JP2017034667A - Piezoelectric vibrating piece and piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric vibration piece and a piezoelectric transducer capable of preventing a desired oscillation frequency from being obtained and temperature characteristics from being lowered by unnecessary vibration of a piezoelectric plate in which a mesa part is formed.SOLUTION: A piezoelectric vibration piece includes: a piezoelectric plate 11 in which at least one stage of a mesa part 50 is formed on each of front and rear principal surfaces 11A, 11B and a pair of excitation electrodes 34A, 34B which is arranged on the mesa part 50 and used for driving the piezoelectric plate 11. Positions of end sides 51A, 52A of at least one stage of the mesa part 50 are set to the positions where an anti-node of unnecessary vibration to the main vibration during excitation of the piezoelectric plate 11 is avoided.SELECTED DRAWING: Figure 4

Description

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

  2. Description of the Related Art Conventionally, a mesa-type piezoelectric vibrating piece in which a mesa portion is formed on each main surface of a piezoelectric plate in a piezoelectric vibrating piece formed from an AT-cut quartz crystal substrate is known. In the mesa-type piezoelectric vibrating piece, the thickness of the central region of the piezoelectric plate as the vibration region (mesa portion) is set to be thicker than the thickness of the peripheral portion of the piezoelectric plate. With this configuration, vibration energy can be confined in the vibration region. This makes it possible to reduce the crystal impedance (hereinafter referred to as the CI value) of the piezoelectric vibrating piece.

JP 2013-102472 A

  By the way, when the mesa-type piezoelectric vibrating piece as described above is vibrated, unnecessary vibration (for example, bending vibration) with respect to the thickness-shear vibration that is the original vibration mode is generated. If the unnecessary vibration and the thickness shear vibration cause coupling (coupling), there is a problem that a desired oscillation frequency cannot be obtained or the temperature characteristics of the piezoelectric vibrating piece are lowered.

  Therefore, the present invention has been made in view of the above-described circumstances, and a desired oscillation frequency cannot be obtained or temperature characteristics are deteriorated due to unnecessary vibration of the piezoelectric plate on which the mesa portion is formed. The present invention provides a piezoelectric vibrating piece and a piezoelectric vibrator capable of preventing the above-described problem.

  The piezoelectric vibrating piece of the present invention is disposed on the piezoelectric plate so as to include the piezoelectric plate having at least one mesa portion formed on at least one of the main surfaces of the front and back sides, and the mesa portion, A pair of excitation electrodes for driving the lead electrode, and a routing electrode for connecting the excitation electrode and the mount electrode, and the piezoelectric plate is formed in a square shape in plan view, and the length of one side of the piezoelectric plate Let L be the distance between the other side intersecting the one side of the piezoelectric plate and the end side of the mesa portion at any stage among the plurality of mesa portions, and m and n are natural numbers ( When m> n), the distance W1 is set to satisfy [nL / (2m−1)] × 0.8 <W1 <[nL / (2m−1)] × 1.2. It is characterized by.

  By comprising in this way, it can suppress that a thickness shear vibration and an unnecessary vibration generate | occur | produce at the time of the vibration of a piezoelectric vibrating piece. For this reason, it is possible to prevent the piezoelectric vibrating piece from obtaining a desired oscillation frequency and the temperature characteristics of the piezoelectric vibrating piece from deteriorating.

  In the piezoelectric resonator element according to the aspect of the invention, the distance W1 may be a distance between the end side of the uppermost mesa portion and the other side of the plurality of mesa portions.

  With this configuration, it is possible to more effectively suppress the coupling between the thickness shear vibration and the unnecessary vibration during the vibration of the piezoelectric vibrating piece.

  In the piezoelectric vibrating piece of the present invention, the piezoelectric plate is formed in a quadrangular shape in plan view, the length of one side of the piezoelectric plate is L, the other side intersecting the one side of the piezoelectric plate, and the excitation electrode The distance W2 is [nL / (2m−1)] × 0.8 <W2 <[nL /, where W2 is the distance between the edges and m and n are natural numbers (m> n). (2m−1)] × 1.2 is set.

  With this configuration, it is possible to reliably suppress the occurrence of unnecessary vibrations themselves when the piezoelectric vibrating piece vibrates. For this reason, it is possible to effectively prevent the piezoelectric vibrating piece from obtaining a desired oscillation frequency and the temperature characteristics of the piezoelectric vibrating piece from being deteriorated.

  In the piezoelectric vibrating piece according to the present invention, the piezoelectric plate is formed of an AT-cut quartz substrate, and the longitudinal direction of the piezoelectric plate is the Z′-axis direction of the quartz crystal axis.

With this configuration, a low CI value can be maintained even when the piezoelectric plate 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 the piezoelectric vibrating piece of the present invention, the piezoelectric plate is formed by performing wet etching, and the end side of the mesa unit is an end side that is not the ridge line of the mesa unit. It is characterized by.

  With this configuration, even when the piezoelectric plate is formed by performing wet etching, the piezoelectric vibrating piece cannot obtain a desired oscillation frequency, or the temperature characteristics of the piezoelectric vibrating piece are reduced. Can be prevented.

  A piezoelectric vibrator according to the present invention includes the piezoelectric vibrating piece according to any one of the above items and a package on which the piezoelectric vibrating piece is mounted.

  With this configuration, it is possible to provide a piezoelectric vibrator that can prevent a desired oscillation frequency from being obtained or a temperature characteristic from being deteriorated.

  According to the present invention, it is possible to suppress the occurrence of the coupling between the thickness shear vibration and the unnecessary vibration when the piezoelectric vibrating piece vibrates. For this reason, it is possible to prevent the piezoelectric vibrating piece from obtaining a desired oscillation frequency and the temperature characteristics of the piezoelectric vibrating piece from deteriorating.

It is a top view of the piezoelectric vibrating piece in the embodiment of the present invention. It is a disassembled perspective view of the piezoelectric vibrator in the embodiment of the present invention. It is sectional drawing of the piezoelectric vibrator in embodiment of this invention. It is shape explanatory drawing of the mesa part in embodiment of this invention. It is a distribution map of vibration energy of a piezoelectric plate in an embodiment of the present invention, and (a) to (d) show a state in which the position of the end side of the upper mesa portion is changed. It is sectional drawing to which a part of piezoelectric plate at the time of performing the wet etching process in embodiment of this invention was expanded.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In describing the configuration of each figure, an XY′Z ′ coordinate system is used. Each axis in the XY′Z ′ coordinate system has the following relationship with the crystal axis of crystal described later. That is, the X axis is an electrical axis, the Z ′ axis is an axis inclined by 35 degrees and 15 minutes around the X axis with respect to the Z axis, which is an optical axis, and the Y ′ axis is orthogonal to the X axis and the Z ′ axis. It is an axis to do. In the X-axis direction, the Y′-axis direction, and the Z′-axis direction, the arrow direction in the figure is defined as the + direction and the direction opposite to the arrow is defined as the − direction.

(Piezoelectric vibrating piece)
FIG. 1 is a plan view of the piezoelectric vibrating piece 10.
As shown in the figure, the piezoelectric vibrating piece 10 includes a piezoelectric plate 11, mount electrodes 31 and 32, and an excitation electrode 34. The piezoelectric plate 11 is formed of an AT cut quartz substrate.

  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, and the processing is easy. The piezoelectric plate 11 is formed to have a uniform thickness with the Y′-axis direction as the thickness direction, and has main surfaces 11A and 11B on both surfaces in the Y′-axis direction.

The piezoelectric plate 11 includes a rectangular plate-shaped vibrating portion 12 and a pair of mount portions 14 and 15 for mounting the vibrating portion 12.
The vibration part 12 has a quadrangular shape in plan view, and is formed so that the longitudinal direction is along the Z′-axis direction. A mesa portion 50 protrudes from the vibrating portion 12 on one main surface 11A and the other main surface 11B of the piezoelectric plate 11. The mesa portion 50 is formed in two steps, and is formed on the lower mesa portion 51 protruding from the main surfaces 11A and 11B, and protruded on the lower mesa portion 51, and has a surface area larger than that of the lower mesa portion 51. And a small upper mesa portion 52. The piezoelectric plate 11 is not limited to a rectangular plate shape, and includes a plate having a corner C surface and a corner R surface, an oval shape, and the like. In this case, the “side of the piezoelectric plate 11” described later is a distance obtained by extending the sides from the base points of the corners C and R and connecting the intersections.

  One excitation electrode 34A is formed on the upper mesa 51 formed on the one main surface 11A, and the other excitation electrode 34B is formed on the upper mesa 51 formed on the other main surface 11B. Yes. Each excitation electrode 34A, 34B is formed in a rectangular shape in plan view so as to cover most of the surface of each upper mesa portion 51, and is opposed so as to overlap in the thickness direction of the piezoelectric plate 11. Details of the method for determining the shape of the mesa 50 and the shapes of the excitation electrodes 34A and 34B will be described later.

The pair of mount portions 14 and 15 are formed at both ends in the longitudinal direction (Z′-axis direction) on the + X side of the vibration portion 12 and are disposed so as to protrude from the vibration portion 12.
The first mount portion 14 is disposed so as to be in contact with the side surface of the vibration portion 12 facing the + X direction at the corner portion located in the (+ X, + Z ′) direction of the vibration portion 12. On the other hand, the second mount portion 15 is disposed at a corner portion of the vibration portion 12 located in the (+ X, −Z ′) direction so as to be in contact with the side surface facing the + X direction of the vibration portion 12.

The first mount unit 14 includes first mount electrodes 31A and 31B. One first mount electrode 31A is formed on one main surface 11A, and is connected to one excitation electrode 34A via a lead wiring 36A (lead electrode). The other first mount electrode 31B is formed on the other main surface 11B.
One first mount electrode 31 </ b> A and the other first mount electrode 31 </ b> B are connected to each other via a first side electrode 37 formed on the side surface of the first mount portion 14. The surface of the first mount portion 14 is formed by the first mount electrodes 31 </ b> A and 31 </ b> B and the first side surface electrode 37.

On the other hand, the second mount unit 15 includes second mount electrodes 32A and 32B. One second mount electrode 32A is formed on one main surface 11A. The other second mount electrode 32B is formed on the other main surface 11B, and is connected to the other excitation electrode 34B via a lead wiring 36B (lead electrode).
One second mount electrode 32 </ b> A and the other second mount electrode 32 </ b> B are connected to each other via a second side electrode 38 formed on the side surface of the second mount portion 15. The surface of the second mount portion 15 is formed by the second mount electrodes 32A and 32B and the second side surface electrode 38.

(Piezoelectric vibrator)
Next, the piezoelectric vibrator 1 including the piezoelectric vibrating piece 10 will be described with reference to FIGS. 2 and 3.
FIG. 2 is an exploded perspective view of the piezoelectric vibrator 1, and FIG. 3 is a cross-sectional view of the piezoelectric vibrator 1. In FIG. 3, the scales of the film thicknesses of the mount electrodes 31 and 32 and the excitation electrodes 34A and 34B are changed for easy understanding.
As shown in FIG. 2, the piezoelectric vibrator 1 has a piezoelectric vibrating piece 10 accommodated inside a cavity C of a package 5. The package 5 is formed by overlapping the base substrate 2 and the lid substrate 3.

  The base substrate 2 includes a bottom wall portion 2a formed in a substantially rectangular plate shape, and a side wall portion 2b erected from the peripheral edge portion of the bottom wall portion 2a. The bottom wall portion 2a and the side wall portion 2b are formed of a ceramic material or the like.

  A pair of internal electrodes 7 are formed on the surface of the bottom wall 2 a inside the cavity C. The pair of internal electrodes 7 are formed at positions corresponding to the pair of mount portions 14 and 15 of the piezoelectric vibrating piece 10. A pair of external electrodes (not shown) is formed on the surface of the bottom wall portion 2a outside the cavity C. The internal electrode 7 and the external electrode are connected by a through electrode (not shown) that penetrates the bottom wall 2a in the thickness direction. In addition, the structure which connects an internal electrode and an external electrode by the interlayer electrode formed between the layers of a ceramic layer may be sufficient instead of connecting with a penetration electrode.

  The lid substrate 3 is formed in a rectangular plate shape using a ceramic material, a metal material, or the like. The peripheral portion of the lid substrate 3 is bonded to the end surface of the side wall portion 2 b of the base substrate 2. A cavity C is formed in a region surrounded by the bottom wall portion 2 a and the side wall portion 2 b of the base substrate 2 and the lid substrate 3.

  As shown in detail in FIG. 3, the piezoelectric vibrating reed 10 housed in the cavity C is mounted on the bottom wall 2 a of the base substrate 2 via a mounting member 9 such as a conductive adhesive. More specifically, the first mount electrode 31 and the second mount included in the pair of mount portions 14 and 15 of the piezoelectric vibrating piece 10 with respect to the pair of internal electrodes 7 formed on the bottom wall portion 2a of the base substrate 2. The electrode 32 is mounted via the mounting member 9. At this time, the mounting member 9 contacts the pair of mount parts 14 and 15. Accordingly, the piezoelectric vibrating piece 10 is mechanically held by the package 5 and the first mount electrode 31, the second mount electrode 32, and the internal electrode 7 are electrically connected.

Under such a configuration, when a voltage is applied to a pair of external electrodes (not shown), the piezoelectric vibrating piece 10 undergoes thickness-shear vibration, which is the main vibration. Note that the thickness shear vibration is vibration that is greatly displaced in the X-axis direction. On the other hand, the piezoelectric vibrating piece 10 generates unnecessary vibrations relative to the main vibration (thickness shear vibration). Here, the vibration in the bending vibration mode will be described as an unnecessary vibration.
Here, the shape of the mesa portion 50 formed to protrude on the one main surface 11A and the other main surface 11B of the piezoelectric plate 11, and the excitation electrodes 34A and 34B formed on the mesa portion 50, respectively. The shape is determined based on the position (displacement) of the node of unnecessary vibration. This will be described in detail below.

(Mesa part shape and excitation electrode shape determination method)
FIG. 4 is an explanatory diagram for explaining the shape of the mesa unit 50.
In FIG. 4, the scale of each part is appropriately changed for easy understanding of the explanation (the same applies to FIG. 6 below). In the following description, a method for determining the shape of the mesa unit 50 based on the vibration displacement in the bending vibration mode that has the greatest influence on the main vibration will be described as unnecessary vibration. Furthermore, the piezoelectric plate 11 is formed by, for example, dry etching (anisotropic etching) processing, so that the side surface 11C of the piezoelectric plate 11, the end side 51A of the lower mesa unit 51, and the end side 52A of the upper mesa unit 52 are formed. Are substantially orthogonal to the main surfaces 11A and 11B, respectively.

  FIG. 4 shows bending vibration generated in the X-axis direction as the bending vibration mode. In the bending vibration mode, the vibration node vibrates so that the node of the vibration is located at the end side in the X-axis direction of the piezoelectric plate 11. According to the earnest study by the present inventors, the unnecessary vibrations are the main vibrations because the edges of the upper mesa portion 52, the lower mesa portion 51, and the excitation electrodes 34A and 34B are located at the nodes of the unnecessary vibration. It was found that the effect on slabs can be suppressed (simulation results will be described later). This is because if the unnecessary vibrations are greatly displaced at these edges, the unnecessary vibrations are further dispersed starting from these edges and easily coupled with the main vibration. 52, when the displacement of the unnecessary vibrations at the edges of the lower mesa 51 and the excitation electrodes 34A and 34B is small, the coupling between the unwanted vibration and the main vibration is difficult to occur, or even if the coupling occurs, the main vibration It is thought that the impact on

  From the above considerations, in the present embodiment, the upper mesa portion 52, the lower mesa portion 51, the excitation are arranged so that unnecessary vibrations are not displaced at the edges of the upper mesa portion 52, the lower mesa portion 51, and the excitation electrodes 34A and 34B. The feature is that the dimensions of the electrodes 34A and 34B are designed. That is, as shown in FIGS. 1 and 4, the length of one side of the piezoelectric plate 11 (for example, the length of the side along the X direction, hereinafter simply referred to as one side) is L, and is orthogonal to the one side of the piezoelectric plate 11. The distance between the other side (for example, the side along the Z ′ direction, hereinafter, simply referred to as the other side) and the end side 52A of the upper mesa portion 52 is W1, and the other side of the piezoelectric plate 11 and the excitation electrodes 34A and 34B. When the distance between the side edges 34a and 34b of the second plate is W2, the distance between the other side of the piezoelectric plate 11 and the side edge 51A of the lower mesa 51 is W3, and m and n are natural numbers, Relational expressions can be derived (where m> n).

  First, at both ends of one side of the piezoelectric plate 11, the nodes of the bending vibration mode coincide as described above. Further, from the viewpoint of the symmetry of vibration, the unnecessary vibration is displaced in the same phase from the center of one side to both ends of the one side. For example, if the bending vibration displacement at the position furthest away from the central portion is “convex upward”, the bending vibration displacement at the position furthest away from the other is also “convex upward”. Therefore, the position of the node of the unnecessary vibration is a jump position that is separated from the outer shape end by an integer multiple of the distance obtained by dividing the outer shape L by an integer. For example, if there are six node positions (including the outer edge) in the outer shape L, W = L ÷ (2m−1), where W is the position from the node to the node. However, m = 3.

  Next, if the edge 51A of the lower mesa 51, the edge 52A of the upper mesa 52, and the edges 34a and 34b of the excitation electrodes 34A and 34B are respectively located at the bending vibration nodes, the unnecessary vibration becomes the main vibration. In view of the fact that the effect is low, W1, W2, and W3 shown in FIG.

And according to the inventors' earnest study, if W1, W2, and W3 are within a range of about ± 20%, it becomes possible to effectively reduce the influence of unnecessary vibration on the main vibration. .
That is, each distance W1, W2, W3 is respectively
[n ₁ L / (2m−1)] × 0.8 <W1 <[n ₁ L / (2m−1)] × 1.2 (1) (1)
[n ₂ L / (2m−1)] × 0.8 <W2 <[n ₂ L / (2m−1)] × 1.2 (2) (2)
[n ₃ L / (2m−1)] × 0.8 <W3 <[n ₃ L / (2m−1)] × 1.2 (3) (3)
It is set to satisfy. Even when one side of the piezoelectric plate 11 is a side along the Z ′ direction and the other side of the piezoelectric plate 11 is a side along the X direction, the distances W1, W2, and W3 are expressed by the equations (1) to (3). ). However, m and n are particularly effective when divided by 20 or less, but the effect is reduced when divided by a natural number greater than that.

  That is, the end side 52A of the upper mesa portion 52, the end side 51A of the lower mesa portion 51, and the end sides 34a and 34b of the excitation electrodes 34A and 34B are respectively centered on the positions P1, P2, and P3 of the bending vibration nodes. It is located within the range of ± 20%. By forming the mesa portion 50 in this manner, the coupling between the bending vibration and the thickness shear vibration can be effectively suppressed. In addition, by forming the excitation electrodes 34A and 34B in this way, it is possible to suppress the occurrence of bending vibration itself. If at least one of W1, W2, and W3 satisfies the above relational expression, an effect that cannot be obtained by the conventional technique can be obtained, but more preferably, all of W1 to W3 satisfy the above relational expression. Good to be.

More specifically, the effect of the shape of the mesa unit 50 will be described with reference to FIG.
FIG. 5 is a distribution diagram of the vibration displacement of the main vibration of the piezoelectric plate 11, and (a) to (d) show a state in which the position of the end side 52 </ b> A of the upper mesa portion 52 is changed. In FIG. 5, m = 3 and n = 1 are set. In FIG. 5, the shape of the lower mesa 51 is fixed (the position of the end 51A is fixed). In addition, the range (refer to E1 part) shown in the figure in the figure shows the range in which the thickness shear vibration as the main vibration is remarkably generated (hereinafter, this range is referred to as vibration energy E1). It shows that the thickness shear vibration is generated with a large displacement at the center of the double circle. In addition, in the state where the coupling with the unnecessary vibration is not generated, the main vibration is generated in the substantially circular region. However, when the coupling with the unnecessary vibration is generated, the displacement of the main vibration is the unnecessary vibration ( Therefore, the range of displacement of the thickness shear vibration is expressed by a non-circular irregular shape.

First, as shown in FIG. 5A, in the case of W1 = [n ₁ L / (2m−1)], that is, the edge 52A of the upper mesa portion 52 at the position P1 of the bending vibration node as unnecessary vibration. It can be seen that in the upper mesa portion 52, the coupling between the main vibration and the unnecessary vibration is suitably suppressed. That is, it can be confirmed that the thickness shear vibration as the main vibration is conspicuously concentrated in the substantially circular shape in the figure.

Further, as shown in FIG. 5B, in the case of W1 = [n ₁ L / (2m−1)] × 1.1, that is, the position of the end side 52A of the upper mesa portion 52 is an unnecessary vibration. When it is at a position deviated by 10% from the position P1 of the bending vibration, and when W1 = [n ₁ L / (2m−1)] × 1.2 as shown in FIG. Even when the position of the edge 52A of the upper mesa portion 52 is shifted by 20% from the position P1 of the bending vibration node as unnecessary vibration, the substantially circular range (E1) in the upper mesa portion 52. It can be confirmed that the displacement of the main vibration is generated within (the vibration energy of the main vibration is preferably confined).

On the other hand, as shown in FIG. 5D, in the case of W1 = [n ₁ L / (2m−1)] × 1.3, that is, the position of the end side 52A of the upper mesa portion 52 is unnecessary vibration. As a result, the coupling between the flexural vibration as the unnecessary vibration and the main vibration becomes remarkable, and the vibration energy E1 is dispersed, resulting in the displacement of the main vibration. It can be confirmed that the shape of the region where the sag occurs is broken. That is, when the position of the end side 52A of the upper mesa 52 is in a range exceeding ± 20% from the position P1 of the bending vibration, the shape of the range (E1) indicating the region where the main vibration is displaced is obtained. It will collapse. This is because the bending vibration and the thickness-shear vibration start to be coupled to cause vibration leakage.

The same can be said for the lower mesa portion 51. That is, by setting the position of the edge of the lower mesa portion 51 so as to satisfy the above relationship, it is possible to effectively reduce the coupling between the thickness shear vibration as the main vibration and the bending vibration as the unnecessary vibration. It becomes possible.
In addition, an effect will appear if only one side of the four sides of the mesa part satisfies the above relational expression.

In FIG. 4 described above, the side surface 11C of the thick electric plate 11, the end side 51A of the lower mesa portion 51, and the end side 52A of the upper mesa portion 52 are formed, for example, by performing dry etching. However, the case where each of the main surfaces 11A and 11B is substantially orthogonal to each other has been described.
On the other hand, the definition of each distance W1, W2, and W3 when the piezoelectric plate 11 is formed by performing wet etching (isotropic etching), for example, will be described below.

FIG. 6 is an enlarged cross-sectional view of a part of the piezoelectric plate 11 when wet etching is performed, and corresponds to FIG. 4 described above.
As shown in the figure, when the piezoelectric plate 11 is formed by performing wet etching, the shape of the side surface 11C of the piezoelectric plate 11, the end side 51A of the lower mesa 51, and the end 52A of the upper mesa 52 is The main surfaces 11A and 11B are inclined or curved without being orthogonal to each other. In such a case, the side surface 11 </ b> C of the piezoelectric plate 11, the end side 51 </ b> A of the lower mesa unit 51, and the end side 52 </ b> A of the upper mesa unit 52 form the “ridge line” that forms the flat surface (top surface) of each mesa unit 51, 52. ".
That is, when the piezoelectric plate 11 is formed by performing wet etching (isotropic etching), the distances W1, W2, and W3 are distances between the other side of the piezoelectric plate 11 and the ridge line of the mesa portion. In addition, when the end sides 51A and 52A of the mesa portion are formed of a plurality of inclined surfaces or curved surfaces having different degrees of inclination, it is also possible to calculate W1, W2, and W3 based on each ridgeline.

As described above, in the above-described embodiment, in determining the shape of the mesa unit 50 and the shape of the excitation electrodes 34A and 34B in the piezoelectric vibrating piece 10 having the mesa unit 50, the other side of the piezoelectric plate 11 and the upper mesa unit. 52, the distance W1 between the edge 52A, the distance W2 between the other side of the piezoelectric plate 11 and the ends 34a, 34b of the excitation electrodes 34A, 34B, and the other side of the piezoelectric plate 11 and the lower mesa portion 51. The distance W3 to the end side 51A is set so as to satisfy the expressions (1) to (3), respectively.
For this reason, in the mesa part 50, the coupling of the bending vibration and the thickness shear vibration can be effectively suppressed. The same applies to the excitation electrodes 34A and 34B. Therefore, it is possible to reliably prevent the piezoelectric vibrating piece 10 from obtaining a desired oscillation frequency and the temperature characteristics of the piezoelectric vibrating piece 10 from being deteriorated.

The piezoelectric plate 11 is formed of an AT-cut quartz substrate, and is formed so that the longitudinal direction of the piezoelectric plate 11 is the Z′-axis direction in the crystal crystal axis.
Here, when the AT-cut quartz substrate undergoes 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 the present embodiment, by making the longitudinal direction of the piezoelectric plate 11 along the Z′-axis direction of the AT-cut quartz substrate, a low CI value can be maintained even in downsizing.

The present invention is not limited to the above-described embodiment, and includes various modifications made to the above-described embodiment without departing from the spirit of the present invention.
For example, in the above-described embodiment, the mounting member 9 is brought into contact with the other main surface 11B of the piezoelectric vibrating piece 10. However, the present invention is not limited to this, and the mounting member 9 may be brought into contact with the main surface 11A.

  In the above-described embodiment, the case where the unnecessary vibration is the bending vibration and the shapes of the mesa unit 50 and the excitation electrodes 34A and 34B are determined based on the displacement of the bending vibration has been described. However, the present invention is not limited to this, and the shape of the mesa unit 50 and the excitation electrodes 34A and 34B may be determined based on the displacement of other unnecessary vibrations (vibrations other than the thickness shear vibrations) instead of the bending vibrations. Good. Even in this case, the same effects as those of the above-described embodiment can be obtained.

Further, in the above-described embodiment, the case where the mesa unit 50 is formed in two stages of the lower mesa unit 51 and the upper mesa unit 52 has been described. However, the present invention is not limited to this, and the mesa portion 50 only needs to be formed in at least one stage. Further, for example, the mesa unit 50 may be configured with three or more stages.
Furthermore, when two or more stages are formed, the first-stage mesa part is formed at a position that becomes a node of unnecessary vibration in a specific mode, and the second-stage mesa part does not need a mode different from the first stage. Even if it is formed at a position to be a vibration node, the same effect as described above can be obtained. Further, even in the same mode, the natural numbers m and n may be different. In these cases, it is not necessary to form the mesa portion 50 so that the center of the length L of one side of the piezoelectric plate 11 coincides with the center.

Furthermore, in the above-described embodiment, the case where the shapes of the lower mesa portion 51 and the upper mesa portion 52 are determined based on the positions of the nodes of the bending vibration has been described. However, the present invention is not limited to this, and it is only necessary that the shape of at least one of the lower mesa 51 or the upper mesa 52 is determined based on the position of the unnecessary vibration node.
In particular, by determining the shape of the upper mesa portion 52 based on the position of the node of the unnecessary vibration, the coupling between the bending vibration and the thickness shear vibration can be effectively suppressed. Further, when the mesa unit 50 is formed in a plurality of stages of three or more stages, at least the shape of the uppermost mesa part is determined based on the position of the node of the unnecessary vibration, so that the bending vibration and the thickness-shear vibration are linked. It is possible to effectively suppress the formation.

  Further, in the above-described embodiment, a case has been described in which the shapes of the excitation electrodes 34A and 34B are determined based on unnecessary vibrations in addition to the mesa unit 50. However, the present invention is not limited to this, and it is only necessary that at least one of the lower mesa 51 or the upper mesa 52 is formed based on unnecessary vibration. And each excitation electrode 34A, 34B does not need to be formed based on unnecessary vibration. That is, the excitation electrodes 34 </ b> A and 34 </ b> B may be formed so as to protrude from the mesa unit 50, that is, include the mesa unit 50. Even in this case, it is possible to prevent the piezoelectric vibrating reed 10 from obtaining a desired oscillation frequency and the temperature characteristics of the piezoelectric vibrating reed 10 from being deteriorated as compared with the conventional case.

Furthermore, in the above-described embodiment, when determining the shape of the mesa unit 50 and the shapes of the excitation electrodes 34A and 34B, the distance W1 between the other side of the piezoelectric plate 11 and the end side 52A of the upper mesa unit 52, the piezoelectric A distance W2 between the other side of the plate 11 and the end sides 34a and 34b of the excitation electrodes 34A and 34B, and a distance W3 between the other side of the piezoelectric plate 11 and the end side 51A of the lower mesa portion 51, respectively. It set so that Formula (1)-(3) might be satisfy | filled. In other words, the end side 52A of the upper mesa portion 52, the end side 51A of the lower step mesa portion 51, and the end sides 34a and 34b of the excitation electrodes 34A and 34B are respectively located at the positions of the nodes of the unnecessary vibration (the bending vibration nodes). The case where it is located within a range of ± 20% centering on the positions P1, P2, P3) has been described.
However, the present invention is not limited to this, and the positions of the end side 52A of the upper mesa portion 52, the end side 51A of the lower mesa portion 51, and the end sides 34a and 34b of the excitation electrodes 34A and 34B are at least unnecessary vibrations. Any position that avoids the position of the belly is acceptable. By configuring in this way, it is possible to prevent the piezoelectric vibrating reed 10 from obtaining a desired oscillation frequency and the temperature characteristics of the piezoelectric vibrating reed 10 from being deteriorated as compared with the conventional case.

  In the above-described embodiment, the mesa portion 50 has a rectangular shape. However, the shape of the mesa portion 50 is not limited to this, and may be a shape having a corner C surface or a corner R surface, an oval shape, an elliptical shape, or the like. In that case, if the side connecting the base points of the corner C and the corner R is set so as to satisfy the above-described formula, an effect is obtained.

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric vibrator 5 ... Package 10 ... Piezoelectric vibration piece 11 ... Piezoelectric plate 11A ... One main surface (main surface) 11B ... Other main surface (main surface) 34A ... One excitation electrode (excitation electrode) 34a, 34b ... End Side 34B ... other excitation electrode (excitation electrode) 50 ... mesa part 51 ... lower mesa part 51A, 52A ... end side 52 ... upper mesa part

Claims (6)

A piezoelectric plate having at least one mesa portion formed on at least one of the main surfaces of the front and back sides;
A pair of excitation electrodes disposed on the piezoelectric plate so as to include the mesa portion and driving the piezoelectric plate;
A routing electrode connecting the excitation electrode and the mount electrode;
With
The piezoelectric plate is formed in a square shape in plan view,
The length of one side of the piezoelectric plate is L,
The distance between the other side intersecting with the one side of the piezoelectric plate and the end side of the mesa unit at any stage among the plurality of mesa units is W1,
When m and n are natural numbers (m> n),
The distance W1 is
[nL / (2m−1)] × 0.8 <W1 <[nL / (2m−1)] × 1.2
A piezoelectric vibrating piece characterized by being set to satisfy   2. The piezoelectric vibrating piece according to claim 1, wherein the distance W <b> 1 is a distance between the end side of the uppermost mesa portion and the other side of the plurality of mesa portions. The piezoelectric plate is formed in a square shape in plan view,
The length of one side of the piezoelectric plate is L,
The distance between the other side intersecting the one side of the piezoelectric plate and the end side of the excitation electrode is W2,
When m and n are natural numbers (m> n),
The distance W2 is
[nL / (2m−1)] × 0.8 <W2 <[nL / (2m−1)] × 1.2
The piezoelectric vibrating piece according to claim 1, wherein the piezoelectric vibrating piece is set so as to satisfy The piezoelectric plate is formed of an AT cut quartz substrate,
The longitudinal direction of the piezoelectric plate is the Z′-axis direction in the crystal axis,
The piezoelectric vibrating piece according to any one of claims 1 to 3, wherein:   5. The piezoelectric vibrating piece according to claim 1, wherein the end side of the mesa portion is a ridge line of the mesa portion. The piezoelectric vibrating piece according to any one of claims 1 to 5,
A package on which the piezoelectric vibrating piece is mounted;
A piezoelectric vibrator characterized by comprising:

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