Method for adjusting frequency of piezoelectric vibration device and piezoelectric vibration device

Abstract

To provide a frequency adjusting method for a piezoelectric vibration device that makes it possible to suppress a molten metal layer from remaining on an underlying metal layer as a ball-shaped lump.SOLUTION: In a frequency adjusting method for a quartz crystal oscillator 100, a metal film 36 for adjusting frequency composed of an underlying metal layer 36a and a metal layer 36b stacked on top of the underlying metal layer 36a is formed on a first main surface 301 opposing to a second excitation electrode 112 of a second sealing member 30, and the second sealing member 30 is made of crystal. The metal film 36 for adjusting frequency is irradiated with a laser from an external source of the second sealing member 30 at a plurality of locations at a predetermined interval. By transmitting the laser through the inside of the second sealing member 30 to heat the underlying metal layer 36a, at least a portion of the metal layer 36b is evaporated by melting and is adhered to the second excitation electrode 112 so that a frequency is adjusted.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a method for adjusting the frequency of a piezoelectric vibration device and a piezoelectric vibration device. [Background technology]

[0002] Conventionally, the manufacturing process of a piezoelectric vibration device such as a quartz crystal unit includes a frequency adjustment process, in which the frequency of the quartz crystal unit is adjusted to fall within a predetermined target frequency range (see, for example, Patent Document 1). When the frequency adjustment process is performed after the vibration portion of the quartz crystal unit is sealed with a sealing member, a beam such as a laser is irradiated from outside the quartz crystal unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5762811 Summary of the Invention [Problem to be solved by the invention]

[0004] The frequency-adjusting metal film used to adjust the frequency of the piezoelectric vibrating device described above consists, for example, of a base metal layer formed on a sealing member of the piezoelectric vibrating device and a metal layer formed on the base metal layer. The metal layer on the base metal layer is melted and evaporated by irradiating it with a beam, and the evaporated metal is then deposited on the excitation electrode of the vibrating section of the quartz crystal vibrating plate, thereby achieving frequency adjustment. However, there is a possibility that a portion of the molten metal layer solidifies into a ball-shaped mass and remains on the base metal layer as foreign matter. In this case, there is a concern that the ball-shaped mass of the metal layer may peel off from the base metal layer and adhere to the excitation electrode of the vibrating section.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a frequency adjustment method for a piezoelectric vibration device, and a piezoelectric vibration device, which can prevent the molten metal layer from forming ball-shaped lumps and remaining on the underlying metal layer. [Means for solving the problem]

[0006] The present invention provides a method for solving the above-mentioned problems as follows: That is, the present invention provides a method for adjusting the frequency of a piezoelectric vibration device in which at least a vibration portion of a piezoelectric vibration plate having a vibration portion on which an excitation electrode is formed is hermetically sealed by a sealing member, wherein a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, and at least a portion of the sealing member on which the frequency-adjusting metal film is formed is made of a light-transmitting material; the main surface of the sealing member and a second main surface on the side not facing the piezoelectric diaphragm are smooth surfaces, and the arithmetic mean roughness of the main surface and the second main surface is 1 nm or less; A beam is irradiated from outside the sealing member onto the frequency adjustment metal film at multiple locations spaced apart at a predetermined interval, and the beam is transmitted through the inside of the sealing member to heat the underlying metal layer, thereby melting and evaporating at least a portion of the metal layer, and adhering it to the excitation electrode, thereby performing frequency adjustment.

[0007] According to the frequency adjustment method for a piezoelectric vibration device, the metal layer above the base metal layer is melted and evaporated, and the evaporated metal adheres to the excitation electrode, thereby increasing the mass of the excitation electrode and shifting the frequency to a lower level. In this case, a beam is irradiated at multiple locations on the frequency adjustment metal film at a predetermined interval, so that metal layers and exposed portions of the base metal layer that are not covered by the metal layer are alternately formed on the surface of the frequency adjustment metal film. As a result, the remaining metal layer is located near the melted but not evaporated metal layer, and the melted but not evaporated metal layer is attracted toward the remaining metal layer, adhering to the remaining metal layer and solidifying. This prevents the melted but not evaporated metal layer from solidifying into a ball-shaped mass and remaining on the base metal layer. As a result, the ball-shaped mass of the metal layer is prevented from peeling off from the base metal layer and adhering to the excitation electrode of the vibration section.

[0008] In the method for adjusting the frequency of a piezoelectric vibrating device, it is preferable that the beam is irradiated linearly onto the frequency-adjusting metal film in a planar view, and that the linear irradiation of the beam is performed multiple times at each of the multiple locations.

[0009] The present invention also provides a piezoelectric vibration device in which a vibration section on which an excitation electrode is formed is hermetically sealed by a sealing member, and a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, and the frequency-adjusting metal film has an exposed portion where a part of the base metal layer is not covered with the metal layer and is exposed, and the exposed portion is formed in a plurality of places at predetermined intervals. The metal layer and the exposed portion are alternately formed in stripes on the surface of one frequency-adjusting metal film. It is characterized by:

[0010] According to the above-described piezoelectric vibration device, during frequency adjustment, the metal layer that was melted but not evaporated by laser irradiation of the frequency adjustment metal film is located near the metal layer that was melted but not evaporated. Therefore, the metal layer that was melted but not evaporated is attracted toward the remaining metal layer, adheres to the remaining metal layer, and solidifies. This prevents the metal layer that was melted but not evaporated from solidifying into a ball-shaped mass and remaining on the base metal layer. As a result, after frequency adjustment, the metal layer that became a ball-shaped mass is prevented from peeling off from the base metal layer and adhering to the excitation electrode of the vibrating section. In addition, by making the base metal layer exposed by the exposed portion of the frequency adjustment metal film function as a getter material, gas generated in the internal space of the piezoelectric vibration device can be captured by the base metal layer. This prevents changes in the frequency of the piezoelectric vibration device over time due to gas generation. [Effects of the Invention]

[0011] According to the frequency adjustment method for a piezoelectric vibration device of the present invention, a beam is irradiated onto the frequency-adjusting metal film at multiple locations spaced apart by a predetermined distance, so that metal layers and exposed portions of the underlying metal layer that are not covered by the metal layer are alternately formed on the surface of the frequency-adjusting metal film. Therefore, since there is a metal layer that remains unmelted near the metal layer that melted but did not evaporate, the metal layer that melted but did not evaporate is attracted toward the remaining metal layer, adheres to the remaining metal layer, and solidifies. This prevents the metal layer that melted but did not evaporate from solidifying into ball-shaped lumps and remaining on the underlying metal layer. As a result, the ball-shaped lumps of the metal layer are prevented from peeling off from the underlying metal layer and adhering to the excitation electrode of the vibration section.

[0012] Furthermore, according to the piezoelectric vibration device of the present invention, during frequency adjustment, the metal layer that was melted but not evaporated by laser irradiation of the frequency adjustment metal film is located near the metal layer that was melted but not evaporated. Therefore, the metal layer that was melted but not evaporated is attracted toward the remaining metal layer, adheres to the remaining metal layer, and solidifies. This prevents the metal layer that was melted but not evaporated from solidifying into a ball-shaped mass and remaining on the base metal layer. As a result, after frequency adjustment, the metal layer that became a ball-shaped mass is prevented from peeling off from the base metal layer and adhering to the excitation electrode of the vibrating section. In addition, by making the base metal layer exposed by the exposed portion of the frequency adjustment metal film function as a getter material, gas generated in the internal space of the piezoelectric vibration device can be captured by the base metal layer. This prevents changes in the frequency of the piezoelectric vibration device over time due to gas generation. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating each component of a quartz crystal resonator according to a first embodiment. [Figure 2] 3 is a schematic plan view of a first main surface side of a first sealing member of a quartz crystal resonator. FIG. [Figure 3] 3 is a schematic plan view of the second main surface side of the first sealing member of the quartz crystal resonator. FIG. [Figure 4] 1 is a schematic plan view of a first main surface side of a quartz crystal plate according to an embodiment of the present invention. [Figure 5] 2 is a schematic plan view of the second main surface side of the quartz crystal plate according to the present embodiment. FIG. [Figure 6] 3 is a schematic plan view of the first main surface side of the second sealing member of the quartz crystal resonator. FIG. [Figure 7] 4 is a schematic plan view of the second main surface side of the second sealing member of the quartz crystal resonator. FIG. [Figure 8] 1A to 1C are schematic cross-sectional views illustrating a method for adjusting the frequency of a crystal resonator according to an embodiment of the present invention. [Figure 9] 9 is a view corresponding to FIG. 8 showing a frequency-adjusting metal film according to a modified example. [Figure 10]FIG. 10 is a schematic plan view showing a method of irradiating a frequency-adjusting metal film with a laser. [Figure 11] FIG. 2 is a schematic plan view showing a metal film for adjusting the frequency of the crystal resonator according to the present embodiment. [Figure 12] 7 is a view corresponding to FIG. 6 and showing a first main surface of a second sealing member of a quartz crystal resonator according to a modified example. [Figure 13] 8A and 8B are views showing a method for adjusting the frequency of a crystal resonator according to a modified example. [Figure 14] FIG. 6 is a schematic diagram showing the configuration of a quartz crystal resonator according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] [First embodiment] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following preferred embodiments, a piezoelectric resonator device to which the present invention is applied is a quartz resonator.

[0015] First, the basic structure of a quartz crystal unit 100 according to this embodiment will be described. As shown in Fig. 1, the quartz crystal unit 100 is configured to include a quartz crystal vibrating plate (piezoelectric vibrating plate) 10, a first sealing member 20, and a second sealing member 30. In this quartz crystal unit 100, the quartz crystal vibrating plate 10 is bonded to the first sealing member 20, and the quartz crystal vibrating plate 10 is bonded to the second sealing member 30, thereby forming a package with a substantially rectangular parallelepiped sandwich structure. That is, in the quartz crystal unit 100, the first sealing member 20 and the second sealing member 30 are bonded to both main surfaces of the quartz crystal vibrating plate 10, respectively, to form an internal space (cavity) of the package, and the vibrating unit 11 (see Figs. 4 and 5) is hermetically sealed in this internal space.

[0016] The crystal unit 100 according to this embodiment has a package size of, for example, 1.0 × 0.8 mm, and is designed to be compact and low-profile. To accommodate this compact design, the package does not have castellations, but rather uses through-holes (described below) to ensure electrical continuity between electrodes. The crystal unit 100 is also designed to be electrically connected to an external circuit board (not shown) via solder.

[0017] Next, the quartz crystal plate 10, the first sealing member 20, and the second sealing member 30 of the quartz crystal unit 100 will be described with reference to Figures 1 to 7. Note that the description here focuses on the individual components that are not bonded together and are configured as individual components. Figures 2 to 7 merely show one example of the configuration of the quartz crystal plate 10, the first sealing member 20, and the second sealing member 30, and are not intended to limit the scope of the present invention.

[0018] As shown in FIGS. 4 and 5, the quartz crystal vibrating plate 10 according to this embodiment is a piezoelectric substrate made of quartz crystal, and both of its main surfaces (first main surface 101 and second main surface 102) are polished (mirror-finished) to form flat, smooth surfaces. In this embodiment, an AT-cut quartz crystal plate that vibrates in thickness-shear mode is used as the quartz crystal vibrating plate 10. In the quartz crystal vibrating plate 10 shown in FIGS. 4 and 5, both main surfaces 101 and 102 of the quartz crystal vibrating plate 10 are in the XZ' plane. In this XZ' plane, the direction parallel to the short side (short side) of the quartz crystal vibrating plate 10 is the X-axis direction, and the direction parallel to the long side (long side) of the quartz crystal vibrating plate 10 is the Z'-axis direction. Note that AT-cut is a processing technique in which artificial quartz crystal is cut at an angle of 35°15' around the X-axis with respect to the Z-axis, one of the three crystal axes of the artificial quartz crystal: the electrical axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). In an AT-cut quartz plate, the X-axis coincides with the crystal axis of the quartz. The Y'-axis and Z'-axis coincide with axes tilted approximately 35°15' from the Y-axis and Z-axis of the quartz crystal (this cutting angle can be changed slightly to adjust the frequency-temperature characteristics of the AT-cut quartz plate). The Y'-axis and Z'-axis directions correspond to the cutting direction when the AT-cut quartz plate is cut.

[0019] A pair of excitation electrodes (first excitation electrode 111 and second excitation electrode 112) are formed on both main surfaces 101, 102 of the quartz crystal vibration plate 10. The quartz crystal vibration plate 10 has a substantially rectangular vibrating portion 11, an outer frame portion 12 that surrounds the outer periphery of the vibrating portion 11, and a holding portion (connecting portion) 13 that holds the vibrating portion 11 by connecting the vibrating portion 11 and the outer frame portion 12. In other words, the quartz crystal vibration plate 10 is configured such that the vibrating portion 11, the outer frame portion 12, and the holding portion 13 are integrally formed. The holding portion 13 extends (protrudes) in the -Z' direction from only one corner of the vibrating portion 11 located in the +X direction and the -Z' direction to the outer frame portion 12. A through portion (slit) 10a that penetrates the thickness of the quartz crystal vibration plate 10 is provided between the vibrating portion 11 and the outer frame portion 12. In this embodiment, the quartz crystal vibration plate 10 is provided with only one holding portion 13 that connects the vibration portion 11 and the outer frame portion 12, and the through portion 10a is formed continuously so as to surround the outer periphery of the vibration portion 11.

[0020] The first excitation electrode 111 is provided on the first main surface 101 side of the vibrating section 11, and the second excitation electrode 112 is provided on the second main surface 102 side of the vibrating section 11. Input / output lead-out wiring (first lead-out wiring 113, second lead-out wiring 114) is connected to the first excitation electrode 111 and the second excitation electrode 112 to connect these excitation electrodes to external electrode terminals. The first lead-out wiring 113 on the input side is led out from the first excitation electrode 111 and connected to a connection bonding pattern 14 formed on the outer frame section 12 via a holding section 13. The second lead-out wiring 114 on the output side is led out from the second excitation electrode 112 and connected to a connection bonding pattern 15 formed on the outer frame section 12 via a holding section 13.

[0021] Both main surfaces (first main surface 101, second main surface 102) of the quartz crystal vibrating plate 10 are provided with diaphragm-side sealing portions for bonding the quartz crystal vibrating plate 10 to the first sealing member 20 and the second sealing member 30. A diaphragm-side first bonding pattern 121 is formed as the diaphragm-side sealing portion on the first main surface 101, and a diaphragm-side second bonding pattern 122 is formed as the diaphragm-side sealing portion on the second main surface 102. The diaphragm-side first bonding pattern 121 and the diaphragm-side second bonding pattern 122 are provided on the outer frame portion 12 and are formed in an annular shape in a plan view.

[0022] As shown in FIGS. 4 and 5, five through holes are formed in the quartz-crystal vibrating plate 10, penetrating between the first main surface 101 and the second main surface 102. Specifically, the four first through holes 161 are provided in the four corner regions of the outer frame portion 12. The second through hole 162 is provided in the outer frame portion 12 on one side of the vibrating portion 11 in the Z′-axis direction (the −Z′ direction side in FIGS. 4 and 5). A connection bonding pattern 123 is formed around each of the first through holes 161. A connection bonding pattern 124 is formed on the first main surface 101 side of the second through hole 162, and a connection bonding pattern 15 is formed on the second main surface 102 side of the second through hole 162.

[0023] The first through-holes 161 and the second through-holes 162 have through-hole electrodes formed along their inner walls to connect the electrodes formed on the first main surface 101 and the second main surface 102. The central portions of the first through-holes 161 and the second through-holes 162 form hollow through-holes that penetrate between the first main surface 101 and the second main surface 102. The outer peripheral edge of the diaphragm-side first bonding pattern 121 is located close to the outer peripheral edge of the first main surface 101 of the quartz-crystal vibrating plate 10 (outer frame 12). The outer peripheral edge of the diaphragm-side second bonding pattern 122 is located close to the outer peripheral edge of the second main surface 102 of the quartz-crystal vibrating plate 10 (outer frame 12). In this embodiment, an example has been given in which five through holes are formed between the first main surface 101 and the second main surface 102, but instead of forming through holes, it is also possible to cut out a portion of the side surface of the first sealing member 20 and form a castellation with an electrode coated on the inner wall surface of the cut-out area (the same applies to the second sealing member 30).

[0024] 2 and 3, the first sealing member 20 is a rectangular parallelepiped substrate formed from a single AT-cut quartz crystal plate, which is a translucent material. The second main surface 202 of this first sealing member 20 (the surface that bonds to the quartz crystal vibrating plate 10) is polished (mirror-finished) to a flat, smooth surface. Although the first sealing member 20 does not have a vibrating part, by using an AT-cut quartz crystal plate like the quartz crystal vibrating plate 10, the thermal expansion coefficients of the quartz crystal vibrating plate 10 and the first sealing member 20 can be made the same, thereby suppressing thermal deformation of the quartz crystal unit 100. The X-, Y-, and Z'-axes of the first sealing member 20 are also oriented in the same directions as those of the quartz crystal vibrating plate 10.

[0025] As shown in FIG. 2, first and second wiring terminals 22 and 23 and a metal film 28 for shielding (ground connection) are formed on the first main surface 201 of the first sealing member 20 (the outer main surface not facing the quartz-crystal vibrating plate 10). The first and second wiring terminals 22 and 23 are provided as wiring for electrically connecting the first and second excitation electrodes 111 and 112 of the quartz-crystal vibrating plate 10 to the external electrode terminal 32 of the second sealing member 30. The first and second terminals 22 and 23 are provided at both ends in the Z′-axis direction, with the first terminal 22 on the +Z′-direction side and the second terminal 23 on the −Z′-direction side. The first and second terminals 22 and 23 are formed to extend in the X-axis direction. The first terminal 22 and the second terminal 23 are formed in a substantially rectangular shape.

[0026] The metal film 28 is provided between the first and second terminals 22, 23 and is arranged at a predetermined distance from the first and second terminals 22, 23. The metal film 28 is provided in almost all of the regions of the first main surface 201 of the first sealing member 20 where the first and second terminals 22, 23 are not formed. The metal film 28 is provided from the end of the first main surface 201 of the first sealing member 20 in the +X direction to the end in the −X direction.

[0027] 2 and 3, six through holes are formed in the first sealing member 20, penetrating between the first main surface 201 and the second main surface 202. Specifically, four third through holes 211 are provided in the four corner (corner) regions of the first sealing member 20. Fourth and fifth through holes 212, 213 are provided in the +Z' direction and -Z' direction in FIGS. 2 and 3, respectively.

[0028] In the third through hole 211 and the fourth and fifth through holes 212, 213, through electrodes for establishing electrical continuity between the electrodes formed on the first main surface 201 and the second main surface 202 are formed along the inner wall surfaces of the respective through holes. The central portions of the third through hole 211 and the fourth and fifth through holes 212, 213 form hollow through portions that penetrate between the first main surface 201 and the second main surface 202. The through electrodes of two third through holes 211, 211 located diagonally on the first main surface 201 of the first sealing member 20 (the third through hole 211 located at the corner in the +X direction and the +Z′ direction in FIGS. 2 and 3 , and the third through hole 211 located at the corner in the −X direction and the −Z′ direction) are electrically connected to each other by the metal film 28. Furthermore, the through electrode of the third through hole 211 located at the corner in the −X direction and the +Z′ direction and the through electrode of the fourth through hole 212 are electrically connected by the first terminal 22. The through electrode of the third through hole 211 located at the corner in the +X direction and the −Z′ direction and the through electrode of the fifth through hole 213 are electrically connected by the second terminal 23.

[0029] A sealing member-side first bonding pattern 24 is formed on the second main surface 202 of the first sealing member 20 as a sealing member-side first sealing portion for bonding to the quartz-crystal vibrating plate 10. The sealing member-side first bonding pattern 24 is formed in an annular shape in a plan view. Furthermore, on the second main surface 202 of the first sealing member 20, connection bonding patterns 25 are formed around the third through holes 211. A connection bonding pattern 261 is formed around the fourth through hole 212, and a connection bonding pattern 262 is formed around the fifth through hole 213. Furthermore, a connection bonding pattern 263 is formed on the opposite side of the connection bonding pattern 261 in the longitudinal direction of the first sealing member 20 (the -Z' direction side), and the connection bonding pattern 261 and the connection bonding pattern 263 are connected by a wiring pattern 27. The outer periphery of the sealing member-side first bonding pattern 24 is provided close to the outer periphery of the second main surface 202 of the first sealing member 20.

[0030] 6 and 7, the second sealing member 30 is a rectangular parallelepiped substrate formed from a single AT-cut quartz crystal plate, which is a light-transmitting material, and the first main surface 301 (the surface that bonds to the quartz crystal plate 10) and the second main surface 302 (the outer main surface that does not face the quartz crystal plate 10) of this second sealing member 30 are polished to a flat, smooth surface. Note that the second sealing member 30 also uses an AT-cut quartz crystal plate like the quartz crystal plate 10, and it is desirable that the orientations of the X-axis, Y-axis, and Z'-axis are the same as those of the quartz crystal plate 10.

[0031] A sealing member-side second bonding pattern 31 is formed on the first main surface 301 of the second sealing member 30 as a sealing member-side second sealing portion for bonding to the quartz-crystal vibrating plate 10. The sealing member-side second bonding pattern 31 is formed in an annular shape in a plan view. The outer periphery of the sealing member-side second bonding pattern 31 is provided close to the outer periphery of the first main surface 301 of the second sealing member 30.

[0032] Furthermore, a frequency-adjusting metal film 36 used to adjust the frequency of the quartz crystal resonator 100 is formed on the first main surface 301 of the second sealing member 30. The frequency-adjusting metal film 36 has a two-layer structure made of two types of metal with different melting temperatures (melting points). As shown in FIG. 8 , the frequency-adjusting metal film 36 includes a base metal layer 36a and a metal layer 36b laminated on the base metal layer 36a. The base metal layer 36a is preferably 50 nm thick, and the metal layer 36b is preferably 100 nm thick. The base metal layer 36a is preferably 50 to 500 nm thick, and the metal layer 36b is preferably 100 to 500 nm thick. A thickness of less than 50 nm for the base metal layer 36a is not preferable because it cannot withstand laser irradiation. A thickness of more than 500 nm for the base metal layer 36a is not preferable because it causes wafer warping and reduces production efficiency due to the thick film. Furthermore, if the thickness of the metal layer 36b is less than 100 nm, it is not preferable because it cannot withstand laser irradiation, and if the thickness of the metal layer 36b is more than 500 nm, it is not preferable because the wafer warps and the thick film reduces production efficiency.

[0033] In the frequency-adjusting metal film 36, the melting temperature of the base metal layer 36a is set higher than the melting temperature of the metal layer 36b, and the difference in melting temperature between the base metal layer 36a and the metal layer 36b is preferably 1500° C. or more. Furthermore, the metal layer 36b is made of the same material (e.g., Au) as the second excitation electrode 112. In this case, since the melting temperature of Au is 1064° C., the base metal layer 36a can be made of, for example, any of W (tungsten: melting temperature 3387° C.), Mo (molybdenum: melting temperature 2623° C.), Ta (tantalum: melting temperature 3020° C.), and Re (rhenium: melting temperature 3186° C.).

[0034] The frequency adjustment metal film 36 is provided at a position facing the second excitation electrode 112 at a predetermined interval. The distance L1 in the vertical direction (Y-axis direction) between the second excitation electrode 112 and the frequency adjustment metal film 36 is 2 to 200 μm.

[0035] The first and second main surfaces 301, 302 of the second sealing member 30 are polished to form smooth surfaces, and the arithmetic mean roughness Ra of the first and second main surfaces 301, 302 is 1 nm or less. In addition, the arithmetic mean roughness Ra of the surface of the metal layer 36b of the frequency-adjusting metal film 36 is 3 nm or less.

[0036] Four external electrode terminals 32 are provided on the second main surface 302 of the second sealing member 30. The external electrode terminals 32 are electrically connected to an external circuit board provided outside the quartz crystal unit 100. The external electrode terminals 32 are located at the four corners (corner portions) of the second main surface 302 of the second sealing member 30.

[0037] As shown in FIGS. 6 and 7 , the second sealing member 30 has four through holes formed therein that penetrate between the first main surface 301 and the second main surface 302. Specifically, the four sixth through holes 33 are provided in the four corner regions (corner portions) of the second sealing member 30. In the sixth through holes 33, through electrodes are formed along the inner wall surfaces of the sixth through holes 33 to ensure electrical continuity between the electrodes formed on the first main surface 301 and the second main surface 302. The through electrodes formed on the inner wall surfaces of the sixth through holes 33 in this manner provide electrical continuity between the electrodes formed on the first main surface 301 and the external electrode terminals 32 formed on the second main surface 302. The central portions of the sixth through holes 33 form hollow through portions that penetrate between the first main surface 301 and the second main surface 302. Furthermore, on the first main surface 301 of the second sealing member 30, connection bonding patterns 34 are formed around the sixth through holes 33, respectively.

[0038] In the quartz crystal unit 100 including the quartz crystal vibrating plate 10, first sealing member 20, and second sealing member 30 configured as described above, the quartz crystal vibrating plate 10 and the first sealing member 20 are diffusion bonded together with the first vibration plate bonding pattern 121 and the first sealing member bonding pattern 24 overlapping each other, and the quartz crystal vibrating plate 10 and the second sealing member 30 are diffusion bonded together with the second vibration plate bonding pattern 122 and the second sealing member bonding pattern 31 overlapping each other, thereby producing a sandwich-structured package as shown in Fig. 1. This hermetically seals the internal space of the package, i.e., the space housing the vibrating unit 11.

[0039] At this time, the connection bonding patterns are also diffusion bonded while overlapping each other. By bonding the connection bonding patterns together, electrical continuity is achieved among the first excitation electrode 111, the second excitation electrode 112, and the external electrode terminal 32 in the quartz crystal unit 100. Specifically, the first excitation electrode 111 is connected to the external electrode terminal 32 via the first extension wiring 113, the wiring pattern 27, the fourth through-hole 212, the first terminal 22, the third through-hole 211, the first through-hole 161, and the sixth through-hole 33, in that order. The second excitation electrode 112 is connected to the external electrode terminal 32 via the second extension wiring 114, the second through-hole 162, the fifth through-hole 213, the second terminal 23, the third through-hole 211, the first through-hole 161, and the sixth through-hole 33, in that order. Furthermore, the metal film 28 is connected to earth (ground connection, using part of the external electrode terminal 32) via the third through-hole 211, the first through-hole 161, and the sixth through-hole 33 in this order.

[0040] In the quartz crystal unit 100, the various bonding patterns are preferably formed by stacking multiple layers on the quartz crystal plate, with a Ti (titanium) layer and an Au (gold) layer formed from the bottom layer onwards by vapor deposition or sputtering. Furthermore, if the other wiring and electrodes formed on the quartz crystal unit 100 have the same configuration as the bonding patterns, the bonding patterns, wiring and electrodes can be patterned simultaneously, which is also preferable.

[0041] In the quartz crystal resonator 100 configured as described above, the sealing portions (seal paths) 115, 116 that hermetically seal the vibrating portion 11 of the quartz crystal vibrating plate 10 are formed in an annular shape in a plan view. The seal path 115 is formed by diffusion bonding (Au-Au bonding) the above-mentioned diaphragm-side first bonding pattern 121 and the sealing member-side first bonding pattern 24, and the outer and inner edge shapes of the seal path 115 are formed in a substantially octagonal shape. Similarly, the seal path 116 is formed by diffusion bonding (Au-Au bonding) the above-mentioned diaphragm-side second bonding pattern 122 and the sealing member-side second bonding pattern 31, and the outer and inner edge shapes of the seal path 116 are formed in a substantially octagonal shape.

[0042] Next, a frequency adjustment method for the quartz crystal resonator 100 according to this embodiment will be described with reference to Fig. 8. The frequency adjustment in this embodiment is a process of adjusting the mass of the second excitation electrode 112 of the vibration portion 11 of the quartz crystal vibrating plate 10 to adjust the oscillation frequency to a desired value. The frequency adjustment is performed on each of the quartz crystal resonators 100 in a wafer state during the manufacturing process of the quartz crystal resonators 100, but it may also be performed on each of the quartz crystal resonators 100 that have been singulated from the wafer state.

[0043] 8, the frequency is adjusted by irradiating the frequency-adjusting metal film 36 with a laser from outside the second sealing member 30, transmitting the laser through the inside of the second sealing member 30 to heat the base metal layer 36a, thereby melting and evaporating (vaporizing) at least a part of the metal layer 36b, and attaching the evaporated metal to the second excitation electrode 112. In other words, the laser melts and evaporates the metal layer 36b above the base metal layer 36a, and the evaporated metal attaches to the second excitation electrode 112, thereby increasing the mass of the second excitation electrode 112 and shifting the frequency to a lower side.

[0044] The laser is irradiated perpendicularly onto the second sealing member 30. A visible light laser capable of transmitting through the second sealing member 30 made of quartz crystal is used as the laser. Specifically, a green laser with a wavelength of approximately 532 nm can be used. The laser output is adjusted to a value that does not penetrate the base metal layer 36a of the frequency adjustment metal film 36. The laser heats the base metal layer 36a, which in turn heats the metal layer 36b above the base metal layer 36a. As described above, the melting temperature of the base metal layer 36a is higher than the melting temperature of the metal layer 36b. Therefore, when the base metal layer 36a is heated to a temperature higher than the melting temperature of the metal layer 36b, the metal layer 36b melts, and a portion of the melted metal layer 36b evaporates. Since the inside of the quartz crystal unit 100 is a vacuum, the evaporated metal moves upward in a substantially straight line, and when it reaches the surface 112a of the second excitation electrode 112, it is cooled and solidified on the surface 112a of the second excitation electrode 112. As a result, the metal evaporated from the frequency-adjusting metal film 36 adheres to the surface 112a of the second excitation electrode 112.

[0045] The metal layer 36b may have a multilayer structure made up of a plurality of metal layers. In this case, Ag (silver: melting temperature 962°C) or Al (aluminum: melting temperature 660°C) can be used for the metal layer 36b in addition to Au. When the metal layer 36b has a multilayer structure, the uppermost metal layer only needs to be made of the same material (e.g., Au) as the second excitation electrode 112. The base metal layer 36a may also have a multilayer structure made up of a plurality of metal layers. In this case, it is preferable that a metal layer with a higher melting temperature (e.g., a W layer) be arranged in a lower layer (closer to the second sealing member 30) and a metal layer with a lower melting temperature (e.g., a Mo layer) be arranged in an upper layer (closer to the metal layer 36b).

[0046] An auxiliary metal layer 36d (see FIG. 9) may be formed between the base metal layer 36a and the second sealing member 30. By using a metal with high adhesion to quartz crystal, such as Ti (titanium), Cr (chromium), or Ni (nickel), for the auxiliary metal layer 36d, the adhesion between the frequency-adjusting metal film 36 and the second sealing member 30 can be improved. The auxiliary metal layer 36d is required to have a melting temperature that is sufficiently higher than that of the metal layer 36b. However, unlike the base metal layer 36a, the auxiliary metal layer 36d is not required to have a melting temperature difference of 1500°C or more with the metal layer 36b. For example, if the auxiliary metal layer 36d is made of Ti and the metal layer 36b is made of Au, the melting temperature of Ti is 1672°C, and the difference in melting temperature with Au is approximately 600°C. Even if the auxiliary metal layer 36d is slightly melted by the laser irradiation during frequency adjustment, the presence of the base metal layer 36a on the auxiliary metal layer 36d prevents the molten auxiliary metal layer 36d from scattering onto the second excitation electrode 112.

[0047] Furthermore, there is a risk that the auxiliary metal layer 36d melted by the heat of laser irradiation will diffuse into the upper underlying metal layer 36a, lowering the melting temperature of the underlying metal layer 36a. However, by making the film thickness of the auxiliary metal layer 36d thinner than that of the underlying metal layer 36a, it is possible to irradiate the laser without melting the underlying metal layer 36a (only the metal layer 36b can be evaporated).

[0048] By controlling the number of laser pulses irradiated onto the metal base layer 36a, the sweep distance, the number of sweeps, etc., it is possible to control the mass of metal adhering to the second excitation electrode 112, and therefore the amount of frequency adjustment. For example, by continuously irradiating the laser with a low laser output and a narrow pulse interval, it is possible to efficiently heat the metal base layer 36a and evaporate only the metal layer 36b. In this case, it is possible to obtain the amount of frequency adjustment according to the laser sweep distance, enabling highly accurate frequency adjustment.

[0049] The frequency-adjusting metal film 36 is irradiated with a laser beam by irradiating it linearly while sweeping the laser spot SP. As shown in FIG. 10, the irradiation lines LN formed by the sweep of the laser spot SP are arranged in parallel, allowing the laser to irradiate a desired region of the frequency-adjusting metal film 36. The sweep direction (direction of arrow A) of the laser spot SP is the same for all irradiation lines LN. The laser spot SP is repeatedly swept multiple times for each irradiation line LN, and after multiple laser sweeps are performed for one irradiation line LN, laser sweeps are performed for the adjacent irradiation line LN. The pitch P1 of the laser sweep (the interval in the direction perpendicular to the sweep direction) is set to be larger than the diameter D1 (irradiation diameter) of the laser spot SP (P1>D1), so that adjacent irradiation lines LN in the direction perpendicular to the sweep direction do not interfere with (overlap with) each other in a plan view.

[0050] By irradiating the frequency-adjusting metal film 36 with a laser beam, the underlying metal layer 36a is heated, and the metal layer 36b above the underlying metal layer 36a is melted and evaporated. The underlying metal layer 36a is exposed in the region where the metal layer 36b has evaporated. After the frequency adjustment, as shown in FIG. 11 , exposed portions 361 are formed in the frequency-adjusting metal film 36, where parts of the underlying metal layer 36a are exposed and not covered by the metal layer 36b. The exposed portions 361 are formed linearly at multiple locations spaced apart at predetermined intervals. The exposed portions 361 are formed at positions corresponding to the irradiation lines LN shown in FIG. 10 , and the metal layer 36b and the exposed portions 361 are alternately formed in stripes on the surface of the frequency-adjusting metal film 36.

[0051] Here, when laser irradiation is performed on the frequency adjustment metal film 36 such that adjacent irradiation lines LN overlap each other (in Fig. 10, when P1 < D1), almost all of the metal films 36b may melt. In this case, a part of the melted metal layer 36b may solidify into a ball-shaped mass (Au ball) and remain as foreign matter on the base metal layer 36a. Then, after frequency adjustment, the metal layer 36b that has become a ball-shaped mass may peel off from the base metal layer 36a and adhere to the second excitation electrode 112.

[0052] On the other hand, according to the present embodiment, laser irradiation is performed on the frequency adjustment metal film 36 so that adjacent irradiation lines LN do not overlap, and on the surface of the frequency adjustment metal film 36, the metal layer 36b and the exposed portion 361 are alternately formed in a stripe pattern (see Fig. 11). For this reason, since the metal layer 36b that has remained without melting is located in the vicinity of the metal layer 36b that has melted but not evaporated, the metal layer 36b that has melted but not evaporated is attracted toward the remaining metal layer 36b side and adheres to the remaining metal layer 36b and solidifies. As a result, it is possible to suppress the solidification of the metal layer 36b that has melted but not evaporated into a ball-shaped mass (Au ball) and remaining on the base metal layer 36a. As a result, it is possible to suppress the peeling of the metal layer 36b that has become a ball-shaped mass from the base metal layer 36a and its adhesion to the second excitation electrode 112.

[0053] The width of the exposed portion 361 (the distance between adjacent metal layers 36b) corresponds to the diameter (irradiation diameter) D1 of the laser spot SP. In this embodiment, the width of the exposed portion 361 is slightly smaller than the diameter (irradiation diameter) D1 of the laser spot SP. The smaller the width of the exposed portion 361, the more stringent the laser irradiation conditions. Therefore, considering the minimum irradiation dose required to melt the metal layer 36b and the maximum irradiation dose required to prevent the laser from penetrating the base metal layer 36a, the width of the exposed portion 361 is preferably 30 to 55 μm, and more preferably 45 to 55 μm. If the width of the exposed portion 361 is 30 μm or less, the laser irradiation conditions become more stringent, making stable frequency adjustment difficult. On the other hand, if the width of the exposed portion 361 is 55 μm or more, the distance from the center of the laser spot SP to the remaining metal layer 36b increases. As a result, a part of the molten metal layer 36b no longer satisfies the conditions for being attracted to the remaining metal layer 36b, and a solidified ball-shaped mass is generated.

[0054] Furthermore, it is preferable to form the metal layer 36b (the metal layer where the exposed portion 361 is formed) in a portion corresponding to the irradiation line LN (see FIG. 10) formed by the sweep of the laser spot SP thinner than the other portions of the metal layer 36b. By providing such thin and thick portions in the metal layer 36b, the thick portions of the metal layer 36b have a relatively larger heat capacity than the thin portions. This makes the thick portions of the metal layer 36b less likely to heat up than the thin portions, so the molten metal layer 36b tends to remain in the thick portions of the metal layer 36b, which have a relatively lower temperature. As a result, the molten metal layer 36b can be prevented from spreading laterally (in a direction perpendicular to the sweep direction).

[0055] According to the frequency adjustment method for the quartz crystal unit 100 of this embodiment, the metal layer 36b above the base metal layer 36a is melted and evaporated, and the evaporated metal adheres to the second excitation electrode 112, thereby increasing the mass of the second excitation electrode 112 and shifting the frequency to a lower value. In this case, the desired frequency adjustment amount can be obtained by controlling the number of laser pulses, sweep distance, etc. Furthermore, by preventing the laser from penetrating the frequency adjustment metal film 36, damage to the second excitation electrode 112 can be suppressed. As a result, frequency adjustment can be performed without significantly degrading the characteristics of the quartz crystal unit 100, even after the vibration portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30.

[0056] In this embodiment, the laser is irradiated so as not to penetrate the base metal layer 36a, and the laser does not penetrate the frequency adjustment metal film 36, which more reliably avoids damaging the second excitation electrode 112. This makes it possible to easily adjust the frequency without degrading the characteristics of the quartz crystal unit 100, even after the vibrating portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30.

[0057] In this embodiment, the difference between the melting temperature of the metal base layer 36a and the melting temperature of the metal layer 36b is 1500°C or more. By irradiating the metal base layer 36a with a laser to a temperature equal to or higher than the melting temperature of the metal layer 36b but lower than the melting temperature of the metal base layer 36a, the metal base layer 36a does not melt, but only the metal layer 36b melts, and some of the molten metal can be evaporated. The evaporated metal adheres to the second excitation electrode 112, increasing the mass of the second excitation electrode 112 and shifting the frequency to a lower side. This allows for easy frequency adjustment without degrading the characteristics of the crystal unit 100, even after the vibration portion 11 of the crystal vibration plate 10 is sealed with the first and second sealing members 20 and 30. Even if the melting temperature of the underlying metal layer 36a is higher than that of the metal layer 36b, if the difference in melting temperatures is small, it is difficult to melt only the metal layer 36b, and the underlying metal layer 36a may melt at the same time.

[0058] In this embodiment, the first main surface 301 of the second sealing member 30 and the second main surface 302 opposite to the first main surface 301 are smooth surfaces, which can suppress reflection and refraction of the laser when the laser is incident on the second main surface 302 of the second sealing member 30 and when the laser is emitted from the first main surface 301 of the second sealing member 30, thereby reducing laser energy loss. As a result, even after the vibrating portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30, high-precision frequency adjustment can be performed according to the number of laser pulses, sweep distance, number of sweeps, etc.

[0059] Furthermore, the metal layer 36b is formed from the same Au (gold) as the second excitation electrode 112, and since the metal layer 36b is made of the same material as the second excitation electrode 112, the characteristics do not change before and after frequency adjustment, and therefore fluctuations in the characteristics of the quartz crystal resonator 100 after sealing can be suppressed.

[0060] Furthermore, the base metal layer 36a is formed of W (tungsten) or the like, and the base metal layer 36a exposed to the internal space of the quartz crystal unit 100 functions as a getter material, thereby enabling the base metal layer 36a to capture gas generated in the internal space of the quartz crystal unit 100. Alternatively, a metal layer (e.g., a W layer) 37 (see FIG. 12) identical to the base metal layer 36a may be formed as a separate layer in a region separate from the base metal layer 36a, and this metal layer 37 may function as a getter material. In this case, the metal layer 37 is preferably formed in a region not facing the second excitation electrode 112.

[0061] Furthermore, by using a visible light laser that has low absorption and high transmittance for the second sealing member 30 made of, for example, quartz or glass, as the laser, it is possible to reduce power loss and damage to the second sealing member 30, making it suitable for frequency adjustment.

[0062] Furthermore, the space sealing the vibration part 11 of the quartz crystal vibration plate 10 is a vacuum, allowing the evaporated metal to move in a substantially linear manner, thereby preventing it from scattering to the surroundings. Furthermore, the evaporated metal can be attached to the second excitation electrode 112 without lowering its temperature.

[0063] In this embodiment, the vertical distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36 is 2 to 200 μm. By minimizing the distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36, the metal evaporated from the frequency adjustment metal film 36 moves in a substantially linear manner, preventing it from scattering to the surroundings. This ensures that the evaporated metal adheres to the second excitation electrode 112, and makes it easy to perform high-precision frequency adjustment even after the vibration portion 11 of the quartz crystal vibration plate 10 is sealed with the first and second sealing members 20 and 30.

[0064] Furthermore, since the outer peripheral edge of the frequency-adjusting metal film 36 is located inside the outer peripheral edge of the second excitation electrode 112 in plan view, even if an exposed portion of the base metal layer 36a of the frequency-adjusting metal film 36 comes into contact with the second excitation electrode 112 when the vibrating portion 11 is bent due to an external impact, adhesion between the base metal layer 36a and the second excitation electrode 112 can be prevented. Furthermore, metal evaporated from the frequency-adjusting metal film 36 can be prevented from scattering outside the second excitation electrode 112, and the evaporated metal can be reliably adhered to the second excitation electrode 112. This makes it easy to perform high-precision frequency adjustment even after the vibrating portion 11 of the quartz crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30.

[0065] In this embodiment, the quartz crystal unit 100 includes a first sealing member 20 that covers the first main surface of the vibrating portion 11 of the quartz crystal vibrating plate 10, and a second sealing member 30 that covers the second main surface of the vibrating portion 11 of the quartz crystal vibrating plate 10. The first sealing member 20 and the quartz crystal vibrating plate 10 are bonded together, and the second sealing member 30 is bonded together, thereby hermetically sealing the vibrating portion 11 of the quartz crystal vibrating plate 10. The first sealing member 20 and the second sealing member 30 are made of quartz crystal. Using a three-layer structure like this makes it possible to reduce the size and thickness of the quartz crystal unit 100. Even after sealing the vibrating portion 11 of the quartz crystal vibrating plate 10 with the first and second sealing members 20 and 30, the size and thickness of the reduced-size and reduced-thickness quartz crystal unit 100 can be adjusted with high precision.

[0066] Furthermore, in the quartz crystal resonator 100 of the present embodiment described above, the frequency-adjusting metal film 36 is formed on the first main surface 301 facing the second excitation electrode 112 of the second sealing member 30. The frequency-adjusting metal film 36 has exposed portions 361, which are portions of the base metal layer 36a that are not covered with the metal layer 36b and are exposed, and the exposed portions 361 are formed in multiple locations at predetermined intervals. In this way, the metal layer 36b and the exposed portions 361 are alternately formed in stripes on the surface of the frequency-adjusting metal film 36 (see FIG. 11 ). According to this, during frequency adjustment, when the frequency-adjusting metal film 36 is irradiated with a laser, the remaining metal layer 36b that has not melted is located near the metal layer 36b that has melted but not evaporated. Therefore, the remaining metal layer 36b that has melted but not evaporated is attracted toward the remaining metal layer 36b and adheres to the remaining metal layer 36b to solidify. This prevents the metal layer 36b that has melted but not evaporated from solidifying into ball-shaped lumps (Au balls) and remaining on the underlying metal layer 36a. As a result, after the frequency adjustment, the metal layer 36b that has become ball-shaped lumps can be prevented from peeling off from the underlying metal layer 36a and adhering to the second excitation electrode 112.

[0067] In addition, by making the underlying metal layer 36a exposed by the exposed portion 361 of the frequency-adjusting metal film 36 function as a getter material, gas generated in the internal space of the quartz crystal unit 100 can be captured by the underlying metal layer 36a. Materials such as W (tungsten) and Ti (titanium) are preferred for the underlying metal layer 36a. This makes it possible to suppress changes in the frequency of the quartz crystal unit 100 over time that are caused by gas generation.

[0068] Furthermore, since the quartz crystal vibration plate 10 is configured to include a vibration portion 11 and an outer frame portion 12 that surrounds the vibration portion 11, the distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36 can be made very small compared to a configuration in which a sealing member is bonded to a base using adhesive, and as described above, high-precision frequency adjustment can be performed.

[0069] The embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present invention should not be interpreted solely by the above-described embodiments, but should be defined by the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included.

[0070] In the above embodiment, the frequency adjustment metal film 36 is provided on the first main surface 301 of the second sealing member 30 facing the second excitation electrode 112. However, the second sealing member 30 may not be provided with a frequency adjustment metal film, and the frequency adjustment metal film may be provided on the second main surface 202 of the first sealing member 20 facing the first excitation electrode 111. Alternatively, as shown in FIG. 13 , the frequency adjustment metal film 26 may be provided on the second main surface 202 of the first sealing member 20, and the frequency adjustment metal film 36 may be provided on the first main surface 301 of the second sealing member 30. The frequency adjustment metal film 26 of the first sealing member 20 has a configuration similar to that of the frequency adjustment metal film 36 of the second sealing member 30 in the above embodiment. The frequency adjustment metal film 26 has a laminated configuration in which a base metal layer 26a made of, for example, W (tungsten) and a metal layer 26b made of the same material as the first excitation electrode 111 (for example, Au) are laminated.

[0071] 13, frequency adjustment can be performed using both the frequency-adjusting metal films 26, 36. By irradiating the frequency-adjusting metal film 26 on the first sealing member 20 side of the quartz crystal resonator 100 with a laser, frequency adjustment can be performed at two locations, on the first sealing member 20 side and the second sealing member 30 side. In this case, frequency adjustment can be performed simultaneously at two locations, on the first sealing member 20 side and the second sealing member 30 side, or can be performed at each location in turn.

[0072] In the above embodiment, the frequency adjustment is performed using a visible light laser, but the frequency adjustment may also be performed using a beam such as an electron beam, etc. In this case, the desired frequency adjustment amount can be obtained by controlling the beam output, irradiation time, etc.

[0073] In the above embodiment, the internal space of the quartz crystal unit 100 is evacuated, but the internal space of the quartz crystal unit 100 may be filled with low-pressure nitrogen, argon, or the like.

[0074] In the above embodiment, the quartz crystal vibrating plate 10 is an AT-cut quartz crystal plate, but other materials may be used. Also, while the vibrating portion 11 of the quartz crystal vibrating plate 10 is rectangular, the vibrating portion may be shaped like a tuning fork.

[0075] In the above embodiment, the first sealing member 20 and the second sealing member 30 are formed from quartz plates, but the first sealing member 20 and the second sealing member 30 may be formed from, for example, glass. In this case, an infrared laser that can transmit through the first sealing member 20 and the second sealing member 30 may be used. As the infrared laser, for example, a YAG laser with a wavelength of approximately 1064 nm may be used. Note that only a portion of the first sealing member 20 and the second sealing member 30 may be formed from a light-transmitting material such as quartz or glass.

[0076] In the above embodiment, the quartz crystal vibration plate 10 is provided with only one holding portion 13 connecting the vibrating portion 11 and the outer frame portion 12, but two or more holding portions 13 may be provided. Also, a through portion 10a that penetrates the quartz crystal vibration plate 10 in the thickness direction is provided between the vibrating portion 11 and the outer frame portion 12, but a quartz crystal vibration plate configured without a through portion may also be used. Also, in the above embodiment, a framed quartz crystal vibration plate 10 is used that includes the vibrating portion 11 and the outer frame portion 12 that surrounds the vibrating portion 11, but a quartz crystal vibration plate configured without an outer frame portion may also be used.

[0077] Second Embodiment In the first embodiment, a three-layer structure crystal unit 100 was used in which the crystal vibration plate 10 was sandwiched between the first sealing member 20 and the second sealing member 30, but crystal units with other structures may also be used. For example, a crystal unit may be used in which the crystal vibration plate is housed inside a base with a recess made of an insulating material such as ceramic, glass, or crystal, and a lid is bonded to the base.

[0078] 14 is a schematic diagram illustrating the components of a quartz crystal resonator (piezoelectric resonator device) 400 according to the second embodiment. As shown in FIG. 14, the quartz crystal resonator 400 has a structure in which a quartz crystal vibrating plate (vibration portion) 60 is housed inside a base 40 having a recess 401, and a lid 50 is bonded to the base 40. A first excitation electrode 601 and a second excitation electrode 602 are formed on each of the two main surfaces of the quartz crystal vibrating plate 60.

[0079] In the quartz crystal unit 400, a frequency-adjusting metal film 51 is formed on the back surface (the surface facing the base 40) of the lid 50, which serves as a sealing member. Similar to the frequency-adjusting metal film 36 of the first embodiment, the frequency-adjusting metal film 51 is configured to include a base metal layer 51a and a metal layer 51b. The lid 50 is formed from a material (such as quartz or glass) that has high laser transmittance, and after the lid 50 is bonded to the base 40 and the quartz crystal vibrating plate 60 is sealed in the package, the base metal layer 51a can be heated by laser irradiation from the front surface of the lid 50 (the surface not facing the base 40).

[0080] As a result, even in the quartz crystal oscillator 400, a laser is irradiated onto the frequency-adjusting metal film 51 from outside the base 40, and the laser passes through the inside of the base 40 to heat the underlying metal layer 51a, thereby melting and evaporating (vaporizing) at least a portion of the metal layer 51b, and the evaporated metal is then attached to the excitation electrode (in this example, the first excitation electrode 601), thereby enabling frequency adjustment. [Explanation of symbols]

[0081] 100 Quartz crystal unit (piezoelectric vibration device) 10 Quartz crystal diaphragm (piezoelectric diaphragm) 11 Vibration unit 111 1st excitation electrode 112 2nd excitation electrode 20 First sealing member (sealing member) 30 Second sealing member (sealing member) 301 First main surface 36 Frequency adjustment metal film 36a Undercoat metal layer 36b metal layer 361 Exposed part

Claims

1. A method for adjusting the frequency of a piezoelectric vibration device in which at least a vibration portion of a piezoelectric vibration plate having a vibration portion on which an excitation electrode is formed is airtightly sealed with a sealing member, comprising: a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, At least a part of the sealing member on which the frequency adjustment metal film is formed is made of a light-transmitting material, the main surface of the sealing member and a second main surface on a side not facing the piezoelectric diaphragm are smooth surfaces, and the arithmetic mean roughness of the main surface and the second main surface is 1 nm or less, a beam is irradiated onto the frequency adjusting metal film from outside the sealing member at a plurality of locations spaced apart by a predetermined distance; A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the beam is passed through the inside of the sealing member to heat the underlying metal layer, thereby melting and evaporating at least a portion of the metal layer, and adhering it to the excitation electrode, thereby adjusting the frequency.

2. 2. The method for adjusting the frequency of a piezoelectric vibration device according to claim 1, A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the beam is irradiated linearly onto the frequency adjustment metal film in a planar view.

3. 3. The method for adjusting the frequency of a piezoelectric vibration device according to claim 2, A method for adjusting the frequency of a piezoelectric vibration device, characterized in that the linear irradiation of the beam is performed multiple times at each of the multiple locations.

4. A piezoelectric vibration device in which a vibration section on which an excitation electrode is formed is airtightly sealed by a sealing member, a frequency-adjusting metal film made of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrode, the frequency-adjusting metal film has an exposed portion in which a part of the underlying metal layer is not covered with the metal layer and is exposed, and the exposed portion is formed at a plurality of locations spaced apart by a predetermined distance; A piezoelectric vibrating device characterized in that the metal layer and the exposed portion are alternately formed in stripes on the surface of a single frequency-adjusting metal film.

Images