JP2018110350A - Piezoelectric vibration piece and piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibration piece and a piezoelectric vibrator which can reduce change of stress generated in a metal film caused by temporal change.SOLUTION: A piezoelectric vibration piece 10 includes: a piezoelectric plate 11; a stress reducing layer 18; and an excitation electrode 51. The piezoelectric plate 11 is formed of an AT-cut crystal substrate, and includes a first surface 11A and a second surface 11B opposed to each other in a thickness direction. A first stress reducing layer 18A of the stress reducing layer 18 is formed on the first surface 11A, and a second stress reducing layer 18B thereof is formed on the second surface 11B. A first excitation electrode 51A of the excitation electrode 51 is formed on the first stress reducing layer 18A, and a second excitation electrode 51B thereof is formed on the second stress reducing layer 18B.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a piezoelectric vibrating piece and a piezoelectric vibrator.

  Conventionally, a piezoelectric vibrating piece formed from an AT-cut quartz substrate includes a piezoelectric plate and excitation electrodes formed on the front and back surfaces of the piezoelectric plate. The piezoelectric vibrating reed vibrates in thickness by being applied with a voltage between the excitation electrodes. In addition, the piezoelectric vibrating piece is mounted on the package via a mounting member (for example, a conductive adhesive) in a mount region located at the end of the piezoelectric plate. The excitation electrode is formed on a piezoelectric plate (see, for example, Patent Document 1).

JP-A-2005-318312

  However, it is conceivable that the stress applied to the piezoelectric plate by the excitation electrode changes with the passage of time, and that the frequency and temperature characteristics drift due to the stress. In particular, when the excitation electrode has a film structure of two or more layers, the stress change of the excitation electrode due to a change with time is relatively large. For this reason, there has been a demand for practical application of a technique capable of suppressing the influence of stress due to the change with time of the excitation electrode (that is, the metal film).

  The present invention has been made in view of such circumstances, and an object thereof is to provide a piezoelectric vibrating piece and a piezoelectric vibrator that can relieve a change in stress generated in a metal film due to a change with time.

  In order to solve the above problems, a piezoelectric vibrating piece according to an aspect of the present invention includes a piezoelectric plate formed of an AT-cut quartz crystal substrate, a first surface and a second surface that face each other in the thickness direction of the piezoelectric plate. A piezoelectric vibrating piece, comprising: a stress relaxation layer formed on the metal layer; and a metal film formed on the stress relaxation layer.

  According to this configuration, the stress relaxation layer is formed on the first surface and the second surface of the piezoelectric plate, and the metal film is formed on the stress relaxation layer. Therefore, the stress change generated in the metal film due to the change over time can be relaxed by the stress relaxation layer before being transmitted to the piezoelectric plate. Thereby, the stress transmitted from the metal film to the piezoelectric plate can be suppressed, and the frequency and temperature characteristics of the piezoelectric plate can be stabilized.

In the above aspect, the metal film may be an excitation electrode.
According to this structure, the stress transmitted to the site | part which forms an excitation electrode among piezoelectric plates can be suppressed. Thereby, the frequency and temperature characteristics of the piezoelectric plate can be particularly stabilized.

  In the above aspect, the piezoelectric plate may be formed in a rectangular shape having a longitudinal direction in the Z′-axis direction of the AT-cut quartz crystal substrate in a plan view as viewed from the thickness direction.

  According to this configuration, the AT-cut quartz substrate is configured by the X axis and the Z ′ axis. Under such a configuration, when the AT-cut quartz substrate is undergoing thickness shear vibration, electric polarization occurs in the X axis and the Z ′ axis. Electric polarization is a charge bias, which is sinusoidal on the X axis and linear on the Z ′ axis. By setting the long side to the Z ′ axis where the electric polarization is linear, the side where the strongest charge is generated can be lengthened. The crystal impedance (hereinafter referred to as the CI value) becomes even lower when the region where the strong charge is generated becomes wider. Accordingly, it is possible to maintain a lower CI value by setting the Z ′ axis as a long side. In particular, a low CI value can be maintained even when the piezoelectric plate is downsized.

  The said aspect WHEREIN: You may provide the protrusion part which protruded in the direction orthogonal to the said thickness direction from the said piezoelectric plate.

The protrusion was protruded from the piezoelectric plate in a direction perpendicular to the thickness direction. This protrusion can be attached to the mounting member to form a mount region. Thereby, the mounting member can be separated from the piezoelectric plate, and excellent vibration characteristics can be obtained.
By the way, the thickness shear vibration, which is the main vibration mode of the AT-cut quartz substrate, is a vibration greatly displaced in the X-axis direction. According to this configuration, by arranging the pair of protrusions along the Z′-axis direction orthogonal to the X-axis direction where the displacement of the piezoelectric plate is large, the protrusions fixed to the package via the mounting member are The displacement of the piezoelectric plate in the X-axis direction is not hindered. Thereby, generation | occurrence | production of an unnecessary vibration can be suppressed in a protrusion part. Therefore, more excellent vibration characteristics can be obtained.

  In the above aspect, the piezoelectric plate has a mesa portion that bulges in the thickness direction of the piezoelectric plate, and the mesa portion has a top surface that forms a top portion of the bulging mesa portion, The stress relaxation layer may be formed on the surface.

  According to this configuration, by forming the stress relaxation layer on the top surface, a stress change generated in the excitation electrode due to a change with time can be efficiently relaxed by the stress relaxation layer. Thereby, the stress transmitted from the excitation electrode to the piezoelectric plate can be effectively suppressed.

  The said aspect WHEREIN: The said mesa part may have an inclined surface which inclines toward the said top surface from the outer periphery of the said mesa part.

According to this configuration, the inclined surface is formed between the top surface and the surface of the protruding portion that faces the top surface. Therefore, compared with the case where a step of 90 ° is formed between the top surface and the surface facing the top surface of the projecting portion, the surface between the top surface and the surface facing the top surface of the projecting portion is formed. It can be connected with a gentle slope.
That is, unnecessary vibrations can be prevented from being induced at the boundary between the top surface and the inclined surface. Thereby, CI value can be reduced and a vibration characteristic can be improved.

In the above aspect, the stress relaxation layer may be an amorphous layer.
According to this configuration, the stress relaxation layer is formed of an amorphous layer. The amorphous layer is homogeneous and isotropic and has no crystals, so there is no weak structure such as a grain boundary or lattice defect. In addition, the amorphous layer does not contribute to excitation. Therefore, the stress change of the metal layer (that is, the excitation electrode) can be efficiently relaxed. Thereby, the stress change transmitted from the metal layer to the piezoelectric plate can be effectively suppressed.

A piezoelectric vibrator according to an aspect of the present invention includes the piezoelectric vibrating piece and a package on which the piezoelectric vibrating piece is mounted.
According to this configuration, since the above-described piezoelectric vibrating piece is provided, it is possible to obtain a piezoelectric vibrator that can alleviate a change in stress generated in the metal film due to a change with time.

According to one aspect of the present invention, the stress relaxation layer is formed on the piezoelectric plate, and the metal film is formed on the stress relaxation layer. Therefore, a stress change generated in the metal film due to a change with time can be relaxed by the stress relaxation layer. Thereby, the stress transmitted from the metal film to the piezoelectric plate can be suppressed, and the frequency and temperature characteristics of the piezoelectric plate can be stabilized.
That is, according to the aspect of the present invention, it is possible to provide a piezoelectric vibrating piece and a piezoelectric vibrator that can alleviate a change in stress generated in a metal film due to a change with time.

It is a top view which shows the piezoelectric vibrating piece which concerns on 1st Embodiment of this invention. 1 is an exploded perspective view showing a piezoelectric vibrator according to a first embodiment of the present invention. It is sectional drawing which shows the piezoelectric vibrator which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the piezoelectric vibrating piece which concerns on 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
(Piezoelectric vibrating piece)
FIG. 1 is a plan view of a piezoelectric vibrating piece 10 according to the first embodiment. FIG. 2 is an exploded perspective view of the piezoelectric vibrator 1 according to the first embodiment. 3 is a cross-sectional view corresponding to the line III-III in FIG.
As shown in FIGS. 1 to 3, the piezoelectric vibrating piece 10 includes a piezoelectric plate 11, a stress relaxation layer 18 (first stress relaxation layer 18 </ b> A, second stress relaxation layer 18 </ b> B), and an excitation electrode 51 (first excitation electrode). 51A, second excitation electrode 51B), mount electrodes 13A and 13B, and routing wirings 16A and 16B.

The piezoelectric plate 11 is formed of an AT-cut quartz substrate, and vibrates in a thickness-slip mode by a voltage applied by each excitation electrode 51A, 51B.
Here, the AT cut is a rotation around the X axis with respect to the Z axis among the three crystal axes of the electric axis (X axis), the mechanical axis (Y axis), and the optical axis (Z axis), which are crystal axes of artificial quartz. This is a processing method of cutting in a direction (Z′-axis direction) inclined by 35 degrees 15 minutes. The piezoelectric vibrating piece 10 having the piezoelectric plate 11 cut out by the AT cut has an advantage that the frequency temperature characteristic is stable, the structure and shape are simple, the processing is easy, and the CI value is low.
In the following description, the XY′Z ′ coordinate system is used when describing the configuration of each figure. In this XY′Z ′ coordinate system, the Y ′ axis is an axis orthogonal to the X axis and the Z ′ axis. In the X-axis direction, the Y′-axis direction, and the Z′-axis direction, the arrow direction in the figure is defined as a + direction, and the direction opposite to the arrow is described as a − direction.

The piezoelectric plate 11 is formed in a rectangular shape with the Z′-axis direction as the longitudinal direction in a plan view viewed from the Y′-axis direction. The piezoelectric plate 11 is formed with the thickness direction along the Y′-axis direction. The piezoelectric plate 11 has an outer periphery that connects the first surface 11A to the Y′-axis direction + side, the second surface 11B to the Y′-axis direction − side, and the first surface 11A and the second surface 11B to the outside of the XZ ′ plane. And an end face 11C.
The first surface 11 </ b> A and the second surface 11 </ b> B are surfaces that face each other in the thickness direction of the piezoelectric plate 11.

The first surface 11 </ b> A of the piezoelectric plate 11 includes a first mesa unit 20 formed at the center and a peripheral surface 24 surrounding the first mesa unit 20. Further, the second surface 11 </ b> B of the piezoelectric plate 11 includes a second mesa portion 30 formed in the center portion and a side edge surface 34 surrounding the second mesa portion 30.
It should be noted that the portion of the piezoelectric plate 11 outside the mesa parts 20 and 30 (specifically, the piezoelectric element including the edge surface 24, the edge surface 34, and the outer peripheral end surface 11C) in plan view as viewed from the Y′-axis direction. The portion of the plate 11) is called the edge portion 40.

  The first mesa portion 20 bulges in the Y′-axis direction + side at the central portion of the first surface 11A. The first mesa unit 20 includes a first top surface 21 that forms the top of the first mesa unit 20, and a first inclined surface 22 that surrounds the first top surface 21.

  The first inclined surface 22 connects the first top surface 21 and the edge surface 24. Of the first inclined surface 22, the inner peripheral edge is formed continuously with each side of the outer peripheral edge of the first top surface 21, and the outer peripheral edge is formed continuously with the inner peripheral edge of the edge surface 24. The first inclined surface 22 is inclined toward the Y′-axis direction + side from the outer peripheral edge (that is, the outer peripheral edge of the first inclined surface 22) 20 a of the first mesa portion 20 toward the first top surface 21 (center). Yes.

The second mesa portion 30 bulges in the Y′-axis direction − side at the central portion of the second surface 11B. The second mesa unit 30 includes a second top surface 31 that forms the top of the second mesa unit 30, and a second inclined surface 32 that surrounds the second top surface 31.
The second inclined surface 32 connects the second top surface 31 and the edge surface 34. Of the second inclined surface 32, the inner peripheral edge is formed continuously with each side of the outer peripheral edge of the second top surface 31, and the outer peripheral edge is formed continuously with the inner peripheral edge of the edge surface 34. The second inclined surface 32 is inclined toward the Y′-axis direction − side from the outer peripheral edge (that is, the outer peripheral edge of the second inclined surface 32) 30 a of the second mesa portion 30 toward the second top surface 31 (center). Yes.

The stress relaxation layer 18 is formed on the first top surface 21 and the second top surface 31. Specifically, the first stress relaxation layer 18 </ b> A is formed on the first top surface 21. A second stress relaxation layer 18 </ b> B is formed on the second top surface 31.
The first stress relaxation layer 18A and the second stress relaxation layer 18B are non-metallic materials in which a change in stress over time is suppressed. Specifically, an amorphous layer or the like is used as the first stress relaxation layer 18A and the second stress relaxation layer 18B. Examples of the material for the amorphous layer include SiO, SiN, and Si.

  The amorphous layer is homogeneous and isotropic and has no crystals, so there is no weak structure such as a grain boundary or lattice defect. In addition, the amorphous layer does not contribute to excitation. That is, the first stress relaxation layer 18A is a layer that can relax the temporal stress change of the first excitation electrode 51A. The second stress relaxation layer 18B is a layer that can relax the change in stress over time of the second excitation electrode 51B.

Excitation electrodes 51 are formed on the first stress relaxation layer 18A and the second stress relaxation layer 18B. Specifically, the first excitation electrode 51A is formed on the first stress relaxation layer 18A. A second excitation electrode 51B is formed on the second stress relaxation layer 18B.
The first excitation electrode 51 </ b> A is a metal film having a central relaxation layer 53 laminated on the first stress relaxation layer 18 </ b> A and an outer peripheral relaxation layer 54 formed along the outer peripheral edge of the central relaxation layer 53. The outer peripheral relaxation layer 54 is laminated in an inclined manner at a portion along the first top surface 21 of the first inclined surface 22.
The first excitation electrode 51A is formed in a rectangular shape having the Z′-axis direction as a longitudinal direction in a plan view as viewed from the Y′-axis direction.

The second excitation electrode 51B is a metal film having a central relaxation layer 56 laminated on the second stress relaxation layer 18B and an outer peripheral relaxation layer 57 formed along the outer peripheral edge of the central relaxation layer 56. The outer peripheral relaxation layer 57 is laminated in an inclined manner in a portion of the second inclined surface 32 along the second top surface 31.
The second excitation electrode 51B is formed in a rectangular shape with the Z′-axis direction as the longitudinal direction in a plan view viewed from the Y′-axis direction.
The first excitation electrode 51A and the second excitation electrode 51B are formed so as to overlap in a plan view viewed from the Y′-axis direction.

  The first excitation electrode 51 </ b> A and the second excitation electrode 51 </ b> B have outer peripheral relaxation layers 54 and 57 in addition to the central relaxation layers 53 and 56. Therefore, the area of the excitation electrodes 51A and 51B can be secured as compared with the case where the excitation electrodes are formed only on the central relaxation layers 53 and 56. As a result, the CI value can be reduced and the vibration characteristics can be improved.

  Further, by forming the first stress relaxation layer 18 </ b> A on the first top surface 21, the first stress relaxation layer 18 </ b> A can be interposed between the first top surface 21 and the central relaxation layer 53. Therefore, the stress change generated in the first excitation electrode 51A due to the change with time can be efficiently relaxed by the first stress relaxation layer 18A before being transmitted to the first mesa unit 20. That is, the stress change transmitted from the first excitation electrode 51A to the first mesa unit 20 can be effectively suppressed.

By forming the second stress relaxation layer 18 </ b> B on the second top surface 31, the second stress relaxation layer 18 </ b> B can be interposed between the second top surface 31 and the central relaxation layer 56. Therefore, the stress change generated in the second excitation electrode 51B due to the change over time can be efficiently relaxed by the second stress relaxation layer 18B before being transmitted to the second mesa unit 30. That is, the stress change transmitted from the second excitation electrode 51B to the second mesa unit 30 can be effectively suppressed.
As described above, the frequency and temperature characteristics of the piezoelectric plate 11 can be stabilized by effectively suppressing the stress change transmitted from the excitation electrodes 51A and 51B to the mesa portions 20 and 30.

  Further, the first stress relaxation layer 18A and the second stress relaxation layer 18B are formed of an amorphous layer excellent in stress relaxation. Therefore, the stress of the first excitation electrode 51A can be efficiently relaxed by the first stress relaxation layer 18A. The stress of the second excitation electrode 51B can be efficiently relaxed by the second stress relaxation layer 18B. Thereby, the stress transmitted from the first excitation electrode 51A and the second excitation electrode 51B to the piezoelectric plate 11 can be effectively suppressed.

In addition, the planar view outline of the excitation electrodes 51A and 51B can be appropriately changed according to the planar view outline of the top surfaces 21 and 31.
Further, the first excitation electrode 51A may have only the central relaxation layer 53 laminated on the first stress relaxation layer 18A on the first surface 11A. The second excitation electrode 51B may have only the central relaxation layer 56 laminated on the second stress relaxation layer 18B on the second surface 11B.
Since the first excitation electrode 51A is laminated only on the first stress relaxation layer 18A and the second excitation electrode 51B is laminated only on the second stress relaxation layer 18B, the stress transmitted from each excitation electrode 51A, 51B to the piezoelectric plate 11 Change can be mitigated more effectively.

The piezoelectric plate 11 further has protrusions (the first protrusion 12A and the second protrusion 12B) at both ends of the edge portion 40 on the + side in the X-axis direction and separated in the Z′-axis direction. . In other words, the first protrusion 12 </ b> A and the second protrusion 12 </ b> B are formed side by side in the Z′-axis direction of the piezoelectric plate 11.
12 A of 1st protrusion parts are formed in the parallelogram by planar view. The first projecting portion 12A extends in the XZ′-axis direction from the corner portion of the edge portion 40 on the + X-axis direction and the Z′-axis direction + side toward the + Z′-axis direction toward the + X′-axis direction. doing.

  A first mount electrode 13A is formed on the first protrusion 12A. The first mount electrode 13A is formed over the entire surface of the first protrusion 12A (specifically, the first surface 11A, the second surface 11B, and the outer peripheral end surface 11C). The first mount electrode 13A is formed on the first surface 11A of the piezoelectric plate 11 (on the surface on the Y′-axis direction + side of the first protrusion 12A) via the routing wiring 16A. Are connected to the first excitation electrode 51A.

  The 2nd protrusion part 12B is formed in the parallelogram by planar view. The second protrusion 12B extends in the XZ′-axis direction from the corner portion of the edge portion 40 on the + X-axis direction and the Z′-axis direction−side toward the −Z′-axis direction toward the + X-axis direction. doing. That is, the protrusion 12B is separated from the first protrusion 12A in the Z′-axis direction of the quartz crystal axis.

A second mount electrode 13B is formed on the second protrusion 12B. The second mount electrode 13B is formed over the entire surface of the second protrusion 12B (specifically, the first surface 11A, the second surface 11B, and the outer peripheral end surface 11C). The second mount electrode 13B is provided on the second surface 11B of the piezoelectric plate 11 (on the surface on the Y′-axis direction − side of the second protrusion 12B) via the routing wiring 16B. Are connected to the second excitation electrode 51B.
The mount electrode 13B only needs to be formed on at least the surface on the second surface 11B side (the Y′-axis direction-side of the second protrusion 12B).

The mount electrodes 13A and 13B and the lead wirings 16A and 16B are formed of a single layer film of metal such as gold, or a laminated film having a metal such as chromium as a base layer and a metal such as gold as an upper layer. .
Moreover, although the thickness in the Y′-axis direction of the projecting portions 12A and 12B is equal to the thickness of the edge portion 40, it may be equal or less.

(Piezoelectric vibrator)
Next, the piezoelectric vibrator 1 including the piezoelectric vibrating piece 10 will be described.
As shown in FIG. 2, the piezoelectric vibrator 1 of the present embodiment is one in which a piezoelectric vibrating piece 10 is accommodated in a cavity C of a package 5. The package 5 is formed by overlapping the case 2 and the lid 3. The case 2 is often made of ceramic, and the lid 3 is often made of Kovar or ceramic. Both are fixed by, for example, seam welding, gold-tin bonding, adhesion by resin, and the like, and the internal hollow portion is sealed under reduced pressure.

The case 2 includes a bottom wall 2a formed in a rectangular shape in plan view, and a side wall 2b erected in the + Y′-axis direction from the peripheral edge of the bottom wall 2a.
The side wall part 2b is formed over the entire periphery in the peripheral part of the bottom wall part 2a.
A pair of internal electrodes 7 is formed on a surface (bottom wall surface) located on the + side in the Y′-axis direction of the bottom wall portion 2a. The pair of internal electrodes 7 are formed apart from each other in the Z′-axis direction. In addition, a pair of external electrodes (not shown) is formed on a surface (bottom wall rear surface) located on the Y′-axis direction − side of the bottom wall portion 2a. The internal electrode 7 and the external electrode are electrically connected by a through electrode (not shown) that penetrates the bottom wall 2a in the thickness direction.
In addition, the connection form of the internal electrode 7 and the external electrode is not limited to this, for example, in the form of connecting the internal electrode 7 and the external electrode via wiring extending in the surface direction of the ceramic sheet. There may be.

The lid 3 is formed in a plate shape having a rectangular shape in plan view. The peripheral edge of the lid 3 is bonded to the end surface of the side wall 2b of the case 2 from the + Y′-axis direction.
A cavity C is formed in a region surrounded by the bottom wall 2 a and the side wall 2 b of the case 2 and the lid 3.

As shown in FIG. 3, the piezoelectric vibrating piece 10 is accommodated in the cavity C.
The piezoelectric vibrating piece 10 is mounted on the bottom wall portion 2a of the case 2 via a mounting member 9 such as a conductive paste. More specifically, with respect to the pair of internal electrodes 7 formed on the bottom wall portion 2a of the case 2, the mount electrodes 13A, 13B (projections 12A, 12B) corresponding to the piezoelectric vibrating piece 10 are provided on the second surface 11B. Implemented from the side. Thereby, the piezoelectric vibrating reed 10 is mechanically held by the package 5 and the mount electrodes 13A and 13B and the internal electrode 7 are electrically connected to each other.

  According to this configuration, the projecting portions 12A and 12B are used as the mount region for mounting the piezoelectric vibrating reed 10 on the package 5, so that the vibration region (the portion where the excitation electrodes 51A and 51B are formed) and the mount are mounted. A space between the areas can be secured. Thereby, it is possible to suppress vibration energy generated in the vibration region from propagating to the mounting member 9 and the package 5 through the mount region, and to suppress vibration leakage.

A pair of protrusions 12A, 12B protrude from the piezoelectric plate 11 in a direction perpendicular to the thickness direction, and the pair of protrusions 12A, 12B are attached to the mounting member 9 to form a mount region. As a result, the mounting member 9 can be separated from the piezoelectric plate 11, and excellent vibration characteristics can be obtained.
The piezoelectric plate 11 is formed of an AT cut quartz substrate. The thickness shear vibration, which is the main vibration mode of the AT-cut quartz substrate, is a vibration that is greatly displaced in the X-axis direction. According to this configuration, the pair of protrusions 12A and 12B (see FIG. 2) are arranged along the Z′-axis direction orthogonal to the X-axis direction where the displacement of the piezoelectric plate 11 is large. Therefore, the pair of protrusions 12A and 12B fixed to the package 5 via the mounting member 9 does not hinder the displacement of the piezoelectric plate 11 in the X-axis direction. Thereby, it can suppress that unnecessary vibration generate | occur | produces in a pair of protrusion part 12A, 12B. Therefore, more excellent vibration characteristics can be obtained.

Furthermore, since the adhesion area between the piezoelectric plate 11 and the mounting member 9 can be ensured, the bonding strength between the mounting member 9 and the piezoelectric plate 11 can be ensured.
Further, for example, the thickness of the projecting portions 12A and 12B is formed to be equal to or less than the thickness at the outer peripheral edges of the inclined surfaces 22 and 32 in the piezoelectric plate 11 (that is, the outer peripheral edges 20a and 30a of the mesa portions 20 and 30). Is also possible. As a result, vibration energy propagating from the vibration region to the protrusions 12A and 12B can be reduced. Therefore, unnecessary vibrations generated at the outer peripheral edge of the protrusions 12A and 12B can be suppressed.
As a result, it is possible to provide the piezoelectric vibrating piece 10 having excellent vibration characteristics over a long period of time while achieving downsizing.

  Furthermore, the protruding portions 12A and 12B protrude from the outer peripheral edges of the inclined surfaces 22 and 32 (the outer peripheral edges 20a and 30a of the mesa portions 20 and 30). Thereby, it is possible to suppress the mounting member 9 from adhering to the main vibration region (the portion including the top surfaces 21 and 31 where the excitation electrodes 51A and 51B are formed in the piezoelectric plate 11). As a result, the above-described vibration leakage can be suppressed, and the vibration in the vibration region can be suppressed from being hindered by the mounting member 9, and excellent vibration characteristics can be obtained.

Moreover, the 1st inclined surface 22 is formed between the 1st top surface 21 and the surface which faces the 1st top surface 21 among protrusion part 12A, 12B. Therefore, the first top surface 21 and the protrusions are compared to the case where a 90 ° step is formed between the first top surface 21 and the surface of the protrusions 12A and 12B that faces the first top surface 21. Between 12A and 12B, the surface facing the first top surface 21 can be gently connected. Similarly, it is possible to gently connect the second top surface 31 and the surface of the projecting portions 12A and 12B that faces the second top surface 31.
Thereby, it can suppress that an unnecessary vibration is induced in the boundary part of the top surfaces 21 and 31 and the inclined surfaces 22 and 32. FIG. As a result, the CI value can be reduced and the vibration characteristics can be improved.

Further, in the first embodiment, the piezoelectric plate 11 is formed in a rectangular shape having the longitudinal direction in the Z′-axis direction of the AT-cut quartz crystal substrate as viewed from the Y′-axis direction.
According to this configuration, a low CI value can be maintained even when the piezoelectric plate 11 is downsized.
That is, the AT-cut quartz crystal substrate is composed of an X axis and a Z ′ axis. Under such a configuration, when the AT-cut quartz substrate is undergoing thickness shear vibration, electric polarization occurs in the X axis and the Z ′ axis. Electric polarization is a charge bias, which is sinusoidal on the X axis and linear on the Z ′ axis. By setting the long side to the Z ′ axis where the electric polarization is linear, the side where the strongest charge is generated can be lengthened. The CI value becomes lower as the region where the strong charge is generated becomes wider. Therefore, it is possible to maintain a lower CI value by setting the Z ′ axis as a long side. In particular, a low CI value can be maintained even when the piezoelectric plate is downsized.

In the first embodiment, the pair of protrusions 12A and 12B protrudes in the surface direction of the piezoelectric plate 11 from both ends of the piezoelectric plate 11 that are separated from each other in the Z′-axis direction of the AT-cut quartz crystal substrate. did.
According to this configuration, since the projecting portions 12A and 12B are arranged along the longitudinal direction of the piezoelectric plate 11, the piezoelectric vibrating piece 10 can be more stably mounted on the package.
Furthermore, although the planar view outer shape of the projecting portions 12A and 12B is formed in a parallelogram shape, it may be formed in a rectangular shape or a trapezoidal shape.

[Second Embodiment]
Next, the piezoelectric vibrating piece 100 of the second embodiment will be described.
FIG. 4 is a cross-sectional view of the piezoelectric vibrating piece 100 according to the second embodiment.
As shown in FIG. 4, the piezoelectric vibrating piece 100 has a piezoelectric plate 101 formed of an AT-cut quartz crystal substrate. Reverse mesa portions 103 and 106 are formed on the piezoelectric plate 101. Specifically, the piezoelectric vibrating piece 100 includes a piezoelectric plate 101, a stress relaxation layer 112 (first stress relaxation layer 112A, second stress relaxation layer 112B), and an excitation electrode 114 (first excitation electrode 114A, second excitation). An electrode 114B), a mount electrode, and a lead wiring. The mount electrode and the routing wiring are not shown in order to facilitate understanding of the configuration of the piezoelectric vibrating piece 100.

The piezoelectric plate 101 is a rectangular parallelepiped, and reverse mesa portions 103 and 106 are formed at the center portions of the first surface 101A and the second surface 101B, respectively. Specifically, the first reverse mesa portion 103 is formed in a concave shape at the center of the first surface 101A. A second reverse mesa portion 106 is formed in a concave shape at the center of the second surface 101B.
The first surface 101 </ b> A and the second surface 101 </ b> B are surfaces that face each other in the thickness direction of the piezoelectric plate 101.

The first reverse mesa portion 103 has a bottom surface 104 formed in the center and an inclined surface 105 formed in an inclined shape along the outer peripheral edge of the bottom surface 104. The bottom surface 104 is formed in parallel to the first surface 101A.
A first stress relaxation layer 112 </ b> A is formed on the bottom surface 104. A first excitation electrode 114A is formed on the first stress relaxation layer 112A. That is, the first stress relaxation layer 112A is interposed between the bottom surface 104 and the first excitation electrode 114A.

  The first excitation electrode 114A is a metal film. The first stress relaxation layer 112A is a layer formed of an amorphous material such as SiO, SiN, or Si. Therefore, as in the first embodiment, the stress change generated in the first excitation electrode 114A due to the change over time can be efficiently relaxed by the first stress relaxation layer 112A before being transmitted to the bottom surface 104 of the first reverse mesa portion 103. That is, the stress change transmitted from the first excitation electrode 114A to the bottom surface 104 can be effectively suppressed.

The second reverse mesa unit 106 includes a bottom surface 107 formed at the center and an inclined surface 108 formed in an inclined shape along the outer peripheral edge of the bottom surface 107. The bottom surface 107 is parallel to the second surface 101 </ b> B and is formed with respect to the bottom surface 104 of the first reverse mesa unit 103.
A second stress relaxation layer 112B is formed on the bottom surface 107. A second excitation electrode 114B is formed on the second stress relaxation layer 112B. That is, the second stress relaxation layer 112B is interposed between the bottom surface 107 and the second excitation electrode 114B.

  The second excitation electrode 114B is a metal film. The second stress relaxation layer 112B is a layer formed of an amorphous material such as SiO, SiN, or Si, for example. Therefore, similarly to the first embodiment, the stress change generated in the second excitation electrode 114B due to the change over time can be efficiently relaxed by the second stress relaxation layer 112B before being transmitted to the bottom surface 107 of the second reverse mesa unit 106. That is, the stress change transmitted from the second excitation electrode 114B to the bottom surface 107 can be effectively suppressed.

  Thus, the frequency and temperature characteristics of the piezoelectric plate 101 can be stabilized by effectively suppressing the stress change transmitted from the excitation electrodes 115A and 114B to the reverse mesa portions 103 and 106. That is, the piezoelectric vibrating piece 100 according to the second embodiment can obtain the same operations and effects as the piezoelectric vibrating piece 10 according to the first embodiment.

  The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ...... Piezoelectric vibrator 5 ......... Package 9 ......... Mounting member 10,100 ... Piezoelectric vibrating piece 11, 101 ... Piezoelectric plate 11A, 101A ... 1st surface 11B, 101B ... 2nd surface 12A, 12B ... 1st 1. Second protrusion (protrusion)
18, 112... Stress relaxation layer 18A, 112A... First stress relaxation layer 18B, 112B... Second stress relaxation layer 20, 30... First and second mesa portions (mesa portions)
20a, 30a ... outer peripheral edges of first and second mesas 21, 31 ... first and second top surfaces (top surfaces)
22, 32 ... 1st, 2nd inclined surface (inclined surface)
51 …… Excitation electrode (metal film)
51A, 51B ... 1st, 2nd excitation electrode 103, 106 ... 1st, 2nd reverse mesa part (reverse mesa part)
104, 107 ... bottom 105, 108 ... inclined surface

Claims (8)

A piezoelectric plate formed of an AT-cut quartz substrate;
A stress relaxation layer formed on the first surface and the second surface facing each other in the thickness direction of the piezoelectric plate;
A metal film formed on the stress relaxation layer,
A piezoelectric vibrating piece characterized by that. The metal film is an excitation electrode;
The piezoelectric vibrating piece according to claim 1. In a plan view seen from the thickness direction, the piezoelectric plate is formed in a rectangular shape with the Z′-axis direction of the AT-cut quartz crystal substrate as a longitudinal direction,
The piezoelectric vibrating piece according to claim 1 or 2, wherein A projecting portion projecting from the piezoelectric plate in a direction perpendicular to the thickness direction;
The piezoelectric vibrating piece according to claim 1, wherein: The piezoelectric plate is
A mesa portion that bulges in the thickness direction of the piezoelectric plate;
The mesa part is
Having a top surface forming the top of the bulging mesa portion;
The stress relaxation layer is formed on the top surface;
The piezoelectric vibrating piece according to claim 1, wherein: The mesa part is
Having an inclined surface inclined from the outer peripheral edge of the mesa portion toward the top surface;
The piezoelectric vibrating piece according to claim 5. The stress relaxation layer is an amorphous layer;
The piezoelectric vibrating piece according to claim 1, wherein: The piezoelectric vibrating piece according to any one of claims 1 to 7,
And a package on which the piezoelectric vibrating piece is mounted.

Images