JP2008218951A - Piezoelectric device with convex vibration piece - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric device capable of exhibiting superior vibration characteristics, even when its piezoelectric vibration piece is supported in a cantilever manner. <P>SOLUTION: The piezoelectric device includes a convex piezoelectric vibrating piece 20, with a cross-section in the thickness direction which becomes thinner as its both ends 20a, 20c are approached from its center 20b; and a package 36, having an inner bottom 37 on which one end 20a of both the ends 20a, 20c of the piezoelectric vibration piece 20 is bond-fixed. The piezoelectric vibration piece 20 has, on its free end 20c, a projection 50 that projects on a side facing the inner bottom 37 of the package. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a piezoelectric device in which a convex-shaped piezoelectric vibrating piece is joined to a package in a cantilever manner.

  Conventionally, piezoelectric devices have been used in small information devices such as HDDs (hard disk drives), mobile computers, and IC cards, mobile communication devices such as mobile phones, car phones, and paging systems, and measuring devices such as gyro sensors. The device is widely used.

FIG. 6 is a schematic longitudinal sectional view of a conventional piezoelectric device 1 (see, for example, Patent Document 1).
The piezoelectric device 1 in this figure has a piezoelectric vibrating piece 2 and a package 3 to which the piezoelectric vibrating piece 2 is bonded and fixed.
The piezoelectric vibrating reed 2 is provided with excitation electrodes 4 and 4 in the central portion, and the vibration energy of the main vibration is concentrated in the central portion so that a high Q value and good temperature characteristics can be obtained. The cross section is formed into a convex shape that becomes thinner from the central portion toward both end portions.
Such a piezoelectric vibrating piece 2 has one end 2 a bonded to the package 3 via an adhesive 5 and is bonded to the package 3 in a cantilever manner.

FIG. 7 is a schematic longitudinal sectional view of a piezoelectric device 10 showing another conventional example (see, for example, Patent Document 2).
The piezoelectric device 10 in this figure is different from the piezoelectric device 1 in FIG. 6 in that a piezoelectric vibrating piece 12 is bonded and fixed to a package 13 in a double-supported manner. That is, in the piezoelectric device 10, the peripheral portion 12 a of the piezoelectric vibrating piece 12 protrudes in the vertical direction from the central portion, and the peripheral portion 12 a is bonded and fixed to the package 13.

Japanese Patent Laid-Open No. 8-186457 Japanese Patent Laid-Open No. 58-157213

  Incidentally, in the piezoelectric device 1 in FIG. 6, the piezoelectric vibrating reed 2 is bonded and fixed to the package 3 in a cantilevered manner. The piece 2 may come into contact with the inner bottom 3a of the package 3, which may affect the vibration characteristics. In particular, since the piezoelectric vibrating reed 2 is convex, the swollen central excitation electrode 4 may come into contact with the inner bottom 3a of the package 3 before the free end 2b, and vibration characteristics may change. Will rise. In order to prevent such a situation from occurring, when the piezoelectric vibrating reed 2 is joined to the package 3, the free end 2b is lifted up while utilizing the shrinkage of the adhesive 5 during curing. However, work processing is difficult and the number of processes is increased as compared with piezoelectric devices other than the convex type.

  In this regard, in the piezoelectric device 10 of FIG. 7, since the piezoelectric vibrating piece 12 is bonded and fixed to the package 13 in a double-supported manner, the possibility that the central portion of the piezoelectric vibrating piece 12 contacts the package 13 is greatly reduced. . However, the bonding area of the piezoelectric vibrating piece 12 and the package 13 is large, and the distortion of the package 13 is easily transmitted to the piezoelectric vibrating piece 12 when the piezoelectric vibrating piece 12 is bonded to the package 13. Problems such as unstable characteristics are likely to occur.

  An object of the present invention is to provide a piezoelectric device having excellent vibration characteristics even when the piezoelectric vibrating piece is supported in a cantilever manner.

  According to the first aspect of the present invention, the convex piezoelectric vibrating piece having a thickness that decreases from the center toward both ends, and one end of the piezoelectric vibrating piece are bonded with an adhesive. A piezoelectric device including a package having an inner bottom, wherein the piezoelectric vibrating reed is a piezoelectric device in which a protrusion projecting toward the inner bottom side of the package is provided on a lower surface of a free end portion of the piezoelectric vibration piece. Achieved.

According to the configuration of the first invention, the piezoelectric device has a convex-shaped piezoelectric vibrating piece having one end portion bonded to the inner bottom with an adhesive and bonded to the package in a so-called cantilever manner. There is a high possibility that the swelled central portion of the piezoelectric vibrating piece contacts the package. However, the piezoelectric vibrating reed is provided with a protrusion protruding on the inner bottom side of the package on the lower surface of the free end. For this reason, for example, even when the piezoelectric vibrating piece is shaken in the thickness direction due to a drop impact, the protruding portion of the free end is brought into contact with the inner bottom of the package before the central portion of the piezoelectric vibrating piece. Thus, it is possible to effectively prevent the central portion of the piezoelectric vibrating piece, that is, the main vibration region from coming into contact with the inner bottom of the package.
Thus, according to the present invention, it is possible to provide a piezoelectric device having excellent vibration characteristics even when the piezoelectric vibrating piece is supported in a cantilever manner.

A second invention is characterized in that, in the configuration of the first invention, the protrusion is substantially spherical.
According to the configuration of the second invention, since the protrusion is substantially spherical, the area where the protrusion and the piezoelectric vibrating piece are in contact with each other is reduced, and the adverse effect on the vibration characteristics of the protrusion can be effectively prevented. Also, if the protrusion is substantially spherical, the area where the protrusion and the package come into contact is small and curved, so that dust or dust is less likely to be generated due to friction between the protrusion and the package, and the vibration characteristics are stabilized. Can do.

A third invention is characterized in that, in the configuration of the first or second invention, the protrusion is non-conductive.
According to the configuration of the third aspect of the invention, since the protrusion is nonconductive, an increase in stray capacitance in the package can be prevented. In particular, when a conductive pattern is routed around the inner bottom of the package, it is possible to suppress the influence exerted by the contact of the protruding portion with the package.

According to a fourth aspect of the invention, in any one of the first to third aspects, the protrusion is formed by epitaxially growing a free end of the piezoelectric vibrating piece.
According to the configuration of the fourth aspect of the invention, since the protrusion is formed by epitaxially growing the free end of the piezoelectric vibrating piece, an increase in stray capacitance is suppressed as compared with the case where the protrusion is formed of a metal bump. In addition, the generation of gas can be suppressed as compared with the case where the protrusion is formed of resin. Furthermore, batch processing is facilitated by epitaxial growth.

According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, the outer shape of the piezoelectric vibrating piece is formed in a quadrangular shape in plan view, and the corners of the excitation electrode provided in the central portion. The portion is chamfered or rounded, and the protrusion is provided at a corner of the free end.
According to the configuration of the fifth invention, in the plan view, the outer shape of the piezoelectric vibrating piece is formed in a square shape, and the corner portion of the excitation electrode provided in the central portion is chamfered or rounded, so that the free end In the region of the part, the corner is the position farthest from the excitation electrode. Since the protrusion is provided at a position farthest from the excitation electrode, it is difficult to be affected by the main vibration and can effectively prevent an adverse effect on the vibration characteristics.

According to a sixth invention, in any one of the first to fifth inventions, the protrusion is the first protrusion, and the piezoelectric vibrating piece protrudes upward on the upper surface of the free end portion thereof. A feature is that a second protrusion is provided.
According to the configuration of the sixth invention, since the piezoelectric vibrating piece is provided with the second protrusion protruding upward on the upper surface of the free end portion thereof, the piezoelectric vibrating piece has both the upper surface side and the lower surface side. Protrusions will be provided on. Therefore, the piezoelectric vibrating piece can be bonded to the package without having to select the upper surface and the lower surface alternatively. Furthermore, contact between the central portion of the piezoelectric vibrating piece and the lid can also be prevented on the lid side that seals the package.

According to a seventh invention, in any one of the first to sixth inventions, the inner bottom of the package is a flat surface.
According to the configuration of the seventh invention, since the inner bottom of the package is a flat surface, the package can be formed at low cost. That is, since the piezoelectric device is provided with the projection as in the first invention, it is not necessary to provide a special device for avoiding contact with the central portion of the piezoelectric vibrating piece on the package side. The bottom can be flat and the price of the package can be reduced.

1 and 2 show a piezoelectric device 30 according to a first embodiment of the present invention. FIG. 1 is a schematic plan view of the piezoelectric device 30, and FIG. 2 is a schematic sectional view taken along line AA of FIG. is there.
Note that the piezoelectric device means all products in which a piezoelectric vibrating piece is accommodated in a package regardless of the name of a piezoelectric vibrator or a piezoelectric oscillator.
The piezoelectric device 30 in these drawings shows an example in which a piezoelectric vibrator is configured, and the piezoelectric vibrating piece 20 is bonded and fixed to the inner bottom 37 of the package 36 in a cantilever manner.

In the present embodiment, for example, the package 36 is formed by laminating first and second substrates 36a and 36b formed by molding an aluminum oxide ceramic green sheet as an insulating material in order from the bottom, and then sintering. Is formed.
The second substrate 36 b is a substrate for forming a space surrounding the piezoelectric vibrating piece 20. In other words, a predetermined hole is formed on the inner side, so that a predetermined inner space S1 is formed on the inner side of the package 36 when stacked on the first substrate 36a. This internal space S1 becomes a cavity for accommodating the piezoelectric vibrating piece 20.

  Further, a brazing material 44 such as low-melting glass is applied to the opening end surface of the second substrate 36b on the side opened to the upper side in FIG. It is sealed. Even after the lid 39 is sealed, the metal film portion such as the excitation electrode provided on the piezoelectric vibrating piece 20 is irradiated with the laser beam LB so that the frequency can be adjusted by the mass reduction method. It is made of a material that transmits light, such as glass.

  The first substrate 36a is a substrate for forming the bottom of the package 36, and the inner bottom surface (that is, the inner bottom) 37 exposed to the internal space S1 is a flat surface. That is, by providing the protrusion 50 described later, the contact between the main vibration region of the piezoelectric vibrating piece 20 and the package 36 is remarkably reduced, so that the inner bottom 37 of the package 36 can be made a smooth plane. The protrusion 50 will be described in detail later.

  The inner bottom 37 exposed in the internal space S1 is provided with mounting electrodes 31 and 31 formed by nickel plating and gold plating on, for example, tungsten metallization. Each of the mounting electrodes 31, 31 is routed through the package 36 and connected to the mounting terminal portions 38, 38, thereby having different polarities and supplying a driving voltage to the piezoelectric vibrating piece 20. It becomes an electrode.

Then, a conductive adhesive such as silicone, epoxy, or polyimide is applied to the upper surfaces of the mounting electrodes 31, 31 as the adhesives 43, 43, and the piezoelectric vibrating reed 20 on the adhesives 43, 43. Only the one end portion 20a in the longitudinal direction is placed and the adhesives 43 and 43 are cured, so that the mounting electrodes 31 and 31 and the piezoelectric vibrating piece 20 are electrically and mechanically connected. For the adhesive 43 of this embodiment, a silicone-based conductive adhesive that is more flexible than an epoxy-based adhesive is used in order to prevent involvement of vibration leakage between the piezoelectric vibrating piece 20 and the package 36. It has been. The adhesive 43 has such a height that a portion other than the one end portion 20a of the piezoelectric vibrating piece 20 does not come into contact with the package 36 in a steady state (that is, other than an abnormal state such as a drop impact). It has been applied.
1 and 2, a conductive adhesive is used as the adhesive 43, but the present invention is not limited to this. For example, electrical connection is performed by wire bonding, and the adhesive is mechanically used. Only an adhesive that is bonded may be used.

The piezoelectric vibrating piece 20 is made of, for example, quartz or the like, and other piezoelectric materials such as lithium tantalate and lithium niobate can be used.
In the case of the present embodiment, the piezoelectric vibrating piece 20 has a convex shape that becomes thinner from the central portion 20b toward both end portions (in the case of FIG. 2, both end portions in the longitudinal direction) 20a, 20c in the cross section in the thickness direction. As a result, the vibration energy of the main vibration is concentrated in the central portion, the contour vibration is attenuated to reduce the coupling with the main vibration, the Q value is increased, and good temperature characteristics are obtained.

Excitation electrodes 24 and 25 are formed on the center portion 20b of the upper and lower surfaces, which are the main surfaces of the piezoelectric vibrating piece 20 as described above. The excitation electrodes 24 and 25 are electrodes for exciting the main vibration, and occupy most of the area excluding the peripheral portion as shown in FIG.
In addition, the piezoelectric vibrating piece 20 is formed such that the excitation electrodes 24 and 25 are drawn out to one end 20a (a region having a smaller thickness than the central portion 20b) of the both ends 20a and 20c. 35 is formed. The extraction electrodes 34 and 35 formed on the one end 20a are portions that are electrically and mechanically connected to the mounting electrodes 31 and 31 described above via the adhesives 43 and 43. The piezoelectric vibrating piece 20 is substantially horizontal so that its main surface faces the inner bottom 37 and the lid 39, and is electrically and mechanically connected to the package 36 in a cantilever manner.
The excitation electrodes 24 and 25 and the extraction electrodes 34 and 35 are formed by, for example, gold plating on a base layer (not shown) made of chrome plating, and the excitation electrode 24, the extraction electrode 34, and the excitation electrode 25. And the extraction electrode 35 are integrally formed.

Here, the piezoelectric vibrating reed 20 is provided with a protrusion 50 that protrudes toward the inner bottom 37 of the package 36 on the lower surface of the free end 20c. The protrusion 50 is a protrusion provided so that the main vibration region of the piezoelectric vibrating piece 20 does not contact the package 36.
Specifically, the protrusion 50 is a peripheral portion where the excitation electrodes 24 and 25 of the piezoelectric vibrating piece 20 are not provided, and is disposed at the other end opposite to the one end 20 a joined to the package 36. ing. The protruding portion 50 protrudes from the other end portion (that is, the free end portion) 20c toward the inner bottom side (lower side in FIG. 2), and the lower end 50a of the protruding portion 50 of the piezoelectric vibrating piece 20 is projected. Compared with the most swollen position of the central portion 20b, the center portion 20b protrudes to be the same or more closer to the inner bottom 37 side.

Such protrusions 50 can be formed using metal bumps, non-conductive resin, epitaxial growth, or the like. When the protrusion 50 is a metal bump, a pad made of the same material as that of the excitation electrode 25 is provided in a region where the protrusion 50 of the piezoelectric vibrating piece 20 is provided. For example, an Au bump can be used. If this metal bump is used, the stray capacitance in the package 36 may be increased. In particular, when a conductive pattern is drawn around the inner bottom 37 of the package 36, the conductive pattern is contacted. This increases the risk of a short circuit.
In this regard, when the protrusion 50 is formed of resin, the resin is non-conductive, so there is no problem of stray capacitance or short circuit when formed of metal bumps. Further, when the protrusion 50 is formed of a resin, it is preferable to use a resin having a high viscosity so that the free end portion 20c having a small area can be formed in an arbitrary shape, and an epoxy resin or the like is preferably used. it can. In the case of this resin, since gas is generated from the solvent, this gas may adhere to the piezoelectric vibrating piece 20 and change the vibration characteristics.
Therefore, the protrusion 50 is more preferably formed by epitaxially growing the free end portion 20c of the piezoelectric vibrating piece 20. Specifically, a metal mask provided with a through hole is arranged in a portion where the protrusion 50 of the free end portion 20c of the piezoelectric vibrating piece 20 is to be formed, and a crystal is grown by vapor phase epitaxy particularly suitable for mass production. Good.

The region where the protrusions 50 are provided is a so-called contour vibration region, and there is no problem if it is formed so as to avoid even the coupling of the main vibration and the contour vibration.
However, depending on the position where the protrusion 50 is provided, the balance when the piezoelectric vibrating piece 20 vibrates is lost, which has an adverse effect. For this reason, in FIG. 1, only one location is arranged near the center in the width direction of the free end 20 c of the piezoelectric vibrating piece 20 to balance the width direction of the piezoelectric vibrating piece 20.

  Speaking of the region where the protrusion 50 is provided, when approaching the main vibration region of the piezoelectric vibrating piece 20, that is, the excitation electrodes 24 and 25, there is a high possibility that the main vibration and the contour vibration are combined. Therefore, as shown in FIG. 3 which is a schematic plan view of a piezoelectric device 60 according to a modification of the piezoelectric device 30 of FIG. The corners R2 and R2 of the excitation electrodes 24 and 25 formed on the central portion 20b of the main surface (upper and lower surfaces) are chamfered or rounded, or the entire excitation electrodes 24 and 25 are formed into a circular shape or an oval shape, and the free end portion A corner 20d farthest from the excitation electrodes 24 and 25 may be formed in the region 20c, and a protrusion 50 may be provided on the corner 20d. Also when provided at the corner 20d, the protrusion 50 is preferably provided at both corners 20d and 20d of the free end 20c in consideration of the balance in the width direction of the piezoelectric vibrating piece 20. In FIG. 3, portions denoted by the same reference numerals as those used in the description of FIGS. 1 and 2 have a common configuration.

  Further, as shown in FIGS. 1 and 2, the shape of the protrusion 50 may be formed in a cylindrical shape, but the present invention is not limited to this, and may be a triangular prism shape, a rectangular shape, a frustum shape, or the like. There may be. More preferably, as shown in FIG. 3, which is a schematic plan view of the piezoelectric device 60 according to the above-described modification, and FIG. 4, which is a sectional view taken along the line BB in FIG. It is good to. That is, if the protrusion 50 is substantially spherical, the area where the protrusion 50 and the piezoelectric vibrating piece 20 are in contact with each other is reduced while securing the strength of the protrusion 50 itself, and this adversely affects the vibration characteristics of the protrusion. It can be effectively prevented. Further, when the protrusion 50 is substantially spherical, the area where the protrusion 50 and the package 36 contact is small and curved, and therefore, the friction between the protrusion 50 and the package 36 hardly generates dust or dust, and vibration is caused. The characteristics can be stabilized.

  In the case of the present embodiment, the protrusion 50 does not come into contact with the inner bottom 37 of the package 36 as shown in FIG. The protrusion 50 and the package 36 may be in contact with each other. Even in this case, since the protrusion 50 and the package 36 are not joined and are movable with respect to each other, vibration leakage from the piezoelectric vibrating piece 20 to the package 36 side, vibration of the package 36, and the like. It is possible to effectively suppress the transmission of distortion and distortion to the protrusion 50.

  The first embodiment of the present invention is configured as described above. The piezoelectric device 30 includes a central portion 20b that is a main vibration region in which a convex-shaped piezoelectric vibrating piece 20 is joined to a package 36 in a cantilever manner. The free end portion 20c of the piezoelectric vibrating piece 20 protrudes toward the inner bottom 37 so that the thickness direction is equal to or greater than the position of the central portion 20b. Protruding portion 50 is provided. For this reason, for example, even when the piezoelectric vibrating piece 20 is shaken in the thickness direction due to a drop impact, the protruding portion 50 of the free end 20c is formed on the package 36 before the central portion 20b of the piezoelectric vibrating piece 20. It will contact the inner bottom 37. Therefore, it is possible to prevent the central portion 20 b of the piezoelectric vibrating piece 20 from contacting the inner bottom 37 of the package 36.

  In the case of the present embodiment, since the piezoelectric vibrating piece 20 is disposed substantially horizontally (that is, the main surface faces the inner bottom 37 and the lid 39), the protrusion 50 is formed in the thickness direction. The excitation electrode 25 is prevented from contacting the inner bottom 37 by projecting toward the inner bottom 37 so as to be equal to or greater than the position of the central portion 20b. However, the degree of protrusion of the protrusion 50 according to the present invention is not limited to this. For example, the piezoelectric vibrating piece 20 is mounted so as to be inclined so that the one end 20a side is high and the free end 20c side is low in a steady state. In this case, the protrusion 50 may be on the upper side (lid side) from the most swelled position of the central portion 20b.

FIG. 5 is a schematic longitudinal sectional view of the piezoelectric device 62 according to the second embodiment of the present invention, and corresponds to FIG.
In this figure, the portions denoted by the same reference numerals as those used in the description of FIGS. 1 to 4 have the same configuration, and therefore, a duplicate description will be omitted, and hereinafter, differences will be mainly described.
The piezoelectric device 62 is different from the piezoelectric device 30 of FIGS. 1 to 4 only in the portion of the protrusion 50.

That is, the protrusions 50 of the piezoelectric device 62 are provided on both the upper and lower surfaces of the piezoelectric vibrating piece 20.
Specifically, as in FIGS. 1 to 4, a protrusion 50 is provided on the lower surface of the piezoelectric vibrating piece 20 (that is, the main surface on the inner bottom 37 side), and the protrusion on the lower surface is the first protrusion. Part 50a.
On the other hand, a second protrusion 50 b is provided on the upper surface of the piezoelectric vibrating piece 20 (that is, the main surface on the lid 39 side), and the second protrusion 50 b is a free end of the piezoelectric vibrating piece 20. The portion 20c protrudes upward (that is, on the lid 39 side) so as to be equal to or greater than the position of the central portion 20b in the thickness direction.

In the present embodiment, the second protrusion 50b and the first protrusion 50a have the same configuration. The first protrusion 50a and the second protrusion 50b have substantially the same shape so as to be substantially symmetrical with respect to the center line CL in the thickness direction of the piezoelectric vibrating piece 20, and have a free end 20c. Are provided at substantially the same position in plan view.
Note that the first and second protrusions 50a and 50b may be in contact with the package 36 or the lid 39 in a steady state (that is, other than an abnormal state such as a drop impact), but at least Any one of the protrusions 50 is prevented from contacting. This avoids a state in which the piezoelectric vibrating piece 20 is sandwiched between the package 36 and the lid 39 via the first and second protrusions 50a and 50b and the free end 20c of the piezoelectric vibrating piece 20 is fixed. can do.

  The piezoelectric device 62 according to the second embodiment of the present invention is configured as described above, and the free end portion 20c of the piezoelectric vibrating piece 20 has a second protruding in the thickness direction above the center portion 20b. Therefore, the piezoelectric vibrating reed 20 is provided with the protrusions 50 on both the upper surface side and the lower surface side. Therefore, the piezoelectric vibrating piece 20 can be joined to the package 36 without having to select the upper surface side and the lower surface side alternatively. Furthermore, contact between the central portion 20b of the piezoelectric vibrating piece 20 and the lid 39 can also be prevented on the lid 39 side that seals the package 36.

  The present invention is not limited to the above-described embodiment. Each configuration of the embodiment and each modified example can be appropriately combined or omitted, and can be combined with other configurations not shown.

1 is a schematic plan view of a piezoelectric device according to a first embodiment of the present invention. FIG. 2 is a schematic sectional view taken along line AA in FIG. 1. The schematic plan view of the piezoelectric device which concerns on the modification of the piezoelectric device of FIG. FIG. 4 is a sectional view taken along line BB in FIG. 3. The schematic longitudinal cross-sectional view of the piezoelectric device which concerns on the 2nd Embodiment of this invention. The schematic longitudinal cross-sectional view of the conventional piezoelectric device. FIG. 6 is a schematic longitudinal sectional view of a piezoelectric device showing another conventional example.

Explanation of symbols

  30, 60, 62 ... Piezoelectric device, 20 ... Piezoelectric vibrating piece, 20a ... One end, 20b ... Center, 20c ... Other end, 31 ... Mount electrode, 36. ..Package, 37 ... inner bottom, 39 ... lid, 50 ... projection

Claims (7)

A piezoelectric device comprising a convex-shaped piezoelectric vibrating piece having a thickness that decreases from the center toward both ends, and a package having an inner bottom in which one end of the both ends of the piezoelectric vibrating piece is joined with an adhesive. Because
The piezoelectric device is characterized in that the piezoelectric vibrating reed is provided with a protrusion protruding on the inner bottom side of the package on the lower surface of the free end thereof.   The piezoelectric device according to claim 1, wherein the protrusion is substantially spherical.   The piezoelectric device according to claim 1, wherein the protrusion is non-conductive.   4. The piezoelectric device according to claim 1, wherein the protrusion is formed by epitaxially growing a free end of the piezoelectric vibrating piece. In plan view, the outer shape of the piezoelectric vibrating piece is formed in a square shape, and the corners of the excitation electrode provided in the central portion are chamfered or rounded,
The piezoelectric device according to claim 1, wherein the protrusion is provided at a corner of the free end.   6. The projecting portion according to claim 1, wherein the projecting portion is a first projecting portion, and the piezoelectric vibrating piece is provided with a second projecting portion projecting upward on an upper surface of a free end portion thereof. The piezoelectric device according to any one of the above.   The piezoelectric device according to claim 1, wherein an inner bottom of the package is a flat surface.

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