JP2013141311A - Piezoelectric element, piezoelectric device and method for manufacturing piezoelectric element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal vibration element and crystal oscillator both of which can be further reduced in size.SOLUTION: A crystal oscillator 10 is configured so as to hermetically accommodate a crystal vibration element 1 having a rectangular crystal substrate 2 with one end 2a supported by a pedestal 13 of a package 12 in a cantilever manner. The crystal vibration element 1 has a projection portion 8 at at least one place of corner portions other than a central portion in a width direction located at other end 2b opposite to the one end 2a supported in the cantilever manner. A protruding pillow portion 18 is provided on an inner surface 12c of a main body of the package 12 to receive the projection portion 8, and the crystal vibration element 1 is held by the pedestal 13 and the pillow portion 18 in substantially parallel with the inner surface 12c of the main body.

Description

  The present invention relates to a piezoelectric element having a configuration that can be miniaturized, a piezoelectric device including the piezoelectric element, and a method for manufacturing the piezoelectric element.

  2. Description of the Related Art Conventionally, a crystal resonator element that is a piezoelectric element has an excitation electrode provided at substantially the center of both front and back surfaces of a crystal substrate, and a lead electrode provided from the excitation electrode to one end side of the crystal substrate. . Further, a crystal resonator as a piezoelectric device has a crystal resonator element housed in a ceramic package, and has an internal terminal for bonding an end portion of a lead electrode of the crystal resonator element. The internal terminal and the lead electrode are electrically connected to each other by a conductive adhesive, whereby the crystal resonator element is cantilevered and can be freely vibrated.

  In recent years, with the miniaturization of crystal resonators, the gap between the crystal resonator element and the inner surface of the ceramic package has decreased. Therefore, if there is a variation in the gap due to a difference in the application amount of the conductive adhesive or an inclination of the crystal resonator element with respect to the inner surface of the ceramic package, the excitation electrode of the crystal resonator element and the inner surface of the ceramic package are likely to contact each other. Furthermore, when the inner surface of the ceramic package is warped in the direction of narrowing the gap, the excitation electrode and the inner surface of the ceramic package are more likely to come into contact with each other. When the excitation electrode contacts the inner surface of the ceramic package, the free vibration of the crystal resonator element by the excitation electrode is hindered, and the characteristics of the crystal resonator are affected.

  Therefore, a configuration is disclosed in which a thick protrusion is provided at the end opposite to the end of the lead electrode of the crystal resonator element. According to this configuration, even if there is a gap variation or inclination between the crystal resonator element and the inner surface of the ceramic package, the ceramic package and the thick protrusion of the crystal resonator element abut, and the excitation electrode of the crystal resonator element And the ceramic package do not contact. For this reason, the quartz resonator element can eliminate a factor that obstructs free vibration by the excitation electrode, and can maintain stable characteristics (for example, Patent Document 1).

JP 2004-200777 A

  Here, the vibration displacement energy caused by the excitation electrode that freely vibrates the crystal resonator element is maximum at the central portion of the excitation electrode, and is attenuated as the distance from the central portion increases. Further, when plotting portions where the vibration displacement energy is the same, a plurality of substantially similar ellipses centering on the central portion are drawn, and these ellipses are referred to as isobaric lines. The thick protrusion provided at the end of the crystal resonator element has the effect of preventing direct contact between the excitation electrode and the ceramic package, but the vibration displacement of the isotropic lines that interfere with the thick protrusion. Energy is lost. This loss becomes more influential as the crystal resonator element becomes smaller, and it becomes difficult to maintain stable characteristics of the crystal resonator element. Therefore, the conventional technique has a problem that it is difficult to further reduce the size of the crystal resonator element and the crystal resonator.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples or forms.

  [Application Example 1] A piezoelectric element according to this application example includes a rectangular piezoelectric substrate, and has a protruding portion at the other end of the counter electrode from the one end supported in a cantilever manner. It is provided in at least one corner of the other end portion excluding the central portion in the width direction.

  According to this piezoelectric element, one end portion is cantilevered, and the conversion between electrical energy and mechanical energy, such as deformation and deformation when an electric field is applied, efficiently utilizes the so-called piezoelectric effect. It is possible. At this time, one end portion of the piezoelectric element is fixed to the mounting portion of the housing member for housing the piezoelectric element, and may come into contact with the housing member due to variation in the fixed state or deformation of the housing member. . When the piezoelectric element comes into contact with the housing member, conversion between electric energy and mechanical energy is hindered, and the piezoelectric effect is reduced. The degree to which the piezoelectric effect decreases depends on the portion of the piezoelectric element that comes into contact with the housing member. Therefore, it is difficult for the piezoelectric element to maintain stable characteristics due to the piezoelectric effect. This becomes more prominent as the piezoelectric element becomes smaller. Therefore, a protrusion is provided at a corner other than the central portion in the width direction of the other end of the piezoelectric element, and the protrusion is set so as to contact the housing member, thereby limiting the position where the piezoelectric element contacts the housing member. In this case, at least one protrusion may be provided at a corner other than the central portion in the width direction on the surface side in contact with the housing member of the piezoelectric substrate. Is also possible. In addition, the reason why the protrusions are provided at the corners excluding the central portion in the width direction is that, in the case of a rectangular piezoelectric element, for example, the mechanical energy due to strain is the largest in the vicinity of the center of the rectangle, and from the vicinity of the center. This is due to the tendency to become smaller with distance. In other words, if the protrusion is provided near the center of the piezoelectric element, that is, at the corner farthest from the maximum portion of the mechanical energy, and this protrusion is brought into contact with the housing member, the reduction of the piezoelectric effect is minimized. It is possible to suppress. As a result, the piezoelectric element having the projecting portion is limited in the contact position with the housing member, so that the piezoelectric effect can be substantially maximized and stable characteristics can be maintained. Therefore, even if the piezoelectric element is further reduced in size, the characteristics can be stabilized and the piezoelectric effect can be maintained.

  Application Example 2 In the piezoelectric element according to the application example described above, it is preferable that the protrusions are provided on both sides of the piezoelectric substrate.

  According to this configuration, when the piezoelectric element is attached to the cantilever support state, it is not necessary to confirm each time that the protruding portion is surely directed to the side in contact with the housing member. In other words, it is not necessary to confirm whether the protrusion is provided on the front or back surface of the piezoelectric substrate, and it is easy to attach the piezoelectric element to the cantilever-supported state simply by checking the side of the one end that is cantilevered. Is possible. In this case, the piezoelectric element is more preferably set so that the protrusion is in contact with the same position of the housing member, regardless of which side of the front and back faces the contact side of the housing member.

  [Application Example 3] A piezoelectric device according to this application example is characterized in that the piezoelectric element according to Application Example 1 or 2 is hermetically housed inside a housing member.

  According to this piezoelectric device, the one end supported in a cantilever manner includes a piezoelectric element having a protrusion at a corner other than the central portion in the width direction of the other end of the counter electrode. However, the projecting portion comes into contact with the housing member, and the piezoelectric substrate itself other than the projecting portion is prevented from coming into direct contact with the housing member. In this case, at least one protrusion may be provided at a corner other than the central portion in the width direction on the surface side in contact with the housing member of the piezoelectric substrate. Is also possible. In addition, the reason for providing the protrusions at the corners is that, in the case of a rectangular piezoelectric element, for example, when the mechanical energy due to strain is taken as an example, the size is the largest near the center of the rectangle and tends to decrease as the distance from the center increases. Because. That is, if a protrusion is provided at the corner farthest from the maximum portion of the mechanical energy and the protrusion is brought into contact with the housing member, the reduction in the piezoelectric effect can be minimized. . A piezoelectric device including a piezoelectric element having such a protrusion has a limited contact position with the housing member, can exhibit the piezoelectric effect almost to the maximum, and can maintain stable characteristics. Therefore, even if the piezoelectric device is further downsized, the characteristics can be stabilized and the piezoelectric effect can be maintained.

  Application Example 4 In the piezoelectric device according to the application example described above, it is preferable that the housing member has a convex pillow portion on the inner surface for receiving the protrusion portion of the piezoelectric substrate.

  According to this configuration, the pillow portion of the housing member is in contact with the protruding portion of the piezoelectric element. Therefore, even if the one end supported in a cantilever manner is fixed in a state of being inclined with respect to the inner surface of the housing member, for example, by a conductive adhesive or the like, first, the projection on the other end is the pillow portion. The portion of the piezoelectric element other than the protrusion is difficult to contact the inner surface of the housing member. Accordingly, only the cantilevered portion and the protruding portion of the piezoelectric element are in contact with the housing member, and the piezoelectric effect is stably exhibited. On the other hand, in a piezoelectric element having no protrusion, the portion that contacts the inner surface of the housing member is not constant, and the piezoelectric effect varies depending on which portion is in contact, and the characteristics are not stable. As described above, since the piezoelectric device including the piezoelectric element having the protruding portion is set so that the fixed portion, that is, the protruding portion is in contact with the accommodating member, the variation in the piezoelectric effect is suppressed and the stable characteristic is maintained. It is possible.

  Application Example 5 In the piezoelectric device according to the application example, it is preferable that the piezoelectric element is held substantially parallel to the inner surface by the pillow portion and a pedestal that receives the one end portion of the piezoelectric substrate. .

  According to this configuration, one end of the piezoelectric element is cantilevered by the pedestal provided on the housing member, and the other end is in contact with the pillow through the protrusion. The height of the pedestal and the pillow portion is substantially parallel to the inner surface of the housing member, taking into account the length of one end supported by a conductive adhesive and the like and floating from the pedestal, and the length of the protrusion. Set to hold. In addition, by separating the piezoelectric element from the inner surface of the housing member by the pedestal and the pillow portion, even if warpage or the like occurs on the inner surface of the housing member, the portion of the piezoelectric element other than the protrusions is in contact with the inner surface of the housing member. To be avoided. Such a piezoelectric device having a piezoelectric element held by the pedestal and the pillow portion can always maintain more stable characteristics.

  Application Example 6 A piezoelectric element manufacturing method according to this application example is a method for manufacturing a piezoelectric element having a rectangular piezoelectric substrate, and is opposite to one end portion of the piezoelectric substrate that is cantilevered. A protrusion forming step of forming a protrusion at at least one corner of the other end excluding the central portion in the width direction, and a mesa structure in which the rectangular central portion of the piezoelectric substrate is formed thicker than the peripheral portion And forming the protrusion and forming the mesa structure at the same time.

  According to this piezoelectric element manufacturing method, the piezoelectric substrate is formed in a mesa structure by removing the peripheral portion by processing such as etching and leaving the central portion as a thick portion. A piezoelectric element having such a mesa structure can be reduced in size because the piezoelectric effect is ensured even if the area of the piezoelectric substrate is reduced. This is because in the piezoelectric element, electrical or mechanical energy tends to concentrate on a portion having a large mass, and these energy can be concentrated on a thick portion of the mesa structure. Therefore, the mesa structure piezoelectric element is suitable for further miniaturization. This piezoelectric element is used with one end fixed to the mounting part of the housing member for housing the piezoelectric element, and a protruding part is formed at the corner excluding the central part in the width direction of the other end of the counter electrode. Has been. The reason why the protrusions are provided at the corners other than the central portion in the width direction of the other end is that, for example, the mechanical energy due to strain in the rectangular piezoelectric element is the largest in the vicinity of the center of the rectangle, This is because it tends to decrease as the distance from the vicinity increases. In other words, if the protrusion is provided near the center of the piezoelectric element, that is, at the corner farthest from the maximum portion of the mechanical energy, and this protrusion is brought into contact with the housing member, the reduction of the piezoelectric effect is minimized. It is possible to suppress. As described above, the mesa structure piezoelectric element can be efficiently processed by simultaneously performing the protrusion forming process and the mesa structure forming process.

The perspective view which shows the external appearance of the crystal vibration element which concerns on this embodiment. (A) The top view which shows the structure of the crystal oscillator concerning this embodiment, (b) Sectional drawing which shows the structure of a crystal oscillator. The top view which shows distribution of the vibration displacement energy in a crystal resonator element. The perspective view which shows the formation method of the projection part of a crystal oscillation element, (a) The perspective view which shows the state which apply | coated the resist to the quartz substrate, (b) The perspective view which shows the state after an etching, (c) It is formed in a quartz substrate FIG.

Hereinafter, specific embodiments of the piezoelectric element and the piezoelectric device will be described with reference to the drawings. In the present embodiment, a description will be given by taking a crystal resonator element as an example of a piezoelectric element and a crystal resonator including the crystal resonator element as an example of a piezoelectric device. These crystal resonator elements and crystal resonators have a configuration that suppresses loss of electrical and mechanical energy, and can be reduced in size.
(Embodiment)

  FIG. 1 is a perspective view showing an external appearance of a crystal resonator element according to this embodiment. As shown in FIG. 1, a crystal resonator element 1 includes a quartz crystal substrate (piezoelectric substrate) 2 in which a quartz crystal, which is a piezoelectric single crystal material, is formed in a substantially rectangular parallelepiped thin plate shape, and a quartz crystal substrate 2 placed horizontally and facing upward. A rectangular excitation electrode forming portion 3 (3a) formed in a convex shape at a substantially central portion on the surface side which is the side, and one end portion 2a of the quartz crystal substrate 2 along the longitudinal direction from the rectangular corner portion of the excitation electrode forming portion 3a Lead electrode forming portion 4 (4a) extending in a convex shape. The lead electrode forming portion 4a is formed to be bent in an L shape along the end side at one end portion 2a of the quartz substrate 2, and further, a convex portion having the same shape as the L bent portion is formed on the back surface. It is formed at the counter electrode position on the side.

  Thus, the excitation electrode 5 (5a) of a metal film is formed on the excitation electrode forming portion 3a formed on the surface side of the quartz substrate 2 so as to cover the rectangular portion. The lead electrode forming portion 4a includes a lead electrode 6 (6a) that is a metal film connected to the excitation electrode 5a, and a lead electrode terminal that is a metal film that covers the L-shaped bent portion connected to the lead electrode 6a. 7 (7a) and a lead electrode terminal 7 (7b) which is a metal film that is connected to the lead electrode terminal 7a and covers the convex portion on the back surface side.

  Similarly, a metal film is formed on the back side of the quartz substrate 2 in the same manner as the front side. An excitation electrode 5b is formed on the excitation electrode forming portion 3b on the back side, and a lead electrode 6b connected to the excitation electrode 5b, a lead electrode terminal 7b connected to the lead electrode 6b, and a lead electrode terminal are formed on the lead electrode forming portion 4b. 7b, lead electrode terminals 7a at the counter electrode position on the surface side are formed. That is, if the quartz substrate 2 is rotated around the longitudinal direction, the excitation electrode 5, the lead electrode 6, and the lead electrode terminal 7 are formed in the same arrangement on the side facing the upper surface. This crystal resonator element 1 is a resonator element having a so-called mesa structure in which a substantially central portion is formed in a convex shape as a thick portion.

  The quartz substrate 2 has a protruding portion 8 at the other end 2 b that is the opposite end in the longitudinal direction with respect to the one end 2 a of the quartz substrate 2. The protrusions 8 are located at two corners of the other end 2b excluding the central portion in the width direction, and two protrusions 8a are formed on the front surface side and two protrusions 8b are formed on the back surface side. Yes. The protrusion 8 protrudes at substantially the same height as the convex excitation electrode forming portion 3 and has a rectangular column shape in plan view.

  Here, the crystal forming the crystal resonator element 1 will be briefly described. The crystal substrate 2 of the crystal resonator element 1 is cut out from a crystal column that is a piezoelectric single crystal material. This quartz crystal column is a hexagonal column, and is an electric axis parallel to the hexagonal side in the XY plane of the Z axis which is the optical axis in the longitudinal direction of the column and the hexagonal surface perpendicular to the Z axis. It has an X axis and a Y axis that is a mechanical axis perpendicular to the X axis. Then, when a voltage is applied to the crystal in the X-axis (electric axis) direction, the crystal expands or contracts in the Y-axis (mechanical axis) direction corresponding to the applied voltage direction. When tension or compression is applied in the (axis) direction, a voltage is generated in the X-axis (electric axis) direction. In other words, quartz can convert between electrical energy and mechanical energy.

  In order to effectively use this property of the quartz crystal, the quartz resonator element 1 is a quartz crystal wafer (cut out along the XZ ′ plane inclined about 35 degrees around the X axis in the XZ plane of the crystal column ( A quartz substrate 2 further cut out from (not shown) is used. The quartz resonator element 1 cut out from the quartz column in this way is a thin plate shape along the XZ ′ plane and has a thickness in the Y ′ direction which is the front and back direction. It is what is called. In the crystal resonator element 1, when a voltage is applied between the excitation electrode 5a and the excitation electrode 5b, a so-called thickness shear vibration is generated, and the frequency of regular vibration is maintained. Further, the frequency of the AT-cut quartz crystal resonator element 1 is determined by its thickness, and a stable frequency can be maintained in a wide temperature range.

  Next, a crystal resonator in which the crystal resonator element 1 is housed in a package will be described. FIG. 2A is a plan view showing the configuration of the crystal resonator according to this embodiment. FIG. 2B is a cross-sectional view showing the configuration of the crystal resonator, and is a cross section taken along the line AA ′ of FIG. In FIG. 2 (a), the lid of the package is omitted so that the inside can be easily understood. As shown in FIGS. 2A and 2B, the crystal resonator 10 has a rectangular parallelepiped appearance, and the crystal resonator element 1 is accommodated in a package (accommodating member) 12. The package 12 includes a package body 12b having a recessed portion that is substantially similar to the quartz resonator element 1 in plan view and a package lid 12a for closing the recessed portion in order to accommodate the quartz resonator element 1. Have.

  The package main body 12b includes a pedestal 13 provided on a longitudinal end of a main body inner surface (inner surface) 12c, which is an inner bottom surface of the recessed portion, for cantilevering the lead electrode terminal 7 of the crystal resonator element 1, and a pedestal 13 And a pillow portion 18 for receiving the projection 8 of the crystal resonator element 1 provided on the end side on the counter electrode side. The pedestal 13 in the embodiment is provided at two corners of the edge so as to receive the side of the lead electrode terminal 7b of the crystal resonator element 1, and the surface facing the lead electrode terminal 7b is formed on the inside of the metal film. A terminal 14 is formed. In such a crystal resonator element 1, the lead electrode terminal 7 b is fixed and cantilevered by the conductive adhesive 16 in a state of being electrically connected to the internal terminal 14 of the base 13. An external terminal 15 is provided on the outer bottom surface of the package main body 12 b at a position opposite to the internal terminal 14 of the main body inner surface 2 c, and the external terminal 15 is electrically connected to the internal terminal 14. . Therefore, the crystal resonator element 1 can be connected to the outside via the internal terminal 14 and the external terminal 15.

  Moreover, the pillow part 18 is provided in two places at the edge part of the side of the base 13 and the counter electrode side so that the side of the projection part 8b of the crystal vibration element 1 may be received, respectively. In this case, the height of the pillow portion 18 from the main body inner surface 12 c is the height of the pedestal 13, the thickness of the lead electrode terminal 7 b of the crystal resonator element 1 and the internal terminal 14 of the pedestal 13, and the lead electrode terminal 7 b and the internal terminal 14. And the thickness of the conductive adhesive 16 between them is approximately equal to the total value. Thereby, the crystal resonator element 1 is held substantially parallel to the main body inner surface 12c. In addition, since the gap 20 can be secured by separating the distance between the crystal resonator element 1 and the main body inner surface 12c, even when the main body inner surface 12c is warped toward the crystal resonator element 1, the excitation electrode 5b of the crystal resonator element 1 is used. Can reliably avoid contact with the inner surface 12c of the main body.

  The package main body 12b is made of ceramic and formed integrally with the pedestal 13. The main body inner surface 12c has a pillow portion 18 formed to be equal to the height of the pedestal 13 by metallization. The package body 12b has a co-pearl seam ring (not shown) fixed to the end face of the concave recess with silver solder, and the surface of the seam ring is plated with nickel (Ni). The package lid 12a is formed into a plate shape with the same copal as the seam ring, has a sealing hole (not shown) penetrating the plate-like portion, and nickel (Ni) plating is applied to the surface of the package lid 12a. ing. The crystal resonator element 1 can also be provided so that the lead electrode terminal 7a and the protrusion 8a side face the main body inner surface 12c of the package main body 12b. Moreover, the pillow part 18 can respond easily, if the thickness of the conductive adhesive 16 and the height of the projection part 8 differ, if the formation height of the pillow part 18 is changed.

  In manufacturing the crystal resonator 10 in which the crystal resonator element 1 is accommodated in such a package 12, first, the crystal resonator element 1 is attached to the internal terminal 14 provided on the base 13 of the package body 12 b via the conductive adhesive 16. Fix it. The crystal resonator element 1 is held in a state where the fixed end 1a is cantilevered and the tip of the protrusion 8b provided on the other end 2b abuts on the pillow 18 and is substantially parallel to the inner surface 12c of the main body. Is done. Next, the seam ring and the package lid 12a are seam welded at atmospheric pressure. Thereafter, spherical gold germanium (AuGe) larger than the sealing hole diameter is disposed as a sealing material in the sealing hole of the package lid 12a and heated in a chamber whose pressure is substantially reduced to a vacuum. The inside of the package 12 is decompressed by heating in the decompressed chamber, and the sealing material is melted to close the sealing hole. For this reason, the crystal resonator element 1 is hermetically sealed in the vacuum package 12.

  Here, the excitation electrode 5 of the crystal resonator element 1 is a metal film in which chromium (Cr) is used as a base and gold (Au) is formed thereon on the convex surface portion of the excitation electrode forming portion 3 of the crystal substrate 2. The lead electrode 6 and the lead electrode terminal 7 are metal films in which a convex portion of the lead electrode forming portion 4 is made of chromium (Cr) as a base and gold (Au) is formed thereon. These metal films are formed by a sputtering apparatus or the like and have a thickness of about 0.3 μm. In addition, the conductive adhesive 16 is made by dispersing elastic nickel resin as a base material and nickel fine powder as conductive particles in the base material. Therefore, in the crystal resonator 10, the stress to the crystal resonator element 1 is relaxed by the elasticity of the silicon resin, and the impact resistance is improved.

  Next, FIG. 3 is a plan view showing the distribution of vibration displacement energy in the crystal resonator element. The vibration displacement energy is a calculated value that makes it easy to grasp the displacement at an arbitrary position by converting the vibration displacement, which is the amount that the crystal resonator element 1 vibrates due to the thickness shear vibration, into energy. As shown in FIG. 3, the distribution of the vibration displacement energy is obtained by plotting the positions where the vibration displacement energy values are the same, and a plurality of substantially similar ellipses having a center at the approximate center of the excitation electrode 5 of the crystal vibration element 1. be painted. This ellipse is referred to as, for example, a constant force line 30, and is referred to as a constant force line 30 a, a constant force line 30 b, and a constant force line 30 c in order from the side close to the center.

  In these isobaric lines 30, the vibration displacement energy in the long side direction (X-axis direction) of the crystal resonator element 1 becomes maximum at the approximate center of the excitation electrode 5 of the crystal resonator element 1, and the one end 2a or the other end 2b. As it goes in the direction of, it attenuates and becomes smaller. That is, the magnitude of the vibration displacement energy is expressed by the following lines: isoline 30a> isoline 30b> isoline 30c. In addition, the vibration displacement energy in the short side direction (Z′-axis direction) of the crystal resonator element 1 is maximized at the approximate center of the excitation electrode 5, and the vibration displacement energy is attenuated and becomes smaller toward the end in the longitudinal direction. . That is, the magnitude of the vibration displacement energy is expressed by the following lines: isoline 30a> isoline 30b> isoline 30c. From such an analysis, it has been confirmed that the vibration displacement energy of the quartz crystal vibration element 1 that undergoes thickness shear vibration gradually attenuates toward the peripheral edge of the quartz crystal vibration element 1 with the peak at the approximate center of the excitation electrode 5.

  The isoelectric lines 30 are in contact with the region fixed by the conductive adhesive 16 (FIG. 2) like the lead electrode terminal 7 of the crystal resonator element 1 and the pillow part 18 (FIG. 2) like the protrusion 8. In the case of interference in the region, the vibration displacement energy disappears and does not exist. In the existing elliptic contour lines 30, the vibration displacement energy is small in the ellipse closest to each side of the edge of the crystal resonator element 1, and in this case, the contour lines 30 c. When the force force line 30c is further away from the approximate center of the excitation electrode 5, the force line 30 disappears on the lead electrode terminal 7 or the protrusion 8 and becomes a fictitious one. In the quartz resonator element 1, since the excitation electrode 5 is formed closer to the other end 2 b, the isotropic line 30 that does not reach the protrusion 8 does not reach the lead electrode terminal 7.

  FIG. 3 shows a thick protrusion 40 in a conventional crystal resonator element as a reference. The conventional thick protrusion 40 is provided so as to extend along an end corresponding to the other end 2 b of the crystal resonator element 1. Therefore, the isotropic lines 30c in the conventional crystal resonator element interfere with the extending thick protrusion 40, and the vibration displacement energy disappears. On the other hand, in the crystal resonator element 1, the protrusion 8 is not configured to extend along the other end 2b, but is provided so as to be positioned only at two corners of the other end 2b. Thereby, the isotropic line 30c in the crystal resonator element 1 is prevented from interfering with the protrusion 8, and the loss of vibration displacement energy can be avoided.

  Next, the principal part is demonstrated about the manufacturing process of the crystal vibration element 1 which has the projection part 8 which was demonstrated above. 4A and 4B are perspective views showing a method of forming a protrusion of the crystal resonator element. FIG. 4A is a perspective view showing a state in which a resist is applied to the crystal substrate, and FIG. 4B is a view after etching. FIG. 4C is a perspective view showing protrusions and the like formed on the quartz substrate. FIG. 4 shows a processing method in the thickness direction (Y′-axis direction) of the quartz crystal substrate 2.

  First, as shown in FIG. 4A, the excitation electrode forming portion 3, the lead electrode forming portion 4 and the protruding portion 8 shown in FIG. 1 are formed on the front surface and the back surface of the crystal substrate 2 cut out from the crystal wafer. A resist film 50 covering the portion is formed. As an example of the formation of the resist film 50, first, a negative resist agent is applied onto the entire surface of the quartz substrate 2 by spin coating and baked in an oven furnace. Next, a glass mask is set so as to cover the negative resist agent, and the negative resist is exposed to ultraviolet rays. The glass mask has a transmission part disposed in the excitation electrode formation part 3, the lead electrode formation part 4 and the projection part 8, and a light-shielding part other than the transmission part. UV rays are blocked at the part. In the negative resist agent, the portion facing the transmissive portion exposed to ultraviolet rays is cured. When the quartz substrate 2 is developed with a developer, the portion cured by the ultraviolet light exposure is not dissolved by the development, but the portion not exposed to the ultraviolet light is dissolved by the development. Therefore, after development, the resist film 50 is formed only on the portions where the excitation electrode forming portion 3, the lead electrode forming portion 4 and the protruding portion 8 are formed.

  Next, the front and back portions of the quartz substrate 2 where the resist film 50 is not formed are removed by etching. In the portion where the resist film 50 is formed, the crystal remains in a convex shape without being removed by etching. By such etching, the excitation electrode forming portion 3 and the lead electrode forming portion 4 are formed in a convex shape on the quartz substrate 2, and at the same time, the protruding portion 8 can be formed and processing can be performed efficiently. In addition, since the excitation electrode forming part 3, the lead electrode forming part 4, and the protruding part 8 on the front and back sides are processed by a single etching process, the thickness of the crystal substrate 2 can be accurately ensured. In this case, hydrofluoric acid was used for etching the crystal, but a mixed solution of hydrofluoric acid and ammonium fluoride or the like may be used. As shown in FIG. 4B, the crystal substrate 2 after the etching process has the excitation electrode forming portion 3, the lead electrode forming portion 4, and the protruding portion 8 covered with the resist film 50 formed in a convex shape. ing.

  Then, after the etching, as shown in FIG. 4C, the remaining resist film 50 covering the excitation electrode forming portion 3, the lead electrode forming portion 4 and the protruding portion 8 of the quartz substrate 2 is removed. Thus, the quartz substrate 2 is manufactured. After this, the quartz substrate 2 is formed with chromium (Cr) and gold (Au) metal films on the convex surface portions of the excitation electrode forming portion 3 and the lead electrode forming portion 4, and these metal films are formed as the excitation electrode 5, A lead electrode 6 and a lead electrode terminal 7. The crystal resonator element 1 is completed by forming the metal film.

  Hereinafter, main effects of the embodiment will be described together.

  (1) In the crystal resonator 10, the crystal resonator element 1 has projections 8 at the corners except for the central portion in the width direction of the other end 2b, and the projections 8 are in contact with the pillows 18 of the package 12. It is the structure which touches. With such a configuration, the crystal resonator element 1 having the protruding portion 8 is always limited to a corner portion where the contact position with the pillow portion 18 is constant. Therefore, the crystal resonator element 1 can avoid the excitation electrode 5 other than the projecting portion 8 from coming into contact with the package 12 and can suppress the disappearance of the isotropic line 30 of the vibration displacement energy as much as possible. That is, the crystal unit 10 can suppress the decrease in the piezoelectric effect to a minimum. Therefore, even if the quartz resonator 10 is downsized, the disappearance of the contour lines 30 can be suppressed, the vibration displacement energy can be maintained almost at the maximum, and stable characteristics can be maintained.

  (2) Since the protrusions 8 are provided on both the front and back sides of the quartz substrate 2, it is not necessary to check whether the protrusion 8 is provided on the front or back surface of the quartz substrate 2, and the package 12 It is installed facing the pillow part 18. Thereby, it is possible to easily attach the crystal resonator element 1 to the package 12 in a cantilever support state only by confirming the one end portion 2a side of the crystal resonator element 1 that is cantilevered. Furthermore, even if the crystal resonator element 1 encounters a situation where it abuts on the package lid 12a, the protrusion 8a abuts on the package lid 12a, and the abutment of the excitation electrode 5a and the like can be avoided.

  (3) The crystal resonator element 1 has a mesa structure suitable for miniaturization. In the crystal resonator element 1 having such a mesa structure, when the excitation electrode forming portion 3 and the lead electrode forming portion 4 are formed by etching, the protruding portion 8 can be efficiently formed at the same time. In addition, since the front and back of the quartz substrate 2 are processed by a single etching, the thickness can be precisely processed, and the AT-cut quartz resonator element 1 whose frequency is determined by the thickness reliably retains its characteristics even if it is downsized. can do.

  (4) In the crystal resonator 10, one end 2 a of the crystal resonator element 1 is cantilevered by the pedestal 13 of the package 12, and the protrusion 8 of the other end 2 b is in contact with the pillow portion 18. In this way, even if the crystal resonator element 1 is separated from the main body inner surface 12c of the package 12 by the pedestal 13 and the pillow portion 18, the main body inner surface 12c is warped toward the crystal resonator element 1 side, etc. It can be avoided that the excitation electrode 5b comes into contact with the inner surface 12c of the main body and the contour lines 30 disappear. The crystal resonator 10 having such a configuration can always maintain more stable characteristics.

  In addition, the piezoelectric element and the piezoelectric device are not limited to the above-described embodiment, and the same effects as those of the embodiment can be obtained even in the following modifications.

  (Modification 1) On the other end 2b of the crystal resonator element 1, projections 8a and 8b are provided at corners excluding the two central portions in the width direction on the front side and the back side. However, the present invention is not limited to this configuration. For example, the projection 8 may be provided only on the corners except for the central portion in one width direction on both the front and back sides. Furthermore, the structure by which the projection part 8 was provided only in either the surface side or the back surface side may be sufficient.

  (Modification 2) The projection 8 has a rectangular shape in plan view, but is not limited to this configuration, and may have a round shape or L shape in plan view, and a cone other than a column shape in the height direction. It may be shaped.

  (Modification 3) The protrusion 8 is formed integrally with the quartz substrate 2, but may have a separate structure from the quartz substrate 2.

  (Modification 4) The crystal resonator element 1 may have a mesa structure in which only the excitation electrode 5 is convex. Further, the crystal resonator element 1 is not limited to the mesa crystal resonator element 1 but has a flat crystal substrate without the convex excitation electrode forming portion 3 and the lead electrode forming portion 4. May be.

  (Modification 5) In the present embodiment, the quartz resonator element 1 has been described as an example of a piezoelectric element. However, the piezoelectric element is not limited to quartz, but langasite, lithium tetragonal acid, lithium tantalate, niobic acid. A piezoelectric material such as lithium may be used.

  (Modification 6) In the crystal unit 10, the metal film of the excitation electrode 5, the lead electrode 6, and the lead electrode terminal 7 may be other than the configuration of the embodiment, for example, plating of nickel and silver (Ag), etc. The conductive adhesive 16 for cantilevering the crystal resonator element 1 may be an epoxy resin or the like as a base material.

  (Modification 7) The pillow portion 18 formed on the package 12 of the crystal unit 10 is not formed by metallization, and may be formed integrally with the package body 12b. If the package 12 contains electronic components other than the crystal resonator element 1 in the package 12, these components may be used as the pillow portion 18.

  (Modification 8) Although the inside of the package 12 is sealed in a vacuum state, an inert gas such as nitrogen, helium, or argon may be sealed instead of the vacuum state.

  DESCRIPTION OF SYMBOLS 1 ... Quartz vibration element as a piezoelectric element, 2 ... Quartz substrate as a piezoelectric substrate, 3 ... Excitation electrode formation part, 4 ... Lead electrode formation part, 5 ... Excitation electrode, 6 ... Lead electrode, 8 ... Protrusion part, 10 ... Crystal resonator as piezoelectric device, 12 ... Package as housing member, 12a ... Package lid, 12b ... Package main body, 12c ... Main body inner surface, 13 ... Base, 14 ... Internal terminal, 15 ... External terminal, 16 ... Conductive adhesion Agent: 18 ... Pillow part, 20 ... Gap, 30 ... Contour lines, 40 ... Thick protrusion, 50 ... Resist film.

Claims (6)

A piezoelectric element having a rectangular piezoelectric substrate,
One end supported in a cantilever manner has a protrusion on the other end of the counter electrode,
The piezoelectric element according to claim 1, wherein the protrusion is provided at at least one corner of the other end excluding the central portion in the width direction. The piezoelectric element according to claim 1.
The piezoelectric element according to claim 1, wherein the protrusions are provided on both sides of the piezoelectric substrate.   A piezoelectric device, wherein the piezoelectric element according to claim 1 or 2 is housed in an airtight manner inside the housing member. The piezoelectric device according to claim 3.
The piezoelectric device according to claim 1, wherein the housing member has a convex pillow portion that can abut against the protruding portion of the piezoelectric substrate. The piezoelectric device according to claim 4, wherein
The piezoelectric device is characterized in that the piezoelectric element is held substantially parallel to the inner surface by the pillow portion and a pedestal for receiving the one end portion of the piezoelectric substrate. A piezoelectric element manufacturing method for manufacturing a piezoelectric element having a rectangular piezoelectric substrate,
A projecting portion forming step of forming a projecting portion at at least one corner of the piezoelectric substrate in a cantilever-supported one end portion of the other end of the counter electrode excluding the central portion in the width direction;
A mesa structure forming step of forming the rectangular central part of the piezoelectric substrate in a thicker part than the peripheral part,
The method for manufacturing a piezoelectric element, wherein the protrusion forming step and the mesa structure forming step are performed simultaneously.

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