JPH09106916A - LC filter and frequency adjustment method thereof - Google Patents

Abstract

(57) Abstract: An LC filter having a structure capable of easily performing frequency adjustment is provided. SOLUTION: Lower electrodes 2a and 2b which also serve as a ground electrode are formed on the surface of an insulating substrate 1, and substantially the entire surface of the insulating substrate 1 including the electrodes is covered with a dielectric thin film layer 4 to form the dielectric thin film layer. 4, upper electrodes 6a and 6b are formed in a surface area facing the lower electrodes a and 2b, and parallel resonance capacitors C ₀ and C ₀ are formed by the upper and lower electrodes via the dielectric thin film layer 4. Further, the dielectric thin film layer 4 is covered with the insulating thin film layer 10 over substantially the entire surface thereof, and the inductors L ₁ and L ₂ for parallel resonance are provided in the inductor formation region s secured in advance on the surface.
Of the parallel resonance inductors L ₁ and L ₂ through the conductive through holes h ₁ and h ₂ that penetrate the thin film layers 4 and 10.
One end of was connected to the lower electrodes 2a and 2b, and the other end was connected to the upper electrodes 6a and 6b to form an LC filter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LC filter used for various wireless communication devices such as a portable telephone and a car telephone.

[0002]

2. Description of the Related Art As an LC filter, generally used is one in which a parallel resonance circuit in which a resonance capacitor and an inductor are connected in parallel is carried by a base plate made of a thin or plural insulating substrate such as alumina. Has been. This LC filter can be used as an integrated dielectric filter in which a plurality of through-hole-shaped resonance conductors are formed in a dielectric block or a three-conductor stripline filter in which a foil-shaped resonance conductor is sandwiched between two dielectric substrates. In comparison, it is being favorably adopted for card-sized mobile phones because of its advantages such as thinness and easy miniaturization.

On the other hand, in recent years, there has been an increasing demand for miniaturization, high performance, and high-density mounting of electronic devices and the like. Therefore, further miniaturization of LC filters has been strongly demanded. In order to meet this demand, it is necessary to integrate and miniaturize the filter parts.
In order to meet such requirements, there has been proposed an LC filter in which a dielectric thin film layer or the like is laminated on an insulating substrate to achieve a thin wall.

A conventional LC filter will be described below with reference to FIG. On the surface of the insulating substrate 20, rectangular lower electrodes 21a and 21b are formed in parallel, and each lower electrode 21
The parallel resonance inductors 22a and 22b, which are long in the left and right, are formed in a strip shape by being connected to a and 21b. On the surface of the insulating substrate 20, the dielectric thin film layer 2 is formed so as to cover the lower electrodes 21a and 21b and the inductors 22a and 22b.
7 is coated. Then, on this dielectric thin film layer 27,
Upper electrodes 28a and 28b are formed on the surface regions facing the lower electrodes 21a and 21b. Upper electrodes 28a, 28
In b, the connection ends 29, 29 extend rearward. The connection ends 29, 29 are connected to the parallel resonance inductor 22.
a and 22b are connected through conductive through holes formed in the dielectric thin film layer 27. In addition, on the dielectric thin film layer 27, the relay terminal 3 is provided outside the upper electrodes 28a and 28b.
0, 30 are formed. Thus, the lower electrodes 21a and 21b and the upper electrode 28 are interposed via the dielectric thin film layer 27.
The parallel resonance capacitors C ₀ and C ₀ (see FIG. 6) are formed by arranging the a and 28b in parallel.

Further, on the entire surface of the dielectric thin film layer 27, the upper electrodes 28a, 28b, the relay terminals 30, 30 are formed.
The dielectric thin film layer 31 is covered so as to cover the top. Then, on the dielectric thin film layer 31, at the positions on the upper electrodes 28a and 28b, the input / output electrode 32a, the capacitor electrode 32c,
The input / output electrodes 32b are arranged on the left and right. The input / output electrode 32a is opposed to the upper electrode 28a via the dielectric thin film layer 31 to form an input / output coupling capacitor C ₁ (see FIG. 6), and the input / output electrode 32b is the dielectric thin film layer. An input / output coupling capacitor C ₂ is formed by being opposed to the upper electrode 28b via 31. Further, the capacitor electrode 32
c is an upper electrode 28a, disposed across the 28b, respectively upper electrode 28a, constitute interstage coupling capacitor C ₃ and opposed with 28b. In addition, ground electrodes 34a and 34b are formed on both sides of the dielectric thin film layer 31 so as to be opposed to the relay terminals 30 and 30. Then, the external electric circuit is connected to the input / output electrodes 32a and 32b, and the grounding electrodes 34a and 34b are grounded to form the equivalent circuit shown in FIG.

[0006]

By the way, in the above-mentioned conventional structure, the resonance frequency is adjusted by punching the trimming hole x from the surface of the dielectric thin film layer 31, as shown in FIG.
A parallel resonance capacitor C is provided through the trimming hole x.
_{This is} done by partially removing the upper electrodes 28a and 28b of ₀ and C ₀ (see Japanese Patent Publication No. 6-56813). Therefore, there is a problem in that workability is poor, cracks are likely to occur due to the punching work, and the strength of the substrate is lowered. The present invention relates to an LC filter having a structure capable of easily adjusting a frequency and a frequency adjusting method using the LC filter.

[0007]

According to the present invention, a lower electrode which also serves as a ground electrode is formed on the surface of an insulating substrate, and substantially the entire insulating substrate including the electrode is covered with a dielectric thin film layer,
An upper electrode is formed on a surface area of the dielectric thin film layer facing the lower electrode, and a parallel resonance capacitor is formed by the upper and lower electrodes via the dielectric thin film layer, and a dielectric including the upper electrode. Cover almost the entire thin film layer with an insulating thin film layer,
A parallel resonance inductor is formed in the inductor formation region secured in advance on the surface, and one end of the parallel resonance inductor is connected to the lower electrode of the parallel resonance capacitor through the conductive through hole penetrating the thin film layer. , The other end of which is connected to the upper electrode of the parallel resonance capacitor.

Here, the LC filter resonates at a resonance frequency f ₀ of the following formula which is mainly determined by the capacitance value of the resonance capacitor and the inductance value of the inductor. f ₀ = 1 / (2π (LC) ^1/2 )

The capacitance value of this resonance capacitor is determined by the dielectric constant of the dielectric material used, the thickness of the dielectric layer, and the area of the counter electrodes of the upper and lower electrodes, and the inductance value of the inductor is determined by the conductor length and conductor width. By the way, in the above-mentioned structure, an inductor can be attached later to the inductor formation region. Therefore, since the resonance frequency f ₀ is determined by the capacitance of the resonance capacitor and the value of the inductance of the inductor from the above equation, even if there is variation in the capacitance of the capacitor, it is optimal according to the capacitance. By forming an inductor having an inductance value in the inductor formation region, the required resonance frequency f
It becomes possible to obtain ₀ .

In this structure, the inductor is formed by the following method. That is, an inductor formation region is secured in advance on the insulating substrate between the resonance capacitor, the capacitance value of the resonance capacitor is measured, and the optimum inductance value of the inductor is determined. Is selected from among a plurality of patterns set in advance based on the optimum inductance value, and the inductor is formed in the inductor formation region. That is, the inductor has different inductance depending on the shape such as the conductor length, the conductor width, and the form. Therefore, by selecting a predetermined pattern from patterns of different shapes whose inductance values are predetermined and using this as an inductor,
The resonance frequency can be obtained. Further, even after the inductor is formed, the resonance frequency can be easily adjusted by partially removing the inductor or adding a conductive material.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows an LC filter according to the present invention. This LC filter has an example of a thickness of 0.635 mm.
, A thin insulating substrate 1 made of alumina or the like formed in a rectangular shape having a length of 2 mm and a width of 2 mm supports a parallel resonance circuit composed of a resonance capacitor C ₀ and an inductor L.

That is, on the surface of the insulating substrate 1, rectangular lower electrodes (ground electrodes) 2a and 2b are arranged side by side on the front side in the left and right in the figure. The lower electrodes 2a and 2b are respectively provided with connecting end portions 3a and 3b extending rearward. The lower electrode 2a, 2b is one obtained by forming a Fe-Ni alloy plating layer directly or via an underlying layer, a lower electrode of the resonant capacitor C _0, C _0.

A lower electrode 2 is formed on the surface of the insulating substrate 1.
Almost the entire surface including a and 2b is covered with a dielectric thin film layer 4 made of SiO ₂ . Then, on this dielectric thin film layer 4,
The upper electrode 6 is formed on the surface area facing the lower electrodes 2a and 2b.
a and 6b are formed by sputtering. The connection ends 7, 7 of the upper electrodes 6a, 6b extend rearward. In addition, the upper electrode 6 is formed on the dielectric thin film layer 4.
Relay terminals 8 and 8 are formed by sputtering at positions outside a and 6b. Thus, the dielectric thin film layer 4
Since the lower electrodes 2a and 2b and the upper electrodes 6a and 6b are placed opposite to each other via the capacitor, the parallel resonance capacitors C ₀ and C _{0 are connected.}
Is formed.

Further, on the entire surface of the dielectric thin film layer 4,
S covering the upper electrodes 6a and 6b and the relay terminals 8 and 8
An insulating thin film layer 10 (dielectric thin film layer) made of iO ₂ or polyimide resin is coated. And this insulating thin film layer 1
On the upper side of 0, parallel resonance inductors L ₁ and L
₂ is formed. These parallel resonance inductors L ₁ and L ₂
Has its inner end connected to the connection end portions 7, 7 of the upper electrodes 6a, 6b through conductive through holes h ₁ , h ₁ penetrating the insulating thin film layer 10, and its outer end has a dielectric thin film layer 4 and conductive through-holes h _2, the lower through h ₂ electrodes 2a passing through the insulating film layer 10, 2b of the connection end portion 3a, is 3b electrically connected. Furthermore, on the insulating thin film layer 10,
At the positions on the upper electrodes 6a and 6b, the input / output electrodes 11a, the capacitor electrodes 11c, and the input / output electrodes 11b are arranged side by side. The input / output electrode 11a is opposed to the upper electrode 6a via the insulating thin film layer 10 to form an input / output coupling capacitor C.
₁ , and the input / output electrode 11b is the insulating thin film layer 10
An input / output coupling capacitor C ₂ is formed by being opposed to the upper electrode 6b via the. Furthermore, the capacitor electrode 11
c is an upper electrode 6a, is disposed across the 6b, respectively upper electrode 6a, constituting the interstage coupling capacitor C ₃ and opposed with 6b.

Besides, ground electrodes 13a and 13b are formed on both sides of the insulating thin film layer 10 by sputtering similarly to the relay terminals 8 and 8.

Then, the external electric circuit is connected to the input / output electrodes 11a and 11b, and the ground electrodes 13a and 13b are grounded to form the equivalent circuit shown in FIG.

With this structure, the parallel resonance inductors L ₁ and L ₂ can be formed in the final step. Therefore, after forming the semi-finished product without the parallel resonant inductor L _1, L _2, a parallel resonant inductor L _1,
The inductance value of L ₂ is set by selecting the shape, and the parallel resonance inductors L ₁ and L ₂ are formed in the inductor formation region s by sputtering so that the inductance value is optimized. You can In addition, after formation, the inductors L ₁ and L ₂
It is possible to easily adjust the resonance frequency by partially removing or adding a conductive material.

That is, the relationship between the capacitance value of the resonance capacitor C ₀ , the inductance values of the parallel resonance inductors L ₁ and L ₂ and the resonance frequency f ₀ is f ₀ = 1 / (2π (L
Since a C) ^1/2), in order to obtain the required resonant frequency f _0, examines the capacity of the resonance capacitor C ₀ by volume meter, in accordance with the capacitive value, on the inductance value formula The parallel resonance inductors L ₁ and L ₂ having the inductance value are determined and formed in the inductor formation region s. Here, the parallel resonance inductors L ₁ and L ₂ have different inductances depending on the shapes such as the conductor length, the conductor width, and the form. Therefore, by selecting a predetermined pattern from patterns having different shapes whose inductance values are predetermined and forming the parallel resonance inductors L ₁ and L ₂ , the resonance capacitor C _{0 can be obtained.}
It is possible to obtain the required resonance frequency f ₀ even if there are variations.

In this case, the predetermined pattern is formed by designating the pattern using an automatic exposure device or the like, or by a predetermined inductance value or resonance capacitor C _0.
When a capacitance value of is input, a pattern is automatically selected, and further, an optimum pattern is formed corresponding to the input value, and the optimum pattern is automatically set in the inductor formation region s based on the pattern. It may be formed as desired.
In the configuration that automatically creates this optimum pattern,
Since the relationship between the inductance value and the shape of the inductor is determined in advance by the creation formula, it may be said that an infinite number of patterns are prepared through the creation formula. It can be said that this is an aspect of the configuration in which the selection is made based on the optimum inductance value from among the above patterns. Of course, the inductors L ₁ and L ₂ may be manually formed, or further partially added or removed to adjust the inductance value (resonance frequency). Thus, the parallel resonance inductors L ₁ and L ₂ having the optimum inductance value are formed, and the required resonance frequency is realized.

In this case, the through holes h ₁ and h ₂ penetrating the thin film layers 4 and 10 may be formed in advance, or after forming the inductors L ₁ and L ₂ , the through holes h ₁ and h ₂ are formed.
₁ and h ₂ may be drilled.

FIGS. 3A to 3C show pattern examples of the inductor L formed in the inductor formation region s. In each case, the through holes h ₁ and h ₂ are formed in advance. Yes, that through hole h ₁ , h
_The shape is selected so that both ends are connected to ₂ . The inductance values of the items (a) to (c) are different depending on their widths and shapes. This pattern (a)
(C) is merely an example, and the inductance value can be set by various shape changes such as minutely changing the length and changing the width and the shape of the bypass portion.

Then, the capacitance value of the resonance capacitor C ₀ is measured, the optimum inductance value of the inductor L is determined from the desired resonance frequency f ₀ based on the above equation, and thereafter, from the pattern group. By selecting a pattern having a predetermined inductance value, forming an inductor L in the inductor formation region s by a method such as sputtering or plating, and making a desired connection with the through holes h ₁ and h ₂ , The equivalent circuit shown in FIG. 6 in which the resonance frequency is achieved is configured. In FIG. 1, the insulating thin film layer 10 is formed of a dielectric material, and the insulating thin film layer 10 allows the input / output coupling capacitors C ₁ and C ₂ and the inter-stage coupling capacitor C to be coupled.
_{Although 3} is formed, various forming means are proposed, and the point is that the insulating thin film layer is arranged as the uppermost layer and the inductor formation region s can be secured in the layer.

[0023]

According to the LC filter of the present invention, the inductor forming region s is secured on the uppermost surface and the inductor L for parallel resonance is used.
₁ and L ₂ are formed, and one end of the inductor is connected to the lower electrode of the parallel resonance capacitor and the other end is connected to the upper electrode of the parallel resonance capacitor through the conductive through hole penetrating the thin film layer. because it is made structure, it is possible to form retrofitting of said parallel resonance inductor L _1, L _2, can be properly set an inductance value by the selection of the shape, and after forming, the inductor L _1, L _The resonance frequency can be adjusted accurately and easily by partially deleting ₂ or adding a conductive material. Further, since it is not necessary to form the trimming hole x for the adjustment, neither cracks nor reduction in mechanical strength occur.

In addition, in the inductor forming method, a pattern is selected from a plurality of preset patterns based on an optimum inductance value, and the inductor L is formed in the inductor forming region s by the pattern. The required resonance frequency can be set very easily only by selecting the pattern.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an LC filter.

FIG. 2 is a perspective view of an LC filter.

FIG. 3 is a plan view showing a pattern example of an inductor L.

FIG. 4 is an exploded perspective view of a conventional LC filter.

FIG. 5 is a vertical cross-sectional side view showing a frequency adjusting unit having a conventional configuration.

FIG. 6 is an equivalent circuit diagram.

[Explanation of symbols]

1 insulating substrate 2a, 2b lower electrode 4 dielectric thin film layers 6a, 6b upper electrode 10 insulating film layer 11a, 11b output electrodes 11c capacitor electrode h _1, h ₂ conductive through holes L, L _1, L ₂ parallel resonance inductor C ₀ Resonance capacitor C ₁ , C ₂ , C ₃ Coupling capacitor s Inductor formation area

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideaki Tanaka 14-18 Takatsuji-cho, Mizuho-ku, Nagoya City Nippon Special Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A lower electrode also serving as a ground electrode is formed on the surface of an insulating substrate, and the insulating substrate including the electrode is covered with a dielectric thin film layer on substantially the entire surface of the lower electrode. An upper electrode is formed in the opposing surface region, and a parallel resonance capacitor is formed by the upper and lower electrodes via the dielectric thin film layer. Furthermore, almost the entire dielectric thin film layer including the upper electrode is formed of an insulating thin film layer. A parallel resonance inductor is formed on the surface of the inductor formation area secured in advance, and one end of the parallel resonance inductor is connected to the lower electrode of the parallel resonance capacitor through a conductive through hole penetrating the thin film layer. And an other end of the LC filter connected to the upper electrode of the parallel resonance capacitor. 2. A lower electrode which also functions as a ground electrode is formed on the surface of an insulating substrate, and the insulating substrate including the electrode is covered with a dielectric thin film layer on substantially the entire surface of the insulating substrate to form a lower electrode on the dielectric thin film layer. An upper electrode is formed in the opposing surface region, and a parallel resonance capacitor is formed by the upper and lower electrodes via the dielectric thin film layer. Furthermore, almost the entire dielectric thin film layer including the upper electrode is formed of an insulating thin film layer. In the covering, after measuring the capacitance value of the parallel resonance capacitor and determining the optimum inductance value of the inductor, the inductor is selected from a plurality of patterns preset to have different inductance values. The inductor is selected based on the optimum inductance value, and the inductor is formed in the inductor formation region secured in advance on the surface of the insulating thin film layer, and the dielectric thin film layer is formed. Via a conductive through hole for passing the one end of the inductor is connected to the lower electrode of the parallel resonant capacitor, the frequency adjustment method of the LC filter, characterized in that to connect the other end to the upper electrode of the parallel resonant capacitor.