JP2002100954A - Piezoelectric substrate, piezoelectric vibrator and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric substrate, a piezoelectric vibrator and a method for manufacturing the same, capable of preventing a characteristic deterioration, without having a displacing distribution center deviate from a central position of the substrate, even when a convex type piezoelectric substrate is supported in a cantilever manner. SOLUTION: The convex type piezoelectric substrate comprises tapered surfaces 24 and 25 in a predetermined width from counterposed two edges 22 and 23 of a rectangular plate-like piezoelectric substrate 21 toward the center of the substrate. In this case, the width (a) of the tapered surface 24 provided at the one edge side of the piezoelectric substrate is set larger than the width (b) of the tapered surface 25, provided at the other edge side of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a convex type piezoelectric substrate, a convex type piezoelectric vibrator, and a method of manufacturing the same. The present invention relates to a convex-type piezoelectric substrate, a convex-type piezoelectric vibrator, and a method of manufacturing the same, which can effectively prevent displacement of a displacement distribution.

[0002]

2. Description of the Related Art Conventionally, a quartz vibrating element in which opposing excitation electrodes are attached to two main surfaces of a quartz substrate formed in a required shape such as a rectangular flat plate shape or a rectangular convex shape is used.
A quartz resonator that is excited by a thickness-shear mode vibration to obtain a resonance frequency inversely proportional to the thickness of the quartz substrate,
It is used as a frequency signal source for various devices. In particular,
Quartz resonators using AT-cut quartz substrates have extremely stable temperature characteristics over a wide temperature range, and also have excellent aging characteristics, so they are widely used in various communication devices mainly for mobile communications. I have. FIG. 3 is a diagram showing a state in which the convex type crystal resonator is cantilevered in a package. The convex-type quartz-crystal vibrating element 1 has a tapered surface 5 having an angle equivalent to a predetermined width a, b extending from two opposing edges 3, 4 of a rectangular flat-plate-shaped quartz substrate 2 toward the center of the substrate. 6 are formed on both main surfaces. Also,
Excitation electrodes 7 and 8 are provided at the center of the flat portion of the substrate sandwiched between the tapered surfaces 5 and 6, respectively. This crystal vibrating element 1 includes an electrode 1 formed on an inner bottom surface 11 of a package 10.
It is cantilevered by using a conductive adhesive 12 on 1a or the like. In practice, a lead electrode (not shown) drawn from each of the excitation electrodes 7 and 8 toward the edge of the substrate is electrically connected to the electrode 11 a by the conductive adhesive 12. By the way, the conventional convex type crystal vibrating element 1 has tapered surfaces 5 and 6.
Since the widths a and b are equal to each other, when the one end edge 4 side is fixed by the conductive adhesive 12, the apparent dimension in the longitudinal direction changes, and there is a problem that the symmetry is lost. That is, when both ends in the longitudinal direction of the crystal resonator element 1 are supported by a uniform force, a displacement distribution having a symmetrical shape with respect to the center in the longitudinal direction of the substrate is formed as shown in FIG. However, when only one edge 4 is supported, the center of the displacement distribution of the vibration is shifted in the direction away from the side supported by the adhesive, so that the center of the displacement distribution is flat as shown in FIG. Since the displacement is caused from the center position of the portion and the electrical equivalent circuit constant of the quartz vibrating element is deteriorated, there is a problem that the value is varied due to the manufacturing variation in the bonding process.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and even when a convex type piezoelectric substrate is cantilevered, the center of displacement distribution does not deviate from the center of the substrate, and the characteristic degradation occurs. It is an object of the present invention to provide a piezoelectric substrate, a piezoelectric vibrator, and a method for manufacturing the same, which can prevent the occurrence of the vibration.

[0004]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a first aspect of the present invention is to extend a rectangular plate-like piezoelectric substrate over a required width from two opposing edges to the center of the substrate. Wherein the width of the tapered surface provided on one edge side of the piezoelectric substrate is larger than the width of the tapered surface provided on the other edge side of the piezoelectric substrate. And According to a second aspect of the present invention, a rectangular plate-shaped piezoelectric substrate is provided with a tapered surface extending from two opposing edges toward a central portion of the substrate over a required width. A piezoelectric vibrating element comprising: a piezoelectric substrate having a width greater than a width of a tapered surface provided on the other end side; and excitation electrodes formed on flat surfaces of both main surfaces of the piezoelectric substrate. A package that accommodates the element and supports the cantilever,
Wherein the end of the tapered surface side having a larger width is supported by the package. According to a third aspect of the present invention, two opposing edges of the unpolished piezoelectric substrate are stirred by rotating the drum in a state where the rectangular flat plate-shaped unpolished piezoelectric substrate is contained in a drum together with an abrasive. And forming a tapered surface over a required width from the substrate toward the center of the substrate, wherein the thickness of one edge of the unpolished piezoelectric substrate is set to be larger than the other. By keeping this unpolished piezoelectric substrate in the drum and stirring it together with the abrasive, the width of the tapered surface formed on the thicker edge side is reduced to the width of the tapered surface formed on the other edge. The width is smaller than the width.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1A is an external perspective view of a quartz substrate 21 as a convex piezoelectric substrate according to an embodiment of the present invention, FIG. 1B is a front view thereof, and FIG. FIG. The characteristic configuration of this quartz substrate 21 is that two opposing edges 2
The point is that the widths a and b of the tapered surfaces 24 and 25 formed with the required widths a and b from the bases 2 and 23 toward the center of the substrate satisfy a> b. Therefore, the left and right shapes of the quartz substrate 21 are asymmetric. Further, the crystal vibrating element 20 formed by forming the excitation electrodes 27 and 28 on both main surfaces of the crystal substrate 21 is connected to the electrode 3 on the inner bottom surface 31 of the package 30.
In connection with the use of the conductive adhesive 32 on 1a, the configuration is characterized in that the edge 22 on the tapered surface 24 side with the larger width is connected. In addition, each excitation electrode 2
7 and 28 are formed on the flat surface 29 located between the tapered surfaces 24 and 25, and are formed to face each other. Since the widths a and b of the tapered surfaces 24 and 25 provided on the two opposing edges are made different from each other and the longer edge is cantilevered, the displacement distribution of the vibration is reduced. The center can be matched with the center of the flat surface 29. That is, when the widths of the tapered surfaces 24 and 25 are the same, the center of the displacement distribution of the vibration is shifted in the direction away from the side supported by the adhesive, so that it does not coincide with the substrate center. If the width a is set to be larger than the width b of the other surface 25, the displacement distribution of the vibration coincides with the center of the flat surface 29 when the edge of the tapered surface 24 is supported by the adhesive. That is, the edge 2 of the tapered surface 24 having the larger width
2 is supported by an adhesive, the widths a and b of the tapered surfaces 24 and 25 are experimentally adjusted in advance so that the center of the displacement distribution coincides with the center of the flat surface 29, and the optimum width a , B
Is calculated, the center of the displacement distribution becomes the flat surface 2
9 can be prevented from deteriorating due to the deviation from the center of 9. Next, in the case of manufacturing a convex type piezoelectric substrate, a plurality of flat pieces are accommodated in a hollow polishing drum together with an abrasive, and the drum is rotated around a rotation axis, and the abrasive A method of forming a tapered surface over a required width on both main surfaces near two opposing edges by stirring and sliding is adopted.

When a quartz substrate (piezoelectric substrate) having an asymmetric shape as shown in FIG. 1 is formed by such a conventional polishing method, an asymmetrical quartz substrate as shown in FIG. 2 (a) or (b) is formed. Is used. That is, first, the unpolished quartz substrate 40 shown in FIG. 2A corresponds to one edge of the rectangular flat plate-shaped unpolished quartz substrate 40 and the tapered surface 25 having a shorter width in the quartz substrate shown in FIG. By forming a film 41 of a metal or the like having a uniform thickness and a uniform width (width b) on the upper and lower surfaces of the edge 23 side, the entire thickness of the region of the width b on the edge 23 side is set to a required value in advance. Set thickly. The material constituting the film 41 may be a material other than metal, but preferably has the same hardness as a piezoelectric substrate material such as quartz. Various methods such as vapor deposition and sputtering can be selected as the method for forming the film 41. As shown in FIG. 1, the two main surfaces which become the tapered surfaces 25 having the shorter width are thickened in advance and polished in this state with a polishing agent in a polishing drum for a required time. A convex piezoelectric substrate having a tapered surface having the widths a and b as described above can be formed. That is, when the substrate is stirred and polished together with the abrasive in the polishing drum, the substrate surface on the thin edge 22 side and the substrate surface on the thick edge 23 side are polished at a uniform rate. As a result, the completed convex piezoelectric substrate has an asymmetric shape having widths a and b (a> b) as shown in FIG. The unpolished quartz substrate 40 shown in FIG.
Is equivalent to the case where the thickness of the substrate itself is set to be thicker by using a metal film or the like in FIG. The effect of is aimed at. The thick portion 43 on the side of the edge 23 is also shown in FIG.
As in the case of (a), an optimum thickness value is selected according to the values of the widths a and b to be obtained. In short, the method of the present invention
In order to make the widths of the tapered surfaces 24 and 25 formed on the upper and lower surfaces near the two opposing edges different from each other, the thickness of both main surfaces corresponding to the tapered surface 25 having the shorter width is set in advance. Thickness is set to a required value, and polishing is performed at the same polishing rate in this state. As a result, tapered surfaces 24 and 25 having a desired ratio of width can be obtained. The quartz vibrating element 20 can be obtained by forming the excitation electrodes 27 and 28 on both main surfaces of the convex type quartz substrate 21 manufactured by the above procedure by vapor deposition or the like. In the above embodiment, an example in which quartz is used as the piezoelectric material has been mainly described. However, the present invention can be applied to a piezoelectric substrate and a piezoelectric vibration element using a piezoelectric material other than quartz.

[0007]

As described above, according to the present invention, even when the convex piezoelectric substrate is cantilevered, the center of the displacement distribution does not deviate from the center of the flat portion of the substrate.
It is possible to provide a piezoelectric substrate, a piezoelectric vibrator, and a method for manufacturing the same, which can prevent characteristic deterioration. In other words, in the present invention, the width of the two opposing tapered surfaces is made different by predicting in advance the deviation of the center of the displacement distribution generated when the cantilever is supported, and the end closer to the wider tapered surface Since the edge is supported in the package by the conductive adhesive, the center of the vibration displacement distribution and the center of the flat portion of the substrate are made to coincide with each other, thereby preventing a change in characteristics. Further, in the manufacturing method of the present invention, when the unpolished piezoelectric substrate is polished while being stirred with the abrasive in the drum, the thickness of both main surfaces of the substrate corresponding to the narrower tapered surface is made larger than the other. Since the unpolished substrate is configured to have a required thickness and is polished in the drum, tapered surfaces having different widths can be obtained as a result.

[Brief description of the drawings]

FIG. 1A is an external perspective view of a quartz substrate 21 as a convex piezoelectric substrate according to an embodiment of the present invention,
(b) is a front view thereof, and (c) is a diagram showing a state of cantilever support.

FIGS. 2 (a) and 2 (b) are diagrams showing the configuration of an unpolished piezoelectric substrate used in the method of the present invention, respectively.

FIG. 3 is an explanatory view of a conventional convex type piezoelectric substrate and its cantilever support structure.

FIGS. 4A and 4B are diagrams illustrating a displacement distribution of vibration.

[Explanation of symbols]

Reference Signs List 20 crystal vibrating element (piezoelectric vibrating element), 21 crystal substrate (piezoelectric substrate), 22, 23 edge, 24, 25 tapered surface, 27, 28 excitation electrode, 30 package, 31
Inner bottom surface, 31a electrode, 32 conductive adhesive, 40 unpolished quartz substrate, 41 film.

Claims (3)

[Claims] 1. A convex-type piezoelectric substrate having a tapered surface over a required width from two opposing edges of a rectangular plate-shaped piezoelectric substrate toward a central portion of the substrate. The width of the tapered surface provided on one edge side of
A piezoelectric substrate characterized in that the width is larger than the width of a tapered surface provided on the other edge side. 2. A rectangular plate-shaped piezoelectric substrate has a tapered surface extending from two opposing edges toward a central portion of the substrate over a required width, and the width of the tapered surface provided on one edge is reduced. A piezoelectric substrate having a width larger than a width of a tapered surface provided on the other end side; and an excitation electrode formed on a flat surface of both main surfaces of the piezoelectric substrate. A piezoelectric vibrator comprising: a package that is housed and supported in a cantilever manner, the piezoelectric vibrator being characterized in that an end of the tapered surface having a larger width is supported by the package. 3. An unpolished piezoelectric substrate in the form of a rectangular flat plate, which is held in a drum together with an abrasive by rotating the drum and stirring the unpolished piezoelectric substrate.
A method of manufacturing a convex type piezoelectric substrate, wherein a tapered surface is formed over a required width from one edge toward a substrate center portion, the thickness of one edge of the unpolished piezoelectric substrate being larger than the other. By setting the unpolished piezoelectric substrate in the set asymmetric shape and stirring the unpolished piezoelectric substrate in the drum together with the abrasive, the width of the tapered surface formed on the thick edge side is formed on the other edge. A method for manufacturing a piezoelectric substrate, wherein the width is smaller than the width of a tapered surface.