Information
-
Patent Grant
-
6535093
-
Patent Number
6,535,093
-
Date Filed
Thursday, September 28, 200023 years ago
-
Date Issued
Tuesday, March 18, 200321 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Donovan; Lincoln
- Nguyen; Tuyen T.
Agents
-
CPC
-
US Classifications
Field of Search
US
- 336 65
- 336 83
- 336 183
- 336 192
- 336 200
- 336 232
-
International Classifications
-
Abstract
An inductor includes input-output terminal electrodes, a coil conductor connected between the input-output terminal electrodes, and dividing grooves arranged to extend outwardly of the coil conductor from the end portions of the coil conductor over the terminal electrodes so as to be substantially perpendicular to the winding direction of the spiral coil conductor.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inductor and more particularly, to a surface mount inductor constructed for use in high-frequency circuits and other electronic apparatuses.
2. Description of the Related Art
A conventional surface mount inductor is shown in
FIGS. 11 and 12
.
FIG. 11
is a perspective view showing the appearance of the inductor
1
and
FIG. 12
is a development view of an electrode. In the inductor
1
, terminal electrodes
3
and
4
are provided at both ends of a columnar winding core material which has a spiral coil
2
provided on an external surface thereof. The spiral coil
2
is arranged such that after a thin-film conductor has been formed on the entire surface of the columnar winding core material, a spiral groove
5
is formed in the thin-film conductor. The terminal electrodes
3
and
4
are ring-shaped so as to extend around the columnar winding core.
When an electric current flows through the inductor
1
, electric current I flows into the initial end portion
2
a
of the spiral coil
2
via the terminal electrode
3
as shown in FIG.
12
. Then, the electric current I, which has flowed through the spiral coil
2
, flows from the inductor
1
from the end
2
b
via the terminal electrode
4
.
Since the terminal electrodes
3
and
4
extend around the winding core, the electrodes function as a coil with one turn, that is, as a short-circuited ring. Accordingly, the magnetic field generated by the electric current flowing through the spiral coil
2
crosses the terminal electrodes
3
and
4
which are parallel to the spiral coil
2
, and an induced current i flows through the terminal electrodes
3
and
4
, respectively. In
FIG. 12
, the induced current i flowing through the terminal electrode
4
is not shown. The induced current i dissipates energy while it circulates through the terminal electrodes
3
and
4
. Therefore, the conventional inductor
1
has a problem in that the Q-factor and inductance of the spiral coil
2
are very low.
Up to now, as a solution to this problem, a method of separating the spiral coil
2
and the terminal electrodes
3
and
4
and electrically connecting the coil
2
and electrodes
3
through a lead-out pattern was used. However, this method requires that the inductors be large and prevents the required reduction in weight and size reduction. Thus, it is not possible to use the lead-out pattern.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a small inductor having substantially circular electrodes that are prevented from functioning as a short-circuited ring, while achieving a very high Q-factor and inductance.
According to one preferred embodiment of the present invention, an inductor preferably includes a winding core, a coil conductor extending spirally around the winding core, substantially circular electrodes running nearly around the winding core and located outwardly of the coil conductor, and dividing grooves extending from the ends of the coil conductor over the substantially circular electrodes. Here, the length of the dividing groove is, for example, a half or more of the diameter of the coil conductor.
Since the substantially circular electrodes are partially divided by the dividing grooves, the substantially circular electrodes are prevented from functioning as a short-circuited ring. That is, even when the magnetic flux generated by the current flowing through the coil conductor crosses the substantially circular electrodes, it is difficult for the circulating currents to flow through the substantially circular electrodes.
Therefore, an inductor having superior characteristics can be obtained in which energy loss is suppressed and decreases in the Q-factor and the inductance of the coil conductor are prevented.
Other features, elements, characteristics and advantages of preferred embodiments of the present invention will become apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a perspective view showing a manufacturing step of a first preferred embodiment of an inductor according to the present invention;
FIG. 2
is a perspective view showing a manufacturing step following the step shown in
FIG. 1
;
FIG. 3
is a perspective view showing the appearance of the inductor according to a preferred embodiment of the present invention;
FIG. 4
is a development view of the inductor shown in
FIG. 3
;
FIG. 5
is a perspective view of a second preferred embodiment of the inductor according to the present invention;
FIG. 6
is a development view of the inductor shown in
FIG. 5
;
FIG. 7
is a perspective view showing a third preferred embodiment of the inductor according to the present invention;
FIG. 8
is a development view of the inductor shown in
FIG. 7
;
FIG. 9
is a sectional view showing the condition where the inductor in
FIG. 7
is mounted;
FIG. 10
is a perspective view showing another preferred embodiment of the present invention;
FIG. 11
is a perspective view showing a conventional inductor; and
FIG. 12
is a development view of the inductor shown in FIG.
11
.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Hereinafter, preferred embodiments of an inductor according to the present invention are described with reference to the accompanying drawings.
A preferred embodiment of the inductor according to the present invention and a manufacturing method therefor are described. As shown in
FIG. 1
, a winding core material
11
is columnar, preferably has a substantially rectangular transverse cross section, and is preferably made of a magnetic material such as ferrite, a ceramic material such as nonmagnetic alumina, a resin material, or other suitable material. On all of the surfaces of the winding core material, as shown in
FIG. 2
, a thin-film conductor
14
is formed by a method of plating, sputtering, or other suitable process. The thin-film conductor
14
is preferably made of copper (Cu), silver (Ag), silver-palladium (Ag—Pd), or other suitable material.
Next, both of the left and right ends of the winding core material
11
are inserted into the chucks of the spindle of a laser processing machine (not shown). Then, the left end portion of the winding core material
11
is irradiated with a laser beam
24
and the winding core material is scanned in its longitudinal direction by the laser beam
24
. In this way, the thin-film conductor
14
irradiated with the laser beam
24
is removed to form a dividing groove
15
. The length of the dividing groove
15
is preferably substantially equal to one half or more of the diameter of a spiral coil conductor
22
(to be described later).
Subsequently, the winding core
11
is rotated in the direction of an arrow A by driving the spindle. At the same time, the winding core
11
is irradiated with the laser beam
24
and is scanned in its longitudinal direction by the laser beam
24
. Thus, the portion of thin-film conductor
14
irradiated with the laser beam
24
is removed, and then a groove
17
for the coil is formed, thereby completing a spiral coil
22
. In this way, the coil conductor
22
spirally extending over the outer surface of the middle of the winding core
11
is provided.
Subsequently, after the rotation driven by the spindle has stopped, the winding core
11
is scanned in its longitudinal direction by the laser beam
24
and is irradiated at the right end portion. In this way, a dividing groove
16
is formed. The length of the dividing groove
16
is preferably substantially equal to one half or more of the diameter of the spiral coil conductor
22
.
Next, as shown in
FIG. 3
, by performing nickel plating, tin plating, or other suitable process, on both end portions of the winding core
11
, input-output terminal electrodes
19
and
20
having excellent solderability are formed. The input-output terminal electrodes
19
and
20
are substantially circular so as to extend around the winding core
11
. Furthermore, if required, the coil conductor
22
may be coated with an insulating cladding resin excluding the input-output electrodes
19
and
20
and is baked in order to protect the coil conductor
22
.
In the inductor
10
having the above-described construction, the coil conductor
22
is connected between the input-output terminal electrodes
19
and
20
. The dividing grooves
15
and
16
are arranged such that the grooves are substantially perpendicular to the winding direction of the spiral coil conductor
22
and such that the grooves extend in the outward direction of the coil conductor
22
from the end portions
22
a
and
22
b
of the coil conductor
22
into the terminal electrodes
19
and
20
. Even if such dividing grooves
15
and
16
are provided in the outward direction of the coil conductor
22
, the inductance is not adversely affected.
When an electric current I flows through the inductor
10
, as shown in
FIG. 4
, the electric current I flows into the initial end portion
22
a
of the spiral coil conductor
22
via the terminal electrode
19
. Then, the electric current I which has flowed through the spiral coil conductor
22
flows out of the inductor
10
from the terminal end portion
22
b
via the terminal electrode
20
.
Since the substantially circular terminal electrodes
19
and
20
are partially divided by the dividing grooves
16
and
15
, the electrodes
19
and
20
are prevented from functioning as a short-circuited ring. The magnetic flux generated by the current flowing through the coil conductor
22
impinges on the terminal electrodes
19
and
20
and the circulating induced currents i circulate and flow through the terminal electrodes
19
and
20
. Here, in
FIG. 4
, the induced current i flowing through the terminal electrode
20
is not illustrated. Hereinafter, the same can be said for each of the other preferred embodiments of the present invention. However, as the induced current i is generated only at a great distance away from the coil conductor
22
because of the dividing grooves
15
and
16
, it is difficult for the induced current i to flow through the terminal electrodes
19
and
20
. Therefore, an inductor
10
having a very high Q-factor and inductance of the coil conductor
22
is provided.
The function of the terminal electrodes
19
and
20
as a short-circuited ring can be reliably decreased by setting the length of the dividing grooves
15
and
16
to be at least half of the diameter of the spiral coil conductor
22
. The length of the dividing grooves
15
and
16
is preferably substantially equal to or greater than the diameter of the spiral coil conductor
22
. However, when the Q-factor and the impedance are not required to be so high, a length of the dividing grooves
15
and
16
which is less than half the diameter of the spiral coil conductor
22
may be used.
Furthermore, in the inductor
10
, only the dividing grooves
15
and
16
and the terminal electrodes
20
and
19
are provided. Thus, its dimensions of the inductor are greatly decreased compared with the conventional inductor in which the distance between the coil conductor
22
and the terminal electrodes
19
and
20
is increased by providing extra lead-in patterns. Furthermore, when the inductor
10
is mounted on a printed wiring board or other substrate, it is desirable to mount the inductor
10
so that the surface having the dividing grooves
15
and
16
faces upward in order not to short-circuit the dividing grooves
15
and
16
by solder, conductive adhesive, or such material.
As shown in
FIG. 5
, in an inductor
30
of the second preferred embodiment, a spiral coil conductor
22
is provided in a location displaced to the left from the middle of the inductor. Accordingly, between the coil conductor
22
and a terminal electrode
19
, a substantially circular electrode
31
which extends nearly around a winding core
11
and which is located outside the coil conductor
22
is formed. Furthermore, in
FIG. 5
, the same reference numerals are assigned to corresponding elements in FIG.
1
and repetitive explanations thereof are omitted.
In this case, a dividing groove
15
extends from the terminal end portion
22
b
of the coil conductor
22
over a terminal electrode
20
. A dividing groove
16
extends from the starting end
22
a
of the coil conductor
22
over the substantially circular electrode
31
and does not reach the terminal electrode
19
. The dividing grooves
15
and
16
are arranged so as to extend in a direction which is oblique to the winding direction of the spiral coil conductor
22
.
Thus, since the nearly circular terminal electrode
20
and substantially circular electrode
31
are partially divided by the dividing grooves
15
and
16
, respectively, the electrodes
20
,
31
are prevented from functioning as a short-circuited ring. That is, as shown in
FIG. 6
, when the magnetic flux generated by the current I flowing through the coil conductor
22
crosses the substantially circular electrode
31
and terminal electrodes
19
and
20
, the induced currents i circulate and flow through the substantially circular electrode
31
and the terminal electrodes
19
and
20
, respectively. However, as the induced currents i are generated only at a great distance away from the coil conductor
22
because of the dividing grooves
15
and
16
, it is difficult for the induced currents i to flow through the substantially circular electrode
31
and the terminal electrodes
19
and
20
. Therefore, an inductor
30
having very high Q-factor and inductance of the coil conductor
22
is provided.
As shown in
FIGS. 7 and 8
, in an inductor
35
of the third preferred embodiment, dividing grooves
15
a
-
15
d
and
16
a
-
16
d
are formed on the four external surfaces of a winding core
11
, respectively. Since the nearly circular terminal electrodes
19
and
20
are divided by the dividing grooves
15
a
-
15
d
and
16
a
-
16
d
, respectively, induced currents are generated only at a great distance away from the coil conductor
22
. Therefore, the terminal electrodes
19
and
20
are even more effectively prevented from functioning as a short-circuited ring compared with the case of the first preferred embodiment.
Furthermore, by providing the dividing grooves
15
a
-
15
d
and
16
a
-
16
d
on the four external surfaces (that is, every ninety degrees around the winding core
11
), it is possible to eliminate the directional properties at the time the inductor
35
is mounted.
FIG. 9
shows the condition where the inductor
35
is surface mounted on the pattern
37
of a printed wiring board
38
using solder
36
. The terminal electrodes
19
and
20
are electrically connected to the pattern
37
through the solder
36
. The dividing grooves
15
a
,
15
b
,
15
d
,
16
a
,
16
b
, and
16
d
are seldom short-circuited by the solder
36
. Even if the dividing grooves
15
b
,
15
d
,
16
b
, and
16
d
are short-circuited by the solder
36
, the terminal electrodes
19
and
20
are prevented from functioning as a short-circuited ring by the diving grooves
15
a
and
16
a
provided on the upper surface.
Furthermore, inductors according to the present invention are not limited to the above-described preferred embodiments and various modifications are possible within the spirit and the scope of the invention. For example, the coil conductor may be a conductive wire wound around the external surface of a winding core material. Furthermore, an inductor having a built-in capacitor may be constructed by arranged a dielectric layer so as to cover a coil conductor and providing a capacitor electrode on the dielectric layer. Other inductors having a built-in electrical component such as a resistor may also be constructed.
Furthermore, an inductor
40
shown in
FIG. 10
may be constructed. In the inductor
40
, input-output terminal electrodes
42
and
43
are provided on both ends of a substantially cylindrical winding core material
41
on the external surface of which a spiral coil conductor
44
is provided. The substantially circular input-output terminal electrodes
42
and
43
are partially divided by dividing grooves
45
and
46
.
It should be understood that the foregoing description is only illustrative of preferred embodiments of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variations that fall within the scope of the appended claims.
Claims
- 1. An inductor comprising:a winding core having an external surface and two end surfaces provided at ends of the external surface; a coil conductor spirally extending around the external surface of the winding core; a plurality of substantially circular electrodes extending nearly around the winding core and located outside of the coil conductor, said plurality of substantially circular electrodes being provided at both of said ends surfaces of the winding core; and dividing grooves located in the external surface of the winding core and extending from end portions of the coil conductor into the substantially circular electrodes so as to partially divide the substantially circular electrodes.
- 2. An inductor according to claim 1, wherein the length of the dividing grooves is substantially equal to at least one-half of the diameter of the coil conductor extending spirally therearound.
- 3. An inductor according to claim 1, wherein the winding core has a substantially columnar configuration and a substantially rectangular transverse cross section.
- 4. An inductor according to claim 1, wherein the winding core is magnetic and includes at least one of ferrite, a ceramic material, and a resin material.
- 5. An inductor according to claim 1, further comprising a thin-film conductor material disposed on the external surface of the coil conductor.
- 6. An inductor according to claim 5, wherein the dividing grooves are formed in the thin film conductor material.
- 7. An inductor according to claim 1, further comprising input-output terminal electrodes having a substantially circular shape and arranged to extend around the winding core.
- 8. An inductor according to claim 1, wherein the spiral coil conductor is located at the approximate middle of the winding core.
- 9. An inductor according to claim 1, wherein the spiral coil conductor is located spaced to the left of the approximate middle of the winding core.
- 10. An inductor according to claim 9, wherein the dividing grooves are arranged so as to extend in a direction which is oblique to the winding direction of the spiral coil conductor.
- 11. An inductor according to claim 1, wherein the winding core includes four external surfaces and the dividing grooves are located on each of the four external surfaces of a winding core.
- 12. An inductor comprising:a winding core having an external surface and two end surfaces provided at ends of the external surface; a coil conductor spirally extending around the external surface of the winding core; a plurality of substantially circular electrodes extending nearly around the winding core and located outside of the coil conductor, said plurality of substantially circular electrodes being provided at both of said ends surfaces of the winding core; and dividing grooves located in the external surface of the winding core and arranged to partially divide the substantially circuit electrodes to prevent the substantially circular electrodes from defining a short-circuited ring.
- 13. An inductor according to claim 12, wherein the dividing grooves are arranged to extend from the end portions of the coil conductor into the substantially circular electrodes.
- 14. An inductor according to claim 12, wherein the length of the dividing grooves is substantially equal to at least one-half of the diameter of the coil conductor extending spirally therearound.
- 15. An inductor according to claim 12, wherein the winding core has a substantially columnar configuration and a substantially rectangular transverse cross section.
- 16. An inductor according to claim 12, wherein the winding core is magnetic and includes at least one of ferrite, a ceramic material, and a resin material.
- 17. An inductor according to claim 12, further comprising a thin-film conductor material disposed on the external surface of the coil conductor.
- 18. An inductor according to claim 17, wherein the dividing grooves are formed in the thin film conductor material.
- 19. An inductor according to claim 17, further comprising input-output terminal electrodes having a substantially circular shape and arranged to extend around the winding core.
- 20. An inductor according to claim 12, wherein the spiral coil conductor is located at the approximate middle of the winding core.
- 21. An inductor according to claim 12, wherein the spiral coil conductor is located spaced to the left of the approximate middle of the winding core.
- 22. An inductor according to claim 21, wherein the dividing grooves are arranged so as to extend in a direction which is oblique to the winding direction of the spiral coil conductor.
- 23. An inductor according to claim 12, wherein the winding core includes four external surfaces and the dividing grooves are located on the four external surfaces of a winding core.
Priority Claims (1)
Number |
Date |
Country |
Kind |
11-275024 |
Sep 1999 |
JP |
|
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
5001548 |
Iversen |
Mar 1991 |
A |
Foreign Referenced Citations (3)
Number |
Date |
Country |
1-199418 |
Aug 1989 |
JP |
5-343232 |
Dec 1993 |
JP |
087101815 |
Mar 2000 |
JP |