Piezoelectric vibration element and manufacturing method of the same

Abstract

To provide a piezoelectric vibration element in which an oscillation frequency is accurately adjusted by holding a mass balance of a vibration part in a thickness direction, and a stable oscillation frequency can be obtained, and a manufacturing method thereof.SOLUTION: A piezoelectric vibration element 1 comprises a support part 30; and a vibration part 20 which continuously extends on the support part 30, and on which an excitation electrode 50 is formed, where the vibration part 20 includes a first principal plane 11, a second principal plane 12 opposing the first principal plane 11, a base end part 16 on the support part 30 side, and a tip part 40 on a tip side, and the tip part 40 includes: a tip inclined surface 45 which connects the first principal plane 11 and the second principal plane 12, and inclines so as to develop on the second principal plane 12 side toward the tip side; a first corner part 41 having an obtuse angle which is formed by the tip inclined surface 45 and the first principal plane 11; and a second corner part 42 having an acute angle formed by the tip inclined surface 45 and the second principal plane 12, and has a weight part 65, which adjusts an oscillation frequency of the vibration part 20 to a predetermined target frequency, on the first corner part 41 side in the tip part 40.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a piezoelectric vibration element and a method for manufacturing the same. [Background technology]

[0002] A tuning fork type piezoelectric vibration element, which is one type of piezoelectric vibration element, has a support and a pair of vibration arms extending from the support, and oscillates at a predetermined frequency by forming excitation electrodes on the surfaces of the pair of vibration arms. In this type of piezoelectric vibration element, the dimensions of each part and the excitation electrode pattern are set at the time of design so that a target oscillation frequency is obtained. However, even if it is manufactured based on such design values, the oscillation frequency may deviate from the target value depending on the manufacturing conditions and the surrounding environment, so the oscillation frequency is adjusted in the final stage of manufacturing. Patent Document 1 discloses a piezoelectric vibration element in which a metal film is formed as a weight on the tip of the vibrating arm, and the oscillation frequency is adjusted by trimming this metal film with a laser beam. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-332871 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a tuning fork type piezoelectric vibration element, in order to suppress vibration leakage from the vibrating arm to the outside, it is desirable for the shape to be symmetrical in all directions, namely, the length direction, the width direction, and the thickness direction. However, for example, due to the need to perform a certain processing, the tip surface of the vibrating arm may be formed on a surface that is inclined with respect to the thickness direction. In that case, since the symmetry in the thickness direction is not maintained, it becomes necessary to balance the mass in the thickness direction. However, the above patent document does not describe the technology in this regard, and there is room for improvement.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a piezoelectric vibration element and a manufacturing method thereof that can accurately adjust the oscillation frequency by maintaining the mass balance in the thickness direction of the vibration part, thereby obtaining a stable oscillation frequency. [Means for solving the problem]

[0006] The piezoelectric vibration element of the present invention is a piezoelectric vibration element including a support portion and a vibration portion extending continuously from the support portion and having an excitation electrode formed thereon, wherein the vibration portion includes a first main surface, a second main surface opposite to the first main surface, a base end portion on the support portion side, and a tip portion on the tip side, and the tip portion includes a tip inclined surface connecting the first main surface and the second main surface and inclining so as to protrude toward the second main surface as it approaches the tip side, a first corner portion having an obtuse angle formed by the first main surface and the tip inclined surface, and a second corner portion having an acute angle formed by the second main surface and the tip inclined surface, and a weight portion on the first corner side of the tip portion for adjusting the oscillation frequency of the vibration portion to a predetermined target frequency.

[0007] A manufacturing method for a piezoelectric vibration element of the present invention is a manufacturing method for a piezoelectric vibration element comprising a support portion and a vibration portion extending continuously from the support portion and having an excitation electrode formed thereon, the vibration portion including a first main surface, a second main surface opposite to the first main surface, a base end portion on the support portion side, and a tip portion on the tip side, wherein a tip inclined surface is formed at the tip portion, connecting the first main surface and the second main surface, and inclining so as to protrude toward the second main surface as it approaches the tip side, and a weight portion for adjusting the oscillation frequency of the vibration portion to a predetermined target frequency is disposed on the first corner side of the cross-sectional obtuse angle formed by the first main surface and the tip inclined surface. Effect of the Invention

[0008] According to the present invention, it is possible to provide a piezoelectric vibration element and a manufacturing method thereof in which the mass balance in the thickness direction of the vibration part is maintained so that the oscillation frequency can be accurately adjusted and a stable oscillation frequency can be obtained. [Brief description of the drawings]

[0009] [Figure 1] 1 is a plan view of a piezoelectric vibration element according to an embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Diagram 3] 5A to 5C are process diagrams illustrating a method for manufacturing a piezoelectric vibration element according to an embodiment. [Figure 4] 3 is a cross-sectional view corresponding to FIG. 2, showing the tip of the vibrating part after "Step 1" of the manufacturing method. [Diagram 5] 3 is a cross-sectional view corresponding to FIG. 2 and showing the tip of the vibrating part after "Step 2" of the manufacturing method. [Figure 6] 3 is a cross-sectional view corresponding to FIG. 2 and showing the tip of the vibrating part after "Step 3" of the manufacturing method. [Figure 7] FIG. 11 is a plan view showing a tuning-fork type piezoelectric vibration element having a different shape from that of the embodiment. [Figure 8] FIG. 11 is a plan view showing a tuning-fork type piezoelectric vibration element having a different shape from that of the embodiment. [Figure 9] FIG. 11 is a plan view showing a tuning-fork type piezoelectric vibration element having a different shape from that of the embodiment. [Figure 10] FIG. 11 is a plan view showing a tuning-fork type piezoelectric vibration element having a different shape from that of the embodiment. [Figure 11] 3 is a cross-sectional view corresponding to FIG. 2 and showing a tip portion of a piezoelectric vibration element provided with a weight portion having a different shape from that of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 is a plan view of a piezoelectric vibration element 1 according to the embodiment. Fig. 2 is a cross-sectional view taken along line II-II of Fig. 1. The piezoelectric vibration element 1 according to the embodiment includes a substrate 10 and an excitation electrode 50 formed on the substrate 10. The piezoelectric vibration element 1 is housed in a package (not shown) and constitutes a piezoelectric vibrator together with the package.

[0011] The piezoelectric vibration element 1 of the embodiment is a quartz vibration element in which the substrate 10 is made of a thin plate-like quartz crystal piece. The substrate 10 of the embodiment is formed by processing a quartz crystal plate cut in an orthogonal coordinate system of a quartz crystal raw stone with the electric axis as the X axis, the mechanical axis as the Y axis, and the optical axis as the Z axis into a tuning fork shape. The substrate 10 of the embodiment made of a quartz crystal piece has an XY'Z' coordinate system in which the XY plane of a three-dimensional orthogonal coordinate system consisting of XY is rotated by a cut angle of a predetermined range angle (for example, -7° or more and +7° or less) with the X axis as the rotation axis, and is set to a predetermined vibration frequency range (for example, 32 kHz or more and 33 kHz or less). The oscillation frequency targeted in the piezoelectric vibration element 1 of the embodiment is set to, for example, 32.768 kHz, which is widely used as a reference signal for watches. The material of the substrate 10 is not limited to a quartz crystal piece, and other materials such as ceramic pieces may be used.

[0012] As shown in FIG. 1, the piezoelectric vibration element 1 and the substrate 10 of the embodiment are generally rectangular plate-like members in a plan view. FIG. 1 and FIG. 2 show an XYZ orthogonal coordinate system. In this XYZ orthogonal coordinate system, the longitudinal direction of the piezoelectric vibration element 1 is indicated as the Y axis direction, the width direction (short side direction) perpendicular to the longitudinal direction is indicated as the X axis direction, and the thickness direction perpendicular to the longitudinal direction and the width direction is indicated as the Z axis direction. If the X axis, Y axis, and Z axis correspond to the electric axis, mechanical axis, and optical axis of the above-mentioned quartz rough stone, respectively, the X axis is the electric axis, the Y axis is the mechanical axis, and the Z axis is the optical axis. Strictly speaking, the Y' axis and the Z' axis rotated by a predetermined cut angle (for example, -7° or more and +7° or less) around the X axis (electrical axis) as the rotation axis are the mechanical axis and the optical axis, respectively, but here, the Y' axis and the Z' axis are described as the Y axis and the Z axis.

[0013] In Fig. 1 and Fig. 2, one side (upper side) in the Y-axis direction is indicated by an arrow Y1, and the other side (lower side) is indicated by an arrow Y2. In Fig. 1, one side (left side) in the X-axis direction is indicated by an arrow X1, and the other side (right side) is indicated by an arrow X2. In Fig. 2, one side (upper side) in the Z-axis direction is indicated by an arrow Z1, and the other side (lower side) is indicated by an arrow Z2. In Figs. 4 to 6, which correspond to Fig. 2, the XYZ orthogonal coordinate system, the Y-axis direction, and the Z-axis direction are shown in the same manner as in Fig. 2.

[0014] 1 and 2, the substrate 10 includes a first main surface 11 and a second main surface 12 facing the first main surface 11 in the thickness direction. These main surfaces 11 and 12 are parallel to each other and are in the XY plane perpendicular to the thickness direction of the substrate 10.

[0015] As shown in FIG. 1, the substrate 10 of the piezoelectric vibration element 1 of the embodiment has a symmetrical shape when the X-axis direction is taken as the left-right direction. The substrate 10 includes a substantially rectangular base 13, a pair of vibration parts 20 that generate bending vibration, and a pair of support parts 30 arranged on both sides of the pair of vibration parts 20 in the X-axis direction. The pair of vibration parts 20 includes a first vibration arm 21 and a second vibration arm 22 that are adjacent to each other in the X-axis direction. The pair of support parts 30 includes a first support arm 31 adjacent to the X1 side of the first vibration arm 21 and a second support arm 32 adjacent to the X2 side of the second vibration arm 22. The first support arm 31, the first vibration arm 21, the second vibration arm 22, and the second support arm 32 are arranged in parallel at equal intervals in this order from the X1 side to the X2 side and extend in the Y-axis direction.

[0016] Each of the first vibrating arm 21 and the second vibrating arm 22 extends from the end of the base 13 on the Y1 side to the Y1 side. The first vibrating arm 21 and the second vibrating arm 22 have the same length (dimension in the Y-axis direction). On the Y2 side of the base 13 opposite to the side on which the vibrating arms 21 and 22 extend, a pair of relay parts, the first relay part 15A and the second relay part 15B, extending in the X-axis direction are formed via a constricted part 14 continuing to the base 13. The first support arm 31 extends from the end of the first relay part 15A on the X1 side to the Y1 side. The second support arm 32 extends from the end of the second relay part 15B on the X2 side to the Y1 side.

[0017] The first support arm 31 and the second support arm 32 have the same length (dimension in the Y-axis direction) and extend to near the middle of the length of each of the vibrating arms 21 and 22. The first support arm 31 and the second support arm 32 have uniform width (dimension in the X-axis direction) and are the same. The interval between the first vibrating arm 21 and the first support arm 31 and the interval between the second vibrating arm 22 and the second support arm 32 are the same, but these intervals and the interval between the first vibrating arm 21 and the second vibrating arm 22 may be the same or different. Each of the first vibrating arm 21 and the second vibrating arm 22 includes a base end 16 and a tip end 40 on the Y1 side opposite the base end 16. The base end portion 16 is a portion that is continuous with each of the supporting arm portions 31, 32 via the base portion 13, the constricted portion 14, and each of the relay portions 15A, 15B.

[0018] In the embodiment, the first vibrating arm 21 and the second vibrating arm 22 each have a shape in which the width (dimension in the X-axis direction) on the Y1 side, which is the tip end 40 side, is larger than the width on the Y2 side, which is the base end 16 side. That is, each of the first vibrating arm 21 and the second vibrating arm 22 includes a narrow width portion 23 extending from the base 13 to the Y1 side, and a wide width portion 24 formed on the Y1 side of the narrow width portion 23. The narrow width portion 23 includes the base end 16, and the wide width portion 24 includes the tip end 40. A groove portion 25 is formed on the surface of each narrow width portion 23 of the first vibrating arm 21 and the second vibrating arm 22. These groove portions 25 are formed from the Y1 side end of the base 13 to the Y1 side end of each vibrating arm 21, 22.

[0019] Although the piezoelectric vibration element 1 of the embodiment has a bilaterally symmetrical shape in plan view, the shape of the piezoelectric vibration element of the present disclosure is not limited to a bilaterally symmetrical shape. Therefore, the length, width, and spacing between adjacent arms in the X-direction of each of the vibrating arms 21, 22 and each of the supporting arms 31, 32 are not limited. Furthermore, each of the supporting arms 31, 32 is not an essential component, and each of the relay parts 15A, 15B and the constricted part 14 extending from the supporting arms 31, 32 to the base part 13 are not essential components, but are optional components.

[0020] An excitation electrode 50 is formed on the outer surface of the substrate 10. The excitation electrode 50 includes a first excitation electrode 51 and a second excitation electrode 52 having a polarity different from that of the first excitation electrode 51. The first excitation electrode 51 is provided on the outer wall surface of the narrow portion 23 of the first vibrating arm 21, and is provided on the inner wall surface of the groove portion 25 from the base 13 to the second vibrating arm 22. The second excitation electrode 52 is provided on the outer wall surface of the narrow portion 23 of the second vibrating arm 22, and is provided on the inner wall surface of the groove portion 25 from the base 13 to the first vibrating arm 21. In this way, the excitation electrodes 51 and 52 are arranged in the narrow portion 23 of each vibrating arm 21 and 22 so that the polarity is different between the inner wall surface of the groove portion 25 extending in the Y-axis direction and the outer wall surface facing the inner wall surface. This increases the strength of the generated electric field and reduces the equivalent resistance value, making it easier for each of the vibrating arms 21 and 22 to vibrate.

[0021] For example, a two-layer metal film in which a surface metal film is formed on a base metal film is used as the first excitation electrode 51 and the second excitation electrode 52. Cr, Cr alloy, Ti, Ni, etc. are used as the base metal film, and Pt, Ag, etc. are used as the surface metal film.

[0022] A first wiring portion 17A that is electrically connected to the first excitation electrode 51 is formed on the outer surface of the portion extending from the first support arm 31 to the first relay portion 15A and the base portion 13. A second wiring portion 17B that is electrically connected to the second excitation electrode 52 is formed on the outer surface of the portion extending from the second support arm 32 to the second relay portion 15B and the base portion 13. A first tip electrode 51a that is electrically connected to the first excitation electrode 51 is formed on the outer surface of the wide portion 24 including the tip portion 40 of the first vibrating arm 21, and a second tip electrode 52a that is electrically connected to the second excitation electrode 52 is formed on the outer surface of the wide portion 24 including the tip portion 40 of the second vibrating arm 22. Each wiring portion 17A, 17B and each tip electrode 51a, 52a may have the same structure as each excitation electrode 51, 52, and may be made of the same metal material. In addition, the tip electrodes 51a and 52a are not essential components, but are optional components. When the tip electrodes 51a and 52a are not formed, a first metal film 61 described later may be formed directly on the outer surface of the substrate 10.

[0023] In the piezoelectric vibration element 1 of the embodiment, the tip portions of the first support arm 31 and the second support arm 32 are supported in the above-mentioned package, and the first wiring portion 17A and the second wiring portion 17B are electrically connected to a pair of electrode pads arranged in the package. By supporting the tip portions of the support arms 31, 32 extending in the Y-axis direction, the impact on the package is less likely to be directly transmitted to the vibrating arms 21, 22, and the leakage of the tuning fork vibration generated in these vibrating arms 21, 22 is suppressed.

[0024] 2 is a cross-sectional view taken along line II-II in FIG. 1, showing the tip 40 of the second vibrating arm 22 on the Y1 side. The configuration of the tip 40 of the second vibrating arm 22 will be described below. The tip 40 of the first vibrating arm 21 also has a common configuration. Therefore, the tip 40 of the second vibrating arm 22 will be described as a representative, and the description of the tip 40 of the first vibrating arm 21 will be omitted. In the following, the first vibrating arm 21 and the second vibrating arm 22 will be described as a common part, so that the vibrating arms 21 and 22 may be collectively referred to as the vibrating part 20, and the excitation electrodes 51 and 52 may be collectively referred to as the excitation electrodes 50.

[0025] As shown in FIG. 2, the vibration section 20 includes a first main surface 11 and a second main surface 12. The surface on the tip side (Y1 side) of the tip portion 40 of the vibration section 20 includes a tip inclined surface 45. The tip inclined surface 45 is a surface that connects the first main surface 11 and the second main surface 12. The tip inclined surface 45 of the embodiment is inclined with respect to the thickness direction so as to protrude from the first main surface 11 side to the second main surface 12 side as it approaches the tip side, i.e., the Y1 side. The tip portion 40 includes, in the YZ cross section shown in FIG. 2, a first corner portion 41 that is an obtuse angle formed by the first main surface 11 and the tip inclined surface 45, and a second corner portion 42 that is an acute angle formed by the second main surface 12 and the tip inclined surface 45. The tip inclined surface 45 has an inclination angle θ of, for example, about 5 degrees with respect to the thickness direction, but is not limited thereto.

[0026] The tip 40 of the vibration part 20 has a first metal film 61 formed on the surface of the second tip electrode 52a (corresponding to the first tip electrode 51a in the first vibration arm 21) and a second metal film 62 formed on the surface of the first metal film 61. The first metal film 61 and the second metal film 62 are arranged on the first main surface 11 and the first corner 41 side of the tip inclined surface 45 in the tip 40 of the vibration part 20. By having these metal films 61 and 62, the vibration part 20 is adjusted to oscillate at a target frequency. The process of adjusting the vibration part 20 to oscillate at a target frequency includes a coarse adjustment process of irradiating the first metal film 61 with a laser beam after forming the first metal film 61, and a fine adjustment process of irradiating the second metal film 62 with an ion beam after forming the second metal film 62 on the surface of the first metal film 61 after the coarse adjustment. These steps relate to the manufacturing method of the piezoelectric vibration element of the present disclosure and will be described later.

[0027] The first metal film 61 is a metal film having a predetermined thickness. The first metal film 61 is formed on the surface of the second tip electrode 52a by using a thin film forming means such as deposition or coating of a conductive metal material. The metal material of the first metal film 61 may be the same conductive metal material as that of the second tip electrode 52a, or may be a different conductive metal material. A laser processed portion 61a is formed on the first metal film 61 by irradiation with the above-mentioned laser beam. This laser processed portion 61a is a laser beam mark formed by evaporating and removing a part of the first metal film 61 by irradiation with the laser beam.

[0028] When a portion of the first metal film 61 is removed by irradiation with a laser beam, granular metal chips resulting from incomplete evaporation of the first metal film 61 may adhere to the surface of the first metal film 61. However, the metal chips are covered by the second metal film 62, preventing them from falling off.

[0029] The oscillation frequency at the stage where the first metal film 61 is formed on the tip 40 of the vibration part 20 is adjusted to be, for example, several percent lower than the target oscillation frequency. Then, by performing the above-mentioned coarse adjustment process in which a part of the first metal film 61 is removed by irradiating it with a laser beam to provide the laser processed part 61a, the oscillation frequency of the vibration part 20 is adjusted to a frequency band slightly higher than the target oscillation frequency.

[0030] The second metal film 62 is formed to a predetermined thickness on the surface of the first metal film 61 including the laser processing portion 61a by using a thin film forming means such as sputtering, vapor deposition, plating, etc. of a conductive metal material. The second metal film 62 is formed, for example, by coating a base metal with a main metal. For example, metals such as chromium, nickel, and titanium that have high adhesive strength with the substrate 10 made of a quartz crystal piece are suitable as the base metal of the second metal film 62. The thickness of this base metal is sufficient if it has a thickness of 50 to 500 Å to maintain its function. For the main metal forming the surface of the second metal film 62, precious metals such as gold, silver, and platinum that are difficult to oxidize are suitable to prevent fluctuations in the frequency of the vibration portion 20.

[0031] The thickness of the main metal is preferably such that the entire thickness of the second metal film 62 is 2000 Å or more. This is for the reason of, for example, firmly fixing the above-mentioned metal chips to prevent them from falling off. In addition, the main metal of the second metal film 62 is used as a trimming material when adjusting (fine-tuning) the frequency by the above-mentioned ion beam, so that it becomes thinner than the initial thickness after the frequency adjustment. For this reason, it is necessary to set the thickness after the frequency adjustment to, for example, 1500 Å or more. However, since the above-mentioned precious metals are expensive and difficult to use frequently, the second metal film 62 may have a base metal thickness of 1000 Å or more and a main metal consisting of the surface precious metal film to be irradiated with the ion beam to a thickness of about 1000 Å.

[0032] The oscillation frequency of the vibration part 20 at the stage where the second metal film 62 is formed on the surface of the first metal film 61 is adjusted to be higher than the oscillation frequency when the first metal film 61 is formed and lower than the target oscillation frequency. Then, a fine adjustment process is performed in which the entire surface of the second metal film 62 is irradiated with an ion beam, thereby reducing the thickness of the second metal film 62 overall. This adjusts the oscillation frequency of the vibration part 20 to the target value.

[0033] As shown in FIG. 2, the first metal film 61 and the second metal film 62 are mainly disposed on the surface of the first main surface 11 of the vibrating part 20. The tip part 40 of the vibrating part 20 has a weight part 65 (a part indicated by dots in FIG. 2) in which the first metal film 61 and the second metal film 62 are continuously formed from the first main surface 11 side to the tip inclined surface 45. That is, the weight part 65 is a metal film formed by a thin film forming means. This weight part 65 has a function of adjusting the oscillation frequency by uniformly maintaining the mass balance in the thickness direction of the vibrating part 20. This weight part 65 is disposed on the first corner part 41 side of the obtuse angle formed by the first main surface 11 and the tip inclined surface 45 in the tip part 40.

[0034] The line indicated by the symbol S1 in FIG. 2 indicates the YZ plane at the 1 / 2 position of the thickness of the vibration part 20, and the line indicated by the symbol S2 is a perpendicular line perpendicular to the second main surface 12 from the first corner 41. When considering the mass balance in the thickness direction of the piezoelectric vibration element 1, when comparing the mass on the first main surface 11 side and the mass on the second main surface 12 side with the 1 / 2 thickness plane S1 as a boundary, the second main surface 12 side is heavier by the mass of the protruding part 22G having a triangular cross section surrounded by the tip inclined surface 45, the second main surface 12, the intersection of the 1 / 2 thickness plane S1 and the tip inclined surface 45, and the intersection of the perpendicular line S2 and the second main surface 12. Since this protruding part 22G is on the second corner 42 side, adding mass to the first corner 41 side can bring the balance closer to even. For example, if a mass equivalent to that of protruding portion 22G is given to the first corner 41 side, the balance in the thickness direction can be adjusted evenly. Therefore, it is desirable that weight portion 65 arranged on the first corner 41 side has a mass equivalent to that of protruding portion 22G. This makes it possible to evenly maintain the mass balance in the thickness direction of vibration portion 20, and makes it easy to adjust the oscillation frequency of vibration portion 20 to a target value.

[0035] Next, a frequency adjustment step for adjusting the oscillation frequency of the vibration portion 20 to a target value will be described with reference to Fig. 3. This step includes a method for manufacturing the piezoelectric vibration element of the present disclosure.

[0036] First, the substrate 10 of the piezoelectric vibration element 1 is prepared, in which the tip inclined surface 45 is formed on the tip surface on the Y1 side of the vibration part 20, and the excitation electrode 50, the wiring parts 17A, 17B, and the tip electrodes 51a, 52a are formed. For example, a quartz plate from which a plurality of substrates 10 can be cut is used as a material, and when a plurality of substrates 10 of the same shape are cut and taken from the material, the substrate 10 is cut so as to form the tip inclined surface 45. Thereafter, the excitation electrode 50, the wiring parts 17A, 17B, and the tip electrodes 51a, 52a are formed on the substrate 10 by a thin film forming means such as sputtering or deposition. As a result, the substrate 10 is obtained in which the tip inclined surface 45 is formed on the tip surface on the Y1 side of the vibration part 20, and the excitation electrode 50 is formed on the vibration part 20 (step 1: see FIG. 4). Here, the substrate 10 on which the excitation electrode 50 is formed is manufactured so that the oscillation frequency is higher than the target frequency f0 set at the time of design by a frequency width f1 of about 300 to 5000 Hz. From this state, adjustments are made to approach the target frequency f0 through the following rough adjustment process A and fine adjustment process B.

[0037] In the coarse adjustment process A, first, in order to set the oscillation frequency of the vibration part 20 to be about 10 to 2000 Hz lower than the target frequency f0, a first metal film 61 is formed on the first corner 41 side of the surface of the tip part 40 of each of the vibrating arms 21 and 22 by deposition, coating, or the like of a metal material (process 2: see FIG. 5). In this embodiment, the first metal film 61 is continuously formed from the first main surface 11 to the tip inclined surface 45. The thickness of the first metal film 61 is set to about 0.3 μm or more and 3 μm or less when gold is used, for example. Next, a laser beam is irradiated to the first metal film 61 in a predetermined amount to form a laser processed part 61a in which a part of the first metal film 61 is evaporated and removed. The laser processed part 61a is a laser beam mark, and can be formed by repeating the operation of scanning the laser beam in the width direction (X-axis direction) of each of the vibrating arms 21 and 22. At this time, the second tip electrode 52a on the second main surface 12 side on the back side is removed by the laser beam transmitted through the substrate 10, and a notch 53 is formed. By forming the laser processed portion 61a, the mass of the tip 40 of each vibrating arm 21, 22 is reduced, and the oscillation frequency is adjusted to be slightly higher (about several tens to several hundreds of Hz) than the target frequency f0 (step 3: see FIG. 6). The frequency variation adjusted by the laser beam irradiation is preferably about several Hz to several tens of Hz.

[0038] Next, a second metal film 62 is formed on the surface of the first metal film 61 (step 4: see FIG. 2). The second metal film 62 can be formed by a thin film forming means such as sputtering, vapor deposition, plating, etc. By forming the second metal film 62, the oscillation frequency F is adjusted to be slightly lower (several Hz to several tens of Hz) than the target frequency f0.

[0039] By forming the second metal film 62 on the surface of the first metal film 61 in this manner, the mass of the first metal film 61 adjusted by the laser beam irradiation is maintained as is, as is the frequency variation. Therefore, the reference value used for fine adjustment by the second metal film 62 does not fluctuate.

[0040] The fine adjustment process B is a process for performing fine adjustment to make the oscillation frequency of the vibration part 20 coincide with the target frequency f0, and the frequency is gradually increased by thinning the thickness of the second metal film 62 to approximately coincide with the target frequency f0 (process 5). Process 5 is performed by irradiating the surface of the second metal film 62 with an ion beam to thin the thickness. Since the processing speed of the ion beam is slower than that of the laser beam, the metal film can be gradually thinned from the irradiated portion. Therefore, by controlling the irradiation range and irradiation time, the surface of the second metal film 62 can be finished to a clean state without generating burrs or metal chips.

[0041] By carrying out the above-mentioned coarse adjustment process A and fine adjustment process B, weight portion 65 is also formed at the tip portion 40 of vibrating portion 20 at the same time. Weight portion 65 is formed continuously from first main surface 11 to the first main surface 11 side of tip inclined surface 45, and is disposed so as to cover first corner portion 41. Weight portion 65 is thinned by ion beam irradiation during the coarse and fine adjustment process, and thus the mass is adjusted so as to be equivalent to that of protruding portion 22G as described above.

[0042] In the case of the tuning fork type piezoelectric vibration element 1, the oscillation frequency can be adjusted relatively easily because the adjustment rate of the oscillation frequency can be made higher on the tip portion 40 side than on the base end portion 16 side of the pair of vibration parts 20. In the embodiment, a first metal film 61 and a second metal film 62 are formed on the tip portion 40, and the oscillation frequency is adjusted by trimming these metal films 61, 62, so that the adjustment rate of the oscillation frequency can be made high and the oscillation frequency can be adjusted easily.

[0043] The above is the piezoelectric vibration element 1 and the manufacturing method thereof according to the embodiment. According to this embodiment, the following effects are achieved.

[0044] (1) The piezoelectric vibration element 1 according to the embodiment includes a support portion 30, and a vibration portion 20 extending continuously from the support portion 30 and having an excitation electrode 50 formed thereon. The vibration portion 20 includes a first main surface 11, a second main surface 12 opposite the first main surface 11, a base end portion 16 on the support portion 30 side, and a tip portion 40 on the tip side. The tip portion 40 includes a tip inclined surface 45 connecting the first main surface 11 and the second main surface 12 and inclining so as to protrude toward the second main surface 12 as it approaches the tip side, a first corner 41 which is an obtuse angle formed by the first main surface 11 and the tip inclined surface 45, and a second corner 42 which is an acute angle formed by the second main surface 12 and the tip inclined surface 45. The tip portion 40 has a weight portion 65 on the first corner 41 side for adjusting the oscillation frequency of the vibration portion 20 to a predetermined target frequency.

[0045] According to the piezoelectric vibration element 1 of the embodiment, the tip 40 of the vibration part 20 has the weight part 65 arranged on the first corner part 41 side, so that the mass balance in the thickness direction of the vibration part 20 can be made closer to an even balance. This allows the oscillation frequency of the vibration part 20 to be accurately adjusted, and a stable oscillation frequency can be obtained.

[0046] (2) A manufacturing method of a piezoelectric vibration element according to an embodiment is a manufacturing method of a piezoelectric vibration element 1 comprising a support portion 30, a vibration portion 20 extending continuously from the support portion 30 and having an excitation electrode 50 formed thereon, the vibration portion 20 including a first main surface 11, a second main surface 12 opposite the first main surface 11, a base end portion 16 on the support portion 30 side, and a tip portion 40 on the tip side, wherein a tip inclined surface 45 is formed in the tip portion 40, which connects the first main surface 11 and the second main surface 12 and inclines so as to protrude toward the second main surface 12 as it approaches the tip side, and a weight portion 65 is arranged on the side of a first corner 41 of the cross-sectional obtuse angle formed by the tip inclined surface 45 and the first main surface 11, for adjusting the oscillation frequency of the vibration portion 20 to a predetermined target frequency.

[0047] This allows the mass balance in the thickness direction of the vibration part 20 to be brought closer to an even balance by the weight part 65, and as a result, the oscillation frequency of the vibration part 20 can be accurately adjusted, making it possible to manufacture a piezoelectric vibration element having a stable oscillation frequency.

[0048] (3) In the method for manufacturing the piezoelectric vibration element according to the embodiment, it is preferable that the weight portion 65 is a metal film (the first metal film 61 and the second metal film 62) formed by a thin film forming means.

[0049] As a result, the weight portion 65 can be finely processed by means of an ion beam or the like to reduce the mass, so that the mass balance in the thickness direction of the vibration portion 20 can be adjusted with high precision and easily, and therefore the oscillation frequency of the vibration portion 20 can be accurately adjusted.

[0050] The above is the first piezoelectric vibration element and its manufacturing method according to the embodiment, but the piezoelectric vibration element and its manufacturing method of the present disclosure are not limited to the above embodiment, and even if modifications and improvements are made to the extent that the objective of the present disclosure can be achieved, they will still be included in the scope of the present disclosure.

[0051] The weight section 65 provided at the tip section 40 of the vibration section 20 is preferably disposed at least on one of the first main surface 11 side and the tip inclined surface 45 side. In order to adjust the balance, the weight section 65 is preferably disposed at least on the tip inclined surface 45 side. For example, the weight section 65 provided at the tip section 40 of the vibration section 20 may be disposed on either one of the sides, such as only on the first main surface 11 side or only on the tip inclined surface 45 side, in addition to being disposed in a manner covering the first corner section 41 from the first main surface 11 side to the tip inclined surface 45 as in the above embodiment. This makes it possible to reduce the amount of metal film used as the weight section 65 and improve the degree of freedom in design.

[0052] In the above embodiment, the weight portion 65 is a part of the first metal film 61 and the second metal film 62 that are provided to adjust the oscillation frequency of the entire vibration portion 20, but the weight portion of the present disclosure may be configured as an independent part for adjusting the mass balance in the thickness direction of the vibration portion 20. In that case, the weight portion may be configured of a different type of metal from the metal films 61, 62.

[0053] In the above embodiment, the metal films (first metal film 61 and second metal film 62) for adjusting the oscillation frequency are arranged only on the first main surface 11, but such metal films may also be arranged on the second main surface 12.

[0054] The piezoelectric vibration element can be any type of piezoelectric vibration element, such as a thickness-shear vibration element, a width-extensional vibration element, or a length-extensional vibration element other than a tuning fork type.

[0055] The configuration of the present disclosure can be applied to tuning-fork type piezoelectric vibration elements having shapes other than the shape of the embodiment shown in Fig. 1, for example, piezoelectric vibration elements 110 to 140 shown in Fig. 7 to 10. In these piezoelectric vibration elements 110 to 140, the same components as those in the above embodiment are denoted by the same reference numerals, and their description will be omitted or simplified.

[0056] In the piezoelectric vibration element 110 shown in FIG. 7, a pair of vibration parts 20 having excitation electrodes 50 extend parallel to each other from a base part 101 having wiring parts 17A and 17B, and a tip inclined surface as in the above embodiment is formed on the tip surface of the vibration part 20, and a weight part 65 is provided. The piezoelectric vibration element 120 shown in FIG. 8 has a shape in which a constricted part 101a is formed on the base part 101 of the piezoelectric vibration element 110 shown in FIG. 7. Furthermore, the piezoelectric vibration element 130 shown in FIG. 9 has a tip part 40 of the vibration part 20 having a wide shape. The piezoelectric vibration element 140 shown in FIG. 10 has a base part 104 extending parallel to the pair of vibration parts 20 between the pair of vibration parts 20, and the tip part 40 of the vibration part 20 has a wide shape. In the case of the piezoelectric vibration elements 110 to 140 shown in FIG. 7 to FIG. 10, the base parts 101 and 104 also serve as supports. The bases 101, 104 serving as supports are supported within the above-mentioned package, and the first wiring portion 17A and the second wiring portion 17B formed on the bases 101, 104 are electrically connected to a pair of electrode pads arranged within the package.

[0057] Here, it is preferable that the oscillation frequency of the piezoelectric vibration element 1 can be adjusted effectively and with high sensitivity. In terms of the piezoelectric vibration element 1 according to the above embodiment, it is more effective to arrange the weight portion on the tip end 40 side rather than on the base end 16 side as the weight portion for adjusting the oscillation frequency of the piezoelectric vibration element, and it is most effective to arrange the weight portion on the tip inclined surface 45, which is the most distal end. Fig. 11 specifically shows such an embodiment, in which the weight portion 65 is arranged over the entire surface of the tip inclined surface 45.

[0058] In this case, a first metal film 61 is formed on the entire surface of second tip electrode 52a covering tip inclined surface 45, and a second metal film 62 is further formed on the surface of this first metal film 61. These first metal film 61 and second metal film 62 form a weight portion 65 covering tip inclined surface 45. Each of the metal films 61, 62 that form this weight portion 65 has a roughly constant thickness, and therefore the thickness of weight portion 65 covering tip inclined surface 45 is also roughly constant.

[0059] By arranging the weight 65 on the tip inclined surface 45 that constitutes the tip of the vibration part 20 in this way, the oscillation frequency of the piezoelectric vibration element 1 can be adjusted effectively and with high sensitivity. In addition, since the tip inclined surface 45 is inclined with respect to the thickness direction of the piezoelectric vibration element 1, the area tends to be relatively large. Therefore, the amount of the weight 65 can be increased, and the adjustment range of the oscillation frequency can be increased. In addition, when a piezoelectric vibration element is miniaturized, it is generally difficult to adjust the oscillation frequency while maintaining the characteristics, but by arranging a weight made of, for example, gold having a high specific gravity on the tip inclined surface 45, the oscillation frequency can be easily adjusted.

[0060] When weight portion 65 is disposed on tip inclined surface 45, it may be disposed partially in addition to disposing it so as to cover the entire tip inclined surface 45 as shown in Fig. 11. Furthermore, weight portion 65 may have a constant thickness, or may have a thickness that varies in the thickness direction of piezoelectric vibration element 1. When the thickness is varied, it is preferable because by adjusting the thickness, it is possible to exhibit the function of a balancer that adjusts the mass balance in the thickness direction of vibration portion 20.

[0061] (4) The piezoelectric vibration element 1 according to the embodiment includes a support portion 30 and a vibration portion 20 extending continuously from the support portion 30 and having an excitation electrode 50 formed thereon. The vibration portion 20 includes a first main surface 11, a second main surface 12 opposite the first main surface 11, a base end portion 16 on the support portion 30 side, and a tip portion 40 on the tip side. The tip portion 40 includes a tip inclined surface 45 connecting the first main surface 11 and the second main surface 12 and inclining so as to protrude toward the second main surface 12 as it approaches the tip side, a first corner 41 which is an obtuse angle formed by the first main surface 11 and the tip inclined surface 45, and a second corner 42 which is an acute angle formed by the second main surface 12 and the tip inclined surface 45. The tip inclined surface 45 at the tip portion 40 has a weight portion 65 which adjusts the oscillation frequency of the vibration portion 20 to a predetermined target frequency.

[0062] According to the piezoelectric vibration element 1 of the embodiment, by arranging the weight portion 65 on the side of the tip inclined surface 45 that constitutes the most distal end of the vibration portion 20, the oscillation frequency of the piezoelectric vibration element 1 can be adjusted effectively and with high sensitivity. [Explanation of symbols]

[0063] 1, 110, 120, 130, 140...piezoelectric vibration element, 10...substrate, 11...first main surface, 12...second main surface, 16...base end, 20...vibration portion, 30...support portion, 40...tip portion, 45...tip inclined surface, 41...first corner portion, 42...second corner portion, 50...excitation electrode, 61...first metal film (metal film), 62...second metal film (metal film), 65...weight portion.

Claims

1. A support portion; A piezoelectric vibration element including a vibration part extending continuously from the support part and having an excitation electrode formed thereon, the vibration portion includes a first main surface, a second main surface opposite to the first main surface, a base end portion on the support portion side, and a tip end portion on the tip side, The tip portion is a tip inclined surface that connects the first main surface and the second main surface and inclines toward the second main surface as it approaches a tip side; a first corner portion that is an obtuse angle formed between the first main surface and the tip inclined surface; a second corner portion that is an acute angle formed between the second main surface and the tip inclined surface, A piezoelectric vibration element having a weight portion on the first corner side of the tip portion for adjusting an oscillation frequency of the vibration portion to a predetermined target frequency.

2. The piezoelectric vibration element according to claim 1 , wherein the weight portion is disposed on at least one of the first main surface side and the tip inclined surface side.

3. The piezoelectric vibration element according to claim 1 , wherein the weight portion is disposed on the tip inclined surface side.

4. A support portion; a vibration section extending continuously from the support section and having an excitation electrode formed thereon; The vibration portion includes a first main surface, a second main surface opposite to the first main surface, a base end portion on the support portion side, and a tip end portion on a tip side, a tip inclined surface is formed at the tip portion, the tip inclined surface connecting the first main surface and the second main surface and inclining toward the tip side so as to protrude toward the second main surface; A method for manufacturing a piezoelectric vibration element, comprising: arranging a weight portion for adjusting an oscillation frequency of the vibration portion to a predetermined target frequency on a first corner side of a cross-sectional obtuse angle formed by the first main surface and the tip inclined surface.

5. The method for manufacturing a piezoelectric vibration element according to claim 4 , wherein the weight portion is a metal film formed by a thin film forming means.

6. The method for manufacturing a piezoelectric vibration element according to claim 4 , wherein the weight portion is disposed on at least one of the first main surface side and the tip inclined surface side.

7. The method for manufacturing a piezoelectric vibration element according to claim 4 , wherein the weight portion is disposed on the tip inclined surface side.

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