JP2006033121A - Piezoelectric substrate, piezoelectric vibration element, piezoelectric vibrator, and piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate a defect of causing variations in the resonance frequency of a piezoelectric vibrating element due to adhered adhesive to a diaphragm side of the piezoelectric vibrating element by ensuring a sufficient contact area through the configuration of a broad width for only adhesive application parts even when a wall width of an annular part is reduced by area reduction in the piezoelectric vibrating element wherein exciting electrodes are formed on a principal side of a piezoelectric substrate adopting a configuration of integrally supporting the thin diaphragm with the thick annular part. <P>SOLUTION: In the piezoelectric substrate 2 including the thin diaphragm 4 and the thick annular part 5 with a rectangular outer shape for integrally surrounding an outer circumferential edge of the diaphragm and configured such that at least one principal side is formed to be a recess 3, an extended region 5a is provided to at least two corner insides among four corners of the annular part to form a wide adhering region. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric substrate having a structure in which an ultrathin diaphragm is integrally surrounded by a thick annular portion, a piezoelectric resonator element in which a conductive pattern such as an excitation electrode is formed on the piezoelectric substrate, and a piezoelectric resonator element in the package. Regarding the improvement of the hermetically sealed piezoelectric vibrator and further the piezoelectric oscillator using this piezoelectric vibrator, it is necessary to secure a necessary and sufficient adhesion area by variously devising the shape of the annular portion without increasing the size of the piezoelectric substrate. It relates to the technology that has been made possible.

A surface-mount type piezoelectric device having a structure in which a piezoelectric vibration element is hermetically sealed with a conductive adhesive fixed in a package, such as a crystal resonator, is used in communication devices such as mobile phones and pagers, computers, and the like. In electronic equipment and the like, it is used as a reference frequency generation source, a filter, and the like, but downsizing of piezoelectric devices is also required in response to downsizing of these various equipments.
In addition, a piezoelectric oscillator as a surface-mounting piezoelectric device has a recess in a state where a piezoelectric vibration element and a circuit component constituting an oscillation circuit are housed in a recess formed on an upper surface of a package body made of, for example, ceramic. The opening is sealed with a metal lid.
Conventionally, as a piezoelectric vibration element used in the piezoelectric device as described above, a concave portion is formed by excavating a part of one surface of a piezoelectric substrate so as to cope with a higher frequency of a fundamental wave frequency of 50 MHz or more. A piezoelectric substrate with a structure in which the bottom surface is an ultra-thin diaphragm with a thickness of several μm and the periphery of the diaphragm is integrally surrounded by a thick annular part, and input and output formed on both sides of the diaphragm. There is known a piezoelectric vibration element comprising a common electrode and a ground electrode (Japanese Patent Laid-Open No. 9-55635).
In such a piezoelectric vibration element, if the size of the piezoelectric substrate is further reduced, the area of the thin diaphragm is inevitably reduced, but the area of the diaphragm is increased as much as possible within the limited total area. In order to secure a sufficient free vibration region, it is necessary to reduce the wall width of the annular portion. However, since the impact resistance increases as the size of the piezoelectric substrate is reduced, the function of reinforcing the diaphragm can be maintained to some extent even if the wall width of the annular portion is reduced.

In Japanese Patent Laid-Open No. 3-235408, when the planar shape of the recessed portion of the piezoelectric substrate is rectangular, when one main surface of the piezoelectric vibration element is supported in the package, the piezoelectric is caused by external vibration and impact. Since there is a possibility that the vibration element may be damaged, an invention has been disclosed in which the strength is increased by widening the wall width of the annular portion by variously devising the planar shape of the recessed portion and the annular portion. However, since the impact resistance inevitably increases as the process proceeds, it is not necessary to increase the wall width of the annular portion for the purpose of ensuring the strength. Therefore, by reducing the wall width of the annular portion, it is possible to ensure the area of the diaphragm as much as possible in response to downsizing.
However, when the wall width of the annular portion is reduced in order to cope with the downsizing of the piezoelectric vibration element, there is a disadvantage that it is impossible to secure a sufficient adhesive application area when supported by the adhesive in the case. . In other words, there is a limit to reducing the wall width of the annular portion in response to the miniaturization of the piezoelectric vibration element, and if the wall width is made smaller than the minimum required application diameter of the adhesive, it protrudes from the wall width. When the adhesive spreads to the diaphragm side or climbs up the inner wall of the recess, the adhesive adheres to the diaphragm, and a large distortion is formed in the diaphragm due to hardening shrinkage of the adhesive, etc., and the resonance frequency fluctuates. There is a risk of doing. This will be described with reference to the drawings.
7 and 8 are views showing a state in which the piezoelectric vibration element is supported on a pad in the case by a conductive adhesive. First, FIGS. 7A and 7B are a plan view and a front sectional view showing a bonding state of the piezoelectric vibration element. The piezoelectric vibration element 100 has a configuration in which excitation electrodes 104 are formed on both main surfaces of a piezoelectric substrate 101 having a structure in which an outer periphery of a thin vibration plate 102 is integrally surrounded by a thick annular portion 103. The wall width w of each side of the annular portion 103 is set to a uniform width. When the piezoelectric vibration element 100 is bonded and fixed using the conductive adhesive 112 on the pad 111 provided on the inner bottom surface 110 of the case with the concave portion side facing down, the flat surface side of the piezoelectric substrate is used. If the wall width w of the annular portion becomes smaller than the adhesive application diameter due to the downsizing of the piezoelectric substrate, the adhesive exceeds the wall width w and the diaphragm It will apply | coat to 102 and will generate | occur | produce a distortion.
Next, FIGS. 8A and 8B are a plan view of the concave portion side of the piezoelectric vibration element, and a front cross-sectional view showing a state in which the concave portion is directed upward and bonded and fixed to the bottom surface of the case. In this case, the conductive adhesive 112 applied to the lower surface of the annular portion 103 scoops up the inner wall of the recessed portion and adheres to the thin wall portion to generate distortion.
Japanese Patent Laid-Open No. 9-55635 JP-A-3-235408

  The present invention has been made in view of the above, and in a piezoelectric vibration element in which an excitation electrode is formed on the main surface of a piezoelectric substrate in which a thin vibration plate is integrally supported by a thick annular portion, the area of the piezoelectric vibration element is reduced. Even if the wall width of the annular part is reduced by the above, the adhesive will adhere to the diaphragm side and the resonance frequency will fluctuate by securing a sufficient adhesive area by configuring only the adhesive application part wide. The purpose is to eliminate the problems that lead to.

In order to solve the above-mentioned problems, the invention of claim 1 includes a thin diaphragm and a thick and rectangular annular part integrally surrounding the outer peripheral edge of the diaphragm, and at least one of the main parts is provided. In the piezoelectric substrate having a concave portion on the surface side, an enlarged region is provided inside at least two corners of the four corners of the annular portion to form a wide adhesive region.
In the annular portion having a rectangular planar shape, the insides of the four corners are formed at right angles. However, in the present invention, the enlarged region is formed in a chamfered shape (diagonal straight line or arc) inside the corners. As a result, a wide adhesive region is provided at the corner, so even if the wall width of the annular portion is reduced, it is sufficient to adhere to the inside of the package using the wide adhesive region provided at the corner. A large bonding area can be secured. As the piezoelectric material constituting the piezoelectric substrate, quartz and other various piezoelectric materials can be selected.
The invention of claim 2 is characterized in that, in claim 1, the enlarged region is provided in at least two adjacent corners of the four corners, or two corners in a diagonal direction. To do. It is also possible to provide enlarged regions at not only at least two of the four corners, but also at three and four locations.
A third aspect of the present invention is the method according to the first or second aspect, wherein the piezoelectric substrate is an AT-cut quartz plate, the length in the z-axis direction of the AT-cut quartz plate is longer than the length in the x-axis direction, and the enlarged region is formed. One of the corners to belong to belongs to a region surrounded by the + x direction and the + z direction.
When forming a recess (diaphragm) on the main surface of the AT-cut quartz substrate by etching and forming an enlarged region inside the four corners of the annular portion using a predetermined mask, in the + x direction and the + z direction The corners of the diaphragm located on the bottom surfaces of the corners located in the enclosed region are substantially perpendicular. That is, even if an enlarged region is formed in a corner portion located in a region surrounded by the + x direction and the + z direction, the corner portion of the diaphragm corresponding to the corner portion is not narrowed. Therefore, not only when the enlarged regions are formed at the four corners, but also when the enlarged regions are formed at the two corners and the three corners, the corners are always surrounded by the + x direction and the + z direction. By including the corners located in the region, it is possible to reduce the narrowing of the area of the diaphragm.
A piezoelectric vibration element according to a fourth aspect of the invention is characterized in that an excitation electrode is formed on at least one main surface of the piezoelectric substrate according to the first, second, or third aspect.
According to a fifth aspect of the present invention, a piezoelectric vibrator includes the piezoelectric vibration element according to the fourth aspect and a surface mounting package in which the piezoelectric vibration element is hermetically sealed.
A piezoelectric oscillator according to a sixth aspect of the invention includes the piezoelectric vibration element according to the fourth aspect, or the piezoelectric vibrator according to the fifth aspect, and an oscillation circuit.

  The present invention provides a piezoelectric vibration element in which excitation electrodes are formed on the main surface of a piezoelectric substrate having a structure in which a thin diaphragm is integrally supported by a thick annular portion. Even when the width of the wall to be reduced is reduced, an enlarged region is formed inside at least two corners to secure a wide adhesive application region. By adhering to the inside of the package, it is possible to eliminate the problem that the adhesive adheres to the vibration plate side and causes the resonance frequency to fluctuate.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
FIGS. 1A and 1B are a plan view of a concave portion of a crystal resonator element made of an AT-cut crystal as an example of a piezoelectric resonator element according to an embodiment of the present invention, and a cross-sectional view taken along line AA. 2 (a) and 2 (b) are a plan view of a concave portion side of a conventional quartz resonator element as a comparative example, and a BB cross-sectional view.
1 includes a quartz crystal substrate 2 made of AT-cut quartz as an anisotropic piezoelectric crystal material, excitation electrodes 10a and 10b formed on both main surfaces of the quartz crystal substrate 2, and each excitation. Lead electrodes 11a and 11b extending from the electrodes 10a and 10b, respectively, and connection pads 12a and 12b at the ends of the lead electrodes are provided. The excitation electrode may be formed on one main surface, while the other main surface may be a full earth film.
The quartz crystal substrate 2 according to this embodiment has a rectangular plate-like substrate body that is long in one crystal axis direction (propagation direction of excited waves) of the two plane biaxial directions x and z, for example, the z-axis direction. By forming the recessed portion 3 on one main surface by etching, the ultrathin diaphragm 4 is positioned on the inner bottom surface of the recessed portion 3, and the outer peripheral edge of the diaphragm 4 is formed into the thick annular portion 5. The structure is held integrally. By making the z-axis direction longer, the effective area of the diaphragm 4 becomes wider.
As shown in FIGS. 2A and 2B, the inner wall of the recessed portion of the conventional crystal resonator element is etched obliquely due to the difference in the etching rate, but the four corners inside the annular portion 5 are substantially perpendicular.

The characteristic configuration of the embodiment of the present invention shown in FIG. 1 is that an adhesive application region is formed on each end face of the annular portion corresponding to two corners (corner corners) located on the right side in the z-axis direction (+ z-axis direction). The enlarged region 5a is additionally formed and a wide portion is formed at the corner (one-side two-point support type). That is, a characteristic is that the adhesive application region is widened by forming a triangular enlarged region 5a inside the corner portion by obliquely chamfering the inner corner portion of the annular portion 5 that has been a right angle. is there. In order to form such an enlarged region 5a, etching may be performed after masking not only the end face of the conventional annular portion but also the region corresponding to the enlarged region 5a.
In the case of forming the two enlarged regions 5a as shown in this embodiment, etching is performed using the mask M having an opening shape as shown in FIG.
In this embodiment, the enlarged region is formed inside the two corners on the right side of the quartz substrate 2 in the z-axis direction. However, the present invention is also applicable to the one-side two-point support type in which the enlarged region is formed inside the two left corners. can do.
However, when the concave portion 3 (vibration plate 4) is formed on the main surface of the AT-cut quartz crystal substrate 2 by etching using a predetermined mask, when the crystal axis is drawn with the center of the quartz crystal substrate as the reference point, the + x direction And only the corner of the diaphragm located at the bottom of the corner (upper right corner) located in the area surrounded by + z direction is almost right-angled (the narrowing of the area due to the formation of the enlarged area is avoided). Phenomenon) occurs. That is, even if an enlarged region is formed in a corner portion located in a region surrounded by the + x direction and the + z direction, the area of the corner portion of the diaphragm corresponding to this corner portion is not narrowed by the influence of the enlarged region 5a. . Therefore, not only when the enlarged regions are formed at the four corners, but also when the enlarged regions are formed at the two corners and the three corners, the corners are always surrounded by the + x direction and the + z direction. By including the corners located in the region, the area of the diaphragm 4 can be reduced.
In addition, as shown in FIG. 1 (c), a ¼-circular arc-shaped enlarged region 5a may be formed inside the corner portion to form a wide portion, or may be configured in any other shape. In another embodiment, an example in which a triangular enlarged region 5a is formed will be mainly described.
As described above, in the present invention, the wide area (wide adhesive area) for applying the adhesive is formed by forming the enlarged area 5a in a chamfered shape inside the corner of the rectangular annular part 5 which has been a right angle in the past. Even if the wall width w of the annular portion 5 is reduced to the limit by forming, a sufficient adhesive application area can be secured using the enlarged area 5a, so that the adhesive is prevented from adhering to the diaphragm 4. However, it is possible to stably support the crystal resonator element in the package. In particular, the characteristic of the diaphragm 4 is enlarged by selecting the formation position and shape of the enlarged area 5a so that the effective area of the diaphragm 4 is not significantly reduced by forming the enlarged area 5a. It is possible to prevent a great difference from the case where the region 5a is not formed.

Next, FIGS. 3A and 3B are a plan view and a CC cross-sectional view of a crystal resonator element according to another embodiment of the present invention.
The crystal resonator element 1 according to this embodiment is a diagonal two-point support type, and the outer shape is chamfered inside two corners located on one diagonal line among four corners of the annular portion 5 having a rectangular annular shape. By forming the enlarged region 5a, the two corners are used as wide adhesive application regions.
When forming a recess in the quartz crystal substrate according to this embodiment, etching is performed using a mask M as shown in FIG.
Also in this embodiment, when the wall width w of the annular portion 5 is set to be as small as necessary, an adhesive region having a sufficient width is secured using the enlarged region 5a, and the adhesive is used as the diaphragm. It is possible to prevent problems such as adhering to the surface.
Next, FIGS. 4A and 4B are a plan view and a DD sectional view of a crystal resonator element according to another embodiment of the present invention.
The crystal resonator element 1 according to this embodiment is a four-point support type, and the four corner portions are formed by forming the enlarged region 5a in a chamfered shape inside all four corner portions of the annular portion 5 having a rectangular outer shape. Are all wide adhesive application areas. This type of crystal resonator element 1 includes two electrodes 10 on both surfaces of the diaphragm, and lead electrodes 11 and pads 12 extending from the electrodes are formed at the corners.
When forming a recess in the quartz crystal substrate according to this embodiment, etching is performed using a mask M as shown in FIG.
Also in this embodiment, when the wall width w of the annular portion 5 is set to be as small as necessary, an adhesive region having a sufficient width is secured using the enlarged region 5a, and the adhesive is used as the diaphragm. It is possible to prevent problems such as adhering to the surface.
A crystal resonator can be constructed by hermetically sealing the crystal resonator element 1 in which the excitation electrode and the lead electrode are formed on the crystal substrate 2 having the above-described configuration in a package (not shown). An oscillator can be constructed by combining this crystal resonator element and an oscillation circuit.
Note that the mask M shown in FIG. 6D is a mask for forming enlarged regions at the two corners on the upper side of the drawing. In this example, the mask M is formed in the region surrounded by the + x direction and the + z direction. The enlarged region 5a is formed at the corner (the upper right corner) located.

Next, FIG. 5 is a cross-sectional view showing the configuration of a surface-mounted crystal resonator using the crystal resonator element of the present invention. The crystal resonator 20 has a configuration in which the crystal resonator element 1 is accommodated in a package 21, and the package 21 has a configuration in which a ceramic container 22 is hermetically sealed with a metal lid 30. The ceramic container 22 includes a mounting electrode 23 at the bottom and a connection pad 25 that is electrically connected to the mounting electrode 23 on the inner bottom surface of the housing recess 24. On the connection pad 25, the crystal resonator element 1 is electrically and mechanically connected using a conductive adhesive 26.
In this embodiment, the end surface of the annular portion of the crystal resonator element 1 is bonded to the inner bottom surface of the package 21 with the recessed portion 3 facing downward. On the contrary, the flat surface side is packaged with the recessed portion 3 facing upward. The inner bottom surface of 21 may be adhered and fixed. In this case as well, the adhesive region on the flat surface side is substantially enlarged due to the influence of the enlarged region 5a located on the end surface side of the annular portion, so that the effect of preventing the penetration and interference of the adhesive on the diaphragm side is obtained. Obtainable.
In the above embodiment, quartz is exemplified as the piezoelectric crystal material. However, this is only an example, and the present invention can be applied to piezoelectric substrates made of any piezoelectric crystal material.

(A) And (b) is a concave part side top view of the crystal vibration element which consists of AT cut quartz as an example of the piezoelectric vibration element which concerns on one Embodiment of this invention, and AA sectional drawing, (c) is ( The principal part enlarged view of a). (A) And (b) is a recessed part side top view of the conventional crystal oscillation element as a comparative example, and BB sectional drawing. (A) And (b) is a top view and CC sectional view of a crystal oscillation element concerning other embodiments of the present invention. (A) And (b) is a top view and DD sectional view of a crystal oscillation element concerning other embodiments of the present invention. Sectional drawing which shows the structure of the surface mount-type crystal resonator which uses the crystal resonator element of this invention. (A), (b), (c), and (d) are explanatory drawings of the structure of a mask. (A) And (b) is a front sectional view which shows the state which the concave part side of the conventional piezoelectric vibration element was attached, and the state which adhere | attached and fixed to the bottom surface in a package by making the concave part side downward. (A) And (b) is a flat surface side top view of the conventional piezoelectric vibration element, and a front sectional view showing a state where it is bonded and fixed to the inner bottom surface of the package with the recessed portion side facing upward.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Quartz vibration element (piezoelectric vibration element), 2 Quartz substrate (piezoelectric board | substrate), 3 Concave part, 4 Diaphragm, 5 Annular part, 5a Expansion area, 10a, 10b Excitation electrode, 11a, 11b Lead electrode, 12a, 12b Connection Pad, 20 crystal resonator (piezoelectric resonator), 21 package, 22 ceramic container, 23 mounting electrode, 24 receiving recess, 25 connection pad, 26 conductive adhesive, 30 metal lid

Claims (6)

In a piezoelectric substrate having a thin diaphragm and an annular portion having a thick and rectangular outer shape integrally surrounding the outer peripheral edge of the diaphragm, and having at least one main surface side as a recessed portion,
A piezoelectric substrate, wherein an enlarged region is provided inside at least two corners of the four corners of the annular portion to form a wide adhesive region.   2. The piezoelectric substrate according to claim 1, wherein the enlarged region is provided in at least two adjacent corners of the four corners or two corners in a diagonal direction. The piezoelectric substrate is an AT-cut quartz plate, and the length of the AT-cut quartz plate in the z-axis direction is longer than the length in the x-axis direction,
3. The piezoelectric substrate according to claim 1, wherein one of corners forming the enlarged region belongs to a region surrounded by + x direction and + z direction. 4.   4. A piezoelectric vibration element, wherein an excitation electrode is formed on at least one main surface of the piezoelectric substrate according to claim 1.   A piezoelectric vibrator comprising: the piezoelectric vibration element according to claim 4; and a surface-mounting package in which the piezoelectric vibration element is hermetically sealed. A piezoelectric oscillator comprising the piezoelectric vibration element according to claim 4 or the piezoelectric vibrator according to claim 5 and an oscillation circuit.

Images