JPS5899022A - Piezoelectric resonance parts - Google Patents

Abstract

PURPOSE:To obtain piezoelectric resonance parts having excellent spurious characteristics, by forming a straight-line groove along the lengthwise direction for a piezoelectric plate using length oscillation mode and providing electrodes on the entire surface except the groove. CONSTITUTION:A piezoelectric resonance element 1 serving as a component of piezoelectric resonance parts is provided with a groove 3 along the lengthwise direction l on one major surface of a piezoelectric ceramic base 2. The major surface is equally divided into two with this groove toward the lengthwise direction l. Grooves 4, 5 are respectively provided at the position spaced by 1/3 l from the center of the lengthwise direction intersecting the lengthwise direction. An input electrode 6, an output electrode 7 and independent electrodes 8- 11 are provided on he major plane of the base 2 through being sectioned with the grooves 3-5. A full surface electrode 12 is provided on the other major surface of the base 2. Since this piezoelectric resonance element uses the length oscillation mode, the other oscillation modes are hardly produced and have excellent spurious characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to piezoelectric resonant components such as piezoelectric filters.

For example, the center frequency of a piezoelectric filter for an AM receiver is several 100 kHz, for example 450 kHz,
From various viewpoints such as mass productivity, there are the following three types of filter structures. The first is a Yurmann-shaped filter. This filter requires an IFT, and has the following drawbacks: ■ It is difficult to match the IFT and the piezoelectric resonator, the reliability of the [F] coil is low, ■ It is large, and ■ It is monovalent. . The second type is a three-terminal filter that uses the spreading vibration mode of a square plate and the radial vibration mode of a disc.

This filter is: - Relatively large, especially when using a disk for tertiary high frequency, the size is a problem; - In the case of a square plate, spurious vibrations due to the circular vibration mode are strongly excited. There are drawbacks such as. The third type is a filter that utilizes dual modes of longitudinal vibration of a rectangular plate. This filter has drawbacks such as: (1) it is difficult to adjust the two resonators, (2) the structure is complicated, and (2) it is expensive.

The present invention relates to a piezoelectric resonant component having various features and a structure completely different from that described above, and has the following objects.

An object of the present invention is to provide a piezoelectric resonant component with excellent spurious characteristics.

Another object of the invention is to provide a piezoelectric resonant component with excellent impedance characteristics.

Another object of the invention is to capture small piezoelectric resonant components.

Another object of the present invention is to provide a piezoelectric resonant component with small variations in characteristics from product to product.

Another object of the present invention is to provide a piezoelectric resonant component with excellent manufacturing efficiency.

That is, the gist of the present invention is that in a piezoelectric resonant component using the S length vibration mode, a straight I! This piezoelectric resonant component is characterized in that a groove is formed, an electrode is provided on the entire surface except for the groove portion, and an electrode is provided on the other entire surface of the piezoelectric plate.

Embodiments of the invention will be described below with reference to the drawings.

Figure 1 shows a piezoelectric resonant element 1, which is a component of a piezoelectric resonant component.
shows. In the figure, reference numeral 2 denotes a piezoelectric ceramic substrate, and a groove 3 along the length β direction is provided on the surface of the substrate 2, and one main surface is divided into two equal parts in the length β direction by the groove 3. Further, in the direction intersecting the length β direction, 4.5 points are provided at positions 1z3 from the center of the length β direction. Therefore, on one main surface of the substrate 2, an input electrode 6,
The output electrode 7 and the independent electrodes 8 to 11 are divided into three to five units. Furthermore, a full-surface electrode 12 is provided on the other main surface of the substrate 2 . A length vibration mode that expands and contracts in the quality β direction is used, and the dimensions of each part of the substrate 2 are, for example, when the center frequency is 450 kHz, the length ρ is about 4.0511.

Width is 0.6IIIl11 Thickness is 0.31, Depth of groove 3 is 0.15+am1 Width of groove 3 is 0.15a+m, Groove 4.
The depth and width of electrodes 6 and 7 are the same as electrodes 8 or 9.10
Alternatively, it may be any suitable device that is simply electrically isolated from 11. Figure 2 shows the piezoelectric resonant element shown in Figure 1.
1 electrical symbol. In this way, the piezoelectric resonant element 1 shown in FIG. 1 can be used as a filter element using single mode vibration in the longitudinal direction.

A method of manufacturing this piezoelectric resonant element 1 will be explained below. - Rectangular plate-shaped ceramic sintered body 101 with sides on the order of several cm
Prepare the surface by wrapping. Electrodes are provided on the opposing main surfaces. This electrode is an electrode for polarization processing, and also serves as electrodes 6 to 12. As shown in FIG. 3, the ceramic sintered body 101 imparted with piezoelectricity by polarization treatment is assembled in large numbers to increase manufacturing efficiency, and a piezoelectric resonant element 1 of a predetermined size is formed using a dicing saw 13. At the same time as cutting out, form 3-5. That is, according to the dicing saw 13, the cutting accuracy is as high as 12 μm, so it is possible to cut out the piezoelectric resonant element 1 having an accurate length β, and steps such as frequency selection and frequency adjustment are omitted compared to conventional manufacturing methods. can. For example, when it was desired to obtain one with a center frequency of 455 kl-1z, the variation in the center frequency was kept within a maximum of 1.2 kHz. Further, by forming the grooves 3 to 5, the input electrode 6 and the output electrode 7 having the necessary external dimensions can be obtained by reusing the polarized electrodes.

In this regard, in the conventional manufacturing method, there is a step of printing and etching a pattern of the vibrating electrode on the polarized electrode with resist ink after polarization, and the present invention is clearly simpler. The groove 4.5 reduces the length of the input electrode 6 and the output electrode 7 in the β direction by 2/3, and has the effect of suppressing the third harmonic. Therefore, electrodes 8 to 11 are idle. Dicing saw 1
3, the blade moves in the direction of the arrow in Figure 4 while rotating at high speed, and although it cannot cut deeply, it is sufficiently useful for the thickness of the piezoelectric plate targeted by the present invention.

Further, by moving the dicing saw 13 in the eight directions indicated by the arrows in FIG. 4 and setting appropriate values, it is possible to perform cutting and to form grooves of arbitrary depth. Therefore, one method for cutting or forming grooves is to temporarily fix a plurality of piezoelectric elements 1 together and form grooves or cutting them in the horizontal direction in the figure, as shown in FIG. It is efficient to form and cut the grooves in the vertical direction of the figure afterwards.

5 to 7 show the base 14, and the base 14 includes an input/output terminal plate 15, a conductive rubber sheet 16, which will be described later.
The piezoelectric resonant element 1 and the ground terminal plate 17 are mounted with their mutual positional relationship regulated. As will be described later, when inserting these internal elements into the case 18, the ground terminal plate 17 is designed to have an appropriate contact pressure between the piezoelectric resonant elements 1 by adjusting the shape and dimensions of the ground terminal plate 17 relative to the inner wall surface of the case 18. I'm trying to be able to do that. The base 14 has the following structure. A wall 20.20 is provided integrally with the portion 19 from the long side of the rectangular plate-shaped portion 190, and a wall 20.20 is provided integrally with the portion 19 from both sides.
1 is integrated. Also, these walls 20, 20, 2
Inside the area surrounded by 1.21, there is a pair of columnar bodies 22, 22.
, a set of four columnar bodies 23, 23.2:323 is part 1
9 and are provided separately. Then, the input/output terminal board 15 is attached as symbolically shown by the dashed line in the figure.

As shown more clearly in FIG. 8, the input/output terminal board 15 is
It has an input terminal portion 24 and an output terminal portion 25. In FIG. 5, the input terminal portion 24 is located between the right end of the lower W120 and the lower end of the right low wall 21, between the right columnar body 22 and the right low wall 21, and between the upper I! 20 and columnar body 2 on the upper right
3 and between the columnar body 23 on the left side and the columnar body on the right side. In FIG. 5, the output terminal portion 25 is located between the lower end of the left low wall 21 and the left end of the lower wall 20, between the lower left columnar body 23 and the lower wall 20, and between the lower left columnar body 21 and the left end of the lower wall 20. 23 and the columnar body 23 at the lower right. As is clear from the figure, there are tabers at many places to facilitate fitting.

Next, in FIG. 5, four columnar bodies 23, 23°2
3. Place the conductive rubber sheet 16 as shown in the ninth song in the area surrounded by 23. Further, the piezoelectric resonant element 1 is placed on the rubber sheet 16 with the third to fifth sides facing down.

The piezoelectric resonant element 1 is supported by a pair of columnar bodies 22 and four columnar bodies 23 of the base 14 at a distance of about 1 m. Then, the tips 26 and 27 of the input terminal portion 24 and output terminal portion 25 of the input/output terminal plate 15 come into contact with the input electrode 6 and output electrode 7 of the piezoelectric resonant element 1 via the conductive rubber sheet 16. It is. This rubber sheet 16 is called an anisotropically conductive rubber sheet, and is made of, for example, a silicone rubber sheet with graphite fibers or thin metal wires embedded in the thickness direction. exhibits conductivity,
It exhibits insulating properties in the lateral direction. Therefore, the input electrode 6 and the output electrode 7 of the piezoelectric resonant element 1 can be connected to each other without mutual short-circuiting.
It comes into contact with the tip 26 of the input terminal portion 24 and the tip 27 of the output terminal portion 25 via the anisotropically conductive rubber sheet 16 .

The ground terminal plate is shown more clearly in Figures 10 to 12. The ground terminal plate 17 has a lead portion 28 integrally formed with a substantially H-shaped tip 29, and a contact protrusion 291 at the center.
have. As shown in FIGS. 10 and 12, the distal end portion 29 has an arcuate shape and is provided with necessary elastic force. Further, a portion of the lead portion 28 accommodated in the case 18 has a portion 30 bent into a substantially crank shape. Depending on the degree of bending, the tip portion 29 and the lead portion 28 are not parallel, but their extension lines intersect (for example, the intersecting angle θ-io' is set to >).

The shape of the case 18 is shown more clearly in FIGS. 13-15. As shown in the figure, Taber 3 is used to provide directionality.
1, an opening 3 is formed on the bottom surface of the approximately box-shaped molded body having
It has 2. The inner space has a convex cross-sectional shape expanding toward the back so as to resemble the outer shape of the base 14. The edges of the opening 32 are tapered to facilitate insertion of internal components.
It has 4°.

FIG. 16 shows the base 1 in relation to this invention.
4, the input/output terminal board 15, the rubber sheet 16, and the piezoelectric resonant element 1 are stacked, and the lead frame of the ground terminal board 17 is stacked on the lead frame connection part of the input/output terminal board 15, and the ground terminal board 17 is stacked. This figure shows the state of the piezoelectric resonator 1 before it is inserted into the case 18, with the contact protrusion 291 pressed into contact with the central position of the entire surface electrode 12 of the piezoelectric resonator 1. As is clear from the figure, when looking at the assembled internal elements to be inserted into Kenneth 18 from the side, the ground terminal plate 1
The molded shape of 7 makes it look like a wedge. When the internal element is inserted into the case 18 in this state, the end portion 29 and the bent portion 30 of the ground terminal plate 17 are pressed against the inner wall surface of the case 18, and due to the reaction force, the ground terminal plate 17 is Appropriate pressure is applied to the piezoelectric resonant element 1, the conductive rubber sheet 16, and the input/output terminal plate 15 between the base 14, and after the insertion is completed, the ground terminal plate 17 is shaped like an arch as described above. Since the contact pressure necessary to hold the piezoelectric resonant element 1 is obtained by the elastic force caused by this and the elastic force of the rubber sheet 16, each component is accommodated in the case 18 without any displacement of the components.

Note that FIGS. 17 to 19 show the state of the finished product. The lead portion 28 of the ground terminal plate 11 fits into a recess 201 located in the middle of the lower wall 20 of the base 14 in FIG.

The opening 32 of the case 18 is made of a general sealing resin 35.
sealed by. At this time, since the lower wall 20 of the base 14 in FIG. 5 closes most of the opening 32, sealing is ensured and excess resin does not go around inside. Generally speaking, it goes without saying that the smaller the size of the opening, the more securely the opening can be sealed. However, the smaller the opening, the more difficult it becomes to insert the inner SS product through the opening of the case. As described above, in the present invention, the entire internal parts are assembled into a wedge shape before being inserted, so even if the opening is small, insertion becomes easy, and assembly by machine is possible. Therefore, automatic assembly is possible. It is possible to seal it.

FIG. 20 shows a selection characteristic curve of a filter using one piezoelectric resonant element according to the present invention. FIG. 21 shows the selection characteristic curve of a device in which one IFT is further connected in cascade.

FIG. 22 shows a selection characteristic curve of two piezoelectric resonant elements according to the present invention directly connected in cascade without using a coupling capacitor. FIG. 23 now shows the a-sexual curve. FIG. 24 shows spurious characteristics of a filter in which two piezoelectric resonant elements and rFT- pieces are connected in cascade according to the present invention.

As is clear from the above description, the present invention provides a piezoelectric resonant component using a length vibration mode, in which a straight groove is formed along the length direction on one surface of a piezoelectric plate, and this groove portion is Since this piezoelectric resonant component is characterized in that electrodes are provided on all sides of the piezoelectric plate, and electrodes are provided on the other side of the piezoelectric plate, it has the following effects.

According to this invention, since the mode of use is the length i movement mode, miniaturization is possible. Spreading vibration of conventional square plate t-
When compared to a three-terminal type fill using a board, the volume ratio is reduced to 1/4 with one element.

In the case of two elements, '/4 +'/4-' /a (A) The effect becomes more pronounced as the number of elements increases.

According to this invention, even if the number of elements is increased, the elements are very small and inexpensive, and combined with the fact that the case can be shared, it is possible to upgrade from 1 element to 2 elements to 3 elements. This is possible without increasing costs or changing external dimensions.

According to this invention, since the length vibration mode is used, other vibration modes are difficult to be excited, and therefore, it has excellent noisy characteristics in the long wave band and medium wave band (~2.5 Mt (Z)). Therefore, the piezoelectric vibrating component of the present invention is suitable for, for example, a filter for an intermediate frequency circuit of an AM radio.

Since the piezoelectric vibrating component according to the present invention has a )X impedance, it is less susceptible to fluctuations in external circuit constants.

Since the piezoelectric vibration AL1 component according to the present invention uses the length vibration mode, the impedance remains constant at 12 even if the number of elements changes or the center frequency changes slightly. There is no need to change the specifications.

According to this invention, the coupling does not become too dense even if the elements are not connected by a coupling capacitor, so the coupling capacitor can be omitted, resulting in cost reduction and miniaturization.

According to this invention, compared to those using other modes, the number of elements removed from the power supply board is 6 tons, which saves resources and makes it cheaper.

According to this invention, due to the presence of the groove, the stray capacity between the input and output is small, so compared to the conventional three-terminal filter using the spreading vibration mode of a square plate, the high-frequency side , the selection characteristic curve on the low frequency side has good symmetry.

[Brief explanation of drawings]

Fig. 1 is a perspective view of a piezoelectric resonant element, Fig. 2 is an electrical symbol diagram of the one shown in Fig. 1, Fig. 3 is a front view of a plurality of ceramic sintered bodies, and Fig. 4 explains the present invention. Figure 5 is a front view of the base, Figure 6 is a cutaway view of the base, Figure 7 is a cutaway view of the base, and Figure 8 is a cutaway view of the base. A front view of the terminal board, FIG. 9 is a front view of the rubber sheet, and FIG. 10 is a top view of the ground terminal board.
Fig. 11 is a front view of the case, Fig. 12 is a side view of the case, Fig. 13 is a side view of the case, and Fig. 14 is a front view of the case.
FIG. 15 is a bottom view of the same, FIG. 16 is an exploded sectional view of the piezoelectric resonant component according to the present invention, and FIG. 17 is a front view of the same.
Fig. 18 is a sectional view of the same, Fig. 19 is a broken view seen from the bottom, Figs. 20 to 23 are selection characteristic curve diagrams, and Fig. 24
The figure is a spurious characteristic curve diagram. DESCRIPTION OF SYMBOLS 1...Piezoelectric resonant element, 2...Piezoelectric ceramic substrate, 3-5...Groove, 6...Input electrode, 7... Output electrode, 8 to 11...
・Independent electrode, 12...Full surface electrode, 13...
・・Dancing Saw, 14・・・・Base, 15・
...Input/output terminal board, 16...Conductive rubber sheet, 17...Earth terminal board, 18...
...Case°, 19...Rectangular plate-shaped part, 2
0...Wall, 21...Low wall, 22...
... Column, 23... Column, 24...
...Input terminal part, 25...Output terminal part, 2
6...Tip, 27...Tip, 28...
...Lead part, 29...Tip end part, 30
・・・・・・Folding part, 31・・・・・・Teba,
32...Opening, 33...Inner space, 3
4...Taper, 35...Sealing resin, 101...Ceramic sintered body, 291...
...Contact protrusion. Patent application person Murata Manufacturing Co., Ltd. Figure 5! Figure 3 Figure 130 // 萬/4 u Figure 15 Figure 1 Figure 1 tq Figure

Claims (1)

[Claims] In a piezoelectric resonant component using length vibration mode, a linear groove along the length is formed on one side of the piezoelectric plate, electrodes are provided on the entire surface except for this groove, and the other side of the piezoelectric plate is provided with electrodes. A piezoelectric resonant component characterized in that electrodes are provided on the entire surface of the component.