JPH0638489Y2 - filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a filter in which two three-terminal filter elements and a relay capacitor are connected in parallel, and in particular,
The present invention relates to a filter having a structure in which each of these filter elements and a relay capacitor are formed on different substrates, and these substrates are laminated.

[Prior Art] For example, two electrodes are formed on one main surface of a piezoelectric ceramic substrate such as PZT, and one electrode is formed on the other main surface. Terminal type resonators are used as filters in various electronic circuits. For example, as a filter used in a TV audio intermediate frequency circuit, in order to obtain desired electrical characteristics, as shown in FIG. 5, a first filter element 21 composed of a three-terminal resonator and a second filter element 21 are used. There is one in which the element 22 is connected in parallel, and in order to further improve the characteristics, the relay capacitor 3 is connected in parallel between them.

Such a filter 1 is usually provided on one piezoelectric substrate,
The three-terminal filter elements 21 and 22 and the capacitor 3 are arranged side by side.

However, as described above, since the filter elements 21 and 22 utilize the vibration based on the energy trapping phenomenon, when the distance between the filter elements 21 and 22 is short, the vibration of one element is transmitted to the other element. Will also affect. In order to avoid such an influence, the distance between the filter elements 1 and 2 should be made sufficiently large. As a result,
The size of the piezoelectric substrate of the filter is increased. Further, the area required for mounting the filter is increased, the circuit design is restricted, and the circuit cannot be downsized.

[Related Art] In order to solve the above-mentioned problems, the first and second filter elements and the relay capacitor are formed on respective independent substrates, and each substrate is laminated in a state where the vibration of the filter element is not hindered. A filter having such a structure is described in a prior patent application (Japanese Patent Application No. 60-154405) (published by Japanese Patent Application Laid-Open No. 62-14512) filed by the present applicant. The structure of the filter of this earlier application is
Description will be given with reference to the attached FIG. 6 to FIG.

In FIG. 6, 21 corresponds to the above-mentioned first three-terminal filter element, 22 corresponds to the second three-terminal filter element, and 3
Is equivalent to the relay capacity. Reference numeral 4 is a lid. Each of these members is formed in a flat plate shape having the same size in plan view. Electrodes are formed on these members by a known method such as screen printing.

The first filter element 21 is formed on a polarized ceramic substrate 211 such as PZT. The input-side electrode 2a and the output-side electrode 2c are formed on one surface of the substrate 211 in a state that each has a lead-out portion that extends to the edge of the substrate 211. Further, on the other surface of the substrate 211, a ground side electrode 2b is provided so as to face each part of the input side electrode 2a and the output side electrode 2c,
It is formed in a state having a lead-out portion extending to the edge of the substrate 211. Vibrations due to the energy trapping phenomenon occur at the portions where the electrodes 2a, 2c and the electrode 2b face each other.

The second filter element 22 is configured substantially the same as the first filter element 21. On one surface of the substrate 221 of the second filter element 22, the input side electrode 3c and the output side electrode 3d are provided.
Is formed, and the ground side electrode 3b is formed on the other surface. The input-side electrode 3c of the second filter element 22 is led out to a position corresponding to the output-side electrode 2c of the first filter element 21. In addition, the ground side electrode of the second filter element 22
3b is drawn out to a position corresponding to the earth side electrode 2b of the first filter element 21.

The relay capacitor 3 is provided on the non-polarized dielectric substrate 31. On each surface of the substrate 31, a ground side electrode 4b and a hot side electrode 4c are formed in a state having a lead portion extending to the edge of the substrate 31 so that a part of each face each other to form a capacitor. It The earth side electrode 4b has the first and second electrodes.
Ground electrodes 2b and 3b of filter elements 21 and 22 of
The hot side electrode 4c is also drawn to a position corresponding to the output side electrode 2c and the input side electrode 3c.

The lid body 4 is formed on an insulating substrate 41, and external extraction electrodes 1a to 1d are provided at four corners of the lid body 4.

The lid 4, the first filter element 21, the second filter element 22 and the relay capacitor 3 which have been extended as described above are laminated in the order shown in FIG. 6 and integrated by an insulating adhesive. Such an adhesive may be used on the lower surface of the lid 4 or the first filter element.
It is applied to the upper surface of 21, the lower surface of the first filter element 21 or the upper surface of the second filter element 22, and the lower surface of the second filter element 22 or the upper surface of the relay capacitor 3. At this time, as shown in FIG. 7, for example, as shown in FIG. 7, the adhesive 5 is used so that the vibrations of the resonators of the first and second filter elements 21 and 22 are not hindered and the electrical connection of the electrodes is not hindered. Is applied.

When the above-mentioned lamination is achieved, a laminated body 11 as shown in FIG. 8 is obtained. Since the electrical connection as shown in FIG. 5 cannot be achieved only by stacking, the external electrodes a to d are formed by, for example, conductive paint in order to achieve the desired electrical connection. External electrodes a to d
As shown in FIG. 9 which is an enlarged cross-sectional view taken along lines IX to IX in FIG. 8, is an electrode extending to a predetermined edge of each of the lid body 4, the filter elements 21 and 22, and the relay capacitor 3. Connect to each other. That is, the external electrode a connects the external extraction electrode 1a and the input side electrode 2a to each other, the external electrode b connects the external extraction electrode 1b and the ground side electrodes 2b, 3b and 4b to each other, and the external electrode c The extraction electrode 1c, the output side electrode 2c, the input side electrode 3c and the hot side electrode 4c are connected to each other, and the external electrode d connects the external extraction electrode 1d and the output side electrode 3d to each other. In this way, the filter 1 is configured, and in the use state of the filter 1, the external electrode a is the input side terminal, the external electrode d is the output side terminal, and the external electrode b is the ground side terminal. It In addition, in FIG. 5, in the vicinity of each electrode or the connection point, FIG.
The reference numerals of the electrodes used in the drawings are attached.

As described above, according to the filter 1 described with reference to FIGS. 6 to 9, two 3-terminal filter elements are used.
The size can be reduced without causing mutual interference between 21,22.

[Problems to be Solved by the Invention] However, it has been found that the above-described filter 1 has the following problems.

Referring to FIG. 6, when a material having a particularly high dielectric constant is used for the substrates 41, 211, 221, and 31, an undesired capacitance is formed in the filter 1 as a whole or in each element included in the filter 1. It will be. For example, as shown in FIG. 10, four parallel-connected capacitors due to the respective substrates 41, 211, 221, 31 are formed between the external electrode a serving as the input terminal and the external electrode d serving as the output terminal of the filter 1. To be done. Further, for example, taking the first three-terminal filter element 21 as an example, as shown in FIG. 11, the substrate 211 is provided between the lead-out portion of the input side electrode 2a and the lead-out portion of the output side electrode 2c. The resulting capacitance is formed.

These capacitances reduce the filter characteristics. That is, as shown in FIG. 12, even if the above-mentioned capacitance is not obtained, the waveform as shown by the dotted line is obtained, but due to the presence of such capacitance, the bottom level rises as shown by the solid line. It becomes a wavy waveform.

Therefore, this invention intends to provide a filter capable of minimizing the generation of the above-described capacitance.

[Means for Solving the Problems] In the present invention, the first and second three-terminal filter elements and the relay capacitors are formed on the independent first, second and third substrates, respectively. A state in which the input side electrode, the output side electrode, and the ground side electrode each have a lead-out portion extending to each end portion thereof so as to configure the first and second three-terminal filter elements, respectively. The hot side electrode and the ground side electrode are formed on the third substrate so as to form a relay capacitor, and each has a lead-out portion extending to an edge portion thereof. The substrates are laminated in a state where the vibrations of the first and second three-terminal filter elements are not disturbed, and the first and second three-terminal filter elements and the relay capacitors are connected in parallel on the outer peripheral portion of the laminate. So that
The lead-out portion of the output side electrode of the first substrate, the lead-out portion of the input side electrode of the second substrate and the lead-out portion of the hot side electrode of the third substrate are connected to each other, and the lead-out portion of the first to third substrates is connected. In the filter in which the lead-out portions of the ground electrodes are connected to each other, the above-mentioned problems can be solved as follows.

On each of the first and second substrates forming the first and second filter elements, each ground-side electrode is arranged so as to cross between the lead-out portion of each input-side electrode and the lead-out portion of each output-side electrode. A capacitance reducing extension portion extending from is formed separately from the lead-out portion of the ground side electrode in a region other than the excitation portion.

[Advantageous Effects of the Invention] According to the present invention, since the extension extending from the ground electrode is formed across the input and output in a region other than the excitation portion, the filter element is not affected without affecting resonance characteristics. The capacitance due to the parallel electric field between the input and the output can be reduced.

Therefore, it is possible to prevent the bottom level of the filter waveform from rising, and it is possible to obtain a filter having excellent characteristics.

[Embodiment] A preferred embodiment of the present invention will be described with reference to FIGS. 1 to 4. 1 to 4 respectively correspond to FIGS. 6 to 9 showing the above-mentioned related art. Also, in order to clarify the relationship between these corresponding drawings, the same reference numerals will be used for corresponding parts.

With reference to FIG. 1, a lid body 4, a first three-terminal filter element 21, a second three-terminal filter element 22, and a relay capacitor 3 are shown in order from the top.

In addition to the external extraction electrodes 1a to 1d being formed on the lid body 4, the extension portion 12 is provided on the ground electrode 1b so as to be connected to the external electrode b (FIG. 3) serving as a ground terminal. Is formed on the lower surface according to the figure. The extension 12 extends from the ground-side external extraction electrode 1b to between the external extraction electrodes 1a and 1c and between the external extraction electrodes 1c and 1d.

The first filter element 21 has an input-side electrode 2a having a lead-out portion extending to an end portion of the upper surface of the substrate 211.
And the output side electrode 2c is formed. These electrodes 2a, 2c
Is different from that shown in FIG. 6 in the manner of drawing out to the edge of the substrate 211. Note that such differences are not essential differences. On the lower surface of the substrate 211, a ground side electrode 2b having a lead portion extending to the edge portion thereof is formed, and the ground side electrode 2b has a lead portion of the input side electrode 2a and a lead portion of the output side electrode 2c. An extension 13 is formed in a region other than the excitation part so as to cross the space.

The second filter element 22 has an input-side electrode 3c, which has, on the upper surface of the substrate 221, a lead-out portion that extends to the end edge portion thereof.
And the output side electrode 3d is formed. These electrodes 3c, 3d
The drawing-out mode and the arrangement state of are different from those shown in FIG. 6, but such a difference is not essential.

The lower surface of the substrate 221 is formed with a ground side electrode 3b having a lead portion that extends to the edge portion thereof, and extends from the ground side electrode 3b to form a lead portion of the input side electrode 3c and a lead portion of the output side electrode 3d. An extension portion 14 is formed in a region other than the excitation portion so as to cross the gap.

The relay capacitor 3 includes a ground-side electrode 4b and a hot-side electrode 4c formed so as to face each other with the substrate 31 interposed therebetween. The earth side electrode 4b and the hot side electrode 4c are respectively connected to the substrate 31.
Has a drawer portion extending to the edge portion of the. The hot side electrode 4c is different from that shown in FIG. 6 in the drawing mode, but such a difference is not essential. The ground-side electrode 4b is formed with extensions 15 and 16 so as to surround the lead-out portion of the hot-side electrode 4c.

In order to obtain the laminated body 11 shown in FIG. 3, the lid body 4, the first filter element 21, the second filter element 22 and the relay capacitor 3 shown in FIG. 1 are laminated in this order. The state of application of the adhesive 5 at the time of stacking is shown in FIG.

With reference to FIG. 2, the adhesive 5 is used for the filter elements 21 and 22.
Is applied except for the region that inhibits the vibration of the resonator constituted by. Further, in this embodiment, in order to further reduce the problematic capacitance described above, the adhesive 5 is applied so as to be covered with the adhesive 5 except for the region contributing to the connection.

Next, as shown in FIG. 3, external electrodes a to d are formed on the outer peripheral portion of the laminated body 11 by, for example, conductive paint. As shown in FIG. 4 which is a sectional view taken along the line IV-IV in FIG. 3, no electrical connection is made between the external electrode a and the second filter element 22, for example. In the above, the insulating adhesive 5 is used as the second filter element.
It is formed so as to fill up to the edge of 22 mag. Therefore, as shown in FIG. 9 described above, the external electrodes a or d
Etc., the formed capacitance can be further reduced as compared with the case where the elements and the like enter between all the gap portions of each element.

Note that FIG. 4 shows a part of the extension of the ground electrode, that is, the extension 12, 13, 15.

The filter 1 thus obtained achieves the electrical connection as shown in FIG.

Although the invention has been described with reference to a preferred embodiment, the illustrated embodiment can be modified in several respects.

For example, regarding the adhesive 5, in the above-described embodiment, the insulating adhesive 5 is applied so as to fill the region that does not contribute to the connection, and the external electrodes a to d made of conductive paint or the like are positively prevented from entering. However, such an external electrode may be prevented from entering depending on the method of applying the external electrode,
Furthermore, if the formation of unnecessary capacitance between the external electrodes can be ignored, the inclusion of the external electrodes can be recognized as within the scope of the present invention.

Further, the lid body 4 is included as an element constituting the laminated body 11, but such a lid body may be formed by a member different from the laminated body. Therefore, the external electrodes a to d are not covered by the lid body. The electrical connection does not have to extend to the body 4. Therefore, the extension 12 formed in the lid body 4 may not be necessary.

Further, the extension portions 15 and 16 of the earth side electrode 4b formed in the relay capacitor 3 have a function of further reducing the capacitance due to the parallel electric field between the input and the output.
Since the lower surface of the relay capacitor 3 is attached to the circuit board as it is, the presence of the extension may not be necessary depending on the design of the circuit board.

Further, the stacking order of the first filter element 21, the second filter element 22 and the relay capacitor 3 can be arbitrarily changed.

Further, the extraction direction of the electrode formed in each element can be arbitrarily changed according to design choice.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing respective elements constituting a filter according to an embodiment of the present invention. FIG. 2 is a perspective view showing a coating state of the adhesive 5 on the filter elements 21 and 22 and the relay capacitor 3 shown in FIG. FIG. 3 is a perspective view of a filter including the elements shown in FIG. FIG. 4 is an enlarged sectional view taken along line IV-IV in FIG. FIG. 5 is a circuit diagram of the filter of this invention. 6 to 9 are views for explaining the technique related to the present invention, and correspond to FIGS. 1 to 4, respectively. 10 to 12 are views for explaining the defects of the filter shown in FIGS. 6 to 9. In the figure, 1 is a filter, 3 is a relay capacitance, 5 is an adhesive, 11 is a laminated body, 12 to 16 are extensions, 21 is a first three-terminal filter element, 22 is a second three-terminal filter element, 31,21
1,221 is a substrate, 2a and 3c are input side electrodes, 2b, 3b and 4b are earth side electrodes, 2c and 3d are output side electrodes, 4c is a hot side electrode, a to d
Is an external electrode.

Claims (1)

[Scope of utility model registration request] 1. A first and a second three-terminal filter element and a relay capacitor are formed on independent first, second and third substrates, respectively, and the first and second substrates are provided with the The input-side electrode, the output-side electrode, and the ground-side electrode are formed in a state that each has a lead-out portion that extends to an end portion thereof so as to configure the first and second three-terminal filter elements, respectively. The hot side electrode and the ground side electrode are formed on the substrate in such a state that each has a lead-out portion extending to an end portion thereof so as to form the relay capacitor, and the first to third substrates are the first to third substrates. The first and second three-terminal filter elements are laminated in a state where they do not hinder the vibration, and the first and second three-terminal filter elements and the relay capacitor are connected in parallel at the outer peripheral portion of the laminated body. So that the lead-out portion of the output-side electrode of the first substrate, the lead-out portion of the input-side electrode of the second substrate, and the lead-out portion of the hot-side electrode of the third substrate are connected to each other. And the lead-out portions of the ground-side electrodes of the first to third substrates are connected to each other,
In the filter, the first forming the first and second filter elements
In each of the second substrate and the second substrate, a capacitance-reducing extension portion extending from each ground-side electrode is arranged so as to cross the lead-out portion of each input-side electrode and the lead-out portion of each output-side electrode. A filter, characterized in that it is formed separately from the lead-out portion of the ground-side electrode in a region other than.