Frequency adjusting method for piezoelectric vibration device, and piezoelectric vibration device

Abstract

In a frequency adjusting method for a crystal oscillator (100) in which a frequency adjustment metal film (40) comprising a base metal layer (41) and a metal layer (42) is formed on a first main surface (301) facing a second excitation electrode (112) of a second sealing member (30), the second sealing member (30) is made of crystal, a plurality of recesses (30a) are formed on the first main surface (301) of the second sealing member (30), and the frequency adjustment metal film (40) extends to the recesses (30a), the frequency adjustment is performed by irradiating the frequency adjustment metal film (40) with a laser from the outside of the second sealing member (30), transmitting the laser through the inside of the second sealing member (30) and heating the base metal layer (41) to cause at least a part of the metal layer (42) to evaporate through melting, and attaching the metal layer (42) to the second excitation electrode (112).

Description

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

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

[0002] 2. Description of the Related Art Conventionally, a manufacturing process for 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).

[0003] When performing a frequency adjustment process after sealing the vibration portion of a quartz crystal plate with a sealing member, a laser beam or other beam is irradiated from outside the quartz crystal unit. In this case, if the beam output is too high, the excitation electrode of the vibration portion may be damaged. To address this issue, a method has been proposed in which a frequency adjustment metal film consisting of a base metal layer and a metal layer laminated thereon is provided on the sealing member sealing the excitation electrode of the vibration portion, and the base metal layer is heated by beam irradiation to evaporate (vaporize) the metal layer, and the evaporated metal is then deposited on the excitation electrode, thereby performing frequency adjustment (see, for example, Patent Document 2). However, as the beam irradiation is accumulated, the molten metal may gradually move outside the beam irradiation range, which may reduce the amount of frequency adjustment and make it difficult to reproducibly perform frequency adjustment.

[0004] Patent No. 5762811 International Publication No. 2023 / 054200

[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 easily ensure the amount of frequency adjustment and perform stable frequency adjustment.

[0006] The present invention provides a means for solving the above-described 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 diaphragm having a vibration portion on which excitation electrodes are formed is hermetically sealed by a sealing member, the method comprising: forming a frequency-adjusting metal film made of a base metal layer and a metal layer laminated on the base metal layer on a main surface of the sealing member facing the excitation electrodes; 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 on which the frequency-adjusting metal film is formed has a plurality of recesses formed therein, the frequency-adjusting metal film extending into these recesses; irradiating the frequency-adjusting metal film with a beam from outside the sealing member, transmitting the beam through the interior of the sealing member to heat the base metal layer, thereby melting and vaporizing at least a portion of the metal layer, and attaching the metal layer to the excitation electrodes, 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, increasing the mass of the excitation electrode and shifting the frequency to a lower level. During this process, the metal of the molten metal layer can be retained within the recesses by irradiating the beam. This prevents the metal of the molten metal layer from moving outside the beam irradiation range, thereby preventing a decrease in the frequency adjustment amount and enabling stable frequency adjustment. Furthermore, since multiple recesses are formed, the surface area can be increased compared to when a single recess is formed, improving the evaporation efficiency of the metal of the metal layer.

[0008] In the above-described frequency adjustment method for a piezoelectric vibration device, it is preferable that the opening diameter of the recess is smaller than the irradiation diameter of the beam, and the beam is irradiated so as to encompass the recess in a planar view. In this way, by making the opening diameter of the recess smaller than the irradiation diameter of the beam, it is possible to prevent the beam from irradiating only part of the recess. Since the beam is irradiated so as to encompass the recess in a planar view, the entire recess is located within the irradiation area of ​​the beam, thereby stabilizing the frequency adjustment rate.

[0009] In the above-described method for adjusting the frequency of a piezoelectric vibrating device, it is preferable that the frequency-adjusting metal film is formed along the inner surface of the recess, so that the surface of the frequency-adjusting metal film becomes uneven along the recess, making it easier to retain the metal melted by beam irradiation within the recess.

[0010] In the method for adjusting the frequency of a piezoelectric vibration device, the inner wall surface of the recess is preferably an inclined surface, which makes it easier for the molten metal to remain at the bottom side of the recess.

[0011] In the above-described frequency adjustment method for a piezoelectric vibrating device, the recess preferably has a flat bottom. This allows the beam energy per unit area of ​​the irradiated surface to be smaller on the inclined surface than on the flat bottom, resulting in a relatively low temperature on the inclined surface. As a result, the molten metal near the boundary between the inclined surface and the flat bottom cools and solidifies, and tends to remain in the recess.

[0012] In the method for adjusting the frequency of a piezoelectric vibration device, it is preferable that a plurality of boundary lines are formed on the inner wall surface of the recess, so that the presence of such boundary lines makes it easier for the molten metal to remain on the inner wall surface of the recess.

[0013] In the above-described frequency adjustment method for a piezoelectric vibration device, it is preferable that the multiple recesses are aligned in a plan view. By providing multiple recesses in this way, the surface area can be increased, and the evaporation efficiency of the metal in the metal layer can be improved. This prevents a decrease in the frequency adjustment amount, and enables stable frequency adjustment.

[0014] In the above-described frequency adjustment method for a piezoelectric vibration device, it is preferable that a large number of recesses are provided, and that multiple regions with different numbers of recesses per unit area (formation density) are provided. By providing a large number of recesses in this manner, the surface area of ​​the frequency-adjusting metal film can be increased, thereby improving the evaporation efficiency of the metal in the metal layer. Furthermore, by providing two or more regions with different recess formation densities, more flexible frequency adjustment can be achieved. For example, in a dense region where the recess formation density is relatively high, the surface area of ​​the frequency-adjusting metal film is increased, thereby increasing the evaporation efficiency of the metal in the metal layer, thereby increasing the frequency adjustment amount and enabling efficient frequency adjustment. In a sparse region where the recess formation density is relatively low, the increase in the surface area of ​​the frequency-adjusting metal film is suppressed, thereby suppressing the evaporation efficiency of the metal in the metal layer and suppressing the frequency adjustment amount, thereby enabling fine adjustment of the frequency adjustment amount.

[0015] In the above-described method for adjusting the frequency of a piezoelectric vibration device, the number of recesses formed per unit area of ​​the sealing member is 1500 to 15000 / mm 2 In this way, by providing a large number of recesses, the surface area can be increased, and the evaporation efficiency of the metal in the metal layer can be improved. This makes it possible to prevent a decrease in the amount of frequency adjustment, and to perform stable frequency adjustment.

[0016] In the method for adjusting the frequency of a piezoelectric vibrating device, it is preferable that the opening diameter of the recess is larger than the depth of the recess, thereby making it possible to form a shallow recess with a desired opening diameter, thereby suppressing a decrease in the rigidity of the sealing member.

[0017] The present invention also provides a piezoelectric vibration device in which at least the 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 consisting of a base metal layer and a metal layer laminated on the base metal layer is formed on a main surface of the sealing member facing the excitation electrode, a plurality of recesses are formed on the main surface of the sealing member on which the frequency-adjusting metal film is formed, the frequency-adjusting metal film extends into these recesses, a plurality of recesses are formed in the frequency-adjusting metal film, and the bottom surfaces of the recesses in the frequency-adjusting metal film are in a state where the base metal layer is exposed.

[0018] According to the piezoelectric vibration device, the metal base layer on the bottom surface of the recess provided in the frequency-adjusting metal film functions as a getter material, allowing the metal base layer to capture gas generated in the internal space of the piezoelectric vibration device. Furthermore, by forming multiple recesses, the exposed area of ​​the metal base layer is increased, thereby further improving the efficiency of capturing gas generated in the internal space of the piezoelectric vibration device. Materials for such a metal base layer are preferably tungsten, titanium, or the like. This makes it possible to suppress changes in the frequency of the piezoelectric vibration device over time due to gas generation.

[0019] In the above-mentioned piezoelectric vibration device, a first sealing member covers the first main surface side of the vibration portion of the piezoelectric vibration plate, and a second sealing member covers the second main surface side of the vibration portion of the piezoelectric vibration plate, and the first sealing member and the piezoelectric vibration plate are bonded together, thereby hermetically sealing the vibration portion of the piezoelectric vibration plate, and it is preferable that the sealing member on which the frequency adjustment metal film is formed is made of quartz. In this way, a piezoelectric vibration device with a three-layer structure can be made smaller and thinner, and in such a small and thin piezoelectric vibration device, changes in frequency over time can be suppressed.

[0020] According to the frequency adjustment method for a piezoelectric vibration device of the present invention, the metal layer above the base metal layer is melted and evaporated, and the evaporated metal adheres to the excitation electrode, increasing the mass of the excitation electrode and shifting the frequency to a lower level. During this process, the metal of the metal layer melted by the beam irradiation can be retained within the recess. This prevents the metal of the melted metal layer from moving outside the beam irradiation range, thereby preventing a decrease in the frequency adjustment amount and enabling stable frequency adjustment. Furthermore, since multiple recesses are formed, the surface area can be increased compared to when a single recess is formed, improving the evaporation efficiency of the metal of the metal layer.

[0021] Furthermore, according to the piezoelectric resonator device of the present invention, the metal underlayer on the bottom surface of the recess provided in the frequency-adjusting metal film functions as a getter material, so that gas generated in the internal space of the piezoelectric resonator device can be captured by the metal underlayer, thereby suppressing changes in the frequency of the piezoelectric resonator device over time due to gas generation.

[0022] 1. is a schematic configuration diagram showing each component of a crystal oscillator according to a first embodiment. 1. is a schematic plan view of the first main surface side of a first sealing member of the crystal oscillator of FIG. 1. 2. is a schematic plan view of the second main surface side of the first sealing member of the crystal oscillator of FIG. 1. 3. is a schematic plan view of the first main surface side of a crystal diaphragm of the crystal oscillator of FIG. 1. 4. is a schematic plan view of the second main surface side of the crystal diaphragm of the crystal oscillator of FIG. 1. 5. is a schematic plan view of the first main surface side of a second sealing member of the crystal oscillator of FIG. 1. 6. is a schematic plan view of the second main surface side of the second sealing member of the crystal oscillator of FIG. 1. 7. is a schematic cross-sectional view showing a frequency adjustment method of the crystal oscillator according to the first embodiment. 8. is a schematic diagram showing an enlarged view of a main part of FIG. 9. is a schematic diagram showing the frequency adjustment method. 9. is a schematic configuration diagram showing each component of a crystal oscillator according to a second embodiment. 10. is a schematic plan view of the first main surface side of the first sealing member of the crystal oscillator of FIG. 11. 11. is a schematic plan view of the second main surface side of the first sealing member of the crystal oscillator of FIG. 11. 12 is a schematic plan view of the first main surface side of the crystal vibration plate of the crystal oscillator of Figure 11. FIG. 13 is a schematic plan view of the second main surface side of the crystal vibration plate of the crystal oscillator of Figure 11. FIG. 14 is a schematic plan view of the first main surface side of the second sealing member of the crystal oscillator of Figure 11. FIG. 15 is a schematic plan view of the second main surface side of the second sealing member of the crystal oscillator of Figure 11. FIG. 16 is a schematic cross-sectional view schematically showing a method for adjusting the frequency of a crystal oscillator according to a second embodiment. FIG. 17 is a schematic cross-sectional view schematically showing a method for adjusting the frequency of a crystal oscillator according to Modification 1. FIG. 18 is a view corresponding to Figure 6 showing a frequency-adjusting metal film used in a method for adjusting the frequency of a crystal oscillator according to Modification 2. FIG. 19 is a view corresponding to Figure 6 showing a frequency-adjusting metal film used in a method for adjusting the frequency of a crystal oscillator according to Modification 3. FIG. 19 is a view corresponding to Figure 6 showing a frequency-adjusting metal film used in a method for adjusting the frequency of a crystal oscillator according to Modification 4.

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a case where a quartz crystal resonator device to which the present invention is applied is described as a quartz crystal oscillator (first embodiment) and a case where a quartz crystal resonator device to which the present invention is applied is described as a quartz crystal resonator (second embodiment).

[0024] First Embodiment First, the basic structure of a crystal oscillator 100 according to the first embodiment will be described. As shown in FIG. 1 , the crystal oscillator 100 includes a crystal diaphragm (piezoelectric diaphragm) 10, a first sealing member 20, a second sealing member 30, and an IC chip 51. In this crystal oscillator 100, the crystal diaphragm 10 is bonded to the first sealing member 20, and the crystal diaphragm 10 is bonded to the second sealing member 30 to form a package with a substantially rectangular sandwich structure. An IC chip 51 is mounted on a first main surface 201 of the first sealing member 20, opposite the surface bonded to the crystal diaphragm 10. The IC chip 51, which serves as an electronic component, is a one-chip integrated circuit element that, together with the crystal diaphragm 10, forms an oscillation circuit.

[0025] In the quartz crystal vibration plate 10, a first excitation electrode 111 is formed on one of the principal surfaces, that is, a first principal surface 101, and a second excitation electrode 112 is formed on the other principal surface, that is, a second principal surface 102. In the quartz crystal oscillator 100, a first sealing member 20 and a second sealing member 30 are bonded to both of the principal surfaces (first principal surface 101, second principal surface 102) of the quartz crystal vibration plate 10, respectively, to form an internal space of the package, and the vibrating part 11 (see FIGS. 4 and 5 ) including the first excitation electrode 111 and the second excitation electrode 112 is hermetically sealed in the internal space.

[0026] The crystal oscillator 100 has a package size of, for example, 1.0 x 0.8 mm, and is designed to be compact and low-profile. To accommodate the miniaturization, the package does not have castellations (side electrodes provided in cutouts on the side of the package), but instead uses through-holes (described below) to ensure electrode continuity. The crystal oscillator 100 is also designed to be electrically connected to an external circuit board (not shown) via solder.

[0027] Next, the crystal plate 10, the first sealing member 20, and the second sealing member 30 of the crystal oscillator 100 will be described using Figures 1 to 7. Note that the description here focuses on each component that is configured as a single unit and not bonded together. Figures 2 to 7 merely show one example configuration of the 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.

[0028] As shown in Figures 4 and 5, the quartz crystal vibrating plate 10 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. An AT-cut quartz crystal plate that vibrates in thickness-shear vibration is used as the quartz crystal vibrating plate 10. In the quartz crystal vibrating plate 10 shown in Figures 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.

[0029] A pair of excitation electrodes (first excitation electrode 111 and second excitation electrode 112) are formed on both main surfaces 101 and 102 of the quartz crystal vibration plate 10. The quartz crystal vibration plate 10 includes a substantially rectangular vibrating portion 11, an outer frame portion 12 surrounding the outer periphery of the vibrating portion 11, and a holding portion (connecting portion) 13 that connects the vibrating portion 11 to the outer frame portion 12 and holds the vibrating portion 11. 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) from only one corner of the vibrating portion 11 located in the +X direction and the -Z' direction toward the outer frame portion 12 in the -Z' direction. A through-hole (slit) is provided between the vibrating portion 11 and the outer frame portion 12, penetrating the quartz crystal vibration plate 10 in the thickness direction. In this embodiment, the quartz crystal vibration plate 10 has only one holding portion 13 that connects the vibration portion 11 and the outer frame portion 12, and the through portion is formed continuously to surround the outer periphery of the vibration portion 11.

[0030] 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) for connecting these excitation electrodes to external electrode terminals is connected to the first excitation electrode 111 and the second excitation electrode 112. 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.

[0031] Both main surfaces (first main surface 101, second main surface 102) of the quartz crystal vibration plate 10 are provided with diaphragm-side sealing portions for bonding the quartz crystal vibration 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.

[0032] As shown in FIGS. 4 and 5 , the quartz crystal vibration plate 10 has five through holes formed 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 vibration 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. Furthermore, a connection bonding pattern 124 is formed on the first main surface 101 side around the second through hole 162, and a connection bonding pattern 15 is formed on the second main surface 102 side around the second through hole 162.

[0033] 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 are 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).

[0034] 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 portion, 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 in the quartz crystal oscillator 100. The X-axis, Y-axis, and Z'-axis of the first sealing member 20 are also oriented in the same directions as those of the quartz crystal vibrating plate 10.

[0035] 2, six electrode patterns 22 including mounting pads for mounting an IC chip 51, which is an oscillation circuit element, are formed on a first main surface 201 (the outer main surface that does not face the quartz crystal vibration plate 10) of the first sealing member 20. The oscillation IC 51 is bonded to the electrode patterns 22 using metal bumps (e.g., Au bumps) 52 (see FIG. 1) by FCB (Flip Chip Bonding).

[0036] 2 and 3, six through holes are formed in the first sealing member 20, which are connected to the six electrode patterns 22, respectively, and which penetrate between the first main surface 201 and the second main surface 202. Specifically, four third through holes 211 are provided in the four corner regions of the first sealing member 20. Fourth and fifth through holes 212, 213 are provided in the +Z' direction and the -Z' direction in FIGS. 2 and 3, respectively.

[0037] In the third through hole 211 and the fourth and fifth through holes 212, 213, through electrodes for achieving 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. In addition, the central portions of the third through hole 211 and the fourth and fifth through holes 212, 213 are hollow through portions that penetrate between the first main surface 201 and the second main surface 202.

[0038] 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 vibration plate 10. The sealing member-side first bonding pattern 24 is formed in a ring 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 first sealing member 20 in the longitudinal direction (the -Z' direction side) from 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 periphery of the sealing member-side first bonding pattern 24 is located close to the outer periphery of the second main surface 202 of the first sealing member 20.

[0039] 6 and 7, the second sealing member 30 is a rectangular parallelepiped substrate formed from a single AT-cut quartz plate, which is a light-transmitting material, and the first main surface 301 (the surface that bonds to the quartz plate 10) and the second main surface 302 (the outer main surface that does not face the quartz plate 10) of this second sealing member 30 are formed into flat, smooth surfaces by polishing (mirror finishing). Note that the second sealing member 30 also uses an AT-cut quartz plate like the quartz plate 10, and it is desirable that the orientation of the X-axis, Y-axis, and Z'-axis be the same as that of the quartz plate 10.

[0040] 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 vibration plate 10. The sealing member-side second bonding pattern 31 is formed in a ring 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.

[0041] Furthermore, a frequency-adjusting metal film 40 used for adjusting the frequency of the crystal oscillator 100 is formed on the first main surface 301 of the second sealing member 30. A large number of recesses 40a are formed on the surface of the frequency-adjusting metal film 40, and these recesses 40a are regularly arranged at predetermined intervals in a plan view.

[0042] The frequency-adjusting metal film 40 has a two-layer structure made of two types of metal with different melting temperatures (melting points), and as shown in Figures 8 to 10, includes a base metal layer 41 and a metal layer 42 laminated on the base metal layer 41. The base metal layer 41 is made of, for example, W (tungsten), and the metal layer 42 is made of the same material (for example, Au) as the second excitation electrode 112. Note that the recess 40a is not shown in Figure 8.

[0043] Specifically, as shown in FIG. 9 , a number of recesses 30a each having a substantially circular shape in plan view are formed on the first main surface 301 of the second sealing member 30, inward of the sealing member-side second bonding pattern 31. The recesses 30a are processed by wet etching so as to be recessed into a substantially truncated cone shape relative to the first main surface 301 of the second sealing member 30. The inner bottom surface 30b of each recess 30a is formed as a flat surface, and the inner peripheral surface (inner wall surface) 30c of each recess 30a is formed as an inclined surface. The opening diameter D2 of each recess 30a is, for example, 6 μm, and the depth of each recess 30a is, for example, 2 μm, such that the opening diameter D2 of each recess 30a is larger than the depth of each recess 30a. A plurality of boundary lines are formed on the inner wall surface 30c of each recess 30a by wet etching. When the recess 30a is formed by wet etching, multiple crystal planes inclined at angles specific to the crystal axes of the quartz due to the anisotropy of the AT-cut quartz appear on the inner wall surface 30c of the recess 30a. The intersections of these multiple crystal planes form boundaries.

[0044] The base metal layer 41 and metal layer 42 of the frequency adjustment metal film 40 are deposited along the inner bottom surface 30b and inner wall surface 30c of each recess 30a, and the base metal layer 41 and metal layer 42 of the frequency adjustment metal film 40 extend into each recess 30a. A large number of recesses 40a appear on the surface of the metal layer 42 of the frequency adjustment metal film 40. Note that the number of recesses 30a is not particularly limited, as long as at least two recesses 30a are formed. Furthermore, the frequency adjustment metal film 40 is formed along the inner bottom surface 30b and inner wall surface 30c of each recess 30a, and the recesses 40a are formed on the surface of the frequency adjustment metal film 40. However, the frequency adjustment metal film 40 may be formed so as to fill (bury) the recesses 30a, so that the recesses 40a do not appear on the surface of the frequency adjustment metal film 40.

[0045] The shape of the recess 30a may be a substantially cylindrical shape without any inclined surfaces, or a substantially conical shape (V-shaped in cross section) without a flat inner bottom surface. The recess 30a may also be formed by a method other than wet etching, such as dry etching. When the recess 30a is formed by dry etching, the recess 30a may be formed into a substantially cylindrical shape without any inclined surfaces. On the other hand, when the recess 30a is formed by wet etching, the inner wall surface 30c of the recess 30a can be formed into a gently inclined surface. As described below, this can suppress a decrease in the amount of frequency adjustment by the laser and improve the reproducibility of frequency adjustment.

[0046] In the first main surface 301 of the second sealing member 30, the recesses 30a are regularly aligned in a plan view. In this embodiment, the recesses 30a are arranged in a staggered pattern in a plan view (see FIG. 6), but the recesses 30a may also be arranged in a matrix (regular lattice) in a plan view. When the recesses 30a are arranged in a staggered pattern, the formation density of the recesses 30a per unit area can be further increased. For example, when the number of recesses 30a formed per unit area (formation density) in the second sealing member 30 is 1500 / mm 2 ~15000 pieces / mm 2 It has become.

[0047] The thickness of the base metal layer 41 is, for example, 50 nm, and the thickness of the metal layer 42 is, for example, 100 nm. The thickness of the base metal layer 41 is preferably 50 to 500 nm, and the thickness of the metal layer 42 is preferably 50 to 500 nm. A thickness of the base metal layer 41 less than 50 nm is not preferred because it cannot withstand laser irradiation. A thickness of the base metal layer 41 greater than 500 nm is not preferred because the wafer warps, resulting in a thicker film and reduced production efficiency. A thickness of the metal layer 42 less than 50 nm is not preferred because the base metal layer 41 may be unintentionally corroded during the manufacturing process. A thickness of the metal layer 42 greater than 500 nm is not preferred because the wafer warps, resulting in a thicker film and reduced production efficiency.

[0048] In the frequency-adjusting metal film 40, the melting temperature of the base metal layer 41 is preferably higher than the melting temperature of the metal layer 42, and the difference in melting temperature between the base metal layer 41 and the metal layer 42 is preferably 1500°C or more. Furthermore, the metal layer 42 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 41 may be made of, for example, Mo (molybdenum: melting temperature 2623°C), Ta (tantalum: melting temperature 3020°C), or Re (rhenium: melting temperature 3186°C) instead of W (tungsten: melting temperature 3387°C). The metal layer 42 may have a multilayer structure made of multiple metal layers, in which case the topmost metal layer may be made of the same material (e.g., Au) as the second excitation electrode 112.

[0049] The frequency adjustment metal film 40 is provided at a position facing the second excitation electrode 112 at a predetermined interval. The distance in the vertical direction (Y-axis direction) between the second excitation electrode 112 and the frequency adjustment metal film 40 is 2 to 200 μm. The center (center of gravity) of the frequency adjustment metal film 40 is provided at a position that substantially coincides with the center (center of gravity) of the second excitation electrode 112 in a plan view.

[0050] Four external electrode terminals 32 are provided on the second main surface 302 of the second sealing member 30, and are electrically connected to an external circuit board provided outside the crystal oscillator 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.

[0051] 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 of the second sealing member 30. In the sixth through holes 33, through-electrodes for establishing electrical continuity between the electrodes formed on the first main surface 301 and the second main surface 302 are formed along the inner wall surfaces of the sixth through holes 33. The through-electrodes formed on the inner wall surfaces of the sixth through holes 33 in this manner establish 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-holes 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 .

[0052] In the crystal oscillator 100 including the crystal vibration plate 10, first sealing member 20, and second sealing member 30 configured as described above, the crystal vibration plate 10 and the first sealing member 20 are diffusion bonded together with the vibration plate-side first bonding pattern 121 and the sealing member-side first bonding pattern 24 overlapping each other, and the crystal vibration plate 10 and the second sealing member 30 are diffusion bonded together with the vibration plate-side second bonding pattern 122 and the sealing member-side second 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 vibration unit 11.

[0053] At this time, the above-mentioned connection bonding patterns are also diffusion bonded together while overlapping each other. By bonding the connection bonding patterns together, electrical continuity is obtained between the first excitation electrode 111, the second excitation electrode 112, the IC chip 51, and the external electrode terminals 32 in the crystal oscillator 100.

[0054] Specifically, the first excitation electrode 111 is connected to the IC chip 51 via the first escape wiring 113, the wiring pattern 27, the fourth through hole 212, and the electrode pattern 22 in this order. The second excitation electrode 112 is connected to the IC chip 51 via the second escape wiring 114, the second through hole 162, the fifth through hole 213, and the electrode pattern 22 in this order.

[0055] In the crystal oscillator 100, the various bonding patterns of the crystal plate 10, first sealing member 20, and second sealing member 30 are preferably formed by stacking multiple layers on the 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 electrodes and wiring of the crystal plate 10, first sealing member 20, and second sealing member 30 have the same configuration as the bonding patterns, this is preferable as the bonding patterns, electrodes, wiring, etc. can be patterned simultaneously.

[0056] In the crystal oscillator 100 configured as described above, the sealing portions (seal paths) 115, 116 that hermetically seal the vibrating portion 11 of the crystal vibrating plate 10 are annular in 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 generally octagonal. 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 generally octagonal.

[0057] Next, a frequency adjustment method for the crystal oscillator 100 according to the first embodiment will be described with reference to Figures 8 to 10. 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 crystal vibrating plate 10 to adjust the oscillation frequency to a desired value. The frequency adjustment is performed on each crystal oscillator 100 in wafer form during the manufacturing process of the crystal oscillator 100, but it may also be performed on each crystal oscillator 100 that has been singulated from the wafer state.

[0058] 8, the frequency is adjusted by irradiating the frequency-adjusting metal film 40 from outside the second sealing member 30 with a laser, transmitting the laser through the inside of the second sealing member 30 to heat the base metal layer 41, thereby melting and evaporating (vaporizing) at least a part of the metal layer 42, and attaching the evaporated metal to the second excitation electrode 112. In other words, the laser melts and evaporates the metal layer 42 above the base metal layer 41, 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.

[0059] 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 41 of the frequency adjustment metal film 40. The laser heats the base metal layer 41, which in turn heats the metal layer 42 above the base metal layer 41. As described above, the melting temperature of the base metal layer 41 is higher than the melting temperature of the metal layer 42. Therefore, when the base metal layer 41 is heated to a temperature higher than the melting temperature of the metal layer 42, the metal layer 42 melts and a portion of the molten metal layer 42 evaporates. Because the interior of the quartz crystal oscillator 100 is a vacuum, the evaporated metal moves upward in a substantially linear manner. When it reaches the surface 112 a of the second excitation electrode 112, it is cooled and solidified at the surface 112 a of the second excitation electrode 112. As a result, the metal evaporated from the frequency-adjusting metal film 40 adheres to the surface 112 a of the second excitation electrode 112 .

[0060] By controlling the number of laser pulses, sweep distance, number of sweeps, etc., irradiating the base metal layer 41 with the laser, the mass of metal adhering to the second excitation electrode 112 can be controlled, thereby controlling the frequency adjustment amount. For example, by continuously irradiating with a laser at a low output and a narrow pulse interval, the base metal layer 41 can be efficiently heated and only the metal layer 42 can be evaporated. In this case, it is possible to obtain a frequency adjustment amount corresponding to the laser sweep distance, enabling highly accurate frequency adjustment. Here, the laser irradiation on the frequency adjustment metal film 40 is performed by irradiating the line with a point-like laser spot while sweeping. By arranging the irradiation lines resulting from the laser spot sweep in parallel, the laser can be irradiated to a desired region of the frequency adjustment metal film 40. Furthermore, the laser spot sweep is repeated multiple times for each irradiation line, and after multiple laser sweeps are performed for one irradiation line, laser sweeps are performed for the adjacent irradiation line. The pitch of the laser sweep (the distance between the laser beams in a direction perpendicular to the sweep direction) is set to be larger than the diameter (irradiation diameter) D1 of the laser spot, so that adjacent irradiation lines in a direction perpendicular to the sweep direction do not interfere with (overlap with) each other in a planar view.

[0061] 9 , in this embodiment, a recess 30a is formed in the first main surface 301 of the second sealing member 30, and a recess 40a is formed in the surface of the frequency-adjusting metal film 40. The irradiation diameter D1 of the laser spot is larger than the opening diameter D2 of the recess 30a, and the laser is irradiated so as to encompass the recess in a plan view.

[0062] According to the frequency adjustment method for the crystal oscillator 100 of this embodiment, the metal layer 42 above the base metal layer 41 is melted and evaporated. The evaporated metal adheres to the second excitation electrode 112, increasing the mass of the second excitation electrode 112 and shifting the frequency downward. 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 40, damage to the second excitation electrode 112 can be suppressed. This allows frequency adjustment to be performed without significantly degrading the characteristics of the crystal oscillator 100, even after the vibrating portion 11 of the crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30. During this process, the metal of the metal layer 42 melted by laser irradiation can be retained within the recess 30a. This prevents the metal of the melted metal layer 42 from migrating outside the laser irradiation range, thereby suppressing a decrease in the frequency adjustment amount, enabling stable frequency adjustment and improving the reproducibility of frequency adjustment. Furthermore, since multiple recesses 30a are formed, the surface area can be increased compared to when only one recess 30a is formed, and the efficiency of evaporation of the metal from the metal layer 42 by laser irradiation can be improved.

[0063] In this embodiment, the laser is irradiated so as not to penetrate the underlying metal layer 41, and the laser does not penetrate the frequency adjustment metal film 40, 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 crystal oscillator 100, even after the vibrating portion 11 of the crystal vibrating plate 10 is sealed with the first and second sealing members 20 and 30.

[0064] Furthermore, in this embodiment, the opening diameter D2 of the recess 30a formed in the first main surface 301 of the second sealing member 30 is smaller than the laser irradiation diameter D1, and the laser is irradiated so as to encompass the recess 30a in plan view. In this way, by making the opening diameter D2 of the recess 30a smaller than the laser irradiation diameter D1, it is possible to prevent the laser from being partially irradiated onto the recess 30a. Since the laser is irradiated so as to encompass the recess 30a in plan view, the entire recess 30a is located within the laser irradiation area, and therefore the frequency adjustment rate can be stabilized.

[0065] In this embodiment, the frequency-adjusting metal film 40 is formed along the inner surface of the recess 30a formed in the first main surface 301 of the second sealing member 30. As a result, the surface of the frequency-adjusting metal film 40 becomes uneven along the recess 30a, making it easier to retain the metal melted by laser irradiation within the recess 30a. Furthermore, since the inner wall surface 30c of the recess 30a is an inclined surface, the molten metal can be more easily retained on the bottom side of the recess 30a. Furthermore, since multiple boundary lines are formed on the inner wall surface 30c of the recess 30a by wet etching, the presence of these boundary lines makes it easier to retain the molten metal on the inner wall surface 30c of the recess 30a.

[0066] Furthermore, because the recess 30a has a flat inner bottom surface 30b, the laser energy per unit area of ​​the irradiated surface is smaller on the inclined surface than on the flat surface. Therefore, the inner wall surface (inclined surface) 30c of the recess 30a becomes relatively cold, while the inner bottom surface 30b becomes relatively hot. As a result, as shown in Figure 10, the molten metal near the boundary between the inner wall surface 30c and the inner bottom surface 30b of the recess 30a cools and solidifies into a ball-shaped mass 42a, which tends to remain within the recess 30a.

[0067] In this embodiment, by providing a large number of recesses 30a, it is possible to increase the surface area of ​​the frequency-adjusting metal film 40 formed in the recesses 30a, thereby improving the efficiency of evaporation of the metal in the metal layer 42. This makes it possible to prevent a decrease in the amount of frequency adjustment, to perform stable frequency adjustment, and to improve the reproducibility of frequency adjustment.

[0068] Here, the number of recesses 30a formed per unit area of ​​the second sealing member 30 (formation density) is 1500 to 15000 / mm 2 In this way, by providing a large number of recesses 30a, the surface area can be increased, and the efficiency of evaporation of the metal in the metal layer 42 can be improved. This makes it possible to prevent a decrease in the amount of frequency adjustment, and to perform stable frequency adjustment.

[0069] In this embodiment, the opening diameter D2 of the recess 30 a is larger than the depth of the recess 30 a. This allows the recess 30 a to be formed shallow and have the desired opening diameter D2, thereby preventing a decrease in the rigidity of the second sealing member 30.

[0070] Furthermore, by forming the base metal layer 41 from W (tungsten), the base metal layer 41 exposed to the internal space of the crystal oscillator 100 can function as a getter material, thereby allowing the base metal layer 41 to capture gas generated in the internal space of the crystal oscillator 100.

[0071] Furthermore, by using a visible light laser as the laser, which has low absorption and high transmittance for the second sealing member 30 made of, for example, quartz or glass, power loss and damage to the second sealing member 30 can be reduced, making it suitable for frequency adjustment.

[0072] Furthermore, the space that seals 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.

[0073] In this embodiment, the quartz crystal unit 50 included in the quartz crystal oscillator 100 includes a first sealing member 20 that covers the first main surface of the vibrating portion 11 of the quartz crystal plate 10, and a second sealing member 30 that covers the second main surface of the vibrating portion 11 of the quartz crystal plate 10. The first sealing member 20 and the quartz crystal 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 plate 10. The first sealing member 20 and the second sealing member 30 are made of quartz crystal. In this way, when a quartz crystal unit 50 with a three-layer structure is used, it is possible to reduce the size and thickness of the quartz crystal unit 50. In the quartz crystal oscillator 100 including such a reduced size and thickness, high-precision frequency adjustment can be performed even after the vibrating portion 11 of the quartz crystal plate 10 is sealed with the first and second sealing members 20 and 30.

[0074] In the crystal oscillator 100 of this embodiment, a frequency-adjusting metal film 40 is formed on the first main surface 301 of the second sealing member 30, which faces the second excitation electrode 112. A plurality of recesses 30a are formed on the first main surface 301 of the second sealing member 30 on which the frequency-adjusting metal film 40 is formed. The frequency-adjusting metal film 40 extends into these recesses 30a. The plurality of recesses 40a are formed in the frequency-adjusting metal film 40, and the base metal layer 41 is exposed at the bottom of the recesses 40a in the frequency-adjusting metal film. As shown in FIG. 10 , a plurality of recesses 40a are formed on the surface of the frequency-adjusting metal film 40, and the bottom of each recess 40a is formed as the base metal layer 41. The base metal layer 41 is not covered by the metal layer 42 and is therefore exposed. The base metal layer 41 may be exposed only partially at the bottom of each recess 40a, or the entire bottom of each recess 40a may be exposed. This allows the exposed base metal layer 41 to function as a getter material, allowing the base metal layer 41 to capture gas generated in the internal space of the crystal oscillator 100. Furthermore, the formation of multiple recesses 40a increases the exposed area of ​​the base metal layer 41, thereby further improving the efficiency of capturing gas generated in the internal space of the crystal oscillator 100. Preferred materials for such base metal layer 41 include tungsten and titanium. This makes it possible to suppress changes in the frequency of the crystal oscillator 100 over time that are caused by gas generation.

[0075] 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 between the second excitation electrode 112 and the frequency adjustment metal film 40 can be made very small compared to a configuration in which a sealing member is bonded to a base using adhesive, allowing for highly accurate frequency adjustment.

[0076] Second Embodiment Next, the basic structure of a quartz crystal resonator 100A according to a second embodiment will be described. In the first embodiment, frequency adjustment was performed by irradiating a laser beam from only one side of the quartz crystal oscillator 100 (see FIG. 8 ). In this embodiment, frequency adjustment can be performed by irradiating a laser beam from both sides of the quartz crystal resonator 100A, as shown in FIG. 18 . In the first embodiment, the frequency adjustment metal film 40 was provided only on the second sealing member 30 of the quartz crystal oscillator 100. In this embodiment, a frequency adjustment metal film 60 is provided on the first sealing member 20A in addition to the frequency adjustment metal film 40 provided on the second sealing member 30A of the quartz crystal resonator 100A.

[0077] The quartz crystal resonator 100A according to the second embodiment has a configuration substantially similar to the quartz crystal resonator 50 included in the quartz crystal oscillator 100 according to the first embodiment, and as shown in Fig. 11, is configured with a quartz crystal vibrating plate (piezoelectric vibrating plate) 10A, a first sealing member 20A, and a second sealing member 30A. In this quartz crystal resonator 100A, the quartz crystal vibrating plate 10A is bonded to the first sealing member 20A, and the quartz crystal vibrating plate 10A is bonded to the second sealing member 30A, thereby forming a package with a substantially rectangular sandwich structure. The following will mainly describe the differences from the quartz crystal resonator 50 according to the first embodiment.

[0078] In the quartz crystal resonator 100A, a first sealing member 20A and a second sealing member 30A are bonded to both main surfaces of the quartz crystal plate 10A, respectively, to form an internal space (cavity) within the package, and the vibrating unit 11 (see FIGS. 14 and 15) is hermetically sealed within this internal space. Similar to the first embodiment, AT-cut quartz crystal plates are used for the quartz crystal plate 10A, the first sealing member 20A, and the second sealing member 30A.

[0079] 12 and 13 , unlike the first embodiment, no electrode pattern is provided on a first main surface 201 (the main surface not facing the internal space) of the first sealing member 20A. Also, unlike the first embodiment, no through-holes are provided in the first sealing member 20A.

[0080] Meanwhile, a metal film 29 for shielding (ground connection) is formed on the second main surface 202 (the main surface facing the internal space) of the first sealing member 20A. The metal film 29 is integrally formed with the annular sealing member-side first bonding pattern 24 for bonding to the quartz-crystal vibrating plate 10A. A circular connection bonding pattern 271 and an oval connection bonding pattern 272 are also formed on the second main surface 202 of the first sealing member 20A.

[0081] A frequency-adjustment metal film 60 used for adjusting the frequency of the quartz crystal resonator 100A is formed in the center of the second main surface 202 of the first sealing member 20A. Numerous recesses 60a are formed on the surface of the frequency-adjustment metal film 60, and these recesses 60a are regularly arranged at predetermined intervals in a plan view. Numerous recesses (not shown) are formed on the second main surface 202 of the first sealing member 20A, and these recesses have a configuration substantially similar to the recesses 30a formed on the first main surface 301 of the second sealing member 30 of the quartz crystal oscillator 100 of the first embodiment. The frequency-adjustment metal film 60 is not integral with the metal film 29, and the quartz crystal substrate of the first sealing member 20A is exposed in the portion between the frequency-adjustment metal film 60 and the metal film 29.

[0082] The frequency-adjusting metal film 60 has substantially the same configuration as the frequency-adjusting metal film 40 of the crystal oscillator 100 of the first embodiment, and as shown in Fig. 18, includes a base metal layer 61 and a metal layer 62 laminated on the base metal layer 61. The base metal layer 61 is made of, for example, W (tungsten), and the metal layer 62 is made of the same material (for example, Au) as the second excitation electrode 112. Note that the recess 60a is not shown in Fig. 18.

[0083] 14 and 15 , similar to the first embodiment, the quartz crystal vibration plate 10A 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 13 that holds the vibrating portion 11 by connecting the vibrating portion 11 to the outer frame portion 12. A cutout portion is provided between the vibrating portion 11 and the outer frame portion 12 by cutting out the quartz crystal vibration plate 10A. In this embodiment, the quartz crystal vibration plate 10A has only one holding portion 13 that connects the vibrating portion 11 to the outer frame portion 12, and the cutout portion is formed continuously to surround the outer periphery of the vibrating portion 11.

[0084] Furthermore, 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. The first excitation electrode 111 and the second excitation electrode 112 are connected with lead-out wiring (first lead-out wiring 113, second lead-out wiring 114) for connecting these excitation electrodes to external electrode terminals. The first lead-out wiring 113 is led out from the first excitation electrode 111 and connected to an oval connection bonding pattern 12a formed on the outer frame section 12 via the holding section 13. The second lead-out wiring 114 is led out from the second excitation electrode 112 and connected to a connection bonding pattern 13a formed on the holding section 13.

[0085] A first diaphragm-side bonding pattern 121 is formed on the first main surface 101 of the quartz crystal vibrating plate 10A, and a second diaphragm-side bonding pattern 122 is formed on the second main surface 102 of the quartz crystal vibrating plate 10A. The first diaphragm-side bonding pattern 121 and the second diaphragm-side bonding pattern 122 are provided on the outer frame portion 12 and are formed in an annular shape in a plan view. A circular connection bonding pattern 12b is also formed on the first main surface 101. The connection bonding patterns 12a and 12b are provided on the inner periphery of the first diaphragm-side bonding pattern 121. An oval connection bonding pattern 12c and a circular connection bonding pattern 12d are formed on the second main surface 102. The connection bonding patterns 12c and 12d are provided on the inner periphery of the second diaphragm-side bonding pattern 122. The connection junction pattern 12c is not connected to the connection junction pattern 13a drawn out from the second excitation electrode 112, and is provided at a predetermined distance from the connection junction pattern 13a.

[0086] The quartz crystal vibrating plate 10A has a first through-hole 163 formed therein, penetrating between the first main surface 101 and the second main surface 102. The first through-hole 163 is located in the outer frame 12, on the inner periphery of the diaphragm-side first bonding pattern 121 and the diaphragm-side second bonding pattern 122. The first through-hole 163 is surrounded by the aforementioned connection bonding pattern 12a on the first main surface 101 side and the aforementioned connection bonding pattern 12c on the second main surface 102 side. A through electrode is formed along the inner wall surface of the first through-hole 163 to establish electrical continuity between the electrodes formed on the first main surface 101 and the second main surface 102.

[0087] Two internal wirings are formed on the inner wall surface of the outer frame 12 of the quartz-crystal vibrating plate 10A. Specifically, a first internal wiring 173 is formed on the inner wall surface 105 on the -X side of the outer frame 12 of the quartz-crystal vibrating plate 10A. A second internal wiring 174 is formed on the inner wall surface 106 on the +X side of the outer frame 12 of the quartz-crystal vibrating plate 10A.

[0088] The first internal wiring 173 is provided with a predetermined width in the center of the inner wall surface 105 on the −X-direction side of the outer frame 12. The first internal wiring 173 is provided along the Z′-axis direction. The first internal wiring 173 is connected to the diaphragm-side first bonding pattern 121 provided on the first main surface 101 of the quartz-crystal vibrating plate 10A. The first internal wiring 173 is connected to the diaphragm-side second bonding pattern 122 provided on the second main surface 102 of the quartz-crystal vibrating plate 10A.

[0089] The second internal wiring 174 is provided with a predetermined width in the center of the inner wall surface 106 on the +X-direction side of the outer frame portion 12. The second internal wiring 174 is provided along the Z'-axis direction. The second internal wiring 174 is connected to the diaphragm-side first bonding pattern 121 provided on the first main surface 101 of the quartz-crystal vibrating plate 10A. The second internal wiring 174 is connected to the diaphragm-side second bonding pattern 122 provided on the second main surface 102 of the quartz-crystal vibrating plate 10A. The first internal wiring 173 and the second internal wiring 174 are arranged to face each other with the vibrating portion 11 in between.

[0090] As shown in Figures 16 and 17, a sealing member-side second bonding pattern 31 for bonding to the quartz-crystal vibration plate 10A is formed on the first main surface 301 of the second sealing member 30A. The sealing member-side second bonding pattern 31 is formed in a ring shape in a plan view. The first main surface 301 also has an oval connection bonding pattern 32a, a circular connection bonding pattern 32b, and a connection bonding pattern 32c formed integrally with the connection bonding pattern 32b. The connection bonding pattern 32c extends along the Z'-axis direction. The connection bonding patterns 32a to 32c are provided on the inner periphery of the sealing member-side second bonding pattern 31.

[0091] A frequency-adjustment metal film 40 used for adjusting the frequency of the quartz crystal resonator 100A is formed in the center of the first main surface 301 of the second sealing member 30A. A number of recesses 40a are formed on the surface of the frequency-adjustment metal film 40, and these recesses 40a are regularly arranged at predetermined intervals in a plan view. A number of recesses (not shown) are formed in the first main surface 301 of the second sealing member 30A, and these recesses have substantially the same configuration as the recesses 30a formed on the first main surface 301 of the second sealing member 30 of the quartz crystal oscillator 100 of the first embodiment.

[0092] The frequency-adjusting metal film 40 has substantially the same configuration as the frequency-adjusting metal film 40 of the crystal oscillator 100 of the first embodiment, and as shown in Fig. 18, includes a base metal layer 41 and a metal layer 42 laminated on the base metal layer 41. The base metal layer 41 is made of, for example, W (tungsten), and the metal layer 42 is made of the same material (for example, Au) as the second excitation electrode 112. Note that the recess 40a is not shown in Fig. 18.

[0093] Four external electrode terminals 32 are provided on the second main surface 302 of the second sealing member 30A. The external electrode terminals 32 are electrically connected to an external circuit board provided outside the quartz crystal unit 100A. The external electrode terminals 32 are located at four corners of the second main surface 302 of the second sealing member 30A. In plan view, the external electrode terminals 32 are each provided along the internal space of the package of the quartz crystal unit 100A and are formed in a generally L-shape. In plan view, the external electrode terminals 32 are provided in positions that overlap the outer frame portion 12 of the quartz crystal vibrating plate 10A described above.

[0094] The second sealing member 30A has four second to fifth through holes 362 to 365 formed therein that penetrate between the first main surface 301 and the second main surface 302. The second and third through holes 362 and 363 are provided on the inner periphery of the sealing member-side second bonding pattern 31. Around the second through hole 362, a connection bonding pattern 32a is formed on the first main surface 301 side, and an external electrode terminal 32 is formed on the second main surface 302 side. Around the third through hole 363, a connection bonding pattern 32b is formed on the first main surface 301 side, and an external electrode terminal 32 is formed on the second main surface 302 side. Around the fourth and fifth through holes 364 and 365, the sealing member-side second bonding pattern 31 is formed on the first main surface 301 side, and an external electrode terminal 32 is formed on the second main surface 302 side. The second to fifth through holes 362 to 365 have through electrodes formed along the inner wall surfaces of the second to fifth through holes 362 to 365 to ensure electrical continuity between the electrodes formed on the first main surface 301 and the second main surface 302.

[0095] In the quartz crystal unit 100A including the quartz crystal vibrating plate 10A, first sealing member 20A, and second sealing member 30A configured as described above, the quartz crystal vibrating plate 10A and the first sealing member 20A 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 10A and the second sealing member 30A 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. 11. This hermetically seals the internal space of the package, i.e., the space housing the vibrating portion 11.

[0096] In the quartz crystal unit 100A, 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 first diaphragm-side bonding pattern 121 and the first sealing member-side bonding pattern 24. The outer edge of the seal path 115 is formed in a substantially rectangular shape, and the outer periphery of the seal path 115 is disposed adjacent to the outer periphery of the package. Similarly, the seal path 116 is formed by diffusion bonding (Au-Au bonding) the above-mentioned second diaphragm-side bonding pattern 122 and the second sealing member-side bonding pattern 31. The outer edge of the seal path 116 is formed in a substantially rectangular shape, and the outer periphery of the seal path 116 is disposed adjacent to the outer periphery of the package.

[0097] The above-described connection bonding patterns are also diffusion-bonded together while overlapping each other. By bonding the connection bonding patterns together, electrical conduction is achieved between the first excitation electrode 111, the second excitation electrode 112, and the external electrode terminal 32 in the quartz-crystal resonator 100A. Specifically, the first excitation electrode 111 is connected to the external electrode terminal 32 via the first escape wiring 113, the first through-hole 163, and the second through-hole 362, in that order. The second excitation electrode 112 is connected to the external electrode terminal 32 via the second escape wiring 114, the connection bonding pattern 32c, and the third through-hole 363, in that order. Furthermore, the metal film 29 is provided integrally with the seal path 115, and this metal film 29 is connected to earth (ground connection, using part of the external electrode terminal 32) via the first and second internal wirings 173, 174, the seal path 116, and the fourth and fifth through holes 364, 365 in this order. The electrical conduction paths between the first and second excitation electrodes 111, 112 and the external electrode terminals 32, 32 are not electrically connected to the annular seal paths 115, 116.

[0098] A metal film 29 serving as a ground electrode is provided on the second main surface 202 of the first sealing member 20A (the main surface facing the internal space). The metal film 29 is electrically connected to an external electrode terminal 32 formed on the second main surface 302 of the second sealing member 30 (the main surface not facing the internal space) via first and second internal wirings 173, 174 formed on the inner wall surfaces 105, 106 of the outer frame 12 of the quartz crystal vibrating plate 10A. In this way, since the metal film 29 serving as a ground electrode is provided on the second main surface 202 of the first sealing member 20A and the internal wirings 173, 174 for ground connection are provided on the inner wall surfaces 105, 106 of the outer frame 12 of the quartz crystal vibrating plate 10A, the quartz crystal vibrating plate 10A is less susceptible to the external environment and the ground connection can be made more stable.

[0099] According to this embodiment, in addition to the frequency-adjustment metal film 40 provided on the first main surface 301 of the second sealing member 30A of the quartz-crystal resonator 100A, the frequency-adjustment metal film 60 is also provided on the second main surface 202 of the first sealing member 20A, thereby achieving substantially the same effects as the first embodiment. In addition, in this embodiment, the frequency-adjustment metal film 40 on the second sealing member 30A side of the quartz-crystal resonator 100A is irradiated with a laser, and the frequency-adjustment metal film 60 on the first sealing member 20A side of the quartz-crystal resonator 100A is also irradiated with a laser. This allows frequency adjustment to be performed at two locations, the first sealing member 20A side and the second sealing member 30A side. In this case, frequency adjustment may be performed simultaneously at both locations, the first sealing member 20A side and the second sealing member 30A side, or may be performed sequentially at each location. Alternatively, first, frequency adjustment is performed using the frequency-adjusting metal film 40, and if the amount of frequency adjustment is insufficient compared to the desired amount of frequency adjustment, frequency adjustment may be performed using the frequency-adjusting metal film 60 by an amount that compensates for the deficiency. In the case of the first embodiment, elements such as an IC chip 51, a temperature sensor, a capacitor, and a resistor can be mounted on the first main surface 201 of the first sealing member 20, thereby improving the functionality of the piezoelectric vibration device.

[0100] 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 scope of the claims. Furthermore, all modifications within the scope and meaning equivalent to the claims are included.

[0101] In the above embodiment, the frequency adjustment is performed using a visible light laser, but the frequency adjustment may also be performed using an invisible light laser such as an ultraviolet laser or an infrared laser. In this case, the desired frequency adjustment amount can be obtained by controlling the output power, irradiation time, etc. of the beam of the visible light laser or invisible light laser. Note that the beam may be irradiated by shifting the focus toward the irradiation source of the beam rather than focusing it on the frequency adjustment metal film 40.

[0102] In the above embodiment, the internal space of the piezoelectric vibration device (crystal oscillator 100, crystal unit 100A) is evacuated, but low-pressure nitrogen or argon, for example, may be sealed in the internal space of the piezoelectric vibration device.

[0103] In the above embodiment, the quartz crystal vibrating plates 10 and 10A are AT-cut quartz crystal plates, but other types of quartz crystal plates, such as SC-cut quartz crystal plates or Z-cut quartz crystal plates, may also be used. Also, while the vibrating portions of the quartz crystal vibrating plates 10 and 10A are rectangular, the vibrating portions may be tuning-fork shaped.

[0104] In the above embodiment, the first and second sealing members are formed from quartz plates. However, the first and second sealing members may be formed from, for example, glass. In this case, an infrared laser capable of transmitting through the first and second sealing members may be used. For example, a YAG laser with a wavelength of approximately 1064 nm may be used as the infrared laser. Note that only a portion of the first and second sealing members may be formed from a light-transmitting material such as quartz or glass.

[0105] In the above embodiments, the quartz crystal vibration plate 10, 10A 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. Furthermore, a through-hole penetrating the quartz crystal vibration plate 10, 10A in the thickness direction between the vibrating portion 11 and the outer frame portion 12 is provided, but a quartz crystal vibration plate configured without a through-hole may also be used. Furthermore, in the above embodiments, the quartz crystal vibration plate 10, 10A is used with a frame including the vibrating portion 11 and the outer frame portion 12 surrounding the vibrating portion 11, but a quartz crystal vibration plate configured without an outer frame may also be used.

[0106] In the above embodiment, a piezoelectric resonator device (crystal oscillator 100, crystal unit 100A) with a three-layer structure in which the crystal plate is sandwiched between a first sealing member and a second sealing member is used, but a piezoelectric resonator device with a different structure may also be used. For example, as shown in Figure 19, a crystal unit with a structure (single package structure) in which the crystal plate is housed inside a base made of an insulating material such as ceramic, glass, or crystal and has a recess, and a lid is bonded to the base may be used.

[0107] The single-package crystal unit 100B of the first modified example shown in Figure 19 includes, for example, a ceramic base 73, a borosilicate glass lid 74, a crystal vibration plate 70, and a frequency-adjusting metal film 80. The base 73 is formed in a generally rectangular parallelepiped shape with an opening at the top, and the lid 74 is bonded to the base 73 with a bonding material (e.g., AuSn) 75, thereby closing the opening of the base 73. The crystal vibration plate 70 is housed within the base 73, and is connected to an electrode 76 formed on the inner bottom surface 73a of the base 73 with a conductive adhesive 77. First and second excitation electrodes 71 and 72 are formed on both main surfaces of the crystal vibration plate 70.

[0108] In the crystal unit 100B having such a single package structure, a frequency-adjusting metal film 80 is provided on the inner surface 74a (the main surface facing the first excitation electrode 71) of a lid 74 serving as a sealing member. The frequency-adjusting metal film 80 has a configuration substantially similar to the frequency-adjusting metal films 40 and 60 of the above-described embodiments, including a base metal layer and a metal layer thereon. Numerous recesses (not shown) are formed on the surface of the frequency-adjusting metal film 80, and these recesses are regularly arranged at predetermined intervals in a plan view. Numerous recesses (not shown) are formed on the inner surface 74a of the lid 74, and these recesses have a configuration substantially similar to the recesses 30a formed on the first main surface 301 of the second sealing member 30 of the crystal unit 100 of the above-described first embodiment.

[0109] Then, a beam (e.g., a YAG laser) is irradiated onto the frequency-adjusting metal film 80 from outside the lid 74, and the beam passes through the inside of the lid 74 to heat the underlying metal layer of the frequency-adjusting metal film 80, thereby melting and vaporizing at least a portion of the metal layer of the frequency-adjusting metal film 80 and adhering it to the first excitation electrode 71, thereby enabling frequency adjustment similar to that of the above embodiment. Here, a metal thin film may be formed on the inner surface of the lid 74, in which case it is possible to provide a quartz crystal unit 100B with EMI countermeasures.

[0110] In the above embodiment, a large number of recesses 40a are formed on the surface of the frequency-adjusting metal film 40 used to adjust the frequency of the crystal oscillator 100, and these recesses 40a are regularly arranged at predetermined intervals in a plan view (see FIG. 6 ). However, as shown in Modifications 2 to 4 in FIGS. 20 to 22 , multiple regions with different numbers of recesses 40a per unit area (formation density) may be provided. That is, multiple regions with different numbers of recesses 30a per unit area (formation density) may be provided on the first main surface 301 of the second sealing member 30, and the base metal layer 41 and metal layer 42 of the frequency-adjusting metal film 40 may extend over each recess 30a. In this way, providing two or more regions with different recess 40a (30a) formation densities allows for more flexible frequency adjustment. For example, in a dense region where the recesses 40a are formed at a relatively high density, the surface area of ​​the frequency-adjusting metal film 40 is increased, which increases the efficiency of metal evaporation from the metal layer 42 and increases the amount of frequency adjustment (decrease), enabling more efficient frequency adjustment. In sparse regions where the formation density of the recesses 40a is relatively low, the increase in the surface area of ​​the frequency-adjusting metal film 40 is suppressed, so the evaporation efficiency of the metal in the metal layer 42 is suppressed, the frequency adjustment amount (decrease amount) is suppressed, and fine adjustment of the frequency adjustment amount is made possible.

[0111] In Modification 2 shown in FIG. 20 , the frequency adjustment metal film 40 has two regions with different recess 40a formation densities. A dense region R1, where the recess 40a are formed at a relatively high density, and a sparse region R2, where the recess 40a are formed at a relatively low density, are provided. Half of the frequency adjustment metal film 40 (the upper half in FIG. 20 ) is the dense region R1, and the remaining half of the frequency adjustment metal film 40 (the lower half in FIG. 20 ) is the sparse region R2. Given constant conditions such as laser output, irradiating the dense region R1 with a laser beam results in a larger frequency adjustment amount (decrease) than irradiating the sparse region R2 with a laser beam. Therefore, a more appropriate frequency adjustment amount can be obtained by arbitrarily selecting the laser irradiation region depending on the target frequency adjustment amount. To ensure as large a frequency adjustment amount as possible, laser irradiation can be performed on the dense region R1. To fine-tune the frequency adjustment amount, laser irradiation can be performed on the sparse region R2.

[0112] In the dense region R1, the formation density of the recesses 40a is 4500 to 15000 pieces / mm 2 In the sparse region R2, the formation density of the recesses 40a is preferably 1500 pieces / mm 2 ~ 5 / 6 of dense region R1 (maximum 12,500 pieces / mm 2 In the sparse region R2, the formation density of the recesses 40a is preferably 1500 / mm 2 If the surface area is smaller than this, the effect of improving the frequency adjustment efficiency due to the increased surface area may be reduced. Furthermore, if the formation density of the recesses 40a in the sparse region R2 is greater than 5 / 6 of that in the dense region R1, the difference in surface area between the dense region R1 and the sparse region R2 may be small, potentially narrowing the range of frequency adjustment. The shapes, positions, sizes, and ranges of the dense region R1 and the sparse region R2 described above are merely examples and may be modified in various ways. For example, the dense region R1 may be formed over a larger area than the sparse region R2. Furthermore, three or more regions with different formation densities of the recesses 40a may be provided. For example, a region having a formation density intermediate between the dense region R1 and the sparse region R2 described above may be provided.

[0113] In Modification 3 shown in FIG. 21 , the frequency-adjustment metal film 40 has two regions with different recess 40a formation densities. A dense region R3, where the recess 40a are formed at a relatively high density, and a sparse region R4, where the recess 40a are formed at a relatively low density, are provided. The dense region R3 is a roughly circular region near the center of the frequency-adjustment metal film 40, and the sparse region R4 is an annular region on the outer periphery of this dense region R3. In a quartz crystal resonator, the vibration displacement increases in regions closer to the center of the excitation electrode. Therefore, when a mass load is applied to a region closer to the center, the effect on frequency fluctuations is thought to be greater. Therefore, when frequency adjustment is performed by laser irradiation, the amount of frequency adjustment (decrease) varies depending on whether the laser is irradiated on the central region or the outer periphery of the frequency-adjustment metal film 40 facing the second excitation electrode 112.

[0114] Thus, by providing the dense region R3 in the central region of the frequency adjustment metal film 40, the amount of fluctuation in the frequency adjustment amount due to laser irradiation can be increased, allowing the target frequency adjustment amount to be achieved in a short period of time. Furthermore, by providing the sparse region R4 in the peripheral (outer edge) region of the frequency adjustment metal film 40, the amount of fluctuation in the frequency adjustment amount due to laser irradiation can be reduced, facilitating fine adjustment to the target frequency. Specifically, in the initial stage of frequency adjustment, the dense region R3 in the central region of the frequency adjustment metal film 40 is irradiated with laser to cause large fluctuations in the frequency adjustment amount, and in the next stage, the sparse region R4 in the peripheral region of the frequency adjustment metal film 40 is irradiated with laser to perform fine adjustment to the target frequency. Note that the shapes, positions, sizes, and extents of the dense region R3 and the sparse region R4 described above are merely examples and can be modified in various ways. For example, the dense region R3 may be rectangular, hexagonal, octagonal, or the like. Furthermore, a region with an intermediate formation density may be provided between the dense region R3 and the sparse region R4.

[0115] In Modification 4 shown in FIG. 22 , the frequency adjustment metal film 40 has two regions with different recess 40a formation densities. These regions are a dense region R5, where the recess 40a formation density is relatively high, and a sparse region R6, where the recess 40a formation density is relatively low. Contrary to Modification 3 described above, the roughly circular region toward the center of the frequency adjustment metal film 40 is the sparse region R6, and the annular region on the outer periphery of this sparse region R6 is the dense region R5. In this way, the sparse region R6 is provided in the center region of the frequency adjustment metal film 40, where the fluctuation in the frequency adjustment amount is large, and the dense region R5 is provided in the outer periphery region of the frequency adjustment metal film 40, where the fluctuation in the frequency adjustment amount is small. This allows the effects based on the laser irradiation position and the effects based on the formation density of the recess 40a to cancel each other out, thereby making the frequency adjustment amount by laser irradiation approximately uniform regardless of the laser irradiation position. For example, this can reduce unintended excess or deficiency in the frequency adjustment amount due to a shift in the laser irradiation position. The shapes, positions, sizes, and ranges of the dense region R5 and sparse region R6 described above are merely examples and can be changed in various ways. For example, the sparse region R6 may be rectangular, hexagonal, octagonal, etc. Furthermore, a region having an intermediate formation density may be provided between the dense region R5 and the sparse region R6.

[0116] In the above, the recesses 30a formed on the first main surface 301 of the second sealing member 30 are made to have approximately the same size, and the recesses 40a formed on the frequency-adjusting metal film 40 are made to have approximately the same size. That is, in Modifications 2 to 4, the dense regions and sparse regions as described above are formed by changing the gap between adjacent recesses 30a (40a). However, the dense regions and sparse regions may also be formed by changing the size of the recesses 30a (40a) to change the surface area of ​​the frequency-adjusting metal film 40.

[0117] This application claims priority based on Japanese Patent Application No. 2023-170368, filed in Japan on September 29, 2023, the entire contents of which are incorporated herein by reference.

[0118] REFERENCE SIGNS LIST 10 Quartz crystal vibration plate (piezoelectric vibration plate) 20 First sealing member (sealing member) 30 Second sealing member (sealing member) 30a Recess 40 Frequency adjustment metal film 40a Recess 41 Undercoat metal layer 42 Metal layer 100 Quartz crystal oscillator (piezoelectric vibration device) 111 First excitation electrode 112 Second excitation electrode 301 First principal surface

Claims

1. A method for adjusting the frequency of a piezoelectric vibration device in which at least the vibration portion of a piezoelectric diaphragm having an excitation electrode formed thereon is hermetically sealed by a sealing member, the method comprising: forming a frequency-adjusting metal film consisting of a base metal layer and a metal layer laminated on the base metal layer on a main surface of the sealing member facing the excitation electrode; 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 on which the frequency-adjusting metal film is formed has a plurality of recesses formed therein, the frequency-adjusting metal film extending into these recesses; and irradiating a beam from outside the sealing member onto the frequency-adjusting metal film, transmitting the beam through the inside of the sealing member to heat the base metal layer, thereby melting and evaporating at least a portion of the metal layer, and attaching the metal layer to the excitation electrode, thereby performing frequency adjustment.

2. A method for adjusting the frequency of a piezoelectric vibration device as described in claim 1, characterized in that the opening diameter of the recess is smaller than the irradiation diameter of the beam, and the beam is irradiated so as to encompass the recess in a planar view.

3. A method for adjusting the frequency of a piezoelectric vibration device as claimed in claim 1 or 2, characterized in that the frequency adjustment metal film is formed along the inner surface of the recess.

4. A method for adjusting the frequency of a piezoelectric vibration device according to claim 1 or 2, characterized in that the inner wall surface of the recess is an inclined surface.

5. A method for adjusting the frequency of a piezoelectric vibration device as described in claim 4, characterized in that the recess has a flat bottom surface.

6. A method for adjusting the frequency of a piezoelectric vibration device as described in claim 4, characterized in that a plurality of boundary lines are formed on the inner wall surface of the recess.

7. A method for adjusting the frequency of a piezoelectric vibration device as claimed in claim 1 or 2, characterized in that a large number of the recesses are provided and are aligned in a plane view.

8. A method for adjusting the frequency of a piezoelectric vibration device as described in claim 1 or 2, characterized in that a large number of recesses are provided, and a plurality of regions are provided in which the number of recesses formed per unit area differs.

9. The method for adjusting the frequency of a piezoelectric vibration device according to claim 1 or 2, wherein the number of recesses formed per unit area of ​​the sealing member is 1,500 to 15,000 / mm 2 13. A method for adjusting the frequency of a piezoelectric vibration device, comprising:

10. A method for adjusting the frequency of a piezoelectric vibration device as claimed in claim 1 or 2, characterized in that the opening diameter of the recess is larger than the depth of the recess.

11. A piezoelectric vibration device, comprising a piezoelectric diaphragm having a vibration portion on which an excitation electrode is formed, and at least the vibration portion is hermetically sealed by a sealing member, wherein a frequency-adjusting metal film consisting of a base metal layer and a metal layer laminated on the base metal layer is formed on a main surface of the sealing member facing the excitation electrode, a plurality of recesses are formed on the main surface of the sealing member on which the frequency-adjusting metal film is formed, the frequency-adjusting metal film extends into these recesses, a plurality of recesses are formed in the frequency-adjusting metal film, and the bottom surfaces of the recesses in the frequency-adjusting metal film are in a state where the base metal layer is exposed.

12. A piezoelectric vibration device as described in claim 11, comprising a first sealing member covering a first main surface side of the vibration portion of the piezoelectric vibration plate and a second sealing member covering a second main surface side of the vibration portion of the piezoelectric vibration plate, wherein the first sealing member and the piezoelectric vibration plate are joined and the second sealing member and the piezoelectric vibration plate are joined to form an airtight seal on the vibration portion of the piezoelectric vibration plate, and wherein the sealing member on which the frequency adjustment metal film is formed of the first sealing member and the second sealing member is made of quartz.

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