JPS6259929B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a support structure for a piezoelectric element used in a piezoelectric resonator, a piezoelectric wave device, etc.

Conventionally, the support structure for this type of piezoelectric element is as follows:
Publication of Utility Model Publication No. 44-24888 (name of the invention: ``Small porcelain filter''), Japanese Patent Application Laid-open No. 110547 (Sho 52-110547) (title of invention: ``Small porcelain filter''), Publication of Utility Model Publication No. 41-24095 (name of the invention: ``Small porcelain filter'') Various types have been proposed in Japanese Utility Model Publication No. 43-24122 (named "Piezoelectric Resonator Support Device") and others.

In all of the devices disclosed in these publications, tongues or protrusions are provided on a terminal plate made of an elastic metal plate such as phosphorescent steel, and the spring force of these tongues or protrusions creates a space between the terminal plates. It has a structure that supports a piezoelectric element.

For example, in the "small porcelain filter" proposed in the above-mentioned Japanese Utility Model Publication No. 44-24888,
As shown in FIG. 2, on the split electrode side of the split electrode type three-terminal porcelain piezoelectric element 1 as shown in FIGS. A U-shaped output terminal metal plate 8 with a tongue piece 9 provided thereon is stacked with an insulating plate 7 whose center portion is cut out interposed therebetween, and the tongue piece 6, the input electrode 2 (see FIG. 1a), and the tongue piece are stacked together. 9 and the output electrode 3 respectively, and on the whole surface electrode 4 side, a common terminal metal plate 10 having a tongue piece 11 in the center is arranged, and the tongue piece 11 and the whole surface electrode 4
The inner case 14 and the outer case 13 hold the porcelain piezoelectric element 1 in contact with each other, and the structure is selected to balance the pressure of each metal plate against the porcelain piezoelectric element 1. have.

However, when the support structure of the piezoelectric element is constructed as described above, a terminal board made of an expensive material such as phosphor bronze is required, and the spring force of the tongue piece or protrusion provided on the terminal board is limited within a certain range. It is difficult to regulate the value so that the piezoelectric element has a certain value, and there is a drawback that the characteristics vary depending on the piezoelectric element.

A type in which lead wires are directly soldered to the electrodes of the piezoelectric element has also been proposed, but this has the disadvantage that the lead wires cause parasitic vibration.

The present invention has been made in order to eliminate the above-mentioned drawbacks in the conventional support structure for a piezoelectric element, and is to provide a protruding contact point on a conductive portion reaching the outside on at least a part of the inner wall of an internal space that accommodates a piezoelectric element. A circuit board having an electrode film extending to other electrical parts and capable of fixing the case body with the piezoelectric element in between is provided. By interposing a contact member made of a resilient elastic material (excluding metal spring material) and using its elasticity to sandwich the piezoelectric element between the contact member and the protruding contact, the elasticity of the contact member can be reduced. The purpose of the present invention is to provide a support structure for a piezoelectric element that takes advantage of the small variation to reduce the variation in characteristics, while also attaching the piezoelectric element directly to a circuit board to reduce the number of parts and assembly man-hours. There is.

Hereinafter, an embodiment in which the present invention is applied to a piezoelectric wave device will be described.

3 and 4, reference numeral 21 denotes an electrode having exactly the same configuration as that shown in FIG. 1, which utilizes contour vibration of a piezoelectric ceramic plate 22 made of lead zirconate titanate or the like fired into a rectangular shape. This is a split type three-terminal porcelain piezoelectric element. A ring electrode 23 having a constant width is formed on the peripheral edge of one surface of the piezoelectric ceramic plate 22 of the electrode split type three-terminal porcelain piezoelectric element 21, and a square dot electrode 24 is formed concentrically with the ring electrode 23. These ring electrodes 2
3 and the dot electrode 24 are separated by a gap g, while an entire surface electrode 25 is formed on the entire other surface of the piezoelectric ceramic plate 22.

On the other hand, 26 is a case body that accommodates the electrode split type three-terminal porcelain piezoelectric element 21, and the case body 26 is a case body in which a thin metal plate such as brass is inserted from the center of each side of a rectangular portion. small caulking nail 2
7,..., 27 are punched out into a protruding shape, and then press work is performed to form an internal space 28 in which the electrode split type three-terminal porcelain piezoelectric element 21 is accommodated.
The above-mentioned square-shaped part is drawn into a truncated quadrangular pyramid shape so as to form.

A protruding contact 30 is formed on the bottom 29 of the case body 26 by extruding the center of the bottom 29 toward the internal space 28 in a hemispherical shape during the above-described press working.

Reference numeral 31 designates the split electrode type three-terminal porcelain piezoelectric element 21 as shown in FIG. This is a circuit board such as a printed circuit board into which the element 21 is incorporated.

The circuit board 31 is a so-called double-sided printed circuit board, and has three round holes 35, 3 for attaching rubber contacts 32, 33, and 34, which will be described next.
6 and 37, and the case body 26
Four square holes 38, 39, 40 and 41 are provided into which the caulking claws 27, . . . , 27 are inserted.

Further, on the upper surface of the circuit board 31, there are electrode films 4 extending from two of the three round holes 35, 36 and 37 to other electrical components.
2. Form an electrode film 43 extending from the remaining round hole 37 to other electrical components. On the bottom surface of the circuit board 31, there are 4
Of the square holes 38, 39, 40, and 41, an electrode film 44 extending from the square hole 38 to other electrical components is formed. On the lead-out portions of the electrodes 42 and 43, resist ink or the like (not shown) is applied.
After forming an insulating film, as described later, the circuit board 3
When the case body 26 is attached to the case body 1, electrical conduction between the electrode film 42 or 43 and the case body 26 is prevented. Of course, a notch may be provided at a corresponding location in the case body so that the case body 26 does not come into contact with the electrode films 42 and 43.

Next, the rubber contacts 32, 33, and 34 are made by molding isotropically conductive rubber into a small screw shape, as an example.
3 and 34, the portion corresponding to the head of the screw is used as a contact portion, and the portion corresponding to the screw portion is used as a fitting portion into the round holes 35, 36, and 37. Note that the rubber contacts 32, 33, and 34 are not limited to isotropically conductive rubber, but may be pressure-sensitive conductive or anisotropically conductive rubber.

The piezoelectric wave device in this embodiment is made up of the components having the above-mentioned configuration. These rubber contacts 32, 33 and 34 are connected to the circuit board 31.
After installing the electrode split type three-terminal ceramic element 21
are stacked on the circuit board 31 from the ring electrode 23 and dot electrode 24 sides, the case body 26 is placed over it, and the outside of the case body 26 is coated with silicone rubber (not shown) or the like to seal the inside. ing.

After that, the electrode split type three-terminal ceramic element 21 is
Due to the elasticity of the rubber contacts 32, 33, and 34, the caulking claws 27,
..., 27 to the square holes 38, 39, 40 of the circuit board 31
and 41 and bend its tip, and the tip of the caulking pawl 27 fitted into the square hole 38 is fixed to the electrode film 44 with solder 47, and the remaining caulking pawl 27 is attached to the circuit board 31 as necessary. It is fixed to the electrode films 48, .

Furthermore, among the three rubber contacts 32, 33 and 34 mentioned above, two rubber contacts 32, 33 are located approximately at the center of the pair of opposing sides of the ring electrode 24 of the split electrode type three-terminal ceramic element 21. Round holes 35, 36 and 37 are provided in the circuit board 31 so that one rubber contact 34 comes into contact with the approximate center of the dot electrode 24, respectively, and the ring electrode 23 and the dot electrode 24 are connected to the electrode films 42 and 43, respectively. It is made to conduct electricity.

If the piezoelectric wave device has the above configuration, electrode split type 3
Since the terminal ceramic element 21 can be directly attached to the circuit board 31 via the rubber contacts 32, 33 and 34, it is possible to attach the terminal ceramic element 21 directly to the circuit board 31 via the rubber contacts 32, 33 and 34.
Not only can a special terminal board and special case for supporting the terminal ceramic piezoelectric element 21 be omitted, but also the piezoelectric wave device can be assembled in the process of attaching other electrical components to the circuit board.

On the other hand, the supporting force of the electrode split type three-terminal porcelain piezoelectric element 21 was varied from 10 grams to 200 grams,
When the insertion losses of the piezoelectric wave devices shown in FIGS. 2 and 3 are measured, it is found that the piezoelectric wave device shown in FIG. In contrast, the insertion loss of the piezoelectric transducer shown in Figure 3 is approximately constant at 2.6 dB, as shown by the dotted line in Figure 5, even when the supporting force changes. It can be seen that the insertion loss hardly changes.

In addition, in the same way as above, when the supporting force of the electrode split type three-terminal porcelain piezoelectric element 21 is changed from 10 grams to 200 grams and the change in the center frequency of the piezoelectric wave device is measured, the piezoelectric wave device shown in FIG. , as shown by the solid line in Figure 6, changes from approximately 455.2KHz to 455.9KHz, whereas in the piezoelectric wave generator shown in Figure 3,
As shown by the dotted line, it can be seen that there is almost no change from the approximately constant value of 455.0 KHz.

In the conventional example shown in FIG. 2, the tongue piece 6 of the input terminal metal plate 5 is brought into contact with the central part (also the node of vibration) of the input electrode 2, and the output terminal metal plate 8 The tongue piece 9 must be brought into contact with the center portion of the pair of opposing sides of the output electrode 3 (which is also the node of vibration). Therefore, the tongue 6, the two tongues 9
are lined up in a straight line, and since the piezoelectric element 1 is held only by these tongues 6 and 9, it tilts and unnecessarily contacts the output terminal metal plate 8 and the common terminal metal plate 10, causing various problems. There is a risk that harmful effects may occur, and measures must be taken to prevent this. However, the rubber contacts 35,3
Using rubber contacts 35 and 37, attach the rubber contacts 35 and 37 to the vertices of an isosceles triangle whose base is the line connecting the rubber contacts 35 and 36.
Piezoelectric element 1 is well balanced when 36 and 37 are arranged.
will be held and will not tilt. Therefore, there is no need to take measures to prevent tilting, and there is no characteristic deterioration.

In the embodiment shown in FIG.
5, 36 and 37 to be attached to the circuit board 31, as shown in FIG.
A silicone rubber film 50 having a shape and dimensions slightly larger than the opening end surface of the case body 26 is formed, and three rubber contacts 32 , 33 and 3 are formed on the circuit board 31 by protruding from the silicone rubber film 50 .
4 may be formed.

By doing this, the silicone rubber film 50 can be formed on the circuit board 31 and the rubber contacts 32 and 3 can be formed at the same time.
3 and 34 can be formed on the circuit board 31, while the opening periphery of the case body 26 comes into pressure contact with the silicone rubber film 50 and the inside is sealed, so there is no need for sealing measures for the case body 26. . Further, in this case, an insulating film made of resist ink as shown in FIG. 4 becomes unnecessary.

In addition, in order to apply the present invention to a piezoelectric resonator, a two-terminal ceramic piezoelectric element (not shown) is used in place of the electrode split type three-terminal ceramic piezoelectric element 21 in the above embodiment, and the two-terminal ceramic piezoelectric The element may be supported by one rubber contact (not shown) attached to the circuit board 31 of the protruding contact 30 of the case body 26.

Although the basic embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the electrode split type three-terminal porcelain piezoelectric element 21 or the two-terminal porcelain piezoelectric element A disk-shaped piezoelectric ceramic plate 2 as shown in FIGS. 8a and 8b.
2) that utilizes radial vibration, and electrode split type 3.
The terminal ceramic piezoelectric element 21 may be one that utilizes multi-mode vibration of a piezoelectric ceramic formed in an H shape, as shown in FIG. 8c.

On the other hand, although the rubber contacts 32, 33, 34, etc. are not specifically shown, they may be replaced with a single anisotropically conductive rubber sheet.
is a material in which a conductive film is formed on an insulating resin, or
It may also be made of insulating resin mixed with conductive fibers.

Furthermore, as a circuit board, a so-called single-sided printed through-hole board may be used, in which the electrode films 42 and 43 are also provided on the lower surface side as seen from the figure, and the holes 35 to 41 are plated with through holes. good.

As is clear from the above detailed explanation, the present invention is applicable to protruding contacts such as rubber contacts on a circuit board, in which a piezoelectric element is provided on a case body using the elasticity of an elastic material other than a metal spring. Since the piezoelectric element is supported between the elastic material and the elastic material, the piezoelectric element is supported by the stable elasticity of the elastic material. becomes very small, while
Since the elastic material is attached to the circuit board to support the piezoelectric element, piezoelectric wave devices and piezoelectric resonators can be formed directly on the circuit board, and the assembly of these piezoelectric wave devices and piezoelectric resonators is easy. This can be done simultaneously with the attachment of other electrical components to the circuit board.
Furthermore, according to the present invention, there is no need for a terminal plate made of expensive metal or a special housing case to support the piezoelectric element, as in the past, so the number of parts for the piezoelectric wave device or piezoelectric resonator is reduced. , the cost can be drastically reduced.

[Brief explanation of the drawing]

Figures 1a and b are perspective views of a split-electrode type three-terminal porcelain piezoelectric element as seen from one side and the other side, respectively; Figure 2 is an exploded perspective view of a conventional piezoelectric wave device;
FIG. 3 is a vertical cross-sectional view of a piezoelectric wave device to which the present invention is applied, FIG. 4 is an exploded perspective view of FIG. 3, and FIG.
Figure 6 shows the insertion loss characteristics of the piezoelectric transducer shown in Fig. 2 and the piezoelectric transducer shown in Fig. 3 with respect to their supporting force, and Fig. 6 shows the center frequency fluctuation characteristics of the piezoelectric transducer shown in Fig. 7 are longitudinal sectional views of a modification of the embodiment shown in FIG. 3, and FIGS. 8a, b, and c are perspective views of piezoelectric elements having various shapes, respectively. 21... Electrode split type 3-terminal porcelain piezoelectric element, 22...
Piezoelectric ceramic plate, 23... Ring electrode, 24... Dot electrode, 25... Whole surface electrode, 26... Case body, 27...
Caulking claw, 28...Inner space, 30...Protruding contact,
31... Circuit board, 32, 33, 34... Rubber contact,
42, 43, 44...electrode film.

Claims (1)

[Claims] 1. A piezoelectric element having at least one electrode formed on the front and back sides of a piezoelectric substrate, a case body having an internal space for accommodating the piezoelectric element and having a conductive part reaching the outside on at least a part of its inner wall, and other electrical A circuit board is provided which has an electrode film extending to the component and which can fix the case body with the piezoelectric element in between, and a protruding contact formed by protruding a part of the conductive part of the case body is connected to the piezoelectric element. While the electrode on the front side of the element conducts electricity, a contact member made of a non-metal spring conductive elastic material is interposed between the circuit board and the piezoelectric element, and the electrode on the back side of the piezoelectric element and the above electrode on the circuit board are interposed between the circuit board and the piezoelectric element. 1. A support structure for a piezoelectric element, characterized in that the piezoelectric element is directly mounted on a circuit board together with the other components mentioned above by making the elements conductive with each other.