Inductor devices – Core forms casing
Reexamination Certificate
2001-07-16
2003-02-18
Mai, Anh (Department: 2832)
Inductor devices
Core forms casing
C336S200000, C336S223000, C336S232000, C336S198000, C336S192000
Reexamination Certificate
active
06522230
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a common mode choke coil used for removing noise having the same phase components transmitted from a power supply line or a signal line, and, more particularly, the present invention relates to a small, surface-mountable chip-type common mode choke coil which is used in various electronic circuits.
2. Description of the Related Art
A chip-type common mode choke coil having a winding is available as a chip-type common mode choke coil. In the winding type, a wire is wound upon a winding core portion, and a first end terminal and a second end terminal of the wire are connected to electrodes provided on flanges, one being provided on each end of the winding core portion.
There is one kind of conventional winding, chip-type common mode choke coil formed in the following way. For example, as shown in
FIGS. 8A and 8B
, flanges
53
are disposed, one on each end of a winding core portion
52
. In addition, using immersion, for example, electrode films
56
are applied to legs
55
having grooves
54
on the flanges
53
in order to form four leg-shaped electrodes
57
a,
57
b,
57
c,
and
57
d,
whereby a core
51
is produced. Using the core
51
, as shown in
FIG. 9
, two wires
58
a
and
58
b
are wound upon the winding core portion
52
in order to electrically connect the first and second end terminals thereof to the corresponding electrodes (the electrodes
57
c
and
57
d
in
FIG. 9
) by, for example, thermocompression bonding. Then, as shown in
FIG. 10
, a top plate
60
is mounted so as to cover the top surface of the resulting structure.
However, in the above-described conventional chip-type common mode choke coil, since the grooves
54
are provided in the flanges
53
, each of the legs
55
is thin (that is, has a small cross-sectional area in plan view), so that each of the legs
55
may not have sufficient mechanical strength. This results in the problem that the choke coil is not sufficiently reliable.
In connecting exposed conductors (wire bodies)
59
a
and
59
b
of the terminals of the corresponding wires
58
a
and
58
b
to the corresponding leg-shaped electrodes
57
a
to
57
d,
the problem that the wire
58
a
comes into contact with the electrode
57
d
adjacent to the electrode
57
c
at, for example, location A, and is, thus, shorted arises. Even if the wire
58
a
does not come into contact with the electrode
57
d,
the problems of reduced withstand pressure and insufficient insulation occur when it cannot be separated therefrom by a sufficient distance.
There is another kind of conventional winding, chip-type common mode choke coil that is produced in the following manner. For example, as shown in
FIG. 11
, flanges
53
without grooves are provided, one on each end of a winding core portion
52
, and a plurality of electrodes
57
a,
57
b,
57
c,
and
57
d
are disposed on the corresponding flanges
53
at predetermined intervals so as not to be brought into electrical conduction with each other, whereby a core
51
a
is produced. Using the core
51
a,
as shown in
FIG. 12
, the beginning end and the termination end of each of the two wires
58
a
and
58
b
wound upon the winding core portion
52
are electrically connected to the predetermined electrodes (the electrodes
57
c
and
57
d
in
FIG. 12
) by, for example, thermocompression bonding. Then, as shown in
FIG. 13
, a top plate
60
is mounted so as to cover the top surface of the resulting structure.
In this kind of chip-type common mode choke coil, since grooves are not provided in the flanges
53
, the mechanical strengths of the legs are high. However, as shown in
FIG. 12
, when the wires
58
a
and
58
b
are joined to the electrodes
57
c
and
57
d,
a high-temperature heater chip
61
used for removing the films of the wires
58
a
and
58
b
may remove not only the portions thereof that are connected to the electrodes
57
c
and
57
d,
but also the film of a nearby portion
62
. This may, in particular, cause an exposed conductor
59
b
(wire body) of the wire
58
b
to get shorted to respect to the adjacent electrode
57
c,
so that the choke coil has very low reliability.
The problem that a short circuit failure tends to occur similarly occurs in the previously described choke coil shown in
FIGS. 8
to
10
.
Although, in the two conventional examples, the two-circuit, chip-type common mode choke coils are described as having the aforementioned problems, chip-type common mode choke coils having three or more circuits also have the aforementioned problems.
In addition, although, in the two conventional examples, chip-type common mode choke coils that are provided with top plates are described as having the aforementioned problems, chip-type common mode choke coils which are not provided with top plates also have the aforementioned problems.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a highly reliable chip-type common mode choke coil which prevents a wire from being short-circuited as a result of coming into contact with an adjacent electrode, prevents the withstand pressure from being reduced, and ensures sufficient insulation, while providing sufficiently high mechanical strength because its legs have large cross-sectional areas.
According to a preferred embodiment of the present invention, a chip-type common mode choke coil includes a winding core portion, flanges disposed on both ends of the winding core portion, respectively, a plurality of electrodes disposed on each of the flanges at a predetermined distance from each other so as not to come into electrical conduction with each other, and a plurality of wires wound upon the winding core portion, beginning ends and termination ends of the wires being connected to predetermined electrodes of the plurality of electrodes, wherein protrusions which protrude in an axial direction of the winding core portion are provided in areas between the respective electrodes, at inside surfaces of the respective flanges disposed on both ends of the winding core portion.
By arranging protrusions to protrude in the axial direction of the winding core portion in areas between the corresponding electrodes, at the inside surfaces of the flanges, the stroke distances between the adjacent electrodes are increased, and the adjacent electrodes can be separated from each other by the corresponding protrusions. Therefore, it is possible to reliably prevent the occurrence of a short circuit caused by the wires coming into contact with not only the electrodes to which they are primarily to be connected, but also with the electrodes adjacent thereto.
Therefore, even in the case where not only the portions of the films of the wires which are connected to the electrodes, but also nearby portions thereof are removed when the wires are joined to the corresponding electrodes, for example, by pushing a high-temperature heater chip against the wires, it is possible to prevent the occurrence of a short circuit caused by the wires coming into contact with the corresponding adjacent electrodes, and the occurrence of reduced insulation resistance. Therefore, it is possible to obtain a highly reliable chip-type common mode choke coil.
Since the cross-sectional areas of the flanges (that is, the legs) become larger in correspondence with the protrusions, it is possible to obtain a highly reliable chip-type common mode choke coil having excellent mechanical strength.
In the description of preferred embodiments of the present invention, the phrase “areas between the corresponding electrodes, at the inside surfaces of the flanges” is to be broadly interpreted to refer to the areas between the corresponding electrodes and the areas in the vicinity thereof when the electrodes are disposed on the inside surfaces of the flanges (that is, the opposing surfaces of the two flanges), and to the areas of the inside surfaces of the flanges connected to (formed in correspondence with) the areas between the
Hanato Yoshio
Kasahara Kazuo
Keating & Bennett LLP
Mai Anh
Murata Manufacturing Co. Ltd.
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