Frequency adjustment method for piezoelectric vibration device and piezoelectric vibration device

Abstract

A crystal oscillator (100) has a frequency adjustment metal film (36) comprising a metal underlayer (36a) and a metal layer (36b) formed on the first main surface (301) of a second sealing member (30). In frequency adjustment of the crystal oscillator (100), the frequency adjustment metal film (36) is irradiated with a laser from outside the second sealing member (30) and the metal underlayer (36a) is heated up, whereby at least part of the metal layer (36b) is evaporated by melting and deposited onto a second excitation electrode (112). Irradiation by the beam begins from outside the region of the metal layer (36b). In the scanning direction of the beam, the end portion of the metal layer (36b) is located so as to be on the inside of the end portion of the metal underlayer (36a).

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 Art

[0002] Conventionally, the manufacturing process of a piezoelectric vibration device such as a crystal oscillator includes a frequency adjustment process. By this frequency adjustment process, the frequency of the crystal oscillator is adjusted within a predetermined target frequency range (see, for example, Patent Document 1).

[0003] When the frequency adjustment process is performed after the vibrating portion of the crystal vibrating plate is sealed with a sealing member, a beam such as a laser is irradiated from the outside of the crystal oscillator. In this case, if the output of the beam is too large, the exciting electrode of the vibrating portion may be damaged. In addition, scattered matter and gas may be generated in the internal space of the crystal oscillator.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to solve the above conventional problems, the applicant has proposed, in Japanese Patent Application No. 2021-161534 (not published at the time of the filing of the present application), a frequency adjustment method in which a metal film for frequency adjustment composed of a base metal layer and a metal layer laminated thereon is formed on the main surface facing the exciting electrode of the sealing member, a beam is irradiated onto the metal film for frequency adjustment from the outside of the sealing member, and at least a part of the metal layer is evaporated by melting by heating the base metal layer and adhered to the exciting electrode.

[0006] However, even in the frequency adjustment method of Japanese Patent Application No. 2021-161534, there is a problem that good evaporation of the metal layer does not occur at the ends of the metal film for frequency adjustment, etc., and residues (foreign object shapes) are generated in the metal layer, which may cause frequency fluctuations after adjustment.

[0007] The present invention has been made in consideration of the above-described circumstances, and it is possible to easily perform frequency adjustment without degrading the characteristics of the piezoelectric vibration device even after the vibrating portion of the piezoelectric vibrating plate is sealed by the sealing member, and to provide a piezoelectric vibration device capable of preventing the generation of residues in the metal layer and a frequency adjustment method therefor.

Means for Solving the Problems

[0008] In order to solve the above problems, a piezoelectric vibration device according to a first aspect of the present invention is a method for adjusting the frequency of a piezoelectric vibration device in which a vibrating portion formed with excitation electrodes is hermetically sealed by a sealing member, wherein a metal film for frequency adjustment composed of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the excitation electrodes, a beam is irradiated onto the metal film for frequency adjustment from the outside of the sealing member, the beam is transmitted through the inside of the sealing member to heat the base metal layer, at least a part of the metal layer is evaporated by melting and adhered to the excitation electrodes to perform frequency adjustment, the irradiation of the beam is started at least from outside the region of the metal layer, and in the scanning direction of the beam, the length of the base metal layer is made larger than the length of the metal layer, and the end portion of the metal layer is arranged inside the end portion of the base metal layer.

[0009] According to the above configuration, by melting and evaporating the metal layer above the base metal layer and allowing the evaporated metal to adhere to the excitation electrode, the mass of the excitation electrode can be increased, and the frequency can be shifted to the lower side. At this time, the irradiation of the beam is started from outside the region of the metal layer, and in the scanning direction of the beam, the arrangement is such that the end of the metal layer exists inside the end of the base metal layer, so that the base metal layer surely exists between the metal layer and the sealing member, and the metal layer can be stably heated through the base metal layer. As a result, it is possible to avoid the metal layer material (for example, Au) becoming foreign-shaped residues at the end of the frequency adjustment metal film, and it is possible to prevent the residues from being broken off from the metal layer and adhering to the excitation electrode.

[0010] Further, in the frequency adjustment method of the piezoelectric vibration device, the frequency adjustment metal film has an exposed portion where a part of the base metal layer is exposed without being covered by the metal layer, the exposed portion is formed linearly, and the beam can be configured to be irradiated along the line of the exposed portion.

[0011] According to the above configuration, it is possible to prevent uneven evaporation of the metal layer material (for example, Au) in the irradiation line during beam scanning and prevent the molten metal layer material from remaining in a bridge shape. And it is possible to prevent the generation of residues caused by the metal layer material remaining in a bridge shape.

[0012] Further, in the frequency adjustment method of the piezoelectric vibration device, the beam can be configured to melt the metal layer by irradiating the beam so as not to penetrate the base metal layer.

[0013] According to the above configuration, since the beam does not penetrate the frequency adjustment metal film, it is possible to more surely avoid damaging the excitation electrode.

[0014] Also, in order to solve the above problems, a piezoelectric vibration device according to a second aspect of the present invention is a piezoelectric vibration device in which a vibration part formed with excitation electrodes is hermetically sealed by a sealing member, and on a main surface of the sealing member facing the excitation electrodes, a frequency adjustment metal film composed of a base metal layer and a metal layer laminated thereon is formed. In the frequency adjustment metal film, in at least one direction in plan view, the length of the base metal layer is made larger than the length of the metal layer, and the end of the metal layer is arranged inside the end of the base metal layer.

[0015] Further, in the piezoelectric vibration device, at least the metal layer can be configured to be formed to have the same size as the excitation electrode in plan view or smaller than the excitation electrode.

[0016] According to the above configuration, it is possible to suppress the metal evaporated from the metal layer from scattering outside the excitation electrode, and it is possible to surely attach the evaporated metal to the excitation electrode.

Effects of the Invention

[0017] In the frequency adjustment method and the piezoelectric vibration device of the piezoelectric vibration device of the present invention, the metal layer on the upper layer of the base metal layer is melted and evaporated, and the evaporated metal is attached to the excitation electrode, so that the frequency of the piezoelectric vibration device can be adjusted even after the vibration part is sealed. At this time, by starting the irradiation of the beam from outside the region of the metal layer and arranging the end of the metal layer inside the end of the base metal layer in the scanning direction of the beam, the metal layer can be stably heated through the base metal layer, generation of residues of the metal layer material at the end of the frequency adjustment metal film can be avoided, and it is possible to prevent the residues from being broken off from the metal layer and attaching to the excitation electrode.

Brief Description of the Drawings

[0018]

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Embodiments for Carrying Out the Invention

[0019] 〔First Embodiment〕 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a case where the piezoelectric vibration device to which the present invention is applied is a crystal oscillator will be described.

[0020] First, the basic structure of the crystal oscillator 100 according to the present embodiment will be described. As shown in FIG. 1, the crystal oscillator 100 includes a crystal vibrating plate (piezoelectric vibrating plate) 10, a first sealing member 20, and a second sealing member 30. In this crystal oscillator 100, the crystal vibrating plate 10 and the first sealing member 20 are joined, and the crystal vibrating plate 10 and the second sealing member 30 are joined, thereby forming a package having a substantially rectangular parallelepiped sandwich structure. That is, in the crystal oscillator 100, the first sealing member 20 and the second sealing member 30 are joined to each of the main surfaces of the crystal vibrating plate 10, thereby forming an internal space (cavity) of the package, and the vibrating portion 11 (see FIGS. 4 and 5) is hermetically sealed in this internal space.

[0021] The crystal oscillator 100 according to the present embodiment has, for example, a package size of 1.0×0.8 mm, and is designed to be miniaturized and made low-profile. Further, with the miniaturization, in the package, conduction of electrodes is achieved using through-holes, which will be described later, without forming castellations. Further, the crystal oscillator 100 is electrically connected to an external circuit board (not shown) provided outside via solder.

[0022] Next, each member of the crystal vibrating plate 10, the first sealing member 20, and the second sealing member 30 in the above-described crystal oscillator 100 will be described with reference to FIGS. 1 to 7. Here, each member configured as a single unit not joined will be described. FIGS. 2 to 7 merely show one configuration example of each of the crystal vibrating plate 10, the first sealing member 20, and the second sealing member 30, and these do not limit the present invention.

[0023] As shown in FIGS. 4 and 5, the quartz diaphragm 10 according to this embodiment is a piezoelectric substrate made of quartz, and both of its main surfaces (the first main surface 101 and the second main surface 102) are formed into flat and smooth surfaces by polishing (mirror finishing). In this embodiment, an AT-cut quartz plate that performs thickness-shear vibration is used as the quartz diaphragm 10. In the quartz diaphragm 10 shown in FIGS. 4 and 5, both main surfaces 101 and 102 of the quartz diaphragm 10 are XZ' planes. In this XZ' plane, the direction parallel to the short side direction (short side direction) of the quartz diaphragm 10 is defined as the X-axis direction, and the direction parallel to the long side direction (long side direction) of the quartz diaphragm 10 is defined as the Z'-axis direction. Note that the AT cut is a processing method of cutting out at an angle inclined by 35°15' around the X-axis with respect to the Z-axis among the three crystal axes of synthetic quartz, namely, the electrical axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). In the AT-cut quartz plate, the X-axis coincides with the crystal axis of the quartz. The Y'-axis and the Z'-axis coincide with the axes inclined by approximately 35°15' respectively from the Y-axis and the Z-axis of the crystal axis of the quartz (this cutting angle may be slightly changed within the range of adjusting the frequency-temperature characteristics of the AT-cut quartz diaphragm). The Y'-axis direction and the Z'-axis direction correspond to the cutting directions when cutting out the AT-cut quartz plate.

[0024] A pair of excitation electrodes (the first excitation electrode 111 and the second excitation electrode 112) are formed on both main surfaces 101 and 102 of the quartz diaphragm 10. The quartz diaphragm 10 has a vibration part 11 formed in a substantially rectangular shape, an outer frame part 12 surrounding the outer periphery of the vibration part 11, and a holding part (connecting part) 13 that holds the vibration part 11 by connecting the vibration part 11 and the outer frame part 12. That is, the quartz diaphragm 10 has a configuration in which the vibration part 11, the outer frame part 12, and the holding part 13 are integrally provided. The holding part 13 extends (projects) from only one corner part located in the +X direction and -Z'-direction of the vibration part 11 toward the outer frame part 12 in the -Z'-direction. A through-hole (slit) 10a penetrating in the thickness direction of the quartz diaphragm 10 is provided between the vibration part 11 and the outer frame part 12. In this embodiment, only one holding part 13 that connects the vibration part 11 and the outer frame part 12 is provided on the quartz diaphragm 10, and the through-hole 10a is continuously formed so as to surround the outer periphery of the vibration part 11.

[0025] The first exciting electrode 111 is provided on the first main surface 101 side of the vibrating portion 11, and the second exciting electrode 112 is provided on the second main surface 102 side of the vibrating portion 11. Input / output lead wires (first lead wire 113, second lead wire 114) for connecting these exciting electrodes to external electrode terminals are connected to the first exciting electrode 111 and the second exciting electrode 112. The first lead wire 113 on the input side is drawn from the first exciting electrode 111, passes through the holding portion 13, and is connected to a connection bonding pattern 14 formed on the outer frame portion 12. The second lead wire 114 on the output side is drawn from the second exciting electrode 112, passes through the holding portion 13, and is connected to a connection bonding pattern 15 formed on the outer frame portion 12.

[0026] On both main surfaces (first main surface 101, second main surface 102) of the crystal vibrating plate 10, vibration plate side sealing portions for bonding the crystal vibrating plate 10 to the first sealing member 20 and the second sealing member 30 are provided respectively. As the vibration plate side sealing portion on the first main surface 101, a vibration plate side first bonding pattern 121 is formed, and as the vibration plate side sealing portion on the second main surface 102, a vibration plate side second bonding pattern 122 is formed. The vibration plate side first bonding pattern 121 and the vibration plate side second bonding pattern 122 are provided on the outer frame portion 12 and are formed in an annular shape in plan view.

[0027] Further, as shown in FIGS. 4 and 5, five through holes penetrating between the first main surface 101 and the second main surface 102 are formed in the crystal vibrating plate 10. Specifically, four first through holes 161 are respectively provided in regions at the four corners (corner portions) of the outer frame portion 12. The second through hole 162 is provided in the outer frame portion 12 on one side in the Z' axis direction of the vibrating portion 11 (in FIGS. 4 and 5, the -Z' direction side). Connection bonding patterns 123 are respectively formed around the first through holes 161. Also, around the second through hole 162, a connection bonding pattern 124 is formed on the first main surface 101 side, and a connection bonding pattern 15 is formed on the second main surface 102 side.

[0028] In the first through-hole 161 and the second through-hole 162, through electrodes for establishing electrical connection between the electrodes formed on the first main surface 101 and the second main surface 102 are formed along the inner wall surfaces of the respective through-holes. Also, the central portions of the first through-hole 161 and the second through-hole 162 each form a hollow through portion that penetrates 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 provided in proximity to the outer peripheral edge of the first main surface 101 of the crystal diaphragm 10 (outer frame portion 12). The outer peripheral edge of the diaphragm-side second bonding pattern 122 is provided in proximity to the outer peripheral edge of the second main surface 102 of the crystal diaphragm 10 (outer frame portion 12). In the present embodiment, an example is given in which five through-holes penetrating between the first main surface 101 and the second main surface 102 are formed. However, instead of forming through-holes, a part of the side surface of the first sealing member 20 may be cut out, and a castellated portion in which electrodes are deposited on the inner wall surface of the cut-out region may be formed (the same applies to the second sealing member 30).

[0029] As shown in FIGS. 2 and 3, the first sealing member 20 is a rectangular parallelepiped substrate formed from a single AT-cut crystal plate that is a light-transmissive material. The second main surface 202 (the surface joined to the crystal diaphragm 10) of this first sealing member 20 is formed into a flat and smooth surface by polishing (mirror finishing). Note that although the first sealing member 20 does not have a vibrating portion, by using an AT-cut crystal plate similar to the crystal diaphragm 10, the thermal expansion coefficients of the crystal diaphragm 10 and the first sealing member 20 can be made the same, and thermal deformation in the crystal oscillator 100 can be suppressed. Also, the directions of the X-axis, Y-axis, and Z'-axis in the first sealing member 20 are the same as those in the crystal diaphragm 10.

[0030] On the first main surface 201 of the first sealing member 20 (the outer main surface not facing the crystal vibrating plate 10), as shown in FIG. 2, first and second terminals 22, 23 for wiring and a metal film 28 for shielding (ground connection) are formed. The first and second terminals 22, 23 for wiring are provided as wirings for electrically connecting the first and second excitation electrodes 111, 112 of the crystal vibrating plate 10 and the external electrode terminals 32 of the second sealing member 30. The first and second terminals 22, 23 are provided at both ends in the Z' axis direction, the first terminal 22 is provided on the +Z' direction side, and the second terminal 23 is provided on the -Z' direction side. The first and second terminals 22, 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.

[0031] The metal film 28 is provided between the first and second terminals 22, 23 and is arranged at a predetermined interval from the first and second terminals 22, 23. The metal film 28 is provided in almost all regions of the region 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 in the +X direction to the end in the -X direction of the first main surface 201 of the first sealing member 20.

[0032] Six through-holes penetrating between the first main surface 201 and the second main surface 202 are formed in the first sealing member 20, as shown in FIGS. 2 and 3. Specifically, four third through-holes 211 are provided in the regions at the four corners (corners) of the first sealing member 20. The fourth and fifth through-holes 212, 213 are provided in the +Z' direction and the -Z' direction in FIGS. 2 and 3, respectively.

[0033] In the third through-hole 211 and the fourth and fifth through-holes 212 and 213, through electrodes for connecting 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. Further, the central portions of the third through-hole 211 and the fourth and fifth through-holes 212 and 213 each become through portions in a hollow state penetrating between the first main surface 201 and the second main surface 202. And, the through electrodes of the two third through-holes 211 and 211 (the third through-hole 211 located at the corner in the +X direction and +Z' direction in FIGS. 2 and 3, and the third through-hole 211 located at the corner in the -X direction and -Z' direction) located diagonally on the first main surface 201 of the first sealing member 20 are electrically connected by the metal film 28. Also, the through electrode of the third through-hole 211 located at the corner in the -X direction and +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 -Z' direction and the through electrode of the fifth through-hole 213 are electrically connected by the second terminal 23.

[0034] On the second main surface 202 of the first sealing member 20, a sealing member side first bonding pattern 24 as a sealing member side first seal for bonding to the crystal vibration plate 10 is formed. The sealing member side first bonding pattern 24 is formed in an annular shape in plan view. Also, on the second main surface 202 of the first sealing member 20, connection bonding patterns 25 are respectively formed around the third through-hole 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. Further, a connection bonding pattern 263 is formed on the opposite side (-Z' direction side) of the long axis direction of the first sealing member 20 with respect to the connection bonding pattern 261, and the connection bonding pattern 261 and the connection bonding pattern 263 are connected by a wiring pattern 27. The outer peripheral edge of the sealing member side first bonding pattern 24 is provided close to the outer peripheral edge of the second main surface 202 of the first sealing member 20.

[0035] As shown in FIGS. 6 and 7, the second sealing member 30 is a rectangular parallelepiped substrate formed from a single AT-cut crystal plate which is a light-transmissive material. The first main surface 301 (the surface joined to the crystal vibrating plate 10) and the second main surface 302 (the outer main surface not facing the crystal vibrating plate 10) of this second sealing member 30 are formed into flat and smooth surfaces by polishing (mirror finishing). Note that, also in the second sealing member 30, it is desirable to use an AT-cut crystal plate in the same manner as the crystal vibrating plate 10 and to set the directions of the X-axis, Y-axis, and Z'-axis to be the same as those of the crystal vibrating plate 10.

[0036] On the first main surface 301 of this second sealing member 30, a sealing member side second bonding pattern 31 as a second sealing portion on the sealing member side for bonding to the crystal vibrating plate 10 is formed. The sealing member side second bonding pattern 31 is formed in an annular shape in plan view. The outer peripheral edge of the sealing member side second bonding pattern 31 is provided close to the outer peripheral edge of the first main surface 301 of the second sealing member 30.

[0037] Also, on the first main surface 301 of the second sealing member 30, a frequency adjustment metal film 36 used for frequency adjustment of the crystal oscillator 100 is formed. The frequency adjustment metal film 36 has a two-layer structure made of two types of metals with different melting temperatures (melting points), and includes a base metal layer 36a and a metal layer 36b laminated on this base metal layer 36a. The thickness of the base metal layer 36a is, for example, 50 nm, and the thickness of the metal layer 36b is, for example, 100 nm. Note that the thickness of the base metal layer 36a is preferably 50 to 500 nm, and the thickness of the metal layer 36b is preferably 100 to 500 nm. When the thickness of the base metal layer 36a is less than 50 nm, it cannot withstand laser irradiation, which is not preferable. Also, when the thickness of the base metal layer 36a is greater than 500 nm, the wafer warps and the production efficiency decreases due to thickening, which is not preferable. Also, when the thickness of the metal layer 36b is less than 100 nm, it cannot withstand laser irradiation, which is not preferable. Also, when the thickness of the metal layer 36b is greater than 500 nm, the wafer warps and the production efficiency decreases due to thickening, which is not preferable.

[0038] The reasons will be described later. In the metal film 36 for frequency adjustment, the melting temperature of the base metal layer 36a is higher than that of the metal layer 36b, and preferably, the melting temperature difference between the base metal layer 36a and the metal layer 36b is 1500 °C or more. Further, the metal layer 36b is made of the same material (for example, 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).

[0039] The metal film 36 for frequency adjustment is provided at a position facing the second excitation electrode 112 with a predetermined interval. The distance L1 in the vertical direction (Y-axis direction) between the second excitation electrode 112 and the metal film 36 for frequency adjustment is 2 to 200 μm.

[0040] The metal film 36 for frequency adjustment is formed in a substantially rectangular shape in plan view. The metal film 36 for frequency adjustment is formed slightly smaller than the second excitation electrode 112. In plan view, the outer peripheral edge of the metal film 36 for frequency adjustment is located inside the outer peripheral edge of the second excitation electrode 112.

[0041] The first and second main surfaces 301 and 302 of the second sealing member 30 are smooth surfaces by polishing, and the arithmetic mean roughness Ra of the first and second main surfaces 301 and 302 is 1 nm or less. Also, the arithmetic mean roughness Ra of the surface of the metal layer 36b of the metal film 36 for frequency adjustment is 3 nm or less.

[0042] On the second main surface 302 of the second sealing member 30, four external electrode terminals 32 are provided for electrically connecting to an external circuit board provided outside the crystal oscillator 100. The external electrode terminals 32 are respectively located at the four corners (corner portions) of the second main surface 302 of the second sealing member 30.

[0043] In the second sealing member 30, as shown in FIGS. 6 and 7, four through holes penetrating between the first main surface 301 and the second main surface 302 are formed. Specifically, the four sixth through holes 33 are provided in the regions at the four corners (corners) of the second sealing member 30. In the sixth through hole 33, through electrodes for making the electrodes formed on the first main surface 301 and the second main surface 302 conduct are formed along the inner wall surfaces of the respective sixth through holes 33. Thus, the electrodes formed on the first main surface 301 and the external electrode terminals 32 formed on the second main surface 302 are conducted by the through electrodes formed on the inner wall surfaces of the sixth through holes 33. Further, the central portion of each of the sixth through holes 33 is a hollow through portion penetrating between the first main surface 301 and the second main surface 302. Also, 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.

[0044] In the crystal oscillator 100 including the crystal vibrating plate 10, the first sealing member 20, and the second sealing member 30 having the above configuration, the crystal vibrating plate 10 and the first sealing member 20 are diffusion-bonded in a state where the vibrating plate side first bonding pattern 121 and the sealing member side first bonding pattern 24 are overlapped, and the crystal vibrating plate 10 and the second sealing member 30 are diffusion-bonded in a state where the vibrating plate side second bonding pattern 122 and the sealing member side second bonding pattern 31 are overlapped, thereby manufacturing the package having the sandwich structure shown in FIG. 1. Thereby, the internal space of the package, that is, the accommodation space of the vibrating portion 11 is hermetically sealed.

[0045] At this time, the above-described connection bonding patterns are also diffusion-bonded in a superposed state. And, by bonding the connection bonding patterns to each other, in the crystal oscillator 100, electrical conduction between the first excitation electrode 111, the second excitation electrode 112, and the external electrode terminal 32 is achieved. Specifically, the first excitation electrode 111 is connected to the external electrode terminal 32 via the first lead 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 this order. The second excitation electrode 112 is connected to the external electrode terminal 32 via the second lead 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 this order. Also, the metal film 28 is grounded (using a part of the external electrode terminal 32 for ground connection) via the third through hole 211, the first through hole 161, and the sixth through hole 33 in this order.

[0046] In the crystal oscillator 100, it is preferable that the various bonding patterns are formed by laminating a plurality of layers on the crystal plate, and the Ti (titanium) layer and the Au (gold) layer are formed by vapor deposition or sputtering from the lowermost layer side. Also, if other wirings and electrodes formed on the crystal oscillator 100 have the same configuration as the bonding pattern, the bonding pattern, the wiring, and the electrode can be patterned simultaneously, which is preferable.

[0047] In the crystal oscillator 100 configured as described above, the sealing portions (seal paths) 115 and 116 that hermetically seal the vibrating portion 11 of the 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) of the above-described first bonding pattern 121 on the vibrating plate side and the first bonding pattern 24 on the sealing member side, and the outer edge shape and the inner edge shape 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) of the above-described second bonding pattern 122 on the vibrating plate side and the second bonding pattern 31 on the sealing member side, and the outer edge shape and the inner edge shape of the seal path 116 are formed in a substantially octagonal shape.

[0048] Next, a frequency adjustment method for the crystal oscillator 100 according to the present embodiment will be described with reference to FIG. 8. The frequency adjustment in the present embodiment is a process of adjusting the oscillation frequency by adjusting the mass of the second excitation electrode 112 of the vibrating portion 11 of the crystal vibration plate 10 to a desired value. The frequency adjustment is performed for each of the crystal oscillators 100 in the wafer state in the manufacturing process of the crystal oscillator 100, but it may also be performed for each of the crystal oscillators 100 separated from the wafer state.

[0049] Specifically, as shown in FIG. 8, a laser is irradiated onto the frequency adjustment metal film 36 from the outside of the second sealing member 30, and the laser is transmitted through the inside of the second sealing member 30 to heat the base metal layer 36a, thereby evaporating (vaporizing) at least a part of the metal layer 36b by melting. The frequency adjustment is performed by attaching the evaporated metal to the second excitation electrode 112. That is, the metal layer 36b above the base metal layer 36a is melted and evaporated by the laser, and the evaporated metal adheres to the second excitation electrode 112, so that the mass of the second excitation electrode 112 increases and the frequency shifts to the lower side.

[0050] The laser is irradiated perpendicularly to the second sealing member 30. As the laser, a visible light laser capable of passing through the second sealing member 30 made of quartz is used. Specifically, it is possible to use a green laser with a wavelength of about 532 nm. The output of the laser is adjusted to a value that does not penetrate the base metal layer 36a of the frequency adjustment metal film 36. The base metal layer 36a is heated by the laser, and accordingly, the metal layer 36b above the base metal layer 36a is also heated. As described above, since the melting temperature of the base metal layer 36a is higher than the melting temperature of the metal layer 36b, 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 part of the melted metal layer 36b evaporates. Since the inside of the crystal oscillator 100 is in a vacuum, the evaporated metal moves upward substantially linearly, and when it reaches the surface 112a of the second excitation electrode 112, it is cooled at the surface 112a of the second excitation electrode 112 and solidifies. Thereby, the metal evaporated from the frequency adjustment metal film 36 adheres to the surface 112a of the second excitation electrode 112.

[0051] In addition, the metal layer 36b may have a multilayer structure composed of a plurality of metal layers. In this case, in addition to Au, Ag (silver: melting temperature 962 °C) or Al (aluminum: melting temperature 660 °C) can be used for the metal layer 36b. When the metal layer 36b has a multilayer structure, it is sufficient that the uppermost metal layer is formed of the same material (for example, Au) as the second excitation electrode 112. Also, the base metal layer 36a may have a multilayer structure composed of a plurality of metal layers. In this case, it is preferable to arrange the metal layer with a higher melting temperature (for example, W layer) closer to the lower layer (the side closer to the second sealing member 30) and the metal layer with a lower melting temperature (for example, Mo layer) closer to the upper layer (the side closer to the metal layer 36b).

[0052] Also, an auxiliary metal layer 36d (see FIG. 9) may be formed between the base metal layer 36a and the second sealing member 30. At this time, by using a metal with high adhesion to quartz, such as Ti (titanium), Cr (chromium), Ni (nickel), etc., as the auxiliary metal layer 36d, the adhesion between the frequency adjustment metal film 36 and the second sealing member 30 can be enhanced. Note that the melting temperature of the auxiliary metal layer 36d is required to be sufficiently higher than that of the metal layer 36b, but a melting temperature difference of 1500 °C or more from the metal layer 36b like the base metal layer 36a is not required. For example, when the auxiliary metal layer 36d is Ti and the metal layer 36b is Au, the melting temperature of Ti is 1672 °C, and the melting temperature difference from Au is about 600 °C. Even if some melting occurs in the auxiliary metal layer 36d due to laser irradiation during frequency adjustment, the presence of the base metal layer 36a above the auxiliary metal layer 36d can prevent the melted auxiliary metal layer 36d from scattering onto the second excitation electrode 112.

[0053] In addition, there is a risk that the molten auxiliary metal layer 36d diffuses into the upper base metal layer 36a due to the heat of laser irradiation, causing a decrease in the melting temperature of the base metal layer 36a. However, in this regard as well, by making the film thickness of the auxiliary metal layer 36d thinner than the film thickness of the base metal layer 36a, it is possible to perform laser irradiation without melting the base metal layer 36a (only the metal layer 36b can be evaporated).

[0054] As shown in FIG. 10, laser irradiation of the underlying metal layer 36a can be performed on a desired region by arranging irradiation lines LN parallel to each other by scanning a laser spot SP. At this time, it is preferable that the scanning direction of the laser spot SP (direction of arrow A) is the same for all the irradiation lines LN, and adjacent irradiation lines LN do not overlap in the width direction of the line (direction orthogonal to the scanning direction). Further, for each irradiation line LN, the scanning of the laser spot SP is preferably repeated a plurality of times. After the laser scanning is performed a plurality of times for one irradiation line LN, it is preferable that the laser scanning is performed for the adjacent irradiation line LN. As shown in FIG. 10, in the irradiation line LN where the laser irradiation has ended, the underlying metal layer 36a is exposed due to the evaporation of the metal layer 36b.

[0055] As described above, when the frequency adjustment metal film 36 is irradiated by linearly scanning a laser, as a general property of the laser, the irradiation at the start point of the line becomes unstable. For example, if the laser power increases at the start point of the line, not only does it become difficult to adjust the frequency, but also the underlying metal layer 36a may melt. In order to suppress such melting of the underlying metal layer 36a, if the overall laser output is weakened according to the power at the start point, the efficiency of frequency adjustment decreases.

[0056] Therefore, as shown in FIG. 11, it is preferable that the line scanning of the laser for frequency adjustment starts from outside the region of the frequency adjustment metal film 36 (at least outside the region of the metal layer 36b). Thereby, the power of the laser irradiated to the formation region of the metal layer 36b is stable, and the metal layer 36b can be stably heated while suppressing the melting of the underlying metal layer 36a without weakening the overall laser output.

[0057] Furthermore, the laser irradiated outside the area of the metal film 36 for frequency adjustment is not blocked by the underlying metal layer 36a. At this time, if the unblocked laser reaches the electrodes or wirings (especially the exciting electrodes) of the crystal resonator 10, there is a risk of damage to the electrodes or wirings, which is not desirable. Therefore, when performing laser irradiation from outside the area of the metal film 36 for frequency adjustment, the laser should not hit the areas where the electrodes or wirings are formed on the crystal resonator 10, but should be irradiated only on the area of the crystal itself. As long as it is the crystal area outside the electrodes and wirings, there is no problem even if the laser is irradiated because the laser will transmit through.

[0058] On the other hand, when starting the line scanning of the laser for frequency adjustment from outside the area of the metal film 36 for frequency adjustment, if the metal layer 36b and the underlying metal layer 36a overlap at the end in the scanning direction of the laser of the metal film 36 for frequency adjustment (if the end positions of the metal layer 36b and the underlying metal layer 36a are the same), there is a problem that Au residues in the shape of foreign matter are likely to occur at the end of the metal film 36 for frequency adjustment (when the material of the metal layer 36b is Au). FIG. 12 is a schematic diagram showing a state where Au residues are generated at the end of the metal film 36 for frequency adjustment.

[0059] The generation of such Au residues is considered to be caused by the instability of the heating of the metal layer 36b by laser irradiation at the end of the metal film 36 for frequency adjustment.

[0060] First, the metal film 36 for frequency adjustment is formed by patterning each of the underlying metal layer 36a and the metal layer 36b by etching. Specifically, first, the underlying metal layer 36a is patterned and formed on the second sealing member 30, and then the metal layer 36b is patterned and formed thereon. Due to the variation in the etching rate during the etching of each layer, it is difficult to ensure that the ends of the underlying metal layer 36a and the metal layer 36b exactly match each other. Therefore, for example, it is possible that the end of the underlying metal layer 36a enters inside the end of the metal layer 36b (see FIG. 13).

[0061] When the state shown in FIG. 13 occurs at the end in the laser scanning direction, sufficient heating of the metal layer 36b does not occur at that end. That is, in a location where the underlayer metal layer 36a does not exist between the metal layer 36b and the second sealing member 30, the laser that has passed through the second sealing member 30 is irradiated onto the metal layer 36b. However, since the metal layer 36b has a high reflectivity to the laser, it is not sufficiently heated by direct irradiation of the laser. Thus, when insufficient heating of the metal layer 36b occurs at the end of the frequency adjustment metal film 36, although the Au of the metal layer 36b has melted, it is considered that it does not reach evaporation and re-solidification of Au occurs. And it is considered that Au residues are generated when Au re-solidifies. The generation of such Au residues may break off after the frequency adjustment of the crystal oscillator 100 and adhere to the second excitation electrode 112, undesirably shifting the frequency of the crystal oscillator 100.

[0062] On the other hand, in the crystal oscillator 100 according to the present embodiment, as shown in FIG. 11, at least in the laser scanning direction, the length of the underlayer metal layer 36a is made larger than the length of the metal layer 36b, and the end of the metal layer 36b is arranged to be inside the end of the underlayer metal layer 36a. In this case, when the line scanning of the laser for frequency adjustment starts from outside the region of the metal layer 36b, the underlayer metal layer 36a surely exists between the metal layer 36b and the second sealing member 30, and the metal layer 36b can be stably heated through the underlayer metal layer 36a. As a result, generation of Au residues at the end of the frequency adjustment metal film 36 can be avoided, and it is possible to prevent Au residues from breaking off from the metal layer 36b and adhering to the second excitation electrode 112.

[0063] Further, in FIG. 11, a case is illustrated where the line scanning of the laser is performed from outside the region of the frequency adjustment metal film 36 (that is, outside the region of the base metal layer 36a). However, the present invention is not limited to this, and in practice, it is preferable that the line scanning of the laser is started from outside the region of the metal layer 36b and within the region of the base metal layer 36a. In this case, by starting the laser irradiation from above the base metal layer 36a, the metal layer 36b can be heated with the laser in a stable state, and the risk that the beam not blocked by the base metal layer 36a irradiates the electrodes and wirings can be eliminated.

[0064] Also, when the line scanning of the laser is started from within the region of the base metal layer 36a, the size relationship of the widths of the second excitation electrode 112, the base metal layer 36a, and the metal layer 36b is preferably such that the base metal layer 36a > the second excitation electrode 112 ≥ the metal layer 36b. That is, since the base metal layer 36a > the second excitation electrode 112, the laser irradiation to the second excitation electrode 112 can be reliably prevented by the laser blocking of the base metal layer 36a. Further, since the second excitation electrode 112 ≥ the metal layer 36b (more preferably the second excitation electrode 112 > the metal layer 36b), the metal evaporated from the metal layer 36b can be reliably attached only to the second excitation electrode 112.

[0065] By controlling the number of pulses, the scanning distance, the number of scans, etc. of the laser irradiating the base metal layer 36a, the mass of the metal attached to the second excitation electrode 112 can be controlled, and the frequency adjustment amount can be controlled. For example, by lowering the output of the laser, narrowing the pulse interval, and continuously irradiating, the base metal layer 36a can be efficiently heated to evaporate only the metal layer 36b. In this case, it becomes possible to obtain a frequency adjustment amount corresponding to the scanning distance of the laser, and high-precision frequency adjustment becomes possible.

[0066] According to the frequency adjustment method of the crystal oscillator 100 of the present 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, so that the mass of the second excitation electrode 112 increases and the frequency can be shifted to the lower side. In this case, by controlling the number of laser pulses, the scanning distance, etc., a desired frequency adjustment amount can be obtained. And by preventing the laser from penetrating the frequency adjustment metal film 36, it is possible to suppress damage to the second excitation electrode 112. Thereby, even after the vibrating portion 11 of the crystal vibrating plate 10 is sealed by the first and second sealing members 20 and 30, frequency adjustment can be performed without significantly degrading the characteristics of the crystal oscillator 100.

[0067] In the present embodiment, the laser is irradiated so as not to penetrate the base metal layer 36a, and since the laser does not penetrate the frequency adjustment metal film 36, it is possible to more reliably avoid damaging the second excitation electrode 112. Thereby, even after the vibrating portion 11 of the crystal vibrating plate 10 is sealed by the first and second sealing members 20 and 30, frequency adjustment can be easily performed without degrading the characteristics of the crystal oscillator 100.

[0068] Also, in the present embodiment, the difference between the melting temperature of the base metal layer 36a and the melting temperature of the metal layer 36b is 1500°C or more. By heating the base metal layer 36a to a temperature equal to or higher than the melting temperature of the metal layer 36b and equal to or lower than the melting temperature of the base metal layer 36a by laser irradiation, the base metal layer 36a does not melt, only the metal layer 36b melts, and a part of the melted metal can be evaporated. The evaporated metal adheres to the second excitation electrode 112, so that the mass of the second excitation electrode 112 increases and the frequency can be shifted to the lower side. Thereby, even after the vibrating portion 11 of the crystal vibrating plate 10 is sealed by the first and second sealing members 20 and 30, frequency adjustment can be easily performed without degrading the characteristics of the crystal oscillator 100. Note that even if the melting temperature of the base metal layer 36a is higher than the melting temperature of the metal layer 36b, if the difference in melting temperature is small, it becomes difficult to melt only the metal layer 36b, and melting of the base metal layer 36a may occur simultaneously.

[0069] In this embodiment, the first main surface 301 of the second sealing member 30 and the second main surface 302 on the opposite side of the first main surface 301 are smooth surfaces. When the laser enters from the second main surface 302 of the second sealing member 30 and when the laser exits from the first main surface 301 of the second sealing member 30, reflection and refraction of the laser can be suppressed, and energy loss of the laser can be reduced. Thereby, even after the vibrating portion 11 of the crystal resonator 10 is sealed by the first and second sealing members 20 and 30, high-precision frequency adjustment can be performed according to the number of laser pulses, the scanning distance, the number of scanning times, and the like.

[0070] Also, the metal layer 36b is formed of the same Au (gold) as the second exciting electrode 112. Since the metal layer 36b is made of the same material as the second exciting electrode 112, the characteristics do not change before and after the frequency adjustment. Therefore, variations in the characteristics of the crystal oscillator 100 after sealing can be suppressed.

[0071] Also, the base metal layer 36a is formed of W (tungsten) or the like. By causing the base metal layer 36a exposed in the internal space of the crystal oscillator 100 to function as a getter material, the gas generated in the internal space of the crystal oscillator 100 can be trapped by the base metal layer 36a. Note that a metal layer (for example, a W layer) 37 (see FIG. 14) the same as the base metal layer 36a may be formed as a single layer in a region different from the base metal layer 36a, and this metal layer 37 may be made to function as a getter material. In this case, the metal layer 37 is preferably formed in a region that does not face the second exciting electrode 112.

[0072] Also, by using a visible light laser having a low absorption rate and a high transmittance with respect to the second sealing member 30 made of, for example, crystal or glass as the laser, power loss and damage to the second sealing member 30 can be suppressed, so it is suitable for frequency adjustment.

[0073] In addition, the space in which the vibrating portion 11 of the crystal diaphragm 10 is sealed is in a vacuum state, and since the evaporated metal can be moved substantially linearly, scattering to the surroundings can be suppressed. Further, the evaporated metal can be attached to the second excitation electrode 112 without lowering its temperature.

[0074] In this embodiment, the distance L1 in the vertical direction between the second excitation electrode 112 and the frequency adjustment metal film 36 is 2 to 200 μm. In this way, by making the distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36 small, the metal evaporated from the frequency adjustment metal film 36 can be moved substantially linearly, suppressing scattering to the surroundings. Thereby, the evaporated metal can be surely attached to the second excitation electrode 112, and even after the vibrating portion 11 of the crystal diaphragm 10 is sealed by the first and second sealing members 20 and 30, high-precision frequency adjustment can be easily performed.

[0075] Also, in a plan view, since the outer peripheral edge of the frequency adjustment metal film 36 is located inside the outer peripheral edge of the second excitation electrode 112, even when the exposed portion of the base metal layer 36a of the frequency adjustment metal film 36 comes into contact with the second excitation electrode 112 when the vibrating portion 11 is deflected by an external impact, adhesion between the base metal layer 36a and the second excitation electrode 112 can be prevented. Further, scattering of the metal evaporated from the frequency adjustment metal film 36 to the outside of the second excitation electrode 112 can be suppressed, and the evaporated metal can be surely attached to the second excitation electrode 112. Thereby, even after the vibrating portion 11 of the crystal diaphragm 10 is sealed by the first and second sealing members 20 and 30, high-precision frequency adjustment can be easily performed.

[0076] In this embodiment, the crystal oscillator 100 includes a first sealing member 20 that covers the first main surface side of the vibrating portion 11 of the crystal vibrating plate 10, and a second sealing member 30 that covers the second main surface side of the vibrating portion 11 of the crystal vibrating plate 10. The first sealing member 20 and the crystal vibrating plate 10 are joined, and the second sealing member 30 and the crystal vibrating plate 10 are joined, so that the vibrating portion 11 of the crystal vibrating plate 10 is hermetically sealed. The first sealing member 20 and the second sealing member 30 are made of crystal. Thus, when a crystal oscillator 100 having a three-layer stacked structure is used, it is possible to reduce the size and thickness of the crystal oscillator 100. However, in such a crystal oscillator 100 with reduced size and thickness, even after the vibrating portion 11 of the crystal vibrating plate 10 is sealed by the first and second sealing members 20 and 30, high-precision frequency adjustment can be performed.

[0077] Further, in the crystal oscillator 100 of the present embodiment described above, a frequency adjustment metal film 36 is formed on the first main surface 301 of the second sealing member 30 facing the second excitation electrode 112. At least a part of the base metal layer 36a of the frequency adjustment metal film 36 is not covered by the metal layer 36b and is exposed. According to this, by making the exposed base metal layer 36a function as a getter material, the gas generated in the internal space of the crystal oscillator 100 can be captured by the base metal layer 36a. Thereby, the secular change of the frequency of the crystal oscillator 100 due to the generation of gas can be suppressed.

[0078] In addition, since the crystal vibrating plate 10 is configured to include a vibrating portion 11 and an outer frame portion 12 surrounding the vibrating portion 11, compared with a configuration in which a sealing member is joined to a base using an adhesive, the distance L1 between the second excitation electrode 112 and the frequency adjustment metal film 36 can be made extremely small, and as described above, high-precision frequency adjustment can be performed.

[0079] In the above-described 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 frequency adjustment metal film may not be provided on the second sealing member 30, 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. 15, 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 the same configuration as the frequency adjustment metal film 36 of the second sealing member 30 in the above-described embodiment. The frequency adjustment metal film 26 has a structure in which, for example, a base metal layer 26a made of W (tungsten) and a metal layer 26b made of the same material as the first excitation electrode 111 (for example, Au) are laminated.

[0080] According to the modified example shown in FIG. 15, frequency adjustment can be performed using both the frequency adjustment metal films 26 and 36. Even on the first sealing member 20 side of the crystal oscillator 100, by irradiating the frequency adjustment metal film 26 with a laser, frequency adjustment can be performed at two locations, namely, the first sealing member 20 side and the second sealing member 30 side. In this case, frequency adjustment may be performed simultaneously at the two locations on the first sealing member 20 side and the second sealing member 30 side, or frequency adjustment may be performed one by one in order.

[0081] In the above-described embodiment, frequency adjustment is performed using a visible light laser. However, frequency adjustment may be performed using a beam such as an electron beam. In this case, a desired frequency adjustment amount can be obtained by controlling the output, irradiation time, etc. of the beam.

[0082] In the above-described embodiment, the internal space of the crystal oscillator 100 is evacuated. However, for example, low-pressure nitrogen, argon, etc. may be enclosed in the internal space of the crystal oscillator 100.

[0083] In the above-described embodiment, the crystal vibrating plate 10 is an AT-cut crystal plate, but other materials may be used. Also, although the vibrating portion 11 of the crystal vibrating plate 10 is rectangular, the vibrating portion may have a tuning fork shape.

[0084] In the above-described embodiment, the first sealing member 20 and the second sealing member 30 are formed of a quartz plate, but the first sealing member 20 and the second sealing member 30 may be formed of, for example, glass. In this case, an infrared laser that can penetrate the first sealing member 20 and the second sealing member 30 may be used. As the infrared laser, for example, a YAG laser having a wavelength of about 1064 nm can be used. Note that only a part of the first sealing member 20 and the second sealing member 30 may be formed of a light-transmissive material such as quartz or glass.

[0085] In the above-described embodiment, only one holding portion 13 for connecting the vibrating portion 11 and the outer frame portion 12 is provided on the quartz diaphragm 10, but two or more holding portions 13 may be provided. Further, a through portion 10a penetrating in the thickness direction of the quartz diaphragm 10 is provided between the vibrating portion 11 and the outer frame portion 12, but a quartz diaphragm having a configuration in which no through portion is provided may be used. Further, in the above-described embodiment, the quartz diaphragm 10 with a frame including the vibrating portion 11 and the outer frame portion 12 surrounding the vibrating portion 11 is used, but a quartz diaphragm having a configuration without an outer frame portion may be used.

[0086] 〔Second Embodiment〕 In the first embodiment described above, the metal layer 36b is formed as a rectangular solid electrode, but the present invention is not limited to this. For example, as shown in FIG. 16, the metal layer 36b is formed in a stripe shape on the base metal layer 36a, and the portion between adjacent metal layers 36b may be an exposed portion 361. In other words, on the surface of the frequency adjustment metal film 36 in FIG. 16, the metal layer 36b and the exposed portion 361 are alternately formed in a stripe shape.

[0087] When the metal layer 36b and the exposed portion 361 are alternately formed in a stripe shape in the frequency adjustment metal film 36 as in the example of FIG. 16, the laser scanning is performed along the longitudinal direction of the linear exposed portion 361. At this time, the line width of the exposed portion 361 is set to be smaller than the diameter (irradiation diameter) of the laser spot SP, and the metal layer 36b is heated on both sides of the laser spot SP to be scanned.

[0088] When adjusting the frequency of the crystal oscillator 100, the reason for performing laser scanning such that at least a part of the laser spot SP includes the exposed portion 361 is as follows. As described above, when the frequency adjustment metal film 36 is irradiated with a laser, the underlying metal layer 36a is heated, and the metal layer 36b above the underlying metal layer 36a melts and evaporates. Then, the underlying metal layer 36a is exposed in the region where the metal layer 36b has evaporated. When the metal layer 36b is formed as a solid electrode, in the irradiation line where a predetermined number of laser scans have ended, there may be a case where Au remains in small lumps at the edge of the metal layer 36b (when the metal layer 36b is Au), i.e., Au residue (see Fig. 17). This Au residue may break off from the metal layer 36b and adhere to the second excitation electrode 112 after the frequency adjustment of the crystal oscillator 100 is completed, which may undesirably shift the frequency of the crystal oscillator 100.

[0089] Such Au residue is caused by uneven evaporation of Au in the irradiation line during laser scanning, resulting in molten Au remaining in a bridge shape (Au bridge is generated). That is, even if the Au bridge generated in the irradiation line during laser scanning is finally eliminated, Au residue tends to remain at the ends of the Au bridge.

[0090] On the other hand, in the frequency adjustment metal film 36 of Fig. 16, at least a part of the laser spot SP includes the exposed portion 361, and by performing laser scanning along the exposed portion 361, the generation of Au bridges in the irradiation line during laser scanning can be avoided. As a result, the generation of Au residue can also be avoided. If the generation of Au residue can be avoided, it is possible to prevent the Au residue from breaking off from the metal layer 36b and adhering to the second excitation electrode 112.

[0091] 〔Third Embodiment〕 Since the basic structure of the crystal oscillator 100 according to this embodiment is similar to those of the first and second embodiments, hereinafter, the description of the same configurations as those in the first and second embodiments will be omitted, and only the characteristic parts in this embodiment will be described.

[0092] FIG. 18 is a schematic plan view of the first main surface 301 side of the second sealing member 30 of the crystal oscillator 100 according to the present embodiment. FIG. 19 is a schematic cross-sectional view schematically showing a frequency adjustment method of the crystal oscillator 100 according to the present embodiment. As shown in FIGS. 18 and 19, in the present embodiment, the frequency adjustment metal film 36 has a multilayer structure made of two or more kinds of metals having different melting temperatures (melting points), and in the example shown in FIG. 19, it has a three-layer structure. Specifically, the frequency adjustment metal film 36 includes a base metal layer 36a, a first metal layer 36b laminated on the base metal layer 36a, and a second metal layer 36e laminated on the first metal layer 36b. The first metal layer 36b here corresponds to the metal layer 36b in the second and third embodiments.

[0093] The melting temperature of the second metal layer 36e is higher than that of the first metal layer 36b. The second metal layer 36e may be formed of the same material as the base metal layer 36a, or the base metal layer 36a and the second metal layer 36e may be formed of, for example, W (tungsten). Note that the second metal layer 36e may be formed of a material different from that of the base metal layer 36a. For example, the base metal layer 36a may be formed of W (tungsten), and the second metal layer 36e may be formed of any of Mo (molybdenum), Ta (tantalum), and Re (rhenium).

[0094] An opening is formed in the frequency adjustment metal film 36, and a part of the base metal layer 36a is exposed without being covered by the first and second metal layers 36b and 36e. As shown in FIGS. 19 to 21, the first and second metal layers 36b and 36e each have openings 361a and 361b, and the openings 361a and 361b of the first and second metal layers 36b and 36e communicate with each other so that the base metal layer 36a is exposed. Specifically, by the openings 361a and 361b of the first and second metal layers 36b and 36e communicating with each other, a base metal exposed portion is formed in which a part of the base metal layer 36a is exposed without being covered by the first and second metal layers 36b and 36e. Further, due to the opening 361b of the second metal layer 36e, a first metal exposed portion is formed in which a part of the first metal layer 36b is exposed without being covered by the second metal layer 36e.

[0095] In a plan view, the exposed base metal portion of the base metal layer 36a and the exposed first metal portion of the first metal layer 36b extend linearly. And, between the exposed base metal portion of the base metal layer 36a and the second metal layer 36e, the exposed first metal portion of the first metal layer 36b is provided. Specifically, the exposed first metal portions of the first metal layer 36b are provided on both the left and right sides sandwiching the exposed base metal portion of the base metal layer 36a. Further, the second metal layer 36e is provided on both the left and right sides sandwiching the exposed base metal portion of the base metal layer 36a and the exposed first metal portions of the first metal layer 36b on both the left and right sides thereof. The exposed base metal portion of the base metal layer 36a and the exposed first metal portions of the first metal layer 36b are formed at a plurality of locations with a predetermined interval therebetween. And, along the exposed base metal portion of the base metal layer 36a and the exposed first metal portions of the first metal layer 36b, laser irradiation to the frequency adjustment metal film 36 is performed.

[0096] Next, a frequency adjustment method of the crystal oscillator 100 according to the present embodiment will be described. Since the frequency adjustment method of the present embodiment is similar to the frequency adjustment methods described in the first and second embodiments, the description of the same points as those in the first and second embodiments will be omitted, and only the different points will be described.

[0097] In the present embodiment, as shown in FIG. 19, a laser is irradiated to the frequency adjustment metal film 36 from the outside of the second sealing member 30, and the laser is transmitted through the inside of the second sealing member 30 to heat the base metal layer 36a, so that at least a part of the first metal layer 36b is evaporated (vaporized) by melting, and the evaporated metal is adhered to the second excitation electrode 112 to perform frequency adjustment. That is, the first metal layer 36b above the base metal layer 36a is melted by the laser and evaporated from the opening 361b. That is, the metal evaporated from the first metal layer 36b adheres to the second excitation electrode 112. On the other hand, since the melting temperature of the second metal layer 36e above the first metal layer 36b is higher than that of the first metal layer 36b, it remains in a solid state with little melting.

[0098] Laser irradiation of the metal film 36 for frequency adjustment is performed by linearly irradiating while sweeping the laser spot SP. As shown in FIG. 20, by arranging the irradiation lines LN formed by sweeping the laser spot SP in parallel, laser irradiation is performed on a desired region of the metal film 36 for frequency adjustment. At this time, the sweeping direction (direction of arrow A) of the laser spot SP is the same for all the irradiation lines LN, and each irradiation line LN is set along the base metal exposed portion of the base metal layer 36a and the first metal exposed portion of the first metal layer 36b. Specifically, the irradiation line LN is a line along the approximate center (approximate center of the line width W1) of the base metal exposed portion of the base metal layer 36a, and is also a line along the approximate center (approximate center of the line width W2) of the first metal exposed portion of the first metal layer 36b.

[0099] The sweeping of the laser spot SP is repeated a plurality of times for each irradiation line LN. After performing laser sweeping a plurality of times for one irradiation line LN, laser sweeping is performed on the adjacent irradiation line LN. The pitch P1 of the laser sweeping (interval in the direction orthogonal to the sweeping direction) is set to be larger than the diameter (irradiation diameter) D1 of the laser spot SP (P1 > D1), so that the adjacent irradiation lines LN do not interfere with each other (do not overlap) in a plan view. Also, the line width W1 of the base metal exposed portion of the base metal layer 36a and the line width W2 of the first metal exposed portion of the first metal layer 36b are set to be smaller than the irradiation diameter D1 of the laser spot SP (W1 < D1 and W2 < D1), so that the first metal layer 36b is heated on both sides of the laser spot SP to be swept.

[0100] By irradiating the metal film 36 for frequency adjustment with a laser, the underlying metal layer 36a is heated, and the first metal layer 36b above the underlying metal layer 36a melts and evaporates. At this time, a part of the melted first metal layer 36b may flow outside the laser irradiation range. However, in the present embodiment, as shown in FIG. 21, even if a part of the melted first metal layer 36b flows outward from the laser irradiation range, it adheres to the side surface of the first metal layer 36b that has not melted and the end portion of the second metal layer 36e, and becomes solidified metal 36f. Specifically, the first metal layer 36b with the second metal layer 36e on the upper side warms up more gently than the first metal layer 36b without the second metal layer 36e on the upper side, so it is less likely to melt. Then, the second metal layer 36e serves as a stopper for the first metal layer 36b that has melted and is about to flow outside the laser irradiation range, so that it is possible to suppress the flow of the first metal layer 36b outside the laser irradiation range, and the melted first metal layer 36b can be retained within the laser irradiation range (within the laser spot SP). As a result, the heat of the laser irradiation can be efficiently transmitted to the melted first metal layer 36b retained within the laser irradiation range, and it is possible to suppress a decrease in the frequency adjustment amount caused by a part of the melted first metal layer 36b flowing outside the laser irradiation range.

[0101] In addition, since the metal 36f adhering to the side surface of the first metal layer 36b and the end portion of the second metal layer 36e solidifies in a relatively stable shape, it is possible to suppress the metal 36f from scattering to the outside as foreign matter after the frequency adjustment.

[0102] Here, as shown in FIG. 22, in the metal film 36 for frequency adjustment, it is also possible to adopt a configuration in which the opening 361b is formed only in the second metal layer 36e and no opening is formed in the first metal layer 36b. That is, in the metal film 36 for frequency adjustment, due to the opening 361b of the second metal layer 36e, the first metal exposed portion of the first metal layer 36b is formed, but the underlying metal exposed portion of the underlying metal layer 36a is not formed. In this case, by laser irradiation on the metal film 36 for frequency adjustment, the underlying metal layer 36a is heated, and the first metal layer 36b of the first metal exposed portion melts and evaporates. Then, by attaching the molten first metal layer 36b that tries to flow outward of the laser irradiation range to the first metal layer 36b that has not melted and the second metal layer 36e, it is possible to suppress the molten first metal layer 36b from flowing outside the laser irradiation range, and the molten first metal layer 36b can be retained within the laser irradiation range (within the laser spot SP). In addition, the processing step of forming an opening in the first metal layer 36b becomes unnecessary, and the formation process of the metal film 36 for frequency adjustment can be simplified. Furthermore, a wider area of the first metal layer 36b available for frequency adjustment can be ensured.

[0103] In addition, when the second metal layer 36e is formed of a metal different from the underlying metal layer 36a, if the second metal layer 36e is formed of a material with a large specific heat or a high thermal conductivity, the heat absorption effect by the second metal layer 36e can be improved. For example, by forming the second metal layer 36e of Mo (molybdenum) and the underlying metal layer 36a of W (tungsten), the heat absorption effect by the second metal layer 36e can be enhanced.

[0104] On the other hand, when the second metal layer 36e is formed of the same metal as the underlying metal layer 36a, the formation process of the metal film 36 for frequency adjustment can be simplified, and the productivity can be improved. For example, by forming both the second metal layer 36e and the underlying metal layer 36a of W (tungsten), it becomes unnecessary to consider the melting of the second metal layer 36e, and stable frequency adjustment can be performed.

[0105] As a modification, the second sealing member 30 may not be provided with the frequency adjustment metal film, and the frequency adjustment metal film may be provided on the second main surface 202 facing the first excitation electrode 111 of the first sealing member 20. Alternatively, as shown in FIG. 23, 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 structure in which a base metal layer 26a, a first metal layer 26b, and a second metal layer 26e are laminated, similar to the frequency adjustment metal film 36 of the second sealing member 30 in the present embodiment.

[0106] 〔Fourth Embodiment〕 The frequency adjustment metal films 26 and 36 described in the first to third embodiments may be electrically connected to electrodes and wirings to which a ground potential (GND) is applied during the operation of the crystal oscillator. A configuration example of the crystal oscillator 100 in which the frequency adjustment metal films 26 and 36 can be connected to GND will be described with reference to FIGS. 24 to 28. FIG. 24 is a schematic plan view of the crystal oscillator 100 on the side of the second main surface 202 of the first sealing member 20. FIG. 25 is a schematic plan view of the first main surface 101 side of the crystal vibration plate 10 of the crystal oscillator 100. FIG. 26 is a schematic plan view of the second main surface 102 side of the crystal vibration plate 10 of the crystal oscillator 100. FIG. 27 is a schematic plan view of the first main surface 301 side of the second sealing member 30 of the crystal oscillator 100. FIG. 28 is a schematic plan view of the second main surface 302 side of the second sealing member 30 of the crystal oscillator 100.

[0107] Note that the wiring and electrodes of the crystal oscillator 100 described in the first to third embodiments are designed on the premise that an IC chip for constituting a crystal oscillator together with the crystal oscillator 100 is mounted on the first sealing member 20. On the other hand, the crystal oscillator 100 shown in FIGS. 24 to 28 is not premised on mounting an IC chip on the first sealing member 20, and the design of the wiring and electrodes is different from that of the first to third embodiments. However, in the following description, members having the same functions as the crystal oscillator 100 described in the first to third embodiments will be described with the same member numbers.

[0108] In the crystal oscillator 100 of the present embodiment, on the second main surface 302 of the second sealing member 30, it is assumed that the external electrode terminal 32A arranged in the upper right of FIG. 28 is an electrode connected to GND. This external electrode terminal 32A is connected to the second bonding pattern 31 on the first main surface 301 of the second sealing member 30 via the through hole 33A (see FIGS. 27 and 28). Further, the second bonding pattern 31 on the sealing member side is integrated with the second bonding pattern 122 on the diaphragm side formed on the second main surface 102 side of the crystal diaphragm 10 by bonding the second sealing member 30 and the crystal diaphragm 10.

[0109] In the crystal diaphragm 10, the second bonding pattern 122 on the diaphragm side formed on the second main surface 102 side and the first bonding pattern 121 on the diaphragm side formed on the first main surface 101 side are electrically connected. The electrical connection between the second bonding pattern 122 on the diaphragm side and the first bonding pattern 121 on the diaphragm side can be achieved, for example, by forming a metal film on the inner wall surface of the crystal diaphragm 10 (for example, the inner wall surface in the region A of FIGS. 25 and 26). Further, the first bonding pattern 121 on the diaphragm side is integrated with the first bonding pattern 24 on the sealing member side formed on the second main surface 202 side of the first sealing member 20 by bonding the crystal diaphragm 10 and the first sealing member 20.

[0110] As described above, in the crystal oscillator 100 of the present embodiment, an electrical path is formed in the order of the external electrode terminal 32A, the through hole 33A, the second bonding pattern 31 on the sealing member side, the second bonding pattern 122 on the diaphragm side, the first bonding pattern 121 on the diaphragm side, and the first bonding pattern 24 on the sealing member side, and a ground potential can be applied to this electrical path.

[0111] When the frequency adjustment metal film 26 is formed on the second main surface 202 of the first sealing member 20, as shown in FIG. 24, the frequency adjustment metal film 26 and the sealing member side first bonding pattern 24 are connected by a connection wiring 26c. In this case, the connection wiring 26c can be formed simultaneously with, for example, the base metal layer 26a of the frequency adjustment metal film 26. When the frequency adjustment metal film 36 is formed on the first main surface 301 of the second sealing member 30, as shown in FIG. 27, the frequency adjustment metal film 36 and the sealing member side second bonding pattern 31 are connected by a connection wiring 36c. In this case, the connection wiring 36c can be formed simultaneously with, for example, the base metal layer 36a of the frequency adjustment metal film 36.

[0112] In this way, by connecting the frequency adjustment metal films 26 and 36 to GND, it becomes possible to use the frequency adjustment metal films 26 and 36 as shields for ESD (high-frequency noise) countermeasures.

[0113] 〔Fifth Embodiment〕 In the above first to fourth embodiments, the crystal oscillator 100 having a three-layer structure in which the crystal resonator plate 10 is sandwiched between the first sealing member 20 and the second sealing member 30 is used, but a crystal oscillator having a different structure may also be used. For example, a crystal oscillator having a structure in which a crystal resonator plate is housed inside a base made of an insulating material such as ceramic, glass, or crystal having a recess, and a lid is joined to the base may be used.

[0114] FIG. 29 is a schematic configuration diagram schematically showing each configuration of a crystal oscillator (piezoelectric vibration device) 400 according to this embodiment. As shown in FIG. 29, the crystal oscillator 400 has a structure in which a crystal resonator plate (vibration part) 60 is housed inside a base 40 having a recess 401, and a lid 50 is joined to the base 40. First excitation electrodes 601 and second excitation electrodes 602 are formed on each of the two main surfaces of the crystal resonator plate 60.

[0115] In the crystal oscillator 400, a frequency adjustment metal film 51 is formed on the back surface of the lid 50 serving as a sealing member (the surface facing the base 40). Similar to the frequency adjustment metal film 36 of the first embodiment, the frequency adjustment metal film 51 includes a base metal layer 51a and a metal layer 51b. The lid 50 is made of a material with high transmittance to laser (such as crystal or glass). After the lid 50 is joined to the base 40 to seal the crystal diaphragm 60 in the package, the base metal layer 51a can be heated by laser irradiation from the surface of the lid 50 (the surface not facing the base 40).

[0116] Thus, also in the crystal oscillator 400, by irradiating the frequency adjustment metal film 51 with a laser from outside the base 40, transmitting the laser through the inside of the base 40 to heat the base metal layer 51a, at least a part of the metal layer 51b is evaporated (vaporized) by melting, and the evaporated metal is adhered to the excitation electrode (in this example, the first excitation electrode 601) to perform frequency adjustment.

[0117] All the embodiments disclosed this time are illustrative in all respects and do not serve as a basis for a limiting interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiments, but is defined based on the description in the claims. Also, all changes within the meaning and scope equivalent to the claims are included.

[0118] This application claims priority based on Japanese Patent Application No. 2022-023223 filed in Japan on February 17, 2022. By referring to this, all its contents are incorporated into this application.

Explanation of Reference Numerals

[0119] 10 Crystal diaphragm 11 Vibration part 20 First sealing member (sealing member) 30 Second sealing member (sealing member) 36, 51 Frequency adjustment metal film 36a, 51a Base metal layer 36b, 51b metal layer 100, 400 crystal oscillator (piezoelectric vibration device) 111, 601 first exciting electrode 112, 602 second exciting electrode 301 first main surface 40 base 50 lid (sealing member) 60 crystal vibrating plate (vibrating part)

Claims

1. A method for adjusting the frequency of a piezoelectric vibration device in which a vibrating portion formed with an exciting electrode is hermetically sealed by a sealing member, comprising: A frequency adjustment metal film composed of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the exciting electrode; Irradiating the frequency adjustment metal film with a beam from outside the sealing member, transmitting the beam through the inside of the sealing member to heat the base metal layer, and evaporating at least a part of the metal layer by melting and attaching it to the exciting electrode to perform frequency adjustment; The method for adjusting the frequency of a piezoelectric vibration device, wherein the irradiation of the beam is started from at least outside the region of the metal layer, and in the scanning direction of the beam, the length of the base metal layer is made larger than the length of the metal layer, and the end of the metal layer is arranged inside the end of the base metal layer.

2. The method for adjusting the frequency of a piezoelectric vibration device according to Claim 1, comprising: The frequency adjustment metal film has an exposed portion where a part of the base metal layer is not covered with the metal layer and is exposed; The exposed portion is formed linearly, and the beam is irradiated along the line of the exposed portion. The method for adjusting the frequency of a piezoelectric vibration device is characterized by this.

3. The method for adjusting the frequency of a piezoelectric vibration device according to Claim 1 or 2, comprising: Melting the metal layer by irradiating the beam so as not to penetrate the base metal layer. The method for adjusting the frequency of a piezoelectric vibration device is characterized by this.

4. A piezoelectric vibration device in which a vibrating portion formed with an exciting electrode is hermetically sealed by a sealing member, comprising: A frequency adjustment metal film composed of a base metal layer and a metal layer laminated thereon is formed on a main surface of the sealing member facing the exciting electrode; In the frequency adjustment metal film, in at least one direction in plan view, the length of the base metal layer is made larger than the length of the metal layer, and the end of the metal layer is arranged inside the end of the base metal layer. The piezoelectric vibration device is characterized by this.

5. The piezoelectric vibration device according to Claim 4, comprising: At least the metal layer is formed to have the same size as the exciting electrode in plan view or smaller than the exciting electrode. The piezoelectric vibration device is characterized by this.

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