Laminated inductor and method of producing the same

Details Laminated inductor and method of producing the same Laminated inductor and method of producing the same

2000-10-05

2002-10-15

Donovan, Lincoln (Department: 2832)

Inductor devices

Core forms casing

C336S200000, C336S192000

Reexamination Certificate

active

06466120

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laminated inductor constructed using a laminated ceramic integral firing technique, and a method of producing the same, and more particularly, to a laminated inductor in which a low dielectric constant material layer is arranged between conductor patterns defining a coil conductor, and a method of producing the same.
2. Description of the Related Art Conventionally, laminated inductors using magnetic ceramics have been widely used.
FIGS. 8 and 9
are a cross-sectional view and a perspective view, respectively, showing a conventional laminated inductor.
A laminated inductor
51
includes a sintered ceramic body
52
made of a magnetic ceramic material. A coil conductor
53
is embedded inside of the sintered ceramic body
52
. The coil conductor
53
defines a spiral winding circuit inside of the sintered ceramic body
52
. One end portion
53
a
extends to an end surface
52
a
, while the other end portion
53
b
extends to an end surface
52
b
. Terminal electrodes
54
and
55
are arranged to cover the ends surfaces
52
a
and
52
b
, respectively. Thus, the coil conductor
53
is connected to the terminal electrodes
54
and
55
.
In order to manufacture the above-described sintered ceramic body
52
, conductor patterns constituting a coil pattern are printed on magnetic green sheets, respectively. A plurality of magnetic green sheets each having a conductor pattern printed thereon are laminated, and then magnetic green sheets having no conductor patterns thereon are laminated on the upper side and the lower side of the laminated magnetic green sheets to define a laminated body. The laminated body is then fired so as to produce the sintered ceramic body
52
. Thus, the sintered ceramic body
52
is formed by the well-known laminated ceramic integral firing technique.
Examples of the above-described conductor patterns will be described with reference to FIG.
9
.
FIG. 9
shows the uppermost conductor pattern
53
c
of the coil conductor
53
and the lower conductor pattern
53
d
. The conductor pattern
53
c
is printed on a magnetic green sheet
56
. The end portion
53
a
of the conductor pattern
53
c
extends to one-side edge
56
a
of the magnetic green sheet
56
. Further, a via-hole electrode
57
is located near the inner-side end portion of the conductor pattern
53
c.
A conductor pattern
53
d
is located on the upper side of a magnetic green sheet
58
. The vicinity of one end portion
53
d
1
of the conductor pattern
53
d
is arranged so as to overlap with the via-hole electrode
57
. That is, when the magnetic green sheets
56
and
58
are laminated, the conductor patterns
53
c
and
53
d
are electrically connected to each other through the via-hole electrode
57
. A via-hole electrode
59
is formed in the vicinity of the other end of the conductor pattern
53
d
. The via-hole electrode
59
is electrically connected to a conductor pattern positioned below the conductor pattern
53
d
. In this manner, a plurality of conductor patterns are laminated through magnetic green sheets, respectively, to define the above-described coil conductor
53
.
The laminated inductor
51
is produced by using the laminated ceramic integral firing technique. Accordingly, the control of the number of turns of the coil conductor
53
can be easily performed, and moreover, a small-sized inductance component can be formed.
However, since the conductor patterns at different heights or vertical positions in the coil conductor
53
overlap through magnetic ceramic layers, the generation of stray capacitances between the conductor patterns at the different vertical positions can not be prevented. For this reason, in the laminated inductor
51
, the noise-removing characteristics are reduced, due to the effects of the above-described stray capacitances.
SUMMARY OF THE INVENTION
In order to overcome the problems described above, preferred embodiments of the present invention provide a laminated inductor in which stray capacitances between conductor patterns located at different vertical positions are minimized, and thereby, the noise-removing characteristic is greatly improved.
According to a preferred embodiment of the present invention, a laminated inductor includes a sintered ceramic body, and a coil conductor disposed inside of the sintered ceramic body which includes a sintered ceramic body made of a ceramic, a coil conductor disposed inside of the sintered ceramic body and including two ends which extend to the outer surface of the sintered ceramic body, first and second external electrodes located on the areas to which the coil conductor of the sintered ceramic body extend, respectively, the coil conductor including a plurality of conductor patterns located at different vertical positions in the sintered ceramic body, and a via-hole electrode through which conductor patterns, which are vertically adjacent to each other in the sintered ceramic body, are connected to each other, and low dielectric constant material layers laminated to both sides in the thickness direction of at least one of the plurality of conductor patterns, the low dielectric constant material having a lower dielectric constant than that of the ceramic constituting the sintered ceramic body.
Preferably, a first ring-path corresponding to one turn of the coil conductor is located in a height range where the conductor pattern is located. The first ring-path is defined by the conductor pattern and a low dielectric constant material layer. Also, a second ring-path corresponding to one turn of the coil conductor is defined by the via-hole electrode and a low dielectric constant material layer, and is located in the height range where a via-hole electrode is located.
Moreover, according to another preferred embodiment of the present invention, there is provided a method of producing a laminated inductor in which a coil conductor is located inside of a sintered ceramic body made of a ceramic material. The method includes the steps of preparing a first composite sheet having a conductor pattern defining a portion of the coil conductor and a low dielectric constant material pattern connected to the conductor pattern located on a support film, the conductor pattern and the low dielectric constant material pattern defining a ring-path corresponding to one turn of the conductor pattern, and a ceramic green layer provided on the support film excluding the area where the conductor pattern and the low dielectric constant material pattern are formed, preparing a second composite sheet including a via-hole electrode, a low dielectric constant material pattern formed so as to define together with the via-hole electrode a ring-path corresponding to one turn of the coil conductor, and a ceramic green layer provided on a support film excluding the area where the via-hole electrode and the low dielectric constant material pattern are formed, laminating the first and second composite sheets to each other with the support film between the composite sheets being released in such a manner that the conductor pattern of the first composite sheet overlaps the via-hole electrode of the second composite sheet, repeating the above-described lamination step to produce a laminate body in which a coil conductor including the plurality of conductor patterns and the via-hole electrode, and both ends of the coil conductor are exposed to the outer surface of the laminate body, firing the laminate body to produce a sintered ceramic body, and forming first and second external electrodes to be electrically connected to both ends of the coil conductor on the outer surface of the sintered ceramic body.
Preferably, in the method of producing a laminated inductor according to a preferred embodiment of the present invention, the conductor pattern is formed so as to have 1
times the length of the ring-path, and in the step of laminating the plurality of first composite sheets through the second composite sheets, respectively, a first composite sheet at an upper pos

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