Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
2000-07-06
2003-01-07
Donovan, Lincoln (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C336S083000, C336S232000, C029S602100
Reexamination Certificate
active
06504466
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coil component such as an inductor or other coil component, and a method of producing the same, and more particularly, the present invention relates to a lamination-type coil component including a lamination-type coil included in an element such as a lamination-type inductor, and a method of producing the same.
2. Description of the Related Art
A lamination-type inductor is a typical lamination-type coil component. For example, as shown in
FIGS. 6A and 6B
, the lamination-type inductor has a structure in which a lamination type coil
52
(
FIG. 6B
) including a plurality of internal conductors defining coil patterns
52
a
(
FIG. 6B
) connected together is disposed in an element in the form of a chip element
51
, and moreover, external electrodes
53
a
and
53
b
(
FIG. 6A
) are arranged so as to be connected to both ends of the coil
52
, respectively.
Such a lamination type inductor is produced, for example, by laminating a plurality of magnetic green sheets
54
, each having a coil pattern
52
a
provided on the surface thereof, via a printing method, laminating magnetic green sheets (sheets defining outer layers)
54
a
each having no pattern provided thereon to the upper portion and the lower portion of the stack of laminated magnetic green sheets
54
, press-bonding the sheets, connecting the respective coil patterns
52
a
through via-holes
55
to define a coil
52
, as shown in
FIG. 6B
, firing the laminate (an unfired body), providing conductive paste on both end portions of the body
51
, and firing to form external electrodes
53
a
and
53
b
(FIG.
6
A).
In the conventional lamination-type inductor as shown in
FIG. 7
, the magnetic green sheets
54
each have a coil pattern
52
a
printed or provided on the surface thereof, so that the pattern
52
a
and its surrounding have a difference in height (that is, the portion of the green sheet
54
where the coil pattern
52
a
is printed is thick, while the portion thereof where no coil pattern is printed is thin). Therefore, the lamination and press-bonding of the plurality of magnetic green sheets
54
cannot be evenly pressed to be bonded together. Thus, in the conventional lamination-type inductor, the electrical characteristics become uneven, delamination occurs, and further problems arise. Further, an air layer may be formed between layers. This causes the problem that distributed capacitances are produced between the respective coil patterns
52
a
of the layers, due to the air layers, and the initial electrical characteristics and those after repeated use become different. Therefore, the electrical characteristics are unstable.
To solve the problems discussed above, a method of producing a lamination-type inductor has been proposed (Japanese Examined Patent Application Publication No. 7-123091), in which an auxiliary magnetic layer
56
is provided around the coil pattern
52
a
printed on the surface of each magnetic green sheet
54
in such a manner that the thickness of the auxiliary magnetic layer
56
is greater than that of the coil pattern
52
a
, after firing, as shown in
FIGS. 8 and 9
.
In the case of the lamination-type inductor produced by this method, a gap is formed between the coil pattern
52
a
and the magnetic layer
54
adjacent to the coil pattern
52
a
in the thickness direction (the sintered layer of the magnetic green sheet). Due to the gap
57
having a relative dielectric constant lower than that of the magnetic layer
54
, the distributed capacitances are reduced, and the loss at a high frequency is decreased. Moreover, variations in the electrical characteristics, caused by repeated use, are suppressed.
However, in the case where the auxiliary magnetic layer is thicker than the coil pattern as in the above-described lamination-type inductor, the connection state of the coil patterns on the respective magnetic green sheets connected together through a via-hole becomes unstable, the stability of direct current resistance is insufficient, and the reliability is deteriorated.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a method of producing a lamination-type coil component in which coil patterns provided on each of magnetic green sheets are securely connected to each other through via-holes to form a coil pattern, the direct current resistance is very low, and the stability is excellent with high reliability.
According to a first preferred embodiment of the present invention, a method of producing a lamination type coil component includes the steps of applying an electrode material for formation of a coil to a magnetic green sheet having a via-hole formed therein in an area including the via-hole, arranging the electrode material into a predetermined pattern whereby a coil pattern is formed with the electrode material being filled into the via-hole, providing a magnetic material layer having a thickness which is less than the coil pattern so as to surround the coil pattern, laminating a plurality of magnetic green sheets having the coil pattern and the magnetic material layer provided thereon, whereby a laminate having a coil provided inside thereof is formed, press-bonding the laminate, and heat treating the press-bonded laminate.
By applying an electrode material to form a coil on a magnetic green sheet having a via-hole provided therein in an area including the via-hole, into a predetermined pattern, whereby a coil pattern is formed with the electrode material being filled into the via-hole, arranging a magnetic material layer having a thickness which is less than the coil pattern so as to surround the coil pattern, plural magnetic green sheets containing the magnetic green sheets each having the coil pattern and the magnetic material layer formed thereon are laminated, and the laminate is press-bonded, the thickness of the electrode material in the area where the via-hole is formed as viewed in the plan view is thicker than the magnetic material layer in an area surrounding the magnetic material layer. Thereby, in the press-bonding step, a sufficient pressure is applied to the electrode material constituting the coil pattern and the electrode material in the via-hole. Thus, the coil patterns formed on the respective magnetic green sheets can be securely connected through the via-hole. A lamination-type coil component having very low direct current resistance, excellent stability, and very high reliability is achieved.
In the present invention, the statement that “the magnetic material layer having a thickness which is less than the coil pattern is formed in an area surrounding the coil pattern” means that the sum of the thickness of the electrode material in the via-hole and the thickness of the electrode material constituting the coil pattern is greater than the sum of the thickness of the magnetic green sheet and the thickness of the magnetic material layer in an area surrounding the electrode materials. Accordingly, in the method of producing a lamination type coil component according to preferred embodiments of the present invention, the sum of the thickness of the electrode material in the via-hole and the thickness of the electrode material constituting the coil pattern is greater than the sum of the thickness of the magnetic green sheet and the thickness of the magnetic material layer in the area surrounding the electrode materials.
As a result, in the press-bonding step, the electrode material constituting the coil pattern and the electrode material in the via-hole is sufficiently pressed, and the coil patterns provided on the respective magnetic green sheets are securely connected to each other through the via-hole.
The coil pattern and the magnetic material layer can be formed by different methods. As an example, screen printing, plating, photolithography, or other suitable methods can be used.
Preferably, at least one of the thicknesses of the coil pattern and the magnetic material layer provided on ea
Donovan Lincoln
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Nguyen Tuyen
LandOfFree
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