JPS6214512A - Filter - Google Patents

Abstract

PURPOSE:To make a filter small in size by connecting two 3-terminal filter elements and a repeating capacity in parallel and forming these elements and capacity on substrates independent of one another and laminating substrates without hindering oscillation of filter elements. CONSTITUTION:A filter 1 consists of a plane plate-shaped cover body 4, plane plate-shaped substrates 211 and 221 where the first and the second 3-terminal filter elements 21 and 22 are formed, and a substrate 31 where a repeating capacity 3 is formed. External connection electrodes 1a-1d, 2a-2d,-4a-4d formed in four corners of the cover body 4 and substrates 211, 221, and 31, and filter elements 21 and 22 and the repeating capacity 3 are connected in parallel to external connection electrodes (a), (b), and (c) of the filter 1. The cover 4 and substrates 211, 221, and 31 are laminated without hindering oscillation of the filter 1, thereby making the filter of an IC to make it small in size.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a filter, and particularly to a filter in which two three-terminal filter elements and a relay capacitor are connected in parallel.

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, making use of vibration based on the energy trapping phenomenon. Three-terminal resonators are used as filters in various electronic circuits. For example, in a filter used in a TV audio intermediate frequency circuit, in order to obtain desired electrical characteristics, as shown in FIG. 22 are connected in parallel, and a relay capacitor 3 is connected in parallel between them to further improve the characteristics.

Such a filter 1 is usually constructed such that three terminal filter elements 21, 22 and eight terminals 3 are arranged side by side on one dielectric substrate.

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However, as described above, each filter element utilizes vibrations based on the energy trapping phenomenon, so if the distance between each element is small, the vibrations of one element will affect the other element. Therefore, in order to avoid mutual interference between the parts and to prevent the characteristics of each element from being adversely affected, the distance between the parts must be increased.

For this reason, the dimensions of the piezoelectric substrate of such filters are increased, but as a result, the dimensions of the filter become larger, which increases the area required for mounting the filter and limits the circuit design. The present invention, which has the problem of not being able to be miniaturized, was made in view of the current situation, and its purpose is to connect two 3-terminal filter elements and a relay capacitor in parallel. It is an object of the present invention to provide a connected filter that can be miniaturized without causing mutual interference between parts.

. - In order to achieve the above object, in the present invention, two 3
A filter in which a terminal filter element and a relay capacitance are connected in parallel, wherein both the elements and the capacitance are formed on independent substrates, and each substrate does not inhibit vibration of both filter elements. It is characterized by being integrally laminated in a state in which a lid is provided on top of the laminated body.

In the present invention, the substrate material is not particularly limited as long as it can be made of ceramics, quartz, etc., and has the desired electrical properties and exhibits the mechanical properties necessary for lamination.

Practical Example 1 An embodiment of the filter of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an exploded perspective view showing one embodiment of the present invention, which constitutes the filter 1 of the circuit shown in FIG. 3 described above.

In the figure, 4 is a lid, 21 is a first three-terminal filter element, 22 is a second three-terminal filter element, and 3 is a relay capacitor. Each of these members is formed into a flat plate shape with the same dimensions in plan view, and externally extracted electrodes 1a to 1d12a to 2d13a to 3 are provided at each of the four corners.
cl 4 a to 4 d are provided by a known method such as screen printing. Each electrode includes not only an electrode part on the top surface of the flat plate, but also an electrode part of the same shape formed on the bottom surface.
and an electrode portion formed on the side surface of the flat plate between both electrode portions.

The first filter element 21 is formed on a polarized ceramic substrate 211 such as PZT.

As mentioned above, the external electrodes 2a are provided at the four corners of the substrate.
~2d is provided. The electrode portions of the externally drawn electrodes 2a and 2c on the upper surface side of the substrate are divided into divided electrode portions 2e and 2f formed at the center of the upper surface of the substrate and extraction electrode portions 2g and 2, respectively.
connected through h. The electrode portion of the externally drawn electrode 2b on the lower surface side of the substrate is connected to the common electrode portion 21 formed at the center of the lower surface of the substrate through the extracted electrode portion 2j. Since the common electrode section 21 is formed so as to face the divided electrode section 2e12f as shown in the figure, a thickness oscillation section is generated near the common electrode section 21 due to the energy trapping phenomenon.

The second filter element 22 is also the same as the first filter element 21.
It is configured in the same way. However, in the case of the second filter element 22, as shown in FIG. 1, external extraction electrodes 3c and 3d are connected to the upper surface of the substrate through the divided electrode part 3ei3f and extraction electrode parts 3g and 3h. 31 is a common electrode section, and 3j is an extraction electrode section.

The relay capacitor 3 is provided on a dielectric substrate 31 that is not polarized. The electrode portion of the external connection electrode 4C on the upper surface side of the substrate is the capacitor electrode portion 4e formed at the center of the upper surface of the substrate.
and is connected through the extraction electrode section 4f. The electrode portion of the externally drawn electrode 4b on the lower surface side of the substrate is connected to a capacitor electrode portion 4g formed at the center of the lower surface of the substrate through an extraction electrode portion 4h. Both capacitor electrode portions 4es4g are opposed to each other with the dielectric substrate 31 in between, so they function as a capacitor.

The lid body 4 is formed on an insulating substrate 41, and as described above, externally extending electrodes 1a to 1d are provided at the corners of the substrate 41.

Each resonator is provided on the lower surface of the lid 4 or the upper surface of the first filter element 21, the lower surface of the filter element 21 or the upper surface of the second filter element 22, and the lower surface of the filter element 22 or the upper surface of the relay capacitor 3. 21, 22, an insulating adhesive 5 is applied around the vibrating part A as shown in FIG. 4, and the lid body 4, the first filter element 21,
The second filter element 22 and the relay capacitor 3 are stacked in this order,
They are bonded to each other with an adhesive 5 to form an integral structure (see FIG. 2). Incidentally, FIG. 4 shows, as an example, how the adhesive 5 is applied to the upper surface of the first filter element 21. As shown in FIG. Due to this lamination, the corresponding external electrodes at the four corners of each part are not connected, so the electrodes are connected by sputtering or the like. That is, 1a-2a-3a-4a
11b-2b-3b-4bs lc-2cm3cm4c
The electrodes 1 and 1d-2d-3d-4d are connected to form electrodes a-d on the outer surface of the filter 1. A perspective view of the filter 1 constructed in this manner is shown in FIG.

Thus, the filter 1 has a circuit as shown in FIG. In FIG. 3, reference numerals for each electrode of the filter 1 used in FIGS. 1 and 2 are attached near each electrode.

In the filter of this embodiment, since a space is formed around the vibrating part A of the first and second three-terminal filter elements 21 and 22, the vibrating part can freely vibrate.
Further, since each filter element and relay capacitor are independent due to the laminated structure, there is no mutual interference between the respective parts. Since the upper surface of the filter is the lid 4 and the lower surface is the relay capacitor 3, both filter elements 21, 22 are protected by them, further ensuring free vibration.

In this embodiment, the capacitor electrode portion 4g is exposed on the bottom surface of the filter, but since the external electrode is normally grounded, the filter 1 is placed with the relay capacitor 3 side facing down. It can be attached to the circuit board as is.

Optical IE and Decor - As explained above, according to the present invention, a filter is provided that can be miniaturized without causing mutual interference between the various parts. Furthermore, according to the present invention, the type and thickness of the substrate can be selected to suit the characteristics required for each part, so it is possible to adjust the passband width, which makes it possible to reduce the loss of the filter. It also has the effect of making it easier.

[Brief explanation of drawings]

Fig. 1 is an exploded perspective view of one embodiment of the filter of the present invention;
The figure is a perspective view thereof, FIG. 3 is a circuit diagram of the filter, and FIG. 4 is a diagram illustrating the state of application of adhesive. 1... Filter, 3... Relay capacity, 4... Lid body,
21.22...3-terminal filter element. Patent applicant Murata Manufacturing Co., Ltd. Figure 1 Figure 2 Figure 3? Figure 4

Claims (1)

[Claims] A filter in which two 3-terminal filter elements and a relay capacitor are connected in parallel, and the two elements and the capacitor are formed on independent substrates, and each substrate is connected to both the filter elements. A filter characterized in that the filters are integrally laminated in a state that does not inhibit vibration, and a lid is provided on the laminated body.