JPWO2018212188A1 - Piezoelectric vibration element - Google Patents

Abstract

A base (50), a pair of vibrating arms (60) extending in a first direction (D1) from the base (50) and aligned in a second direction (D2) intersecting the first direction (D1); Provided in the third direction (D3) intersecting the first direction (D1) and the second direction (D2) so as to face the pair of vibrating arms (60) in the first direction (D1). And the pair of holes (70) is a virtual center line (C1) along a first direction (D1) passing the center of the base (50) in the second direction (D2). ).

Description

  The present invention relates to a piezoelectric vibration element.

  The piezoelectric vibrator includes, for example, artificial quartz, and a tuning fork type crystal vibrating element in which a pair of vibrating arms are extended in parallel from the base of the base material and vibrated in the horizontal direction toward or away from each other. Is used. Such piezoelectric vibrators are used in mobile terminals such as mobile computers, portable game machines, mobile phones, IC cards, vibration gyro sensors, and electronic devices such as communication base stations. With the miniaturization and higher performance of electronic devices, improvement in vibration characteristics and reliability of a piezoelectric vibrator and a piezoelectric vibration element incorporated therein is required.

  For example, Patent Document 1 discloses a tuning fork type including a base, two pairs of vibrating arms extending from the base, and a pair of supporting arms extending from the base along the vibrating arms. A bending quartz crystal vibrator configured to extend from a base inside a support arm provided with a pair of vibrating arms, and the support arm has a groove-shaped first recess in the width direction. A configuration is disclosed in which the supporting arms are provided at predetermined intervals without facing each other while having the first recess on the front and back main surfaces of the vibrating arm. According to this, it is possible to damp the vibration leaking from the vibrating arm to the support arm.

  Further, in Patent Document 2, a tuning fork type piezoelectric vibrating reed, which is formed of a piezoelectric material having anisotropy due to etching and is provided with a pair of vibrating arms extending in parallel from the base, each vibrating arm of the base Between the crotch and the crotch, in the direction in which each vibrating arm extends from the center in the width direction of the base or from the center to the more rigid side of each vibrating arm side A configuration is disclosed that forms a cut along. According to this, it is possible to prevent the deterioration of the vibration characteristics due to the difference in the rigidity of the left and right vibrating arms and to suppress the CI (Crystal Impedance) value.

JP, 2011-015102, A Japanese Patent Application Publication No. 2004-236008

  However, in the tuning fork type quartz vibrator described in Patent Document 1, when chemical etching is used to form the outer shape of the element, the asymmetry of the mechanical strength of the material is caused due to the anisotropy of the quartz crystal structure. And asymmetry of the shape due to the residue of the etching process. Due to this asymmetry, in the tuning fork type quartz vibrator, there is a possibility that the rigidity balance of the two vibrating arms is lost and the vibration characteristics are deteriorated. Further, in the piezoelectric vibrating reed described in Patent Document 2, stress concentration may occur in the cut provided in the crotch portion, and the impact resistance may be reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a piezoelectric vibration element capable of improving vibration characteristics and suppressing a decrease in reliability.

  A piezoelectric vibrating element according to one aspect of the present invention includes a base, a pair of vibrating arms extending in a first direction from the base and aligned in a second direction intersecting the first direction, and a pair of vibrating arms at the base A pair of holes are provided along a third direction intersecting the first direction and the second direction so as to face each other in the first direction, the pair of holes passing through the center of the base in the second direction It is asymmetric with respect to a virtual center line along one direction.

  According to the present invention, it is possible to provide a piezoelectric vibration element capable of improving vibration characteristics and suppressing a decrease in reliability.

FIG. 1 is an exploded perspective view schematically showing the configuration of a quartz oscillator. FIG. 2 is a cross sectional view schematically showing a configuration of a cross section taken along line II-II of the crystal unit shown in FIG. FIG. 3 is a plan view schematically showing the configuration of the crystal vibrating element according to the first embodiment. FIG. 4 is a cross sectional view schematically showing a configuration of a cross section taken along line IV-IV of the quartz crystal vibrating element shown in FIG. FIG. 5 is an enlarged plan view more specifically showing the structure of the base of the quartz crystal vibrating element. FIG. 6 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the first embodiment. FIG. 7 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the second embodiment. FIG. 8 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the third embodiment. FIG. 9 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the fourth embodiment. FIG. 10 is a perspective view schematically showing the configuration of a pair of holes of the quartz crystal vibrating element according to the fifth embodiment. FIG. 11 is a cross-sectional view schematically showing a configuration of one of the pair of holes of the quartz crystal vibrating element according to the sixth embodiment, which is opposed to the first vibrating arm in the first direction. FIG. 12 is a cross-sectional view schematically showing a configuration of one of the pair of holes of the quartz crystal vibrating element according to the sixth embodiment facing the second vibrating arm in the first direction. FIG. 13 is a perspective view schematically showing the configuration of a pair of holes of a crystal vibrating element according to a seventh embodiment. FIG. 14 is a flowchart showing manufacturing steps of the crystal vibrating element according to the eighth embodiment. FIG. 15 is a view showing a cross section along the electrical axis of the quartz substrate in the step of cutting the quartz substrate shown in FIG. FIG. 16 is a view showing a cross section along the mechanical axis of the quartz substrate in the step of cutting the quartz substrate shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, in the second embodiment and thereafter, the same or similar components as or to those of the first embodiment are denoted by the same or similar reference numerals as those of the first embodiment, and the detailed description will be appropriately omitted. Further, with regard to the effects obtained in the second and subsequent embodiments, the description of the same effects as those of the first embodiment will be appropriately omitted. The drawings of the respective embodiments are exemplifications, and the dimensions and shapes of the respective parts are schematic, and the technical scope of the present invention should not be interpreted as being limited to the embodiments.

First Embodiment
First, with reference to FIG. 1 to FIG. 3, a quartz crystal vibrating element 10 according to a first embodiment of the present invention and a quartz crystal vibrator 1 including the quartz crystal vibrating element 10 will be described. FIG. 1 is an exploded perspective view schematically showing the configuration of a quartz oscillator. FIG. 2 is a cross sectional view schematically showing a configuration of a cross section taken along line II-II of the crystal unit shown in FIG. FIG. 3 is a plan view schematically showing the configuration of the crystal vibrating element according to the first embodiment.

  In addition, illustration is abbreviate | omitted about electrodes, such as an excitation electrode and the connection electrode with which the quartz crystal vibrating element 10 is equipped, in FIGS. Further, the first direction D1, the second direction D2, and the third direction D3 shown in the drawing are, for example, directions orthogonal to each other. The first direction D1, the second direction D2, and the third direction D3 may be directions intersecting each other at an angle other than 90 °. Further, the first direction D1, the second direction D2, and the third direction D3 are not limited to the direction (positive direction) of the arrow shown in FIG. 1, but also includes the direction (negative direction) opposite to the arrow.

  In the following description, a quartz crystal resonator unit (Quartz Crystal Resonator Unit) including a quartz crystal resonator (Quartz Crystal Resonator) will be described as an example of a piezoelectric vibrator (Piezoelctric Resonator Unit). The quartz crystal vibrating element is a type of piezoelectric vibrating element (Piezoelctric Resonator) that utilizes a quartz crystal element (Quartz Crystal Element) as a piezoelectric element that vibrates according to an applied voltage. However, the piezoelectric vibrator according to each embodiment of the present invention is not limited to the quartz vibrator, and may use a piezoelectric vibrating element made of another piezoelectric piece such as ceramic.

  As shown in FIG. 1, the crystal unit 1 includes a crystal vibrating element 10, a lid member 20, a base member 30, and a bonding member 40. The base member 30 and the lid member 20 are a holder for housing the quartz crystal vibrating element 10. In the example illustrated here, the lid member 20 has a concave shape, specifically a box shape having an opening, and the base member 30 has a flat shape. The shapes of the lid member 20 and the base member 30 are not limited to the above, and for example, the base member may have a concave shape, and the concave member has an opening on the side where both the lid member and the base member face each other. It may be

  The quartz crystal vibrating element 10 has a quartz piece 11. The crystal piece 11 is, for example, a Z plate crystal piece. For example, in an orthogonal coordinate system consisting of an X axis, a Y axis, and a Z axis, rotate in the range of 0 degrees to 5 degrees clockwise around the Z axis and parallel to a plane specified by the X axis and Y axis Plane (hereinafter referred to as “XY plane”; the same applies to planes specified by other axes or other directions) is the main surface of the Z-plate quartz piece, and has a length in the direction parallel to the Z axis Is the thickness of the Z plate crystal piece. The Z plate quartz crystal piece is formed, for example, by etching a quartz substrate obtained by cutting and polishing an ingot of Synthetic Quartz Crystal. The X-axis, the Y-axis, and the Z-axis are crystal axes of quartz, and the X-axis corresponds to an electric axis, the Y-axis corresponds to a mechanical axis, and the Z-axis corresponds to an optical axis. The X axis is a polar axis having a positive direction. Hereinafter, the direction parallel to the Y axis is referred to as the Y axis direction. The same applies to other axial directions. The crystal piece 11 may apply a different cut other than the Z plate crystal piece. For example, the main surface of the crystal piece 11 may be a surface inclined several degrees from the XY plane.

  In the crystal vibrating element 10, the Y axis is parallel to the first direction D1, the X axis is parallel to the second direction D2, and the Z axis is parallel to the third direction D3. In the X axis direction which is a polar axis, the + X axis direction is a positive direction in the second direction D2, and the −X axis direction is a negative direction in the second direction D2. However, the first direction D1 may be along the Y-axis direction, and may be inclined, for example, in the range of -5 degrees to +5 degrees from the Y-axis direction. Similarly, the second direction D2 may be inclined in the range of -5 degrees to +5 degrees from the X axis direction, and the third direction D3 may be inclined in the range of -5 degrees to +5 degrees from the Z axis direction.

  As shown in FIGS. 1 and 3, the quartz crystal vibrating element 10 formed of the quartz plate 11 of the Z plate has a base 50 and a tuning fork having a pair of vibrating arms 60 extending from the base 50 in the first direction D1. Type crystal oscillator (Tuning Fork Type Quartz Crystal Resonator).

  The base 50 has a surface (first main surface) 50 a on the side facing the lid member 20 and a back surface (second main surface) 50 b on the side facing the base member 30. The base 50 is provided with a pair of holes 70 in the third direction D3 so as to face the pair of vibrating arms 60 in the first direction D1. The pair of holes 70 is a first hole 71 positioned on the positive direction side of the second direction D2 with respect to an imaginary center line C1 along the first direction D1 passing the center of the base 50 in the second direction D2. The second holes 72 located on the negative direction side of the second direction D2 are collectively referred to.

  The first hole 71 and the second hole 72 are provided at the root of a first vibrating arm 61 and a second vibrating arm 62, which will be described later. Therefore, the first hole 71 faces the first vibrating arm 61 described later in the first direction D1, and the second hole 72 faces the second vibrating arm 62 described later in the first direction D1. In addition, the first holes 71 and the second holes 72 are arranged at an interval in the second direction D2 as an example.

  However, the positions of the first hole 71 and the second hole 72 with respect to the center line C1 are not limited to the above, and may be provided to exceed the center line C1. Specifically, the first hole 71 may extend to the negative direction side in the second direction D2 with respect to the center line C1, and the second hole 72 may extend in the positive direction in the second direction D2 with respect to the center line C1. It may extend to the side. In addition, the arrangement of the first holes 71 and the second holes 72 is not limited to the above, and may be provided so as to be deviated in the first direction D1, and parts of each other may be arranged in the first direction D1. .

  The first hole 71 and the second hole 72 are asymmetric with respect to the center line C1. That is, the first hole 71 and the second hole 72 are different in volume, position, number, and the like. By providing the first hole 71 and the second hole 72, the rigidity of the base 50 changes asymmetrically with respect to the center line C1. The first hole 71 and the second hole 72 also affect the rigidity balance of the pair of vibrating arms 60. By the way, considering the pair of holes 70 in a neglected manner, the pair of vibrating arms 60 can be formed by the asymmetry of the mechanical strength of the material due to the anisotropy of the crystal structure of quartz and the shape asymmetry by the etching residue. The stiffness balance is broken. For example, when the rigidity of the first vibrating arm 61 is higher than the rigidity of the second vibrating arm 62, the first hole 71 provided at the root of the first vibrating arm 61 is provided at the root of the second vibrating arm 62 Made larger than the second hole 72. Thereby, the rigidity balance of the pair of vibrating arms 60 can be improved by setting the rigidity reduction of the first vibrating arms 61 by the pair of holes 70 to be greater than the rigidity reduction of the second vibrating arms 62. Thus, the stiffness balance of the pair of vibrating arms 60 is calculated or measured, and the asymmetric pair of holes 70 is provided to improve the stiffness balance.

  Similar to the base 50, the pair of vibrating arms 60 also have a surface (first main surface) 60a on the side facing the lid member 20 and a back surface (second main surface) 60b on the side facing the base member 30. . The pair of vibrating arms 60 extends from the positive direction side of the base 50 in the first direction D1, and collectively refers to the first vibrating arms 61 and the second vibrating arms 62 aligned in the second direction D2. The first vibrating arm portion 61 and the second vibrating arm portion 62 are provided so as to sandwich the center line C1, and the first vibrating arm portion 61 is positioned on the positive direction side in the second direction D2 than the second vibrating arm portion 62. ing. The first vibrating arm portion 61 and the second vibrating arm portion 62 are each provided with a first groove 63a with a bottom along the first direction D1 in the first major surface 60a, and the first direction in the second major surface 60b. A bottomed second groove 63b is provided along D1. The first groove 63a and the second groove 63b face each other in the third direction D3. Thus, by providing the first groove 63a and the second groove 63b, the ease of movement of the first vibrating arm 61 and the second vibrating arm 62 is improved, and the first vibrating arm 61 and the second vibrating arm Vibration leakage from the portion 62 to the base 50 can be suppressed.

  The shape of the lid member 20 is concave and has a box shape opened toward the first major surface 32 a of the base member 30. The lid member 20 is joined to the base member 30 to provide an internal space 26 surrounded by the lid member 20 and the base member 30. The crystal vibrating element 10 is accommodated in the internal space 26. The shape of the lid member 20 is not particularly limited as long as the crystal vibrating element 10 can be accommodated, and for example, when the main surface of the top surface portion 21 is viewed in plan, it has a rectangular shape. The shape of the lid member 20 is defined by, for example, a long side parallel to the first direction D1, a short side parallel to the second direction D2, and a height parallel to the third direction D3. Although the material of the cover member 20 is not particularly limited, it is made of, for example, a conductive material such as metal. The lid member 20 containing a conductive material has an electromagnetic shielding function of shielding at least a part of the electromagnetic wave.

  As shown in FIG. 2, the lid member 20 has an inner surface 24 and an outer surface 25. The inner surface 24 is a surface on the inner space 26 side, and the outer surface 25 is a surface opposite to the inner surface 24. The lid member 20 is connected to the top surface 21 facing the first main surface 32 a of the base member 30 and the outer edge of the top surface 21 and is a sidewall extending in a direction intersecting the main surface of the top surface 21. And 22. Further, the lid member 20 has an opposing surface 23 opposed to the first major surface 32 a of the base member 30 at the concave opening end (the end of the side wall 22 closer to the base member 30). The facing surface 23 extends in a frame shape so as to surround the periphery of the crystal vibrating element 10.

  The base member 30 holds the crystal vibrating element 10 so as to be able to excite. The base member 30 has a flat plate shape. The base member 30 has a long side parallel to the first direction D1, a short side parallel to the second direction D2, and a thickness parallel to the third direction D3. The base member 30 has a base 31. The base 31 has a first main surface 32a (front surface) and a second main surface 32b (back surface) facing each other. The base 31 is, for example, a sintered material such as insulating ceramic (alumina). The base 31 is preferably made of a heat resistant material.

  The base member 30 has electrode pads 33a and 33b provided on the first major surface 32a, and external electrodes 35a, 35b, 35c and 35d provided on the second major surface 32b. The electrode pads 33 a and 33 b are terminals for electrically connecting the base member 30 and the crystal vibrating element 10. The external electrodes 35a, 35b, 35c, and 35d are terminals for electrically connecting the unshown circuit board and the crystal unit 1. The electrode pad 33a is electrically connected to the external electrode 35a via the via electrode 34a extending in the third direction D3, and the electrode pad 33b is an external electrode via the via electrode 34b extending in the third direction D3. It is electrically connected to 35b. The via electrodes 34a and 34b are formed in via holes penetrating the base 31 in the third direction D3. The external electrodes 35c and 35d may be dummy electrodes to which no electrical signal or the like is input / output, or may be ground electrodes for supplying a ground potential to the lid member 20 to improve the electromagnetic shielding function of the lid member 20. The external electrodes 35c and 35d may be omitted.

  The conductive holding members 36 a and 36 b are provided between the first major surface 32 a of the base member 30 and the second major surface 50 b of the base 50 of the crystal vibrating element 10. The conductive holding members 36 a and 36 b electrically connect the crystal vibrating element 10 to the pair of electrode pads 33 a and 33 b of the base member 30. The conductive holding members 36 a and 36 b hold the crystal vibrating element 10 on the first main surface 32 a of the base member 30 so as to be able to excite. The conductive holding members 36a and 36b are made of, for example, a conductive adhesive containing a thermosetting resin or an ultraviolet curable resin containing an epoxy resin or a silicone resin as a main component, and in order to impart conductivity to the adhesive. Conductive particles, and the like. Furthermore, a filler may be added to the adhesive for the purpose of increasing the strength or for the purpose of keeping the distance between the base member 30 and the quartz crystal vibrating element 10.

  A sealing member 37 is provided on the first major surface 32 a of the base member 30. In the example shown in FIG. 1, the shape of the sealing member 37 is a rectangular frame when the first main surface 32 a is viewed in plan. When the first major surface 32 a is viewed in plan, the electrode pads 33 a and 33 b are disposed inside the sealing member 37, and the sealing member 37 is provided so as to surround the crystal vibrating element 10. The sealing member 37 is made of a conductive material. For example, by forming the sealing member 37 with the same material as the electrode pads 33a and 33b, the sealing member 37 can be provided simultaneously in the process of providing the electrode pads 33a and 33b.

  The bonding member 40 is provided along the entire circumference of the lid member 20 and the base member 30. Specifically, the bonding member 40 is provided on the sealing member 37 and is formed in a rectangular frame shape. The sealing member 37 and the bonding member 40 are sandwiched between the facing surface 23 of the side wall 22 of the lid member 20 and the first major surface 32 a of the base member 30.

  An internal space (cavity) in which the quartz crystal vibrating element 10 is surrounded by the lid member 20 and the base member 30 by joining the lid member 20 and the base member 30 with the sealing member 37 and the bonding member 40 interposed therebetween. 26 is sealed. The internal space 26 preferably has a pressure lower than the atmospheric pressure, and more preferably a vacuum. According to this, it is possible to reduce the temporal fluctuation of the frequency characteristic of the crystal unit 1 due to the oxidation of the first excitation electrode 81 and the second excitation electrode 82 described later. The sealing member 37 may be provided in a discontinuous frame shape, and the bonding member 40 may also be provided in a discontinuous frame shape.

  Next, the detailed configuration of the pair of vibrating arms 60 and the operation of the crystal vibrating element 10 will be described with reference to FIG. 4. FIG. 4 is a cross sectional view schematically showing a configuration of a cross section taken along line IV-IV of the quartz crystal vibrating element shown in FIG.

  A first excitation electrode 81 and a second excitation electrode 82 are provided on the surfaces of the first vibrating arm 61 and the second vibrating arm 62, respectively. The first excitation electrodes 81 are provided on both side surfaces of the first vibrating arm 61 and the second vibrating arm 62. The two side surfaces are a pair of side surfaces connecting the first main surface 60a and the second main surface 60b. Therefore, the first excitation electrode 81 faces the first vibrating arm 61 and the second vibrating arm 62 so as to sandwich the first vibrating arm 61 and the second vibrating arm 62 in the second direction D2. The second excitation electrode 82 is provided in each of the first groove 63a and the second groove 63b in the first main surface 60a and the second main surface 60b. The second excitation electrode 82 is also provided outside the first groove 63a and the second groove 63b.

  The first excitation electrode 81 and the second excitation electrode 82 are, for example, electrodes made of a metal film of a multilayer structure having nickel (Ni) or chromium (Cr) as an underlayer and gold (Au) as the outermost layer. Since chromium has high adhesion to the crystal piece, peeling of the excitation electrode due to long-term continuous operation can be suppressed. Since gold has high chemical stability, it is possible to suppress the fluctuation of the vibration characteristic due to the oxidation of the excitation electrode.

  The first excitation electrode 81 and the second excitation electrode 82 are electrically connected to the external electrode 35a and the external electrode 35b through the conductive holding member 36a and the conductive holding member 36b, respectively. When the first excitation electrode 81 and the second excitation electrode 82 form an electric field inside the first vibrating arm 61 and the second vibrating arm 62, both side surfaces of the first vibrating arm 61 and the second vibrating arm 62 Stretches based on the magnitude of the voltage of the electric field. By applying an alternating electric field of a specific frequency between the first excitation electrode 81 and the second excitation electrode 82, the first vibrating arm 61 and the second vibrating arm 62 are shown in FIG. 3 as a pair of vibrating arms. It vibrates at a resonant frequency so as to approach or move away from one another in the direction of the arrow illustrated at the tip of 60.

  Next, the configuration of the end face of the base 50 will be described with reference to FIG. FIG. 5 is an enlarged plan view more specifically showing the structure of the base of the quartz crystal vibrating element. The base 50 is formed by cutting a quartz substrate by wet etching described later.

  Crystal has a characteristic that in chemical etching such as wet etching, the etching rate differs depending on the crystal orientation. Therefore, etching residues L1, L2, and L3 having different sizes are generated on the end face of the quartz piece 11 processed by wet etching. The etching residue L1 is a residue extending in the + X axis direction from the first major surface 50a when the first major surface 50a of the base 50 is viewed in plan. Similarly, the etching residue L2 is a residue extending in the −X axis direction from the first major surface 50a, and the etching residue L3 is a residue extending in the Y axis direction from the first major surface 50a. In addition, although an etching residue is actually formed on the end face of the crystal piece 11 as shown in FIG. 5, in the other drawings, the illustration of the etching residue is omitted to simplify the description.

  The etching residue is the largest in the + X axis direction, the second largest in the −X axis direction, and the smallest in the Y axis direction. Therefore, when the first main surface 50a of the base 50 is viewed in plan, the sizes of the etching residues L1, L2, and L3, ie, the widths from the first main surface 50a to the respective tips, become L1> L2> L3. . Further, in FIG. 5, although the size of the etching residue is illustrated as being different only in the + X axis direction, the −X axis direction, and the Y axis direction, actually, the sizes of the etching residue are different in the + X axis direction and the Y axis direction Also, the directions between them and the directions between the −X axis direction and the Y axis direction are different. The balance of rigidity of the pair of vibrating arms 60 is broken due to the anisotropy of the size of the etching residue, that is, the anisotropy of the end face shape of the quartz piece 11, for example, the rigidity of the first vibrating arm 61 is The rigidity of the vibrating arm 62 is higher than that of the vibrating arm 62.

  Next, the configuration of the pair of holes 70 will be described with reference to FIG. FIG. 6 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the first embodiment.

  The first hole 71 and the second hole 72 are bottomed non-through holes (recesses) having the first opening AP11 and the second opening AP12 on the first main surface 50a side of the base 50, respectively. The first hole 71 has a first length L11 in the first direction D1, a first width W11 in the second direction D2, and a first depth D11 in the third direction D3. Further, the first hole 71 is provided at a first distance P11 from the center line C1. The first length L11 corresponds to the length of the first opening AP11 in the first direction D1. The first width W11 corresponds to the width of the first opening AP11 in the second direction D2. The first depth D11 corresponds to the depth in the third direction D3 at the position of the lowest surface farthest from the first major surface 50a. The first distance P11 corresponds to the distance in the second direction D2 from the edge on the center line C1 side of the first opening AP11 to the center line C1. Similarly, the second hole 72 also has a second length L12 in the first direction D1, a second width W12 in the second direction D2, and a second depth D12 in the third direction D3. Further, the second hole 72 is provided at a position of a second distance P12 from the center line C1.

  The first length L11 is larger than the second length L12. The first width W11 and the second width W12 are substantially equal in size. The first depth D11 and the second depth D12 are also approximately equal in size. The first distance P11 and the second distance P12 are also substantially equal. Therefore, the area of the first opening AP11 is larger than the area of the second opening AP12, and the volume of the internal space of the first hole 71 is larger than the volume of the internal space of the second hole 72. Thereby, the reduction rate of the rigidity of the first vibrating arm portion 61 by the first hole 71 is larger than the reduction rate of the rigidity of the second vibrating arm portion 62 by the second hole 72. Therefore, the rigidity balance of the pair of vibrating arms 60 can be improved. In addition, since the 1st hole 71 and the 2nd hole 72 are crevices with a bottom, the 1st depth D11 and the 2nd depth D12 are smaller than thickness T1 in the 3rd direction D3 of base 50. As shown in FIG.

Second Embodiment
Next, the configuration of the pair of holes 270 in the quartz crystal vibrating device 210 according to the second embodiment will be described with reference to FIG. FIG. 7 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the second embodiment. The second embodiment can obtain the same effect as that of the first embodiment.

  The difference from the crystal vibrating element 10 according to the first embodiment is the shapes of the first hole 271 and the second hole 272. Specifically, the first opening AP21 extends in the second direction D2 more than the second opening AP22. More specifically, the first length L21 and the second length L22 have substantially the same size. The first width W21 is larger than the second width W22. The first depth D21 and the second depth D22 are also approximately equal in size. Further, the first distance P21 and the second distance P22 are also approximately equal in size. Thus, the reduction rate of the rigidity of the first vibrating arm portion 261 due to the first hole 271 is larger than the reduction rate of the rigidity of the second vibrating arm portion 262 due to the second hole 272.

Third Embodiment
Next, the configuration of the pair of holes 370 in the crystal vibrating device 310 according to the third embodiment will be described with reference to FIG. FIG. 8 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the third embodiment. The third embodiment can obtain the same effect as that of the first embodiment.

  The difference from the crystal vibrating element 10 according to the first embodiment is the shapes of the first hole 371 and the second hole 372. Specifically, the shapes of the first opening AP31 and the second opening AP32 are substantially equal, and the first depth D31 and the second depth D32 are different. More specifically, the first length L31 and the second length L32 have substantially the same size. The first width W31 and the second width W32 are also substantially equal. The first depth D31 is larger than the second depth D32. In addition, the first distance P31 and the second distance P32 are also substantially equal. Thus, the reduction rate of the rigidity of the first vibrating arm portion 361 due to the first hole 371 is larger than the reduction rate of the rigidity of the second vibrating arm portion 362 due to the second hole 372.

Fourth Embodiment
Next, the configuration of the pair of holes 470 in the crystal vibrating device 410 according to the fourth embodiment will be described with reference to FIG. FIG. 9 is a perspective view schematically showing the configuration of a pair of holes of the crystal vibrating element according to the fourth embodiment. The fourth embodiment can obtain the same effect as that of the first embodiment.

  The difference from the crystal vibrating element 10 according to the first embodiment is that the shapes of the first holes 471 and the second holes 472 are equal, and the positions with respect to the pair of vibrating arms 460 are different. Specifically, the first length L41 and the second length L42 have substantially the same size. The first width W41 and the second width W42 are also substantially equal. The first depth D41 and the second depth D42 are also substantially equal in size. Further, the first distance P41 and the second distance P42 are also approximately equal in size. However, the distance between the first hole 471 and the first vibrating arm 461 is shorter than the distance between the second hole 472 and the second vibrating arm 462. In other words, the first hole 471 is provided closer to the pair of vibrating arms 460 than the second hole 472. Thus, the reduction rate of the rigidity of the first vibrating arm portion 461 due to the first hole 471 is larger than the reduction rate of the rigidity of the second vibrating arm portion 462 due to the second hole 472.

Fifth Embodiment
Next, the configuration of the pair of holes 570 in the crystal vibrating device 510 according to the fifth embodiment will be described with reference to FIG. FIG. 10 is a perspective view schematically showing the configuration of a pair of holes of the quartz crystal vibrating element according to the fifth embodiment. The fifth embodiment can obtain the same effect as that of the first embodiment.

The difference from the crystal vibrating element 10 according to the first embodiment is that the shapes of the first hole 571 and the second hole 572 are equal and the distances from the center line C5 are different. Specifically, the first length L51 and the second length L52 are substantially equal in size. The first width W51 and the second width W52 are also substantially equal. The first depth D51 and the second depth D52 are also substantially equal in size. The first distance P51 is larger than the second distance P42. In other words, the first holes 571 are closer to the end of the base 550 than the second holes 572. Accordingly, the reduction rate of the rigidity of the first vibrating arm portion 561 due to the first hole 571 is larger than the reduction rate of the rigidity of the second vibrating arm portion 562 due to the second hole 572.
Sixth Embodiment
Next, the configuration of the pair of hole groups 670 in the crystal vibrating device 610 according to the sixth embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a cross-sectional view schematically showing a configuration of one of the pair of holes of the quartz crystal vibrating element according to the sixth embodiment, which is opposed to the first vibrating arm in the first direction. FIG. 12 is a cross-sectional view schematically showing a configuration of one of the pair of holes of the quartz crystal vibrating element according to the sixth embodiment facing the second vibrating arm in the first direction. 11 and 12 are cross sections parallel to the XZ plane of the crystal vibrating element 610. FIG. The sixth embodiment can obtain the same effect as that of the first embodiment.

  A difference from the crystal vibrating element 10 according to the first embodiment is that a pair of hole groups 670 facing in the first direction D1 are provided in the base 650. The pair of hole groups 670 consists of a set of three holes and a set of two holes.

  Specifically, a first hole 671, a third hole 673, and a fifth hole 675 are provided as a set of three holes so as to face the first vibrating arm portion 661. The first hole 671 and the fifth hole 675 have a first opening AP61 and a fifth opening AP65 on the first main surface 650a, respectively, and are aligned in the first direction D1. The third hole 673 has a third opening AP63 in the second major surface 650b. The third hole 673 is provided between the first hole 671 and the fifth hole 675 in the first direction D1. The first hole 671, the third hole 673, and the fifth hole 675 are provided such that a portion of each overlaps in the first direction D1, so that vibration leakage from the first vibrating arm 661 is effectively performed. It can be suppressed.

  On the other hand, a second hole 672 and a fourth hole 674 are provided as a set of two holes so as to face the second vibrating arm portion 662. The second hole 672 has a second opening AP62 in the first major surface 650a. The fourth hole 674 has a fourth opening AP64 in the second major surface 650b. Similarly, the second hole 672 and the fourth hole 674 are provided so that parts thereof overlap each other in the first direction D1, so that vibration leakage from the second vibrating arm 662 can be effectively suppressed. Since the number of holes facing the first vibrating arm 661 is larger than the number of holes facing the second vibrating arm 662, the reduction rate of the rigidity of the first vibrating arm 661 due to the first hole 671 is the second The reduction rate of the rigidity of the second vibrating arm 662 due to the hole 672 is larger. The number of holes facing the first vibrating arm 661 and the second vibrating arm 662 is not particularly limited, and the number of holes facing the first vibrating arm 661 is the second vibrating arm 662 The number of holes facing the second vibrating arm 662 may be at least one as long as it is larger than the number of holes facing each other.

Seventh Embodiment
Next, the configuration of the pair of holes 770 in the crystal vibrating device 710 according to the seventh embodiment will be described with reference to FIG. FIG. 13 is a perspective view schematically showing the configuration of a pair of holes of a crystal vibrating element according to a seventh embodiment. The seventh embodiment can obtain the same effect as that of the first embodiment.

  The difference from the crystal vibrating element 10 according to the first embodiment is that the first holes 771 and the second holes 772 are through holes. Specifically, the first hole 771 has a first opening AP71 on the first main surface 750a side, and a third main surface AP73 on the second main surface 750b side. The second hole 772 has a second opening AP72 on the side of the first main surface 750a, and has a fourth main surface AP74 on the side of the second main surface 750b. The first length L71 is larger than the second length L72, and the first width W71 and the second width W72 are substantially equal. The depths of the first hole 771 and the second hole 772 are approximately equal to the thickness T7 of the base 750. Thus, the reduction rate of the rigidity of the first vibrating arm portion 761 due to the first hole 771 is larger than the reduction rate of the rigidity of the second vibrating arm portion 762 due to the second hole 772.

Eighth Embodiment
Next, a method of manufacturing a quartz crystal vibrating element according to the eighth embodiment will be described with reference to FIGS. Further, the generation mechanism of the etching residues L1, L2, and L3 will be described. FIG. 14 is a flowchart showing manufacturing steps of the crystal vibrating element according to the eighth embodiment. FIG. 15 is a view showing a cross section along the electrical axis of the quartz substrate in the step of cutting the quartz substrate shown in FIG. FIG. 16 is a view showing a cross section along the mechanical axis of the quartz substrate in the step of cutting the quartz substrate shown in FIG. The eighth embodiment corresponds to a manufacturing process of the crystal piece 911 applicable to the crystal vibrating element according to each of the above-described embodiments. After the step shown in FIG. 14, a quartz vibrating element is completed through steps of providing electrodes such as excitation electrodes.

  First, a quartz substrate is prepared (S11). The quartz substrate 910 is a plate-like member cut out from a single crystal of artificial quartz so that the XY plane becomes the first major surface 910a and the second major surface 910b, and is, for example, a quartz wafer. The quartz substrate 910 is not limited to a quartz wafer as long as it can form a collective element of quartz oscillation elements, and may be, for example, a member separated from a quartz wafer. The quartz substrate 910 may be planarized by a polishing process such as chemical mechanical polishing after being cut into a flat plate shape. By adjusting the thickness of the quartz substrate 910 by this polishing process, it is possible to adjust the frequency characteristics as a quartz crystal vibrating element.

  Next, a photoresist layer is provided (S12). In step S12, first, the first metal layer 912a is provided on the first major surface 910a of the quartz substrate 910 such that the first metal layer 912a and the second metal layer 912b sandwich the quartz substrate 910, and the second major surface 910b is formed. A second metal layer 912b is provided. The first metal layer 912a and the second metal layer 912b correspond to a corrosion resistant film against an etching solution (for example, ammonium fluoride or buffered hydrofluoric acid) used when etching the quartz substrate 910, and improve the processing accuracy of etching. . As the first metal layer 912a and the second metal layer 912b, for example, a multilayer film having a chromium (Cr) layer and a gold (Au) layer is used. The Cr layer improves the adhesion of the first metal layer 912a and the second metal layer 912b to the quartz substrate 910 as an underlayer. Also, the Au layer improves the corrosion resistance of the first metal layer 912a and the second metal layer 912b as the outermost layer. The method of forming the first metal layer 912a and the second metal layer 912b is not particularly limited. For example, the first metal layer 912a and the second metal layer 912b may be provided by dry plating (dry process) such as evaporation or sputtering. Process).

  In step S12, next, the first photoresist layer 913a is provided on the first metal layer 912a so that the first photoresist layer 913a and the second photoresist layer 913b sandwich the quartz substrate 910, and the second metal layer is formed. A second photoresist layer 913 b is provided on 912 b. The first photoresist layer 913a and the second photoresist layer 913b respectively apply a photoresist solution containing a photoresist material on the first metal layer 912a and the second metal layer 912b, and evaporate the solvent by heating. Film formation. The coating method of the photoresist solution is not particularly limited, and examples thereof include spin coating and spray coating. The photoresist material is a positive photosensitive resin in which the solubility of the exposed portion is high from the viewpoint of improving the processing accuracy of the pattern obtained by developing the first photoresist layer 913a and the second photoresist layer 913b. Is desirable.

  Next, the photoresist layer is exposed (S13). In step S13, the first photoresist layer 913a and the second photoresist layer 913b are irradiated with light such as ultraviolet light through a photomask on which the outline patterns of the plurality of crystal pieces 911 are drawn. The exposure apparatus used for exposure may be a single-sided exposure apparatus that exposes only one of the first photoresist layer 913a and the second photoresist layer 913b, or a double-sided exposure apparatus capable of simultaneously exposing both of them.

  Next, the photoresist layer is developed (S14). When the first photoresist layer 913a and the second photoresist layer 913b are positive photosensitive resin, the exposed portion is developed by immersing the first photoresist layer 913a and the second photoresist layer 913b in a developer. It dissolves in the solution and is removed. As a result, parts of the first metal layer 912a and the second metal layer 912b are exposed based on the external pattern of the quartz piece 911 respectively.

  Next, the quartz substrate is cut by wet etching (S15). In step S15, first, the first metal layer 912a and the second metal layer 912b exposed based on the external pattern of the crystal piece 911 are removed. Thereby, a part of the quartz substrate 910 is exposed based on the external pattern of the quartz piece 911. The first metal layer 912a and the second metal layer 912b are removed by, for example, wet etching of a Cr layer using a cerium-based etching solution and wet etching of an Au layer using an iodine-based etching solution.

  Next, in step S15, the exposed portion of the quartz substrate 910 is etched. The quartz substrate 910 is removed by wet etching using, for example, a hydrofluoric acid-based etching solution. By simultaneously etching the quartz substrate 910 from both sides of the first main surface 910a and the second main surface 910b, the processing speed and the processing accuracy are improved more than the processing method in which the etching processing is performed from one side.

  Next, the photoresist layer is removed (S16). At the stage when the etching of the quartz substrate 910 is finished, the first metal layer 912a and the first photoresist layer 913a remain on the first main surface 910a of the quartz substrate 910, and the second metal layer 912b and The second photoresist layer 913 b remains. The residue of the first photoresist layer 913a and the second photoresist layer 913b is removed from the quartz substrate 910 by solvent cleaning, and then the residue of the first metal layer 912a and the second metal layer 912b is removed.

  In the above-described step S15, since etching speeds (etching rates) of single crystals of quartz differ depending on crystal orientation, etching residues L1, L2, and L3 are formed on the quartz piece 911 formed by etching. The etching residues L1, L2, and L3 are flared portions extending outward from the first major surface 911a in different sizes according to the crystal axis direction when the first major surface 911a of the quartz crystal piece 911 is viewed in plan. It is.

  As shown in FIG. 15, when viewed in a cross section parallel to the XZ plane, the crystal piece 911 has a first major surface 911a, a second major surface 911b, an etching residue L1, and an etching residue L2. The first major surface 911 a and the second major surface 911 b correspond to portions covered with the first metal layer 912 a and the second metal layer 912 b as the quartz crystal substrate 910, respectively. The etching residue L1 corresponds to an end surface connecting the end portions of the first main surface 911a and the second main surface 911b in the + X axis direction (positive direction of the electric axis). The etching residue L2 corresponds to an end surface connecting the end portions of the first main surface 911a and the second main surface 911b in the -X-axis direction (the negative direction of the electric axis).

  In the region in which the etching residue L1 is formed, the quartz substrate 910 is etched in the direction in which the crystal plane is formed, for example. Specifically, the quartz substrate 910 is etched so as to approach the crystal plane from the first major surface 910a, whereby the first end face 911c is formed. Further, the second end face 911 d is formed by etching so as to approach the crystal plane from the second major surface 910 b. The first end surface 911 c is inclined with respect to the first major surface 911 a and the second end surface 911 d is inclined with respect to the second major surface 911 b in accordance with the inclination of the crystal plane with respect to the + X axis direction of the quartz crystal. As a result, the etching residue L1 is connected to the first end surface 911c connected to the first main surface 911a so as to form an obtuse angle on the crystal piece 911 side, and connected to the second main surface 911b so as to form an obtuse angle on the crystal piece 911 side. And an end face 911 d. The first end face 911 c and the second end face 911 d are connected so as to form an angle θ1 on the side of the crystal piece 911 at the tip of the etching residue L1 in the + X axis direction.

  Similarly, in the region where the etching residue L2 is formed, the quartz substrate 910 is etched, for example, to approach the crystal plane from the first major surface 910a, whereby the third end face 911e is formed. Also, the fourth end face 911 f is formed by etching so as to approach the crystal plane from the second major surface 910 b. The third end surface 911 e is inclined with respect to the first major surface 911 a and the fourth end surface 911 f is inclined with respect to the second major surface 911 b in accordance with the inclination of the crystal plane with respect to the −X axis direction of the crystal. As a result, the etching residue L2 is connected to the first main surface 911 a so as to form an obtuse angle on the crystal piece 911 side, and the fourth end surface is formed so as to form an obtuse angle on the crystal piece 911 side. And an end face 911 f. The third end face 911 e and the fourth end face 911 f are connected so as to form an angle θ2 on the side of the crystal piece 911 at the tip of the etching residue L 2 in the −X axis direction. Since the etching rates in the −X axis direction and the + X axis direction are different, the etching residue L2 is smaller than the etching residue L1.

  As shown in FIG. 16, when viewed in a cross section parallel to the YZ plane, the crystal piece 911 has a first major surface 911 a, a second major surface 911 b, and an etching residue L3. The etching residue L3 corresponds to an end surface connecting the end portions of the first major surface 911a and the second major surface 911b in the Y-axis (machine axis) direction.

  In the region where the etching residue L3 is formed, the quartz substrate 910 is etched, for example, to approach the crystal plane from the first major surface 910a, whereby the fifth end face 911g is formed. Further, etching is performed so as to approach the crystal plane from the second major surface 910 b, whereby the sixth end face 911 h is formed. The fifth end face 911 g is inclined with respect to the first major surface 911 a and the sixth end face 911 h is inclined with respect to the second major surface 911 b in accordance with the inclination of the crystal plane with respect to the Y axis direction of the quartz crystal. As a result, the etching residue L3 is composed of the fifth end face 911g and the sixth end face 911h. The fifth end face 911 g and the sixth end face 911 h are connected so as to form an angle θ3 on the side of the crystal piece 911 at the tip of the etching residue L3 in the Y-axis direction. Since quartz has a crystal plane perpendicular to the Y axis, the angle of the fifth end face 911 g with respect to the first major surface 911 a is close to 90 degrees, and the angle of the sixth end face 911 h with respect to the second major surface 911 b is also close to 90 degrees. Therefore, the etching residue L3 is smaller than the etching residue L2. Depending on the etching conditions, the angle of the fifth end surface 911 g with respect to the first main surface 911 a and the angle of the sixth end surface 911 h with respect to the second main surface 911 b are approximately 90 degrees. In that case, the angle θ3 is approximately 180 degrees, and the etching residue L3 does not substantially occur.

  In summary, in the quartz piece 911, the etching residue L3 is smaller than the etching residue L2 and the etching residue L2 is smaller than the etching residue L1 based on the anisotropy of the etching rate according to the crystal orientation of the quartz (L3 <L2 <L1 ). In addition, since the Y axis is not a polar axis, the etching residue on the positive direction side in the Y axis direction has substantially the same size as the etching residue on the negative direction side in the Y axis direction.

  Since the etching residue L2 is smaller than the etching residue L1, the sum of the lengths of the third end face 911e and the fourth end face 911f in the XZ plane is smaller than the sum of the lengths in the XZ plane of the first end face 911c and the second end face 911d. (911 e + 911 f <911 c + 911 d), the angle θ2 is larger than the angle θ1 (θ2> θ1). Further, since the etching residue L3 is smaller than the etching residue L2, the sum of the lengths of the fifth end face 911g and the sixth end face 911h in the YZ plane is greater than the sum of the lengths in the YZ plane of the third end face 911e and the fourth end face 911f. Is small (911 g + 911 h <911 e + 911 f), and the angle θ3 is larger than the angle θ2 (θ3> θ2). Due to the anisotropy of the shape of the etching residue, the rigidity balance of the pair of vibrating arms is broken when the pair of holes is disregarded and considered.

  As described above, according to one aspect of the present invention, the base 50, a pair of vibrating arms 60 extending from the base 50 in the first direction D1 and aligned in the second direction D2 intersecting the first direction D1, and the base 50, and a pair of holes 70 provided along a third direction D3 intersecting the first direction D1 and the second direction D2 so as to face the pair of vibrating arm portions 60 in the first direction D1, The pair of holes 70 is provided with the piezoelectric vibrating element 10 which is asymmetrical with respect to the imaginary center line C1 along the first direction D1 passing the center of the base 50 in the second direction D2.

  According to the above aspect, by providing the pair of holes asymmetric with respect to the center line, the rigidity balance of the pair of vibrating arms can be improved. In addition, vibration leakage from the pair of vibrating arms can be suppressed by the pair of holes. As a result of these, the vibration characteristics of the quartz crystal vibrating element are improved. Since the pair of holes have the opening on the first main surface or the second main surface of the base, concentration of stress can be suppressed as compared with the configuration in which the crotch portion between the pair of vibrating arms is cut. Thereby, the impact resistance of the crystal vibrating element can be improved, and the reduction in reliability can be suppressed.

  The pair of holes 70 may be non-through holes. According to this, the rigid fall of a base and a pair of oscillating arms by providing a pair of holes can be controlled.

  The pair of holes 70 may be through holes. According to this, since the transmission path of the vibration in the base is reduced, the vibration leakage from the pair of vibrating arms can be effectively suppressed.

  The pair of holes 70 may have different lengths L11 and L12 along the first direction D1. According to this, the above effect can be obtained.

  The pair of holes 270 may have different widths W21 and W22 along the second direction D2. According to this, the above effect can be obtained.

  The pair of holes 370 may have different depths D31 and D32 along the third direction D3. According to this, the above effect can be obtained.

  In the pair of holes 570, the magnitudes of the distances P51 and P52 from the center line C5 may be different from each other. According to this, the above effect can be obtained.

  The base 50 and the pair of vibrating arms 60 are provided by quartz crystal, and the electric axis of the quartz crystal may extend along the second direction D2. At this time, when the outer shape of the crystal piece is formed by chemical etching, an etching residue having shape anisotropy is formed. According to this, the rigidity balance of the pair of vibrating arms is lost, and for example, the rigidity of the first vibrating arm becomes higher than that of the second vibrating arm, but by providing the pair of holes in the base, the pair of vibrating arms Rigidity balance can be adjusted.

  The pair of holes 70 includes a first hole 71 provided on the positive direction side of the electrical axis with respect to the center line C1, and a second hole 72 provided on the negative direction side of the electrical axis with respect to the center line C1. The volume of the internal space of the first hole 71 may be larger than the volume of the internal space of the second hole 72. According to this, when the rigidity of the first vibrating arm is higher than that of the second vibrating arm, the rigidity of the first vibrating arm is lower than the rigidity of the second vibrating arm, whereby the pair of vibrating arms The rigidity balance of the part can be improved.

  As described above, according to one aspect of the present invention, it is possible to provide a piezoelectric vibration element capable of improving vibration characteristics and suppressing a decrease in reliability.

  The embodiments described above are for the purpose of facilitating the understanding of the present invention, and are not for the purpose of limiting and interpreting the present invention. The present invention can be modified / improved without departing from the gist thereof, and the present invention also includes the equivalents thereof. That is, those in which persons skilled in the art appropriately modify the design of each embodiment are also included in the scope of the present invention as long as they have the features of the present invention. For example, each element included in each embodiment and its arrangement, material, conditions, shape, size, and the like are not limited to those illustrated, and can be appropriately changed. Further, the elements included in each embodiment can be combined as much as technically possible, and combinations of these are included in the scope of the present invention as long as they include the features of the present invention.

DESCRIPTION OF SYMBOLS 1 ... crystal oscillator 10 ... crystal vibrating element 11 ... crystal piece 30 ... base member 40 ... joining member 50 ... base 60 ... pair of vibrating arm part 61 ... 1st vibrating arm part 62 ... 2nd vibrating arm part 70 ... pair of Hole 71: first hole 72: second hole C1: center line L1, L2, L3: etching residue

Claims (9)

The base,
A pair of vibrating arms extending in a first direction from the base and aligned in a second direction intersecting the first direction;
The base includes a pair of holes provided along a third direction intersecting the first direction and the second direction so as to face the pair of vibrating arms in the first direction,
The piezoelectric vibrating element according to claim 1, wherein the pair of holes is asymmetric with respect to a virtual center line along the first direction passing through a center of the base in the second direction. The pair of holes is a non-through hole,
The piezoelectric vibration element according to claim 1. The pair of holes is a through hole,
The piezoelectric vibration element according to claim 1. The pair of holes have different lengths in the first direction,
The piezoelectric vibration element according to any one of claims 1 to 3. The pair of holes have different widths in the second direction,
The piezoelectric vibration element according to any one of claims 1 to 4. The pair of holes have different depths in the third direction,
The piezoelectric vibration element according to any one of claims 1 to 5. The pair of holes have mutually different magnitudes of distance from the center line,
The piezoelectric vibration element according to any one of claims 1 to 6. The base and the pair of vibrating arms are provided by quartz;
The electrical axis of the crystal extends along the second direction,
The piezoelectric vibration element according to any one of claims 1 to 7. The pair of holes includes a first hole provided on the positive direction side of the electric axis with respect to the center line, and a second hole provided on the negative direction side of the electric axis with respect to the center line. ,
The volume of the inner space of the first hole is larger than the volume of the inner space of the second hole,
The piezoelectric vibration element according to claim 8.

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