDAV) E
2055
into the scanner data buffer E
2026
on the DRAM E
2005
.
Designated E
2027
is a scanner data compression DMA controller which is controlled by the CPU E
1001
through the CPU I/F E
2001
to read processed data (RDYC) E
2056
on the scanner data buffer E
2026
, perform data compression, and write the compressed data (WDYC) E
2057
into the output buffer E
2028
for transfer.
Designated E
2019
is an encoder signal processing unit which, when it receives an encoder signal (ENC), outputs the head drive timing signal E
2049
according to a mode determined by the CPU E
1001
. The encoder signal processing unit E
2019
also stores in a register information on the position and speed of the carriage M
4001
obtained from the encoder signal E
1020
and presents it to the CPU E
1001
. Based on this information, the CPU E
1001
determines various parameters for the CR motor E
0001
. Designated E
2020
is a CR motor control unit which is controlled by the CPU E
1001
through the CPU I/F E
2001
to output the CR motor control signal E
1036
.
Denoted E
2022
is a sensor signal processing unit which receives detection signals E
1032
, E
1025
, E
1026
and E
1027
output from the PG sensor E
0010
, the PE sensor E
0007
, the ASF sensor E
0009
and the gap sensor E
0008
, respectively, and transfers these sensor information to the CPU E
1001
according to the mode determined by the CPU E
1001
. The sensor signal processing unit E
2022
also outputs a sensor detection signal E
2052
to a DMA controller E
2021
for controlling LF/PG motor.
The DMA controller E
2021
for controlling LF/PG motor is controlled by the CPU E
1001
through the CPU I/F E
2001
to read a pulse motor drive table (RDPM) E
2051
from the motor control buffer E
2023
on the DRAM E
2005
and output a pulse motor control signal E
1033
. Depending on the operation mode, the controller outputs the pulse motor control signal E
1033
upon reception of the sensor detection signal as a control trigger.
Designated E
2030
is an LED control unit which is controlled by the CPU E
1001
through the CPU I/F E
2001
to output an LED drive signal E
1038
. Further, designated E
2029
is a port control unit which is controlled by the CPU E
1001
through the CPU I/F E
2001
to output the head power ON signal E
1022
, the motor power ON signal E
1023
and the power supply control signal E
1024
.
5. Operation of Printer
Next, the operation of the ink jet printing apparatus in this embodiment of the invention with the above configuration will be explained by referring to the flow chart of FIG.
10
.
When the printer body M
1000
is connected to an AC power supply, a first initialization is performed at step S
1
. In this initialization process, the electric circuit system including the ROM and RAM in the apparatus is checked to confirm that the apparatus is electrically operable.
Next, step S
2
checks if the power key E
0018
on the upper case M
1002
of the printer body M
1000
is turned on. When it is decided that the power key E
0018
is pressed, the processing moves to the next step S
3
where a second initialization is performed.
In this second initialization, a check is made of various drive mechanisms and the print head of this apparatus. That is, when various motors are initialized and head information is read, it is checked whether the apparatus is normally operable.
Next, steps S
4
waits for an event. That is, this step monitors a demand event from the external I/F, a panel key event from the user operation and an internal control event and, when any of these events occurs, executes the corresponding processing.
When, for example, step S
4
receives a print command event from the external I/F, the processing moves to step S
5
. When a power key event from the user operation occurs at step S
4
, the processing moves to step S
10
. If another event occurs, the processing moves to step S
11
.
Step S
5
analyzes the print command from the external I/F, checks a specified paper kind, paper size, print quality, paper feeding method and others, and stores data representing the check result into the DRAM E
2005
of the apparatus before proceeding to step S
6
.
Next, step S
6
starts feeding the paper according to the paper feeding method specified by the step S
5
until the paper is situated at the print start position. The processing moves to step S
7
.
At step S
7
the printing operation is performed. In this printing operation, the print data sent from the external I/F is stored temporarily in the print buffer. Then, the CR motor E
0001
is started to move the carriage M
4001
in the main-scanning direction. At the same time, the print data stored in the print buffer E
2014
is transferred to the print head H
1001
to print one line. When one line of the print data has been printed, the LF motor E
0002
is driven to rotate the LF roller M
3001
to transport the paper in the sub-scanning direction. After this, the above operation is executed repetitively until one page of the print data from the external I/F is completely printed, at which time the processing moves to step S
8
.
At step S
8
, the LF motor E
0002
is driven to rotate the paper discharge roller M
2003
to feed the paper until it is decided that the paper is completely fed out of the apparatus, at which time the paper is completely discharged onto the paper discharge tray M
1004
a.
Next at step S
9
, it is checked whether all the pages that need to be printed have been printed and if there are pages that remain to be printed, the processing returns to step S
5
and the steps S
5
to S
9
are repeated. When all the pages that need to be printed have been printed, the print operation is ended and the processing moves to step S
4
waiting for the next event.
Step S
10
performs the printing termination processing to stop the operation of the apparatus. That is, to turn off various motors and print head, this step renders the apparatus ready to be cut off from power supply and then turns off power, before moving to step S
4
waiting for the next event.
Step S
11
performs other event processing. For example, this step performs processing corresponding to the ejection performance recovery command from various panel keys or external I/F and the ejection performance recovery event that occurs internally. After the recovery processing is finished, the printer operation moves to step S
4
waiting for the next event.
A form of application where the present invention can effectively be implemented is the ink jet print head in which thermal energy generated by an electrothermal transducer is used to cause film boiling in a liquid to form a bubble.
(First Embodiment)
Some embodiments of the structure of the electrode pad in the print head substrate used in the ink jet printer described above will be explained in the following.
FIG. 11
is a perspective view showing a detailed structure, partly cut away, of the print element substrate (the head chip) H
1100
explained in FIG.
5
. Although a total of six kinds of ink are ejected from the associated columns of ink ejection ports in the head chip H
1100
, the figure shows only two columns of ink ejection ports, each two columns matching a different kind of ink.
The head chip H
1100
is made by forming a variety of films described above on a substrate
11
as a base, which is formed by for example a silicon (Si) of 0.5-1 mm thickness, and then providing a nozzle forming member including ink ejection ports
17
or the like.
To describe in more detail, the base
11
is formed with an ink supply passage
12
shaped like a long groove passing through the base. On both sides of the ink supply passage
12
two columns of heaters
101
are arranged in a zigzag pattern. In addition to these heaters
101
, a second electric wire of aluminum (not shown) is formed by the film deposition technology to supply a drive power to the heaters
101
. Further, the base is also provided with electrode portions
14
for electric connection with the printer body side to supply an electric power to the heaters and a drive signal to the drive IC. The electrode portions
14
are each formed with a plurality of electrode pads
110
, each of which is joined with a ball bump
15
of, for example, gold in a manner described later.
The ink supply passage
12
formed in the substrate is formed by performing anisotropic etching taking advantage of a crystal orientation of the silicon base
11
. When the silicon base has crystal orientations of the <100> in a wafer plane and of the <111> in a thickness direction, an alkaline (KOH, TMAH, hydrazine, etc.) anisotropic etching is performed at an angle of about 55 degrees. This can form the ink supply passage
12
passing through the base
11
.
The substrate is further provided with a nozzle forming member. More specifically, the nozzle forming member is formed with ink ejection ports
17
at locations corresponding to their associated heaters
101
. The ink ejection ports
17
assigned to each kind of ink are arranged in a column
18
, with each ejection port line of the column
18
having an ejection port density of 600 dpi, and the two ejection port lines are arranged zigzag pattern to provide an overall density of 1200 dpi. In forming process of the nozzle forming member, ink passage walls
16
defining ink passages corresponding to the associated heaters
101
are formed by the photolithography as with the ink ejection ports.
In the head chip H
1100
of the above structure, the ink supplied to each ink passage through the ink supply passage
12
produces a bubble as the heater
101
generates heat in response to the drive signal, and the pressure of this bubble ejects the ink.
FIG. 12
is a cross section showing the film structure of the substrate making the head chip H
1100
according to the embodiment above and is a similar section to
FIG. 18
showing a conventional example.
What differs from the conventional film structure shown in
FIG. 18
is the structure of the electrode pads
110
. That is, in this embodiment a surface conductive film to be joined with the ball electrodes is selected to be the first electric wire film
202
, which represents the electric wire formed at lower position in the substrate.
FIG. 13
shows the first electric wire film
202
joined with the ball bump
15
.
The first electric wire film
202
joined with the ball bump
15
forms a common electrode of the matrix wires, as described earlier, and inherently has a relatively large thickness. That is, this wire functions as the common electrode for supplying an electric power or for grounding and has a relatively large film thickness of more than 4,000 Å or preferably about 10,000 Å and a large width pattern to reduce the voltage drop. Even when the protective film is made thin for efficient heat transfer to the ink as described above, because the first electric wire film
202
is under the heater film
204
, there is no need to reduce the thickness of the first electric wire film
202
to secure the satisfactory step coverage. This allows the surface conductive film to have an enough thickness to join the ball bump by ultrasonic bonding, thereby assuring a satisfactory joining.
In this embodiment, the gold ball bump is bonded to the electrode pads
110
by a method applying the wire bonding. Then, the ball bump is loaded to flatten their top portions to facilitate the TAB bonding.
A study conducted by the inventor of the present invention has found that the loss of bump occurs when the first electric wire film made of aluminum or aluminum alloy that forms the surface layer of the electrode pad is 4,000 Å or less in thickness. For example, when the thickness of the surface layer of the pad is set at 2,000 Å equal to the thickness of the second electric wire film which was reduced as part of the process of reducing the thickness of the protective film of the heater portion
101
, the bump loss occurs with a probability of about 1% to 50%. Even 1% of bump loss necessitates the inspection of the entire head chips, causing a significant burden to the production process. On the other hand, the use of the film structure of the electrode pad according to this embodiment enables satisfactory bonding and forming of the ball bump with almost no cost increase.
FIG. 14
shows a process of manufacturing the print head according to this embodiment in which the surface layer of the electrode pad
110
is formed by the first electric wire film
202
. In the figure, the state of the films of the electrode pad portion at each step is schematically shown to the right. It should also be appreciated that the film structure in the entire area of the substrate including the heater portions and through-hole portions is formed simultaneously by some of the following steps.
In step S
1
, a SiN film (first interlayer insulating film
201
) is deposited to a thickness of 14,000 Å, applied with a resist and exposed by a chemical vapor deposition (CVD) device and then patterned by a dry etching device. Next at step S
2
, an aluminum or aluminum alloy film (first electric wire film
202
) is deposited to a thickness of 10,000 Å, applied with a resist and exposed by a sputtering device and then patterned by a dry etching device. At step S
3
, a SiO film (second interlayer insulating film
203
) is deposited to 14,000 Å, applied with a resist and exposed by the CVD device and patterned by a wet etching device. Further at step S
4
, a TaN film (heater film
204
) is deposited to 400 Å by the sputtering device. Then at step S
5
, an aluminum film (second electric wire film
205
) is deposited to a thickness of 2,000 Å by the sputtering device. The process up to this point is performed in the same way as in the heater portion.
At the next step S
6
, an aluminum film (second electric wire film
205
) of 2,000 Å thick and a TaN film (heater film
204
) of 400 Å thick are applied with a resist and exposed and then simultaneously patterned by a dry etching device. This simultaneous patterning removes the second electric wire film
205
and the heater film
204
from the electrode pads
110
. In this embodiment, the use of the simultaneous patterning minimizes a possible increase in the number of steps which may otherwise result when the lower of the two electric wire films, or the first electric wire film
202
, is used as the surface conductive film.
Step S
7
patterns and forms the heater portions
101
by applying a resist to and exposing the aluminum film (second electric wire film
205
) of 2,000 Å thick and then removing the aluminum film with a wet etching device. At this time, the electrode pad portions
110
remain as formed by the step S
6
.
Next step S
8
deposits a SiN film (protective film
206
) to a thickness of 3,000 Å, applies a resist to and exposes the film by the CVD device and patterns the film by a dry etching device.
Next, at step S
9
, a Ta film (wear resistant film
207
) is deposited to a thickness of 2,300 Å, applied with a resist and exposed at other than the electrode pad portions, and then patterned by a dry etching device. At this time, the electrode pad portion
110
remain as formed by the step S
8
.
Then, at final step S
10
, a SiO film (second interlayer insulating film
203
) is removed to a thickness of 14,000 Å, by being applied with a resist and exposed and by a dry etching device to form the electrode pad.
(Second Embodiment)
The electrode pad structure according to the second embodiment of the invention will be described according to the film making process.
FIG. 15
shows the process of manufacturing the print head according to the second embodiment. What differs from the manufacturing process according to the first embodiment shown in
FIG. 14
is that at step S
3
the SiO film (second interlayer insulating film
203
) in the electrode pad portions
110
is formed with a window of 14,000 Å deep. Another differing point is that the TaN (heater film
204
) and the second electric wire film
205
formed over the second interlayer insulating film
203
are removed by step S
5
.
This eliminates the need of step S
10
shown in FIG.
14
. However, the first electric wire film
202
in the electrode pad portion is etched away to some extent by the etching at step S
3
and the subsequent steps. Thus the first electric wire film
202
must be made thicker than shown in the step of FIG.
14
. The amount by which the first electric wire film
202
is made thicker, of course, varies depending on the amount of overetch caused by the etching step.
As can be seen from the foregoing, according to the embodiments of this invention, because the exposed part of the first wire electrode underlying the heater forms the electrode pad, a film which does not need to be reduced in thickness to secure the heater protective film's step coverage even when the protective film is made thinner can be used for the electrode pad. Further, an inherently thick film can be used for the electrode pad. As a result, when the ball bump is joined by an ultrasonic bonding process bonding, the bonding strength can be increased.
As a result, the bonding of ball bump can be stabilized, preventing the ball bump from getting disconnected. This eliminates the head chip inspection step and therefore reduces the number of inspection workers, lowering the cost. Further, in a thin film structure that can meet the conditions for further energy consumption reductions required of the ink jet print head, this invention can stably bond the ball bumps.
The present invention has been described in detail with respect to preferred embodiments, and it will now be apparent from the foregoing to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspect, and it is the intention, therefore, in the apparent claims to cover all such changes and modifications as fall within the true spirit of the invention.
Claims
- 1. A substrate for an ink jet print head that uses thermal energy to eject ink, said substrate comprising:a film structure having a plurality of films laminated on said substrate, the plurality of films including a first electric wire film, a heater film and a second electric wire film formed one upon the other in that order on said substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated on a portion where the second electric wire film is not laminated on the heater film; wherein an electrode pad portion, which is formed at a part of said film structure to make an electrical connection to a power source through a ball bump, is formed by an exposed part of the first electric wire film, the ball bump being formed on the exposed part of the first electric wire film, and a thickness of the first electric wire film is larger than that of the second electric wire film.
- 2. The substrate as claimed in claim 1, wherein said film structure has a protective film over the heater film and the second electric wire film.
- 3. The substrate as claimed in claim 2, wherein the first electric wire film is made from aluminum or aluminum alloy and has a thickness of 4,000 Å or more.
- 4. An ink jet print head which uses thermal energy to eject ink, comprising:a substrate making said ink jet print head, said substrate including: a film structure having a plurality of films laminated on said substrate, the plurality of films including a first electric wire film, a heater film and a second electric wire film formed one upon the other in that order on said substrate, a combination of the heater film and the second electric wire film allowing the thermal energy to be generated on a portion where the second electric wire film is not laminated on the heater film; wherein an electrode pad portion, which is formed at a part of said film structure to make an electrical connection to a power source through a ball bump, is formed by an exposed part of the first electric wire film, the ball bump being formed on the exposed part of the first electric wire film, and a thickness of the first electric wire film is larger than that of the second electric wire film.
- 5. The ink jet print head as claimed in claim 4, wherein said film structure has a protective film over the heater film and the second electric wire film.
- 6. The ink jet print head as claimed in claim 5, wherein the first electric wire film is made from aluminum or aluminum alloy and has a thickness of 4,000 Å or more.
Priority Claims (1)
Number |
Date |
Country |
Kind |
2000-209101 |
Jul 2000 |
JP |
|
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Number |
Name |
Date |
Kind |
4695853 |
Hackleman et al. |
Sep 1987 |
A |
4916464 |
Ito et al. |
Apr 1990 |
A |
5227812 |
Watanabe et al. |
Jul 1993 |
A |