Inductor built-in electronic parts using via holes

Details Inductor built-in electronic parts using via holes Inductor built-in electronic parts using via holes

1996-07-19

2001-04-24

Bettendorf, Justin P. (Department: 2817)

Wave transmission lines and networks

Coupling networks

Frequency domain filters utilizing only lumped parameters

C333S184000, C333S177000

Reexamination Certificate

active

06222427

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electronic parts with an integrally built-in inductor and, more particularly, to electronic parts such as an inductor, an LC resonator, band-pass filter and an LC filter for use in a portable radio equipment, for example.
2. Description of Related Art
FIG. 7
is an equivalent circuit diagram showing one example of an LC filter acting as a band-pass filter to which the present invention can be applied. The LC filter includes two LC resonators R
1
and R
2
. One LC resonator R
1
comprises a first inductor L
1
and a first capacitor C
1
connected in parallel, and the other LC resonator R
2
comprises a second inductor L
2
and a second capacitor C
2
connected in parallel. It is noted that the first and second inductors L
1
and L
2
are electromagnetically coupled to each other. One end of the first LC resonator R
1
is connected to a first input/output terminal T
1
via a third capacitor C
3
and one end of the second LC resonator R
2
is connected to a second input/output terminal T
2
via a fourth capacitor C
4
. Other ends of the first and second LC resonators R
1
and R
2
are connected to ground terminals G, respectively.
FIG. 8
is an exploded perspective view showing a main part of the exemplary prior art LC filter having the equivalent circuit shown in FIG.
7
. The prior art LC filter
1
shown in
FIG. 8
includes four dielectric layers
2
a,
2
b,
2
c
and
2
d
to be laminated together. A first capacitor electrode
3
a
and the like is formed on the upper surface of the first dielectric layer
2
a,
a second capacitor electrode
3
b
and the like is formed on the upper surface of the second dielectric layer
2
b
and a spiral pattern electrode
4
which acts as an inductor element is formed on the upper surface of the third dielectric layer
2
c,
the first, second and third electrodes
3
a,
3
b
and
3
c
being formed of printing conductors by means of thick film printing. The first capacitor C
1
of the first LC resonator R
1
is formed between the first and second capacitor electrodes
3
a
and
3
b
and the first inductor L
1
of the first LC resonator R
1
is formed by the spiral pattern electrode
4
. Similarly, the second capacitor C
2
of the other LC resonator R
2
is formed between other two capacitor electrodes (not shown) on either side of the second dielectric layer
2
b,
and the second inductor L
2
of the second LC resonator R
2
is formed by another pattern electrode (not shown) formed on the upper surface of the third dielectric layer
2
c.
It is noted that external electrodes (not shown) which act as the input/output terminals T
1
and T
2
and the ground terminals G are formed on side faces of the dielectric layers
2
a
through
2
d.
Further, the third and fourth capacitors C
3
and C
4
are formed by other capacitor electrodes (not shown) between one end of each of the LC resonators R
1
and R
2
and the external electrodes which act as the input/output terminals T
1
and T
2
, respectively. The other ends of the LC resonators R
1
and R
2
are connected to the external electrodes which act as the ground terminals G.
Because each capacitor, which is relatively close to an ideal capacitor, is created in the prior art LC filter
1
shown in
FIG. 8
, the Q (quality factor) of the whole is influenced largely by the Q of the built-in inductor. Therefore, in order to improve the Q of the LC filter
1
, it is conceivable to improve the Q of the inductor by increasing a sectional area of the pattern electrode which acts as the inductor element. It is then conceivable to thicken a width of the pattern electrode in order to increase the sectional area of the pattern electrode, because a thickness of the pattern electrode formed by means of thick film printing is only about 10-odd mm. However, the prior art LC filter has had a problem in that when the width of the pattern electrode is thickened, a value of inductance generated by the pattern electrode made within an equal area becomes small and a large floating capacity is generated between the electrodes similar to the capacitor electrodes which vertically face each other. The result is a drop in Q, contrary to the purpose of the design modification. It is noted that this kind of problem also exists in other built-in inductor electronic parts such as prior art inductors and LC resonators in which a pattern electrode acts as an inductor element and is formed by means of thick film printing.
The prior art LC filter
1
shown in
FIG. 8
also has had a problem that although the Q of the whole is improved when the space between the pattern electrode and the vertically disposed capacitor electrode is widened, a thickness of the whole, i.e. the size thereof, is increased and it cannot be mounted within small equipment such as portable radio equipment whose thickness is limited. It is noted that this kind of problem also exists in the other inductor built in electronic parts such as prior art LC resonators in which the pattern electrode which acts as an inductor element and the capacitor electrode are formed, respectively, by means of thick film printing.
Further, the LC filter
1
shown in
FIG. 8
has had a problem in that because a line of magnetic force generated by the pattern electrode crosses with the main surface of the capacitor electrode at almost right angles as shown in
FIG. 9
, a significant eddy current loss is generated on the capacitor electrode by the line of magnetic force, thus dropping the Q of the whole. It is noted that this kind of problem also exists in the other built-in inductor electronic parts such as the prior art LC resonator in which the pattern electrode which acts as an inductor element and the capacitor electrode are formed, respectively, by means of thick film printing.
Accordingly, it is a primary object of the present invention to provide a small built-in inductor electronic parts whose Q is high.
SUMMARY OF THE INVENTION
In order to achieve the aforementioned goal, a built-in inductor electronic part of the present invention is constructed so that an inductor is formed by a via hole penetrating through a plurality of laminated ceramic layers in the thickness direction thereof.
It is noted that the inventive built-in inductor electronic parts may be constructed so that an inductor is formed by a plurality of via holes penetrating through a plurality of laminated ceramic layers in the thickness direction thereof.
Further, the inventive built-in inductor electronic parts may be constructed so that capacitor electrodes are formed between the plurality of ceramic layers.
Because the inductors are formed by the via holes penetrating through the plurality of laminated ceramic layers in the thickness direction thereof, a sectional area of the inductor increases, thereby improving the Q of the built-in inductor electronic parts. A size of the built-in inductor electronic parts may be kept small because an area of the main surface and thickness of the ceramic layer need not be increased.
Accordingly, the present invention allows the small built-in inductor electronic parts whose Q is high to be obtained.
It is noted that a value of inductance may be readily controlled in the inventive inductor because a length of the conductor as the inductor is elongated by forming the inductor by the plurality of via holes penetrating through the plurality of laminated ceramic layers in the thickness direction and the value of inductance will not change so much even if the length of the conductor is changed by small amounts, e.g., the variation of thickness among the ceramic layers.
Further, because the main surface of the capacitor electrode is parallel with lines of magnetic force generated by the inductor created by the via hole when forming the capacitor electrodes between the plurality of ceramic layers, less eddy current loss is generated by the lines of magnetic force on the capacitor electrode and the Q will hardly drop.
The above and other related objects, features and advantages of the present

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