Piezoelectric resonator device

Abstract

The present invention is a crystal vibrator (100) provided with: a crystal vibration plate (10) having a first excitation electrode (111) and a second excitation electrode (112) paired with the first excitation electrode (111); and a first sealing member (20) and a second sealing member (30) that cover both main surfaces of the crystal vibration plate (10), wherein the first sealing member (20) and the crystal vibration plate (10) are joined and the second sealing member (30) and the crystal vibration plate (10) are joined so that a vibration part (11) including the first excitation electrode (111) and the second excitation electrode (112) is hermetically sealed, the first sealing member (20) is provided with a thin-film thermistor (500) on a second main surface (202) facing the vibration part (11), and a through-hole penetrating from a first main surface (201) to the second main surface (202) is not provided.

Description

Piezoelectric Vibration Device

[0001] The present invention relates to a piezoelectric vibration device such as a piezoelectric vibrator.

[0002] In recent years, the operating frequencies of various electronic devices have been increasing and their packages have become smaller (especially lower profile). As a result, piezoelectric resonator devices (e.g., quartz crystal resonators, quartz crystal oscillators, etc.) are also being required to accommodate these trends.

[0003] This type of piezoelectric vibration device has a housing configured as a roughly rectangular parallelepiped package. One such configuration is disclosed in Patent Document 1, which includes a first sealing member and a second sealing member made of glass or quartz, and a piezoelectric vibration plate made of quartz and having excitation electrodes formed on both main surfaces thereof. The first sealing member and the second sealing member are stacked and bonded together via the piezoelectric vibration plate, and the vibration portion (excitation electrodes) of the piezoelectric vibration plate arranged inside the package (internal space) is hermetically sealed. Hereinafter, this type of stacked configuration of a piezoelectric vibration device is referred to as a sandwich structure.

[0004] Patent Publication No. 2022-97055

[0005] Conventionally, piezoelectric vibrating devices with integrated temperature sensors have also been developed. For example, a thermistor is used as such a temperature sensor. The temperature sensor (thermistor) is provided for the purpose of detecting the temperature of the vibrating part of the piezoelectric vibrator in order to adjust the oscillation frequency, which changes with temperature. In other words, there has been a demand for further reducing the difference between the temperature of the vibrating part of the piezoelectric vibrator and the temperature detected by the temperature sensor.

[0006] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a piezoelectric vibration device that can further reduce the difference between the temperature of the vibration part and the temperature detected by the temperature sensor.

[0007] The present invention provides a piezoelectric vibration device comprising: a piezoelectric diaphragm having a first excitation electrode formed on a main surface of a substrate; and a second excitation electrode formed on the main surface of the substrate and paired with the first excitation electrode; and a first sealing member and a second sealing member covering both main surfaces of the piezoelectric diaphragm, wherein the first sealing member and the piezoelectric diaphragm are joined together, and the second sealing member is joined together to provide an internal space in which a vibration part of the piezoelectric diaphragm including the first excitation electrode and the second excitation electrode is hermetically sealed. In this piezoelectric vibration device, the first sealing member has a first sealing member first main surface that does not face the vibration part, and a back surface of the first sealing member first main surface that seals the vibration part. a first sealing member second main surface facing the vibrating section, a thin-film thermistor provided on the first sealing member second main surface, no through-hole penetrating from the first sealing member first main surface to the first sealing member second main surface is provided, the second sealing member has a second sealing member first main surface facing the vibrating section and a second sealing member second main surface that is the back side of the second sealing member first main surface and does not face the vibrating section, and the second sealing member second main surface is provided with a thermistor external terminal electrically connected to the thin-film thermistor and an excitation electrode external terminal electrically connected to each of the first excitation electrode and the second excitation electrode.

[0008] That is, in the piezoelectric vibrating device of the present invention, the first sealing member has a thin-film thermistor on one main surface (the second main surface of the first sealing member) facing the vibrating portion, no through-holes extending from one main surface to the other main surface (the first main surface of the first sealing member), and the second sealing member has an external terminal for thermistor and an external terminal for excitation electrodes on one main surface (the second main surface of the second sealing member) that does not face the vibrating portion. With this configuration, in the piezoelectric vibrating device of the present invention having a sandwich structure, the vibrating portion and the thin-film thermistor serving as a temperature sensor are positioned very close to each other, thereby reducing the temperature difference between the vibrating portion and the thin-film thermistor and the difference between the temperature of the vibrating portion and the temperature detected by the temperature sensor. Furthermore, because the thin-film thermistor is located in the first sealing member rather than in the second sealing member where the external terminals are provided, the path of heat conduction from the external substrate on which the piezoelectric vibrating device is mounted can be closer to the vibrating portion, allowing the thin-film thermistor to detect a temperature closer to the temperature of the vibrating portion.

[0009] Furthermore, if the first sealing member is configured as described above to have a thin-film thermistor on one main surface facing the vibration portion, the thin-film thermistor will not be exposed to the outside of the piezoelectric vibration device, and temperature changes and damage due to external factors can be prevented.

[0010] Furthermore, if the first sealing member does not have a through hole penetrating from one main surface to the other main surface as described above, it is possible to prevent poor formation of the thin-film thermistor due to the presence of the through hole, and the thin-film thermistor can be manufactured stably.

[0011] Furthermore, if a chip thermistor made of a sintered body (such as an NTC thermistor) is used, the thickness increases, making it difficult to take advantage of the low profile that is one of the advantages of the sandwich structure. However, a thin-film thermistor like that of the present invention makes it possible to incorporate a temperature sensor while still achieving a low profile.

[0012] Furthermore, the thin-film thermistor and the thermistor external terminals may be electrically connected to each other by wiring provided inside the piezoelectric vibration device when the first sealing member and the piezoelectric diaphragm are bonded and the second sealing member and the piezoelectric diaphragm are bonded. This configuration prevents the electrical continuity of the thin-film thermistor from being destroyed by external impact, etc., and limits heat conduction to the thin-film thermistor compared to when wiring is provided on the periphery of the piezoelectric vibration device, allowing the thin-film thermistor to exhibit stable performance. Furthermore, the thin-film thermistor and the thermistor external terminals can be electrically connected without providing a through-hole in the first sealing member.

[0013] Furthermore, the first sealing member, the piezoelectric diaphragm, and the second sealing member may each have a substrate made of quartz. With this configuration, heat transferred from the external substrate on which the piezoelectric vibrating device is mounted to the second sealing member via the external terminals can be uniformly conducted to the piezoelectric diaphragm and the first sealing member. More specifically, by using the same material (quartz crystal) for the substrates of each component constituting the piezoelectric vibrating device, the thermal conductivity of each component can be made equal. This means that the difference between the temperature of the vibrating part and the temperature detected by the temperature sensor can be further reduced.

[0014] According to the present invention, it is possible to provide a piezoelectric vibration device that can further reduce the difference between the temperature of the vibration part and the temperature detected by the temperature sensor.

[0015] 10 is a side view of a quartz crystal unit according to the present embodiment. FIG. 11 is a schematic plan view of the first main surface side of a first sealing member of a quartz crystal unit according to the present embodiment. FIG. 12 is a schematic plan view of the second main surface side of the first sealing member of a quartz crystal unit according to the present embodiment. FIG. 13 is a schematic plan view of the first main surface side of a quartz crystal plate of a quartz crystal unit according to the present embodiment. FIG. 14 is a schematic plan view of the second main surface side of a quartz crystal plate of a quartz crystal unit according to the present embodiment. FIG. 15 is a schematic plan view of the first main surface side of a second sealing member of a quartz crystal unit according to the present embodiment. FIG. 16 is a schematic plan view of the second main surface side of a second sealing member of a quartz crystal unit according to the present embodiment. FIG. 17 is an enlarged view of the vicinity of the thin film thermistor in FIG. 3. FIG. 8 is an A-A cross-sectional view of the thin film thermistor in FIG. 8. FIG. 18 is a schematic plan view of the second main surface side of a second sealing member according to a modified example. FIG. 19 is a cross-sectional view of a through-hole in the second sealing member in FIG.

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following preferred embodiments, a piezoelectric resonator device to which the present invention is applied is a quartz resonator.

[0017] First, the basic structure of a quartz crystal unit 100 according to this embodiment (first embodiment) will be described. As shown in FIG. 1 , the quartz crystal unit 100 is configured to include a quartz crystal vibrating plate (piezoelectric vibrating plate) 10, a first sealing member 20, and a second sealing member 30. In this quartz crystal unit 100, the quartz crystal vibrating plate 10 and the first sealing member 20 are joined together at a sealing portion (seal path) 115, and the quartz crystal vibrating plate 10 and the second sealing member 30 are joined together at a sealing portion (seal path) 116, thereby forming a package with a substantially rectangular parallelepiped sandwich structure. That is, in the quartz crystal unit 100, the first sealing member 20 and the second sealing member 30 are joined to both main surfaces of the quartz crystal vibrating plate 10, respectively, to form an internal space (cavity) of the package, and the vibrating portion 11 (see FIGS. 4 and 5 ) is hermetically sealed in this internal space.

[0018] Next, the quartz crystal plate 10, the first sealing member 20, and the second sealing member 30 of the quartz crystal unit 100 will be described with reference to Figures 1 to 7. Note that the description here focuses on the individual components that are not bonded together. Figures 2 to 7 merely show examples of the configuration of the quartz crystal plate 10, the first sealing member 20, and the second sealing member 30, and are not intended to limit the scope of the present invention.

[0019] As shown in FIGS. 4 and 5 , in this embodiment, an AT-cut quartz crystal plate that performs thickness-shear vibration is used as the quartz crystal plate 10. In the quartz crystal plate 10 shown in FIGS. 4 and 5 , both main surfaces 101 and 102 of the quartz crystal plate 10 are in the XZ′ plane. In this XZ′ plane, the direction parallel to the short side (short edge) of the quartz crystal plate 10 is the X-axis direction, and the direction parallel to the long side (long edge) of the quartz crystal plate 10 is the Z′-axis direction. Note that AT-cut is a processing technique in which a quartz crystal is cut at an angle of 35°15′ around the X-axis with respect to the Z-axis, one of the three crystal axes of the quartz crystal: the electrical axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). In an AT-cut quartz crystal plate, the X-axis coincides with the crystal axis of the quartz crystal. The Y'-axis and Z'-axis are inclined approximately 35°15' from the Y-axis and Z-axis of the quartz crystal (this cutting angle may be slightly changed to adjust the frequency-temperature characteristics of the AT-cut quartz crystal plate). The Y'-axis and Z'-axis directions correspond to the cutting direction when the AT-cut quartz crystal plate is cut. Furthermore, both main surfaces of the quartz crystal plate 10 (first main surface 101, second main surface 102) are formed as flat, smooth surfaces that have been polished to a mirror finish, for example.

[0020] The quartz crystal vibration plate 10 includes a substantially rectangular vibrating portion 11, an outer frame portion 12 surrounding the periphery of the vibrating portion 11, and a holding portion 13 connecting the vibrating portion 11 and the outer frame portion 12 to hold 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 cutout portion 10a is provided between the vibrating portion 11 and the outer frame portion 12 by cutting out the quartz crystal vibration plate 10. In this embodiment, the quartz crystal vibration plate 10 includes only one holding portion 13 connecting the vibrating portion 11 and the outer frame portion 12, and the cutout portion 10a is continuously formed to surround the periphery of the vibrating portion 11.

[0021] The thickness of the base material of the quartz crystal vibration plate 10 can be, for example, approximately 40 μm or approximately 60 μm. Furthermore, it is preferable that the vibrating portion 11 of the quartz crystal vibration plate 10 is formed thin relative to the outer frame portion 12, and it is more preferable that the thickness of the vibrating portion 11 is approximately half the thickness of the outer frame portion 12. In this case, it is preferable that the positions of the first main surface 101 of the outer frame portion 12 and the first main surface 101 of the vibrating portion 11 are different in the thickness direction (Y' direction). Note that the thickness of the vibrating portion 11 is related to the vibration characteristics of the quartz crystal unit 100. Therefore, the thickness of the vibrating portion 11 may be adjusted as appropriate to obtain a quartz crystal unit 100 with desired characteristics.

[0022] 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 vibrating plate 10. The first excitation electrode 111 is provided on the first main surface 101 side of the vibrating part 11, and the second excitation electrode 112 is provided on the second main surface 102 side of the vibrating part 11. Lead wiring (first lead wiring 113 and second lead wiring 114) is connected to the first excitation electrode 111 and the second excitation electrode 112 to connect these excitation electrodes to external electrode terminals. The first extraction wiring 113 is drawn out from the first excitation electrode 111 and connected to a connection junction pattern 12a formed on the first main surface 101 side of the outer frame portion 12 via the holding portion 13, and the connection junction pattern 12a is further connected to a connection junction pattern 12e formed on the second main surface 102 side of the outer frame portion 12 via a second front / back routing wiring 18 formed on the inner wall surface of the outer frame portion 12. In addition, the second extraction wiring 114 is drawn out from the second excitation electrode 112 and connected to a connection junction pattern 12d formed on the second main surface 102 side of the outer frame portion 12 via the holding portion 13.

[0023] 4 and 5 , both main surfaces (first main surface 101 and 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, respectively. 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 planar view. The outer peripheral edge of the diaphragm-side first bonding pattern 121 is provided in close proximity to the outer peripheral edge of the first main surface 101 of the quartz crystal vibration plate 10 (outer frame portion 12). The outer peripheral edge of the second diaphragm-side 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 portion 12). In this embodiment, the first diaphragm-side bonding pattern 121 and the second diaphragm-side bonding pattern 122 are connected via a first front-to-back wiring 17 formed on the inner wall surface of the outer frame portion 12. The first front-to-back wiring 17 is located on the inner wall surface of the outer frame portion 12 that is along the Z'-axis direction and on the -X direction side.

[0024] The outer frame 12 also has a first through-hole 161 that penetrates the quartz crystal vibration plate 10 in the thickness direction (between the first main surface 101 and the second main surface 102). Specifically, the first through-hole 161 is provided in the outer frame 12 on the inner periphery of the first vibration plate-side bonding pattern 121 and the second vibration plate-side bonding pattern 122. Around the first through-hole 161, a connection bonding pattern 12b is formed on the first main surface 101 side, and a connection bonding pattern 12g is formed on the second main surface 102 side. The outer frame 12 also has additional connection bonding patterns: a connection bonding pattern 12c is formed on the first main surface 101 side, and a connection bonding pattern 12f is formed on the second main surface 102 side.

[0025] In the first through hole 161, a through electrode for establishing electrical continuity between the electrodes formed on the first main surface 101 and the second main surface 102 is formed along the inner wall surface of the first through hole 161. Furthermore, the central portion of the first through hole 161 forms a hollow through portion that penetrates between the first main surface 101 and the second main surface 102. Note that electrical continuity between the electrodes on the first main surface 101 and the second main surface 102 may be achieved by means other than the through electrode of the through hole (for example, wiring formed on the inner wall surface of the outer frame portion 12, etc.).

[0026] As shown in Figures 2 and 3, the first sealing member 20 is formed as a rectangular parallelepiped substrate made from a single AT-cut quartz crystal plate. The first main surface 201 and second main surface 202 (the surfaces bonded to the quartz crystal vibration plate 10) of this first sealing member 20 are formed as flat, smooth surfaces (mirror-finished). Although the first sealing member 20 does not have a vibrating portion, it is preferable to use an AT-cut quartz crystal plate, similar to the quartz crystal vibration plate 10. In this embodiment, the X-axis, Y-axis, and Z'-axis of the first sealing member 20 are oriented in the same direction as the quartz crystal vibration plate 10. Furthermore, the thickness of the first sealing member 20 is preferably the same as that of the quartz crystal vibration plate 10.

[0027] Furthermore, the first sealing member 20 does not have any through holes that penetrate between the first main surface 201 and the second main surface 202. Therefore, the first main surface 201 of the first sealing member 20 (the upper surface of the quartz crystal unit 100) in this embodiment is a smooth surface on which the quartz crystal that forms the substrate of the first sealing member 20 is exposed over the entire surface.

[0028] As shown in FIG. 3 , a sealing member-side first bonding pattern 24 is formed on the second main surface 202 of the first sealing member 20 as a sealing member-side first sealing portion for bonding to the quartz-crystal vibrating plate 10. The sealing member-side first bonding pattern 24 is formed in an annular shape in a plan view. The outer peripheral edge of the sealing member-side first bonding pattern 24 is provided in close proximity to the outer peripheral edge of the second main surface 202 of the first sealing member 20. The second main surface 202 of the first sealing member 20 is also formed with a connection bonding pattern 22a for bonding to the connection bonding pattern 12a formed on the first main surface 101 of the outer frame portion 12 of the quartz-crystal vibrating plate 10, a connection bonding pattern 22b for bonding to the connection bonding pattern 12b formed on the first main surface 101 of the outer frame portion 12 of the quartz-crystal vibrating plate 10, and a connection bonding pattern 22c for bonding to the connection bonding pattern 12c formed on the first main surface 101 of the outer frame portion 12 of the quartz-crystal vibrating plate 10.

[0029] A thin-film thermistor 500 functioning as a temperature sensor is provided on the second main surface 202 of the first sealing member 20. In this embodiment, the thin-film thermistor 500 is disposed approximately in the center of the second main surface 202 and has a generally rectangular shape in plan view. The thin-film thermistor 500 is connected to the connection bonding pattern 22b by a first thermistor connection electrode 25, and is connected to the sealing member-side first bonding pattern 24 by a second thermistor connection electrode 26.

[0030] Fig. 8 is an enlarged view of the vicinity of thin film thermistor 500 in Fig. 3, and Fig. 9 is a cross-sectional view taken along line AA of thin film thermistor 500 in Fig. 8. Thin film thermistor 500 is composed of a pair of thermistor electrodes 501, 502, a resistive film 503, and a protective film 504. The thickness of thin film thermistor 500 can be set in the range of 1 to 10 µm.

[0031] The pair of thermistor electrodes 501, 502 are each formed in a comb shape with protrusions, and the protrusions of one thermistor electrode 501 and the other thermistor electrode 502 are alternately arranged with a predetermined gap between them so that they do not contact each other. An upper resistive film 503 fits into this gap. That is, the resistive film 503 is provided between the pair of opposing thermistor electrodes 501, 502, and the width of the resistive film 503 is the same as the distance between the opposing thermistor electrodes 501, 502. One thermistor electrode 501 is connected to the first thermistor connection electrode 25, and the other thermistor electrode 502 is connected to the second thermistor connection electrode 26.

[0032] The resistive film 503 is a thin film made of an insulating material and formed so as to cover at least a portion of the pair of thermistor electrodes 501, 502, and in this embodiment is formed in a substantially rectangular shape. Preferably, the resistive film 503 is formed so as to cover the entire pair of thermistor electrodes 501, 502. The insulating material for the resistive film 503 may be, for example, an oxide of an alloy, and more specifically, an MnCoNi-based alloy.

[0033] The protective film 504 is a thin film made of an insulating material and formed to cover the pair of thermistor electrodes 501, 502 and the resistive film 503, and is formed in a substantially rectangular shape in this embodiment. The insulating material that forms the protective film 504 can be, for example, a SiO2-based material.

[0034] The characteristics of the thin film thermistor 500, such as the B constant and resistance value, vary depending on the material configuration, area, and shape of the pair of thermistor electrodes 501, 502 and the resistive film 503. The desired characteristics, such as the B constant and resistance value, are determined by the application and characteristics of the quartz crystal unit 100. Therefore, the material configuration, area, and shape of the pair of thermistor electrodes 501, 502 and the resistive film 503 are changed as appropriate depending on the application and characteristics of the quartz crystal unit 100.

[0035] As shown in Figures 6 and 7, the second sealing member 30 is formed as a rectangular parallelepiped substrate made from a single AT-cut quartz crystal plate. The first main surface 301 (the surface bonded to the quartz crystal plate 10) and the second main surface 302 (the bottom surface of the quartz crystal unit 100) of the second sealing member 30 are formed as flat, smooth surfaces (mirror-finished). The second sealing member 30 preferably uses an AT-cut quartz crystal plate, similar to the quartz crystal plate 10, and the orientations of the X-axis, Y-axis, and Z'-axis are preferably the same as those of the quartz crystal plate 10. Furthermore, the thickness of the second sealing member 30 is preferably the same as that of the quartz crystal plate 10 and the first sealing member 20.

[0036] 7, four external electrode terminals 32a, 32b, 32c, and 32d are provided on the second main surface 302 of the second sealing member 30 (the outer main surface that does not face the quartz crystal vibrating plate 10), which are electrically connected to an external circuit board provided outside the quartz crystal vibrating device 100. Each of the external electrode terminals 32a, 32b, 32c, and 32d is formed in a substantially rectangular shape and is located at one of the four corners of the second main surface 302 of the second sealing member 30. Each of the external electrode terminals 32a, 32b, 32c, and 32d is located at a position that overlaps with the outer frame portion 12 of the quartz crystal vibrating plate 10 described above in a plan view.

[0037] 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, second, third, fourth, and fifth through holes 162, 163, 164, and 165 are provided in the second sealing member 30, respectively.

[0038] In the second, third, fourth, and fifth through holes 162, 163, 164, and 165, 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 second, third, fourth, and fifth through holes 162, 163, 164, and 165. The central portions of the second, third, fourth, and fifth through holes 162, 163, 164, and 165 respectively form hollow through portions that penetrate between the first main surface 301 and the second main surface 302. The through electrode of the second through hole 162 is electrically connected to the external electrode terminal 32a, the through electrode of the third through hole 163 is electrically connected to the external electrode terminal 32b, the through electrode of the fourth through hole 164 is electrically connected to the external electrode terminal 32c, and the through electrode of the fifth through hole 165 is electrically connected to the external electrode terminal 32d.

[0039] As shown in FIG. 6 , 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 an annular shape in a plan view. The outer periphery of the sealing member-side second bonding pattern 31 is located close to the outer periphery of the first main surface 301 of the second sealing member 30. On the first main surface 301 of the second sealing member 30, a connection bonding pattern 33a is formed around the second through hole 162, a connection bonding pattern 33b is formed around the fourth through hole 164, and a connection bonding pattern 33c is formed around the fifth through hole 165. Furthermore, a connection bonding pattern 33d is formed on the opposite side of the second sealing member 30 in the Z′ direction from the connection bonding pattern 33b, and the connection bonding pattern 33b and the connection bonding pattern 33d are connected by a wiring pattern 34.

[0040] In the quartz crystal unit 100 including the quartz crystal vibrating plate 10, first sealing member 20, and second sealing member 30 configured as described above, the quartz crystal vibrating plate 10 and the first sealing member 20 are diffusion bonded together with the diaphragm-side first bonding pattern 121 and the sealing member-side first bonding pattern 24 overlapping each other, and the quartz crystal vibrating plate 10 and the second sealing member 30 are diffusion bonded together with the diaphragm-side second bonding pattern 122 and the sealing member-side second bonding pattern 31 overlapping each other, thereby manufacturing a sandwich-structured package. This hermetically seals the internal space of the package, i.e., the space housing the vibrating portion 11 and the thin-film thermistor 500.

[0041] At this time, the vibrating portion 11 and the thin-film thermistor 500 are arranged facing each other. More specifically, for example, if the thickness of the quartz crystal vibrating plate 10 (outer frame portion 12), the first sealing member 20, and the second sealing member 30 is approximately 40 μm, and the thickness of the vibrating portion 11 is approximately 20 μm, thinner than the outer frame portion 12, the distance between the vibrating portion 11 and the second main surface 202 of the first sealing member 20 is approximately 10 μm. Therefore, in such a case, the thin-film thermistor 500, which has a thickness of 1 to 10 μm, and the vibrating portion 11 are arranged in close proximity, with the distance between them being approximately 9 μm or less. The distance between the vibrating portion 11 and the thin-film thermistor 500 only needs to be large enough so that the vibrating portion 11 and the thin-film thermistor 500 do not come into contact with each other, and is preferably 10 μm or less.

[0042] 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 conduction is established between the first excitation electrode 111 and the external electrode terminal 32a, and electrical conduction is established between the second excitation electrode 112 and the external electrode terminal 32c in the quartz-crystal resonator 100. Specifically, the first excitation electrode 111 is connected to the external electrode terminal 32a via the first escape wiring 113, the connection bonding pattern 12a, the second front-rear wiring 18, the connection bonding pattern 12e, the connection bonding pattern 33a, and the through electrode of the second through-hole 162, in that order. The second excitation electrode 112 is connected to the external electrode terminal 32c via the second escape wiring 114, the connection bonding pattern 12d, the connection bonding pattern 33d, the wiring pattern 34, the connection bonding pattern 33b, and the through electrode of the fourth through-hole 164, in that order.

[0043] Furthermore, the quartz crystal resonator 100 of this embodiment is formed with a sealing portion (seal path) that hermetically seals the vibrating portion 11 of the quartz crystal vibrating plate 10. The seal path is composed of a first seal path 115 formed by diffusion bonding (Au-Au bonding) between the above-mentioned diaphragm-side first bonding pattern 121 and the sealing member-side first bonding pattern 24, and a second seal path 116 formed by diffusion bonding (Au-Au bonding) between the above-mentioned diaphragm-side second bonding pattern 122 and the sealing member-side second bonding pattern 31. The first and second seal paths 115, 116 are not electrically connected to the electrical conduction paths between the first and second excitation electrodes 111, 112 and the external electrode terminals 32 a, 32 c. Specifically, the first seal path 115 is connected to the second seal path 116 via the first front-to-back wiring 17, and the second seal path 116 is further connected to the external electrode terminal 32b via the through electrode of the third through hole 163. Note that the external electrode terminal 32b in this embodiment is earth-connected (ground-connected). That is, the external electrode terminal 32b in this embodiment functions as a ground terminal.

[0044] The thin-film thermistor 500 is also connected to the connection bonding pattern 22b via the first thermistor connection electrode 25. The connection bonding pattern 22b is then connected to the external electrode terminal 32d via the connection bonding pattern 12b, the through electrode of the first through hole 161, and the through electrode of the fifth through hole 165, in that order. Therefore, the thin-film thermistor 500 is electrically connected to the external electrode terminal 32d. Furthermore, the thin-film thermistor 500 is connected to the sealing member-side first bonding pattern 24 via the second thermistor connection electrode 26. Therefore, the thin-film thermistor 500 is grounded.

[0045] Furthermore, when the quartz crystal oscillator 100 is viewed in a planar view (viewed from the Y' direction), it is preferable that the thin film thermistor 500 is arranged so that at least a portion of it overlaps with the vibration part 11, the first excitation electrode 111, and the second excitation electrode 112.

[0046] In the quartz crystal unit 100, the various bonding patterns described above can be formed by stacking multiple layers on a quartz crystal plate, with a Ti (titanium) layer and an Au (gold) layer formed from the bottom layer onward by vapor deposition or sputtering. Furthermore, if other wiring and electrodes formed on the quartz crystal unit 100 have the same configuration as the bonding patterns, the bonding patterns, wiring, and electrodes can be patterned simultaneously. The various bonding patterns, wiring, and electrodes described above may also be formed by photolithography.

[0047] Furthermore, the pair of thermistor electrodes 501, 502 of the thin-film thermistor 500 can be formed by stacking multiple layers on a quartz crystal plate, similar to the various bonding patterns in the quartz crystal unit 100, with a Ti (titanium) layer and an Au (gold) layer formed from the bottom layer on top by vapor deposition or sputtering. The pair of thermistor electrodes 501, 502 of the thin-film thermistor 500 can also be formed by photolithography. In this case, it is preferable to apply a resist by spin coating during photolithography. Applying the resist by spin coating allows for a thin, uniform resist film. In other words, patterning can be more reliably performed when forming the components of the thin-film thermistor 500, such as the thermistor electrodes 501, 502, the resistive film 503, and the protective film 504, by photolithography.

[0048] Furthermore, it is preferable that the wiring patterns connecting the thin film thermistor 500 and the external electrode terminals 32d are not arranged on the outer periphery of the quartz crystal unit 100. In other words, it is preferable that the wiring patterns connecting the thin film thermistor 500 and the external electrode terminals 32d are arranged inside the quartz crystal unit 100. Furthermore, in the first sealing member 20 including the thin film thermistor 500, it is more preferable that the first main surface 201 on the side not including the thin film thermistor 500 and the side peripheral surface connecting the first main surface 201 and the second main surface 202 do not have unevenness such as electrodes or wiring. Note that in the quartz crystal unit 100 of this embodiment, all wiring is arranged inside the sealed state, and electrodes and wiring other than the four external electrode terminals 32a, 32b, 32c, and 32d are not arranged on the outer periphery of the quartz crystal unit 100.

[0049] The above configuration provides a piezoelectric resonator device that can further reduce the difference between the temperature of the vibrating portion and the temperature detected by the temperature sensor. The quartz crystal resonator 100 includes a thin-film thermistor 500 on the second main surface 202 of the first sealing member 20 that faces the vibrating portion 11, no through-holes extending from the second main surface 202 to the first main surface 201 are provided, and the second sealing member 30 includes an external electrode terminal 32d electrically connected to the thin-film thermistor 500 and external electrode terminals 32a, 32c electrically connected to the excitation electrodes 111, 112 on the second main surface 302 that does not face the vibrating portion 11. With this configuration, the quartz crystal resonator 100 of the present invention has a sandwich structure, and the vibrating portion 11 and the thin-film thermistor 500, which is a temperature sensor, are positioned very close to each other, thereby further reducing the temperature difference between the vibrating portion 11 and the thin-film thermistor 500 due to radiant heat. Furthermore, since the thin-film thermistor 500 is provided in the first sealing member 20 rather than the second sealing member 30 on which the external terminals are provided, the path of heat conduction from the external substrate on which the quartz crystal oscillator 100 is mounted can be made closer to the vibrating part 11, and the thin-film thermistor 500 can detect a temperature closer to the temperature of the vibrating part 11.

[0050] Furthermore, as described above, if the first sealing member 20 has the thin-film thermistor 500 on the second main surface 202 facing the vibration portion 11, the thin-film thermistor 500 is not exposed to the outside of the quartz crystal unit 100, preventing temperature changes and damage due to external factors. Furthermore, when bonding the first sealing member 20 and the quartz crystal vibration plate 10, it is possible to prevent the first sealing member 20 from being incompletely held due to unevenness caused by the thin-film thermistor 500, thereby enabling stable manufacturing.

[0051] Furthermore, as described above, if the first sealing member 20 does not have through holes penetrating from the second main surface 202 to the first main surface 201, poor formation of the thin-film thermistor 500 due to the presence of through holes can be prevented, enabling stable production. In particular, resist application by spin coating is preferably performed when forming the thin-film thermistor 500. However, if the first sealing member 20 on which the thin-film thermistor 500 is to be formed has through holes, the uniformity of the resist film formed by spin coating is affected, making uniform resist application difficult. Therefore, the above-described configuration enables the use of spin coating, thereby more reliably forming the thin-film thermistor 500. More specifically, the formation of each component of the thin-film thermistor 500, such as the thermistor electrodes 501 and 502, the resistive film 503, and the protective film 504, using photolithography can be performed with high precision. Even if the thin-film thermistor 500 is formed before the through holes are formed, a metal film must be formed again when the through holes are formed. Therefore, forming the through holes later is undesirable because it may change the shape of the electrode film of the thin film thermistor 500 or the wiring drawn out from the thin film thermistor 500, thereby changing the characteristics of the thin film thermistor 500. In other words, if the first sealing member 20 does not have a through hole penetrating from the second main surface 202 to the first main surface 201 as described above, it is possible to stably form a thin film thermistor 500 having performance more suited to the quartz crystal unit 100.

[0052] Furthermore, while using a chip thermistor (such as an NTC thermistor) made of a sintered body increases the thickness, making it difficult to utilize the low profile that is an advantage of the sandwich structure, the thin-film thermistor 500 of the present invention allows for both the incorporation of a temperature sensor and a low profile. Furthermore, by using the thin-film thermistor 500 of the present invention, the heat capacity can be reduced compared to chip thermistors and the like, allowing for quick tracking of temperature changes in the substrate (quartz crystal in this embodiment). Furthermore, the sensitivity (resolution) can be increased compared to other temperature sensors with small heat capacity (such as those that reference the resistance value of a metal thin film).

[0053] Furthermore, in a state in which the first sealing member 20 and the quartz crystal plate 10 are bonded together and the second sealing member 30 and the quartz crystal plate 10 are bonded together to form the quartz crystal unit 100, the thin film thermistor 500 and the external electrode terminal 32d are electrically connected to each other by wiring provided inside the quartz crystal unit 100. With this configuration, the conduction of the thin film thermistor 500 is prevented from being destroyed by external impact, etc., and heat conduction to the thin film thermistor 500 can be limited compared to when wiring is provided on the outer periphery of the quartz crystal unit 100, allowing the thin film thermistor 500 to exhibit stable performance. Furthermore, the thin film thermistor and the thermistor external terminal can be electrically connected without providing a through-hole in the first sealing member 20.

[0054] Furthermore, in the first sealing member 20 having the thin-film thermistor 500, the first main surface 201 on the side not having the thin-film thermistor 500 and the side peripheral surface connecting the first main surface 201 and the second main surface 202 are configured to have no irregularities such as electrodes or wiring. With this configuration, no irregularities due to wiring (electrodes) are formed on the holding surface when the first sealing member 20 is joined, so there are no elements that interfere with holding, allowing for stable manufacturing.

[0055] Furthermore, the first sealing member 20, the quartz crystal vibrating plate 10, and the second sealing member 30 each have a substrate formed from AT-cut quartz crystal. With this configuration, heat transferred from the external substrate on which the quartz crystal unit 100 is mounted to the second sealing member 30 via the external electrode terminals 32a, 32b, 32c, and 32d can be uniformly conducted to the quartz crystal vibrating plate 10 and the first sealing member 20, further reducing the temperature difference between the vibrating portion 11 and the thin-film thermistor 500. Furthermore, the quartz crystal vibrating plate 10 and the first sealing member 20 can have the same thermal expansion coefficient, thereby suppressing thermal deformation of the quartz crystal unit 100.

[0056] Furthermore, the first sealing member 20, the quartz crystal vibration plate 10, and the second sealing member 30 are all made of AT-cut quartz crystal, and are all the same thickness. With this configuration, heat transferred from the external substrate on which the quartz crystal unit 100 is mounted to the second sealing member 30 via the external electrode terminals 32a, 32b, 32c, and 32d can be conducted more uniformly to the quartz crystal vibration plate 10 and the first sealing member 20, further reducing the temperature difference between the vibration part 11 and the thin-film thermistor 500.

[0057] Furthermore, the quartz crystal vibrating plate 10 has a configuration in which the vibrating portion 11 is formed to be thinner than the outer frame portion 12. This configuration allows for greater freedom in setting the thickness of the thin film thermistor 500. In other words, this increases the degree of freedom in determining the characteristics of the resulting thin film thermistor 500, thereby broadening the options for the characteristics of the quartz crystal vibrator 100.

[0058] It should be noted that the present invention is not limited to the configurations of the above-described embodiments, and many other embodiments are possible. For example, in the present embodiments, the vibrating portion 11 is generally rectangular and has a first excitation electrode 111 on the first main surface 101 and a second excitation electrode 112 on the second main surface 102. However, the vibrating portion 11 may also be shaped like a tuning fork, with a pair of protruding vibrating arms (corresponding to the vibrating portion in each embodiment) having the first excitation electrode 111 and the second excitation electrode 112 on each main surface. In such a case, the crystal vibrating plate 10 including the vibrating portion 11 has a base material formed from XY-cut quartz crystal. It is also preferable that the base materials of the substrates of the first sealing member 20 and the second sealing member 30 are also formed from XY-cut quartz crystal.

[0059] In addition, in this embodiment, the quartz crystal vibration plate 10 and the first and second sealing members 20 and 30 are joined by diffusion bonding (Au-Au bonding), but they may also be joined by a brazing material such as AuSn brazing.

[0060] In addition, in this embodiment, the substrates of the first sealing member 20 and the second sealing member 30 are formed from quartz crystal, but for example, the substrate of at least one of the first sealing member 20 and the second sealing member 30 may be formed from one selected from glass and silicon. Furthermore, in this embodiment, the base material of the quartz crystal vibration plate 10 is formed from AT-cut quartz crystal, but it may be formed from quartz crystal obtained in a different cutting direction. In such a case, it is preferable that the substrates of the first sealing member 20 and the second sealing member 30 bonded to the quartz crystal vibration plate 10 are formed from quartz crystal obtained in the same cutting direction as the quartz crystal vibration plate 10.

[0061] When the quartz crystal unit 100 is mounted on an external substrate, the external electrode terminals 32a, 32b, 32c, and 32d formed on the second main surface 302 of the second sealing member 30 are joined to the external substrate by solder. However, if the through electrodes in the second to fifth through holes 162 to 165 formed in the second sealing member 30 have an Au (gold) film, there is a risk that the solder will wet and spread (crawl up) into the through electrodes along the Au film. Such solder corrosion can cause the Au constituting the Au film to aggregate, which can increase electrical resistance, cause problems such as disconnections, and / or cause poor airtightness of the first and second sealing paths 115 and 116.

[0062] Therefore, as shown in the modified examples in Figures 10 and 11, the external electrode terminals 32a, 32b, 32c, and 32d of the second sealing member 30 and the through electrodes of the second to fifth through holes 162 to 165 are provided with a structure that suppresses the erosion of solder. As shown in Figure 11, the second through hole 162 of the second sealing member 30 is formed with a generally hourglass-shaped cross section having an inclined surface 162a. More specifically, the second through hole 162 has a through portion 162b in the center of the thickness direction of the second sealing member 30, and the opening area gradually decreases from the opening end side (the first main surface 301 side and the second main surface 302 side) to the center. A through electrode 162c is formed on the inner wall surface (the inclined surface 162a) of the second through hole 162. The through electrode 162c provides electrical continuity between the electrode (connection bonding pattern) 33a formed on the first main surface 301 of the second sealing member 30 and the external electrode terminal 32a formed on the second main surface 302. Note that while Fig. 11 only illustrates the external electrode terminal 32a of the second sealing member 30 and the through electrode 162c of the second through hole 162, the other external electrode terminals 32b, 32c, and 32d and the through electrodes of the third to fifth through holes 163 to 165 have the same configuration.

[0063] The connection bonding pattern 33a on the first main surface 301 of the second sealing member 30 has a configuration including a first metal film 33e made of a first conductive metal formed by, for example, vapor deposition on the first main surface 301, and an Au film 33f made of, for example, Au (gold) formed by, for example, vapor deposition on the first metal film 33e. The external electrode terminal 32a on the second main surface 302 of the second sealing member 30 has a configuration including a first metal film 32e made of a first conductive metal formed by, for example, vapor deposition on the first metal film 32e, a second metal film 32f made of a second conductive metal formed by, for example, vapor deposition on the first metal film 32e, and an Au film 32g made of, for example, Au (gold) formed by, for example, vapor deposition on the second metal film 32f. The through electrode 162c of the second through hole 162 includes a first metal film 162d made of a first conductive metal, for example, deposited by vapor deposition on the inclined surface 162a of the second through hole 162, a second metal film 162e made of a second conductive metal, for example, deposited by vapor deposition on the first metal film 162d, and an Au film 162f made of Au (gold), for example, deposited by vapor deposition on the second metal film 162e. The Au film 162f is formed only on the inclined surface 162a on the upper side (first main surface 301 side) of the second through hole 162, but not on the inclined surface 162a on the lower side (second main surface 302 side). In this case, the through electrode 162c of the second through hole 162 can be formed by partially removing the Au film formed on the entire inclined surface 162a of the second through hole 162, for example, by metal etching. In this example, the Au film is removed from the end on the external electrode terminal 32 a side to a portion beyond the center of the through electrode 162 c in the depth direction. Note that the entire Au film may be removed in the through electrode 162 c of the second through hole 162.

[0064] The first metal film 33e of the connection bonding pattern 33a, the first metal film 162d of the through electrode 162c, and the first metal film 32e of the external electrode terminal 32a are integrally formed. The second metal film 162e of the through electrode 162c and the second metal film 32f of the external electrode terminal 32a are integrally formed. The Au film 33f of the connection bonding pattern 33a and the Au film 162f of the through electrode 162c are integrally formed. In this example, Ti (titanium) is used as the first conductive metal, and Ni (nickel) is used as the second conductive metal. The first and second conductive metals described above are merely examples, and other conductive metals may also be used. The multilayer structure of the through electrode 162c, external electrode terminal 32a, and connection bonding pattern 33a described above is merely an example, and the number of layers of each electrode is not particularly limited. For example, the connection junction pattern 33a may have a three-layer structure with a second metal film, similar to the external electrode terminal 32a, or the external electrode terminal 32a may have a two-layer structure without a second metal film, similar to the connection junction pattern 33a.

[0065] In this modification, the Au film 33f of the connection junction pattern 33a and the Au film 32g of the external electrode terminal 32a are not integrally formed. The Au film is removed from the end of the second through-hole 162 on the external electrode terminal 32a side to a portion beyond the center in the depth direction, and the Au film is blocked inside the second through-hole 162. The Au film 33f of the connection junction pattern 33a and the Au film 32g of the external electrode terminal 32a are electrically connected by a first metal film 162d formed of a conductive metal other than Au. In addition to removing the Au film from the through-electrodes 162c of the second through-hole 162, the Au film is also removed from the peripheral portion (periphery) of the external electrode terminal 32a on the second main surface 302. As shown in FIG. 10 , a substantially rectangular portion of the Au film is removed from each of the external electrode terminals 32a to 32d, exposing the second metal film 32f in this portion. Furthermore, an Au film 32g is provided in a substantially L-shape on each of the external electrode terminals 32a to 32d.

[0066] As described above, the Au film, which can serve as a solder corrosion path, is blocked from the external electrode terminal 32a on the second main surface 302 and the through electrode 162c of the second through hole 162, and the first metal film 162d formed of a conductive metal other than Au provides electrical continuity between the connection bonding pattern 33a on the first main surface 301 of the second sealing member 30 and the external electrode terminal 32a on the second main surface 302. By removing the Au film, the corrosion path of the solder in the through electrode 162c can be blocked, thereby suppressing the spread of solder into the through electrode 162c and preventing problems such as increased electrical resistance and broken wires. Furthermore, poor airtightness of the first and second seal paths 115, 116 due to solder creeping up can be suppressed.

[0067] In this modified example, the second to fifth through-holes 162-165 may be further filled with a metal or a conductive resin formed by mixing a metal and a resin. With this configuration, for example, removing the Au film from the through-hole electrodes 162c of the second through-holes 162 and removing the Au film from the peripheral portions of the external electrode terminals 32a on the second main surface 302 surrounding the second through-holes 162 increases the electrical resistance and deteriorates the electrical characteristics of the quartz crystal unit 100. However, the metal or conductive resin in the second through-holes 162 reduces the electrical resistance, thereby preventing deterioration of the electrical characteristics of the quartz crystal unit 100. The metal filling the second to fifth through-holes 162-165 and the metal mixed into the conductive resin may be a metal other than gold (Au), such as silver (Ag).

[0068] In the present invention and this embodiment, the first main surface of the first sealing member of the present invention corresponds to the first main surface 201 of this embodiment, and similarly, the second main surface of the first sealing member corresponds to the second main surface 202, the first main surface of the second sealing member corresponds to the first main surface 301, the second main surface of the second sealing member corresponds to the second main surface 302, the external terminal for the thermistor corresponds to the external electrode terminal 32d, and the external terminal for the excitation electrode corresponds to the external electrode terminals 32a and 32c.

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

[0070] This application claims priority from Japanese Patent Application No. 2024-034635, filed on March 7, 2024, the entire contents of which are incorporated herein by reference.

[0071] The piezoelectric vibration device of the present invention can be used in the industry of manufacturing and selling piezoelectric vibration devices having a sandwich structure.

[0072] REFERENCE SIGNS LIST 10 quartz crystal plate 111 first excitation electrode 112 second excitation electrode 20 first sealing member 201 first main surface 202 second main surface 30 second sealing member 301 first main surface 302 second main surface 32a, 32b, 32c, 32d external electrode terminal 100 quartz crystal resonator 500 thin film thermistor 501, 502 thermistor electrode 503 resistive film 504 protective film

Claims

1. A piezoelectric vibration device comprising: a piezoelectric diaphragm having a first excitation electrode formed on a main surface of a substrate and a second excitation electrode formed on the main surface of the substrate and paired with the first excitation electrode; and first and second sealing members covering both main surfaces of the piezoelectric diaphragm; wherein the first sealing member and the piezoelectric diaphragm are joined together, and the second sealing member is joined together to the piezoelectric diaphragm, thereby providing an internal space in which a vibration portion of the piezoelectric diaphragm including the first excitation electrode and the second excitation electrode is hermetically sealed; wherein the first sealing member has a first sealing member first main surface that does not face the vibration portion, and a first sealing member second main surface that is a back side of the first sealing member first main surface and faces the vibration portion; a thin film thermistor is provided on the first sealing member second main surface; and no through hole is provided that passes through from the first sealing member first main surface to the first sealing member second main surface; and the second sealing member has a second sealing member first main surface that faces the vibration portion, a second sealing member second main surface that is the back side of the first main surface of the second sealing member and does not face the vibration section, and the second sealing member second main surface is provided with a thermistor external terminal electrically connected to the thin film thermistor, and an excitation electrode external terminal electrically connected to each of the first excitation electrode and the second excitation electrode.

2. A piezoelectric vibration device as described in claim 1, characterized in that the thin film thermistor and the external terminal for the thermistor are electrically connected to each other by wiring provided inside the piezoelectric vibration device when the first sealing member and the piezoelectric vibration plate are bonded and the second sealing member and the piezoelectric vibration plate are bonded.

3. A piezoelectric vibration device according to claim 1 or 2, wherein the substrates of the first sealing member, the piezoelectric vibration plate and the second sealing member are each formed from quartz crystal.

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