Inductor devices – Winding with terminals – taps – or coil conductor end...
Reexamination Certificate
2000-08-25
2002-11-12
Donovan, Lincoln (Department: 2832)
Inductor devices
Winding with terminals, taps, or coil conductor end...
C336S083000, C336S200000
Reexamination Certificate
active
06480083
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to coil devices having wires wound around cores and to a method for manufacturing the same. More particularly, the present invention relates to a wire-wound coil device provided with terminal electrodes on flanges provided at the ends of the reel of a core.
2. Description of the Related Art
As shown in
FIG. 8
, a typical wire-wound coil device has a core
53
including a reel
51
, a pair of flanges
52
disposed at the ends of the reel
51
, a wire
54
wound around the reel
51
, and terminal electrodes
55
provided at the lower portions of the flanges
52
and connected to the ends of the wire
54
.
A problem has been found in the above-described wirewound coil device in that as the size of the coil device is reduced, the area of the terminal electrodes
55
(i.e., the size of electrodes) is reduced, and therefore, adhesion of the coil device, when mounted on a printed circuit board or other device by soldering, is reduced, thereby lowering reliability when the coil device is mounted.
Other typical wire-wound coil devices have configurations, for example, as described below.
A coil device shown in
FIG. 9
is configured such that each terminal electrode
55
provided on a leg
56
of a core
53
is provided such that the terminal electrode
55
is disposed to cover the leg
56
to a level of an end surface
56
a
(the outer surface) which is higher than that of a surface
56
b
(the inner surface) opposite to the end surface
56
a
of the leg
56
, and the upper edges of the terminal electrode
55
are inclined at side surfaces
56
c
(the remaining side surfaces) of the leg
56
.
Another coil device shown in
FIG. 10
is configured such that the terminal electrodes
55
are disposed on a pair of flanges
52
provided at the ends of the core
53
so that each terminal electrode
55
extends over an entire bottom surface
52
a
to an end surface
52
c
of the flange
52
.
The components referred to in
FIGS. 9 and 10
are the same as or have the same functions as the component shown in FIG.
8
.
In the coil device shown in
FIG. 9
, the terminal electrodes
55
are located at a high level of each outer end
56
a
of the legs
56
so as to increase the size of the electrodes, thereby improving an adhesive effect in the mounted state by soldering.
In the coil device shown in
FIG. 10
, the terminal electrodes
55
are arranged to extend over the entire bottom surface
52
a
to the end surface
52
c
of the pair of flanges
52
provided at the ends of the core
53
so as to increase the size of the electrodes, thereby improving an adhesive effect in the mounted state by soldering.
In the coil devices of
FIGS. 9 and 10
, the terminal electrodes
55
are arranged to extend to a high level of the outer end surfaces
56
a
of the legs
56
(see
FIG. 9
) or to a high level of the outer end surfaces
52
c
of the flanges
52
(see FIG.
10
), respectively. In this case, the terminal electrodes
55
provided on the outer end surfaces
56
a
of the legs
56
in
FIG. 9
or on the outer end surfaces
52
c
of the flanges
52
in
FIG. 10
vertically interrupt magnetic fluxes, thereby adversely affecting the Q factor.
When an electrode is provided, as in the coil devices shown in
FIGS. 9 and 10
, having the upper edges thereof being disposed at different levels, the manufacturing cost is increased because the device to be manufactured must be maintained inclined during the manufacturing process, or a particular paste-applying device for pasting the electrode must be used.
In addition to the increased cost, the manufacturing process is complex. As the size of the device is further reduced, the manufacturing process of the coil device having the configuration shown in
FIGS. 9 and 10
in which the upper edges of the electrode are disposed at different levels becomes increasingly difficult.
SUMMARY OF THE INVENTION
To overcome the above-described problems, preferred embodiments of the present invention provide a wire-wound coil device and a method for manufacturing the same, in which reliable mounting is achieved by providing large electrode areas even when the size of the coil device is reduced, and a high Q factor in the coil device is maintained.
According to an aspect of preferred embodiments of the present invention, a coil device includes a core including a reel and a pair of flanges provided at the ends of the reel, a terminal electrode disposed on each of the flanges of the core, and a wire wound around the reel of the core, thereby defining a coil, each end of the wire being connected to the terminal electrode. The terminal electrode includes a bottom-surface electrode provided on a bottom surface of the flange, side-surface electrodes provided on side surfaces of the flange, and an end-surface electrode provided at the lower part of an end surface of the flange. The end-surface electrode is provided on the end surface of the flange so that the upper edge of the end-surface electrode is disposed at a first level which is substantially the same as that of the upper edges of the side-surface electrodes in the vicinity of the boundaries between the end surface and each side surface of the flange and is disposed at a second level lower than the first level at an approximate center of the end surface of the flange, whereby the end-surface electrode avoids the majority of magnetic fluxes passing in an axial direction of the coil.
Each terminal electrode includes the bottom-surface electrode provided on the bottom surface of the flange, the side-surface electrodes provided on the side surfaces of the flange, and the end-surface electrode provided at the lower part of the end surface of the flange. The end-surface electrode is arranged at substantially the same height as the side-surface electrodes in the vicinity of the boundaries between the end surface and each side surface of the flange, and the end-surface electrode is arranged lower in height than the side-surface electrodes in the vicinity of the boundaries therebetween at a center of the end surface of the flange. With this configuration, an area of each terminal electrode for achieving sufficient adhesion for mounting is provided. Further, because the end-surface electrode is located spaced from the major portion of magnetic fluxes passing in an axial direction of the coil, the magnetic fluxes are not adversely affected by the end-surface electrode. With this arrangement, a high Q factor is achieved.
According to preferred embodiments of the present invention, the Q-value and the area of the terminal electrodes are balanced, and the adhesion for mounting is improved without adversely affecting the Q factor.
According to preferred embodiments of the present invention, each flange of the pair of flanges is provided with two legs at the lower portion thereof, the two legs being provided by dividing the lower portion of the flange into two parts by a groove, and being provided with the above-described terminal electrodes.
The present invention may be applied to a four-terminal-type coil device having a configuration in which each of a pair of flanges includes two legs at the lower portion thereof. This four-terminal-type coil device has terminal electrodes that operate in the same manner as the terminal electrodes of the above-described coil device according to preferred embodiments of the present invention.
According to another preferred embodiment of the present invention, a method for manufacturing a coil device is provided, the coil device including a core having a reel and a pair of flanges provided at the ends of the reel, a terminal electrode disposed on each of the flanges of the core, and a wire wound around the reel of the core, thereby forming a coil, each end of the wire being connected to the terminal electrode. The method includes the steps of providing a conductive paste for forming the terminal electrodes at a desired thickness on a substantially planar surface of a conductive-paste supporting member, dipping the core in a conduct
Sasaki Koki
Toi Takaomi
Donovan Lincoln
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Nguyen Tuyen T.
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