Piezoelectric vibration device and method for manufacturing a piezoelectric vibration device

Abstract

The present invention provides a piezoelectric vibration device and a method for manufacturing a piezoelectric vibration device that suppresses the creeping of metal brazing material into through holes formed in the second sealing member, while also improving its electrical characteristics. [Solution] The quartz crystal oscillator 100 has a through hole 161 provided in the second sealing member 30, which has a conductive electrode 161c on its inner wall surface that electrically connects the sealing member side first bonding pattern 24 formed on the first main surface 301 with the external terminal 32a, and the inner wall surface has a first inclined portion 161a on the first main surface 301 side and a second inclined portion 161b on the second main surface 302 side, such that the through hole 161 becomes narrower toward the center in the thickness direction of the second sealing member 30, and an embedded metal layer 161d embedded in the second inclined portion 161b as a layer below the conductive electrode 161c.

Description

Technical Field

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

Background Art

[0002] In recent years, the operating frequencies of various electronic devices have been increasing, and the packages have been miniaturized (especially made thinner). Therefore, along with the increase in frequency and the miniaturization of the package, piezoelectric vibration devices (such as crystal resonators, crystal oscillators, etc.) are also required to respond to the increase in frequency and the miniaturization of the package.

[0003] In this type of piezoelectric vibration device, the housing is composed of a package having a substantially rectangular parallelepiped shape. This package is composed of, for example, a first sealing member and a second sealing member made of glass or crystal, and a piezoelectric vibration plate made of crystal with excitation electrodes formed on both main surfaces. The first sealing member and the second sealing member are laminated and joined via the piezoelectric vibration plate. Then, the vibration part (excitation electrode) of the piezoelectric vibration plate piezoelectric vibration element arranged inside the package (internal space) is hermetically sealed (for example, Patent Document 1). Hereinafter, such a laminated form of the piezoelectric vibration device is referred to as a sandwich structure. Further, as a method of mounting such a piezoelectric vibration device on an external circuit board, there is a method of electrically connecting an external terminal formed on the bottom surface of the piezoelectric vibration device to a mounting pad formed on the external circuit board via a metal brazing material such as solder.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when a sandwich-structured piezoelectric vibrator is mounted to an external circuit board or the like by soldering, which is a type of metal brazing material, solder contains tin (Sn). Therefore, if the conductive electrode in the through-hole has an Au (gold) film, the solder may creep up along this Au film within the through-hole and even reach the vibrating part of the piezoelectric diaphragm (piezoelectric vibrating element). The solder that creeps up into the through-hole may diffuse into the conductive electrode and the internal electrode, potentially leading to a decrease in electrical connectivity between the electrode (first excitation electrode, second excitation electrode, etc.) and the corresponding external terminal, vibration inhibition of the piezoelectric vibrating element, and airtightness failure due to corrosion of the metal materials of the first and second sealing members.

[0006] Furthermore, if the outermost layer of the conductive electrode is configured without an Au film to prevent solder from creeping up, the absence of the Au film, which has low conductive resistance, increases the conductive resistance in the through-holes, leading to a problem where the electrical characteristics of the piezoelectric vibrator deteriorate.

[0007] The present invention has been made in view of the above problems, and aims to provide a piezoelectric vibration device and a method for manufacturing a piezoelectric vibration device that can suppress the crawling up of metal brazing material into through holes formed in the second sealing member, and improve electrical characteristics. [Means for solving the problem]

[0008] The present invention relates to a piezoelectric vibration device comprising a piezoelectric vibration element having a first excitation electrode formed on one main surface of a piezoelectric substrate and a second excitation electrode paired with the first excitation electrode, and a first sealing member and a second sealing member covering both main surfaces of the piezoelectric vibration element, wherein the first sealing member and the piezoelectric vibration element are joined, and the second sealing member and the piezoelectric vibration element are joined, thereby providing an internal space in which the vibrating portion of the piezoelectric vibration element, including the first and second excitation electrodes, is hermetically sealed, wherein the second sealing member has a first main surface facing the vibrating portion, a second main surface which is the back surface of the first main surface and does not face the vibrating portion, and a portion that penetrates from the first main surface to the second main surface. The device has a through hole and an external terminal provided on the second main surface, the through hole has a conductive electrode on its inner wall surface that electrically connects an internal electrode formed on the first main surface and the external terminal, the inner wall surface has a first inclined portion on the first main surface side and a second inclined portion on the second main surface side such that the through hole narrows toward the center in the thickness direction of the second sealing member, and has an embedded metal layer embedded as a layer below the conductive electrode in at least the second inclined portion, the conductive electrode does not have gold in at least the outermost layer in the second inclined portion, and the embedded metal layer is a piezoelectric vibration device with a conductivity resistance lower than that of the conductive electrode laminated on the embedded metal layer.

[0009] In other words, the piezoelectric vibration device of the present invention has an embedded metal layer embedded as a layer beneath the conductive electrode in the second inclined portion of the through hole, the conductive electrode does not have gold in at least the outermost layer in the second inclined portion, and the embedded metal layer has a smaller conductivity resistance than the conductive electrode laminated on top of the embedded metal layer. With this configuration, it is possible to reliably prevent the metal brazing material that joins the external circuit board and the piezoelectric vibration device from creeping up into the through hole. More specifically, with the above configuration, it is possible to have a configuration in which the outermost layer of the inclined portion on the second main surface side (second inclined portion) that is joined with the metal brazing material in the through hole does not have gold, which has high wettability with the metal brazing material, and thus the creeping up into the through hole can be suppressed.

[0010] Furthermore, in the second inclined section, where the outermost layer does not contain gold, the conductivity resistance of the conductive electrodes increases, which may worsen the electrical characteristics of the piezoelectric vibration device. However, with the configuration of the present invention, the conductivity resistance of the embedded metal layer provided in the second inclined section is smaller than that of the conductive electrodes laminated on the embedded metal layer, thus improving the electrical characteristics of the piezoelectric vibration device. In other words, it is possible to suppress the creeping of metal brazing material into the through-hole and achieve good electrical characteristics of the piezoelectric vibration device by reducing conductivity resistance.

[0011] Furthermore, the embedded metal layer may be provided from the second inclined portion to the second main surface and may overlap, at least in part, with all the metal layers constituting the external terminals. With such a configuration, the conductivity resistance not only in the second inclined portion but also in the second main surface can be reduced, thereby improving the electrical characteristics of the piezoelectric vibration device.

[0012] Furthermore, the embedded metal layer may have a first metal layer made of titanium or chromium and a second metal layer made of gold, with the second metal layer being covered by conductive electrodes and external terminals. With such a configuration, gold, which has low conductivity, is embedded as the embedded metal layer, making it possible to further reduce the conductivity in the second inclined portion and the second main surface, thereby improving the electrical characteristics of the piezoelectric vibration device. In addition, since the second metal layer made of gold is covered by conductive electrodes and external terminals, the gold, which has high wettability with metal brazing material, does not come into contact with the metal brazing material, and the metal brazing material does not creep up inside the through hole.

[0013] Furthermore, the present invention may include a piezoelectric vibration element manufacturing step for manufacturing a piezoelectric vibration element, a first sealing member manufacturing step for manufacturing a first sealing member, a second sealing member manufacturing step for manufacturing a second sealing member, a first sealing member joining step for joining the piezoelectric vibration element and the first sealing member, and a second sealing member joining step for joining the piezoelectric vibration element and the second sealing member, wherein the second sealing member manufacturing step includes an embedded metal layer forming step for forming an embedded metal layer and a conductive electrode forming step for forming a conductive electrode, and the embedded metal layer forming step may be performed before the conductive electrode forming step. With such a configuration, the manufacturing method can be such that an embedded metal layer is formed in the second inclined portion of the through hole, and then the embedded metal layer is covered with a conductive electrode, and the present invention can be easily realized having an embedded metal layer embedded in the second inclined portion as a lower layer of the conductive electrode. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a piezoelectric vibration device and a method for manufacturing a piezoelectric vibration device that can suppress the crawling up of the metal brazing material into the through hole formed in the second sealing member, while also improving its electrical characteristics. [Brief explanation of the drawing]

[0015] [Figure 1] A side view of a quartz crystal oscillator according to the first embodiment. [Figure 2] A schematic plan view of the first main surface side of the first sealing member of the quartz crystal oscillator according to the first embodiment. [Figure 3] A schematic plan view of the second main surface side of the first sealing member of the quartz crystal oscillator according to the first embodiment. [Figure 4] A schematic plan view of the first main surface side of the quartz crystal diaphragm of a quartz crystal oscillator according to the first embodiment. [Figure 5] A schematic plan view of the second main surface side of the quartz crystal diaphragm of a quartz crystal oscillator according to the first embodiment. [Figure 6] A schematic plan view of the first main surface side of the second sealing member of the quartz crystal oscillator according to the first embodiment. [Figure 7] A schematic plan view of the second main surface side of the second sealing member of the quartz crystal oscillator according to the first embodiment. [Figure 8] Schematic cross-sectional view of the first through-hole of the second sealing member of the crystal oscillator according to the first embodiment.

Mode for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a case where the piezoelectric vibration device to which the present invention is applied is a crystal oscillator will be described.

[0017] <First Embodiment>[ First, the basic structure of the crystal oscillator 100 according to the present embodiment (the first embodiment) will be described. As shown in FIG. 1, the crystal oscillator 100 includes a crystal vibration plate (piezoelectric vibration element) 10, a first sealing member 20, and a second sealing member 30. In this crystal oscillator 100, the crystal vibration plate 10 and the first sealing member 20 are joined at a sealing portion (seal path) 115, and the crystal vibration plate 10 and the second sealing member 30 are joined at a sealing portion (seal path) 116, thereby forming a package having a substantially rectangular parallelepiped sandwich structure It is done. That is, in the crystal oscillator 100, the first sealing member 20 and the second sealing member 30 are joined to each of the main surfaces of the crystal vibration plate 10, thereby forming an internal space (cavity) of the package, and the vibration portion 11 (see FIGS. 4 and 5) is hermetically sealed in this internal space.

[0018] Next, each member of the crystal vibration plate 10, the first sealing member 20, and the second sealing member 30 in the crystal oscillator 100 described above will be described with reference to FIGS. 1 to 7. Here, each member configured as a single body that is not joined will be described. FIGS. 2 to 7 merely show one configuration example of each of the crystal vibration plate 10, the first sealing member 20, and the second sealing member 30, and these do not limit the present invention.

[0019] As shown in FIGS. 4 and 5, in this embodiment, the crystal resonator plate 10 is an AT-cut crystal plate (piezoelectric substrate) that performs thickness-shear vibration. In the crystal resonator plate 10 shown in FIGS. 4 and 5, both main surfaces 101 and 102 of the crystal resonator plate 10 are XZ' planes. In this XZ' plane, the direction parallel to the short side direction (short side direction) of the crystal resonator plate 10 is the X-axis direction, and the direction parallel to the long side direction (long side direction) of the crystal resonator plate 10 is the Z'-axis direction. Note that the AT-cut is a processing method of cutting out at an angle inclined by 35° 15' around the X-axis with respect to the Z-axis among the three crystal axes of the crystal, namely, the electric axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). In the AT-cut crystal plate, the X-axis coincides with the crystal axis of the crystal. The Y'-axis and the Z'-axis coincide with the axes inclined by approximately 35° 15' from the Y-axis and the Z-axis of the crystal axis of the crystal, respectively (this cutting angle may be slightly changed within the range of adjusting the frequency-temperature characteristics of the AT-cut crystal resonator plate). The Y'-axis direction and the Z'-axis direction correspond to the cutting directions when cutting out the AT-cut crystal plate. Further, both main surfaces (the first main surface 101 and the second main surface 102) of the crystal resonator plate 10 are formed as flat and smooth surfaces whose surfaces are finished to a mirror surface by, for example, polish grinding.

[0020] The crystal resonator plate 10 has a vibration portion 11 formed in a substantially rectangular shape, an outer frame portion 12 surrounding the outer periphery of the vibration portion 11, and a holding portion 13 that holds the vibration portion 11 by connecting the vibration portion 11 and the outer frame portion 12. That is, the crystal resonator plate 10 has a configuration in which the vibration portion 11, the outer frame portion 12, and the holding portion 13 are integrally provided. The holding portion 13 extends (projects) from only one corner portion located in the +X direction and -Z' direction of the vibration portion 11 toward the outer frame portion 12 in the -Z' direction. And a cutout portion 10a formed by cutting out the crystal resonator plate 10 is provided between the vibration portion 11 and the outer frame portion 12. In this embodiment, only one holding portion 13 that connects the vibration portion 11 and the outer frame portion 12 is provided on the crystal resonator plate 10, and the cutout portion 10a is continuously formed so as to surround the outer periphery of the vibration portion 11.

[0021] The thickness of the base material of the quartz crystal diaphragm 10 can be, for example, about 40 μm or about 60 μm. Furthermore, the vibrating portion 11 of the quartz crystal diaphragm 10 can be formed to be thinner than the outer frame portion 12. For example, the thickness of the vibrating portion 11 can be about 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). The thickness of the vibrating portion 11 is related to the frequency of the quartz crystal oscillator 100. Therefore, the thickness of the vibrating portion 11 may be adjusted as appropriate to obtain a quartz crystal oscillator 100 having a desired frequency.

[0022] A pair of excitation electrodes (first excitation electrode 111, second excitation electrode 112) are formed on both main surfaces 101 and 102 of the quartz diaphragm 10. 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. Lead wires (first lead wire 113, second lead wire 114) for connecting these excitation electrodes to external terminals are connected to the first excitation electrode 111 and the second excitation electrode 112. The first lead wire 113 is led out from the first excitation electrode 111 and connected via the holding portion 13 to a connecting joint pattern 12a formed on the first main surface 101 side of the outer frame portion 12. Furthermore, the connecting joint pattern 12a is connected via the second front-to-back routing wire 18 formed on the inner wall surface of the outer frame portion 12 to a connecting joint pattern 12e formed on the second main surface 102 side of the outer frame portion 12. In addition, the second lead wire 114 is led out from the second excitation electrode 112 and connected via the holding portion 13 to a connecting joint pattern 12d formed on the second main surface 102 side of the outer frame portion 12.

[0023] Furthermore, as shown in Figures 4 and 5, both main surfaces (first main surface 101, second main surface 102) of the crystal diaphragm 10 are provided with diaphragm-side sealing portions for joining the crystal diaphragm 10 to the first sealing member 20 and the second sealing member 30. A diaphragm-side first joining pattern 121 is formed as the diaphragm-side sealing portion of the first main surface 101, and a diaphragm-side second joining pattern 122 is formed as the diaphragm-side sealing portion of the second main surface 102. The diaphragm-side first joining pattern 121 and the diaphragm-side second joining pattern 122 are provided on the outer frame portion 12 and are formed in an annular shape in plan view. The outer edge of the diaphragm-side first joining pattern 121 is provided close to the outer edge of the first main surface 101 of the crystal diaphragm 10 (outer frame portion 12). The outer edge of the diaphragm-side second bonding pattern 122 is provided close to the outer edge of the second main surface 102 of the crystal diaphragm 10 (outer frame portion 12). In this embodiment, the diaphragm-side first bonding pattern 121 and the diaphragm-side second bonding pattern 122 are connected via a first front-to-back routing wiring 17 formed on the inner wall surface of the outer frame portion 12. The first front-to-back routing wiring 17 is provided on the inner wall surface of the outer frame portion 12, specifically on the inner wall surface in the -X direction, along the Z' axis direction.

[0024] As shown in Figures 2 and 3, the first sealing member 20 is formed from a rectangular substrate made from a single AT-cut quartz plate. The first main surface 201 and the second main surface 202 (the surface that joins to the quartz diaphragm 10) of the first sealing member 20 are formed as flat, smooth surfaces (mirror-finished). Although the first sealing member 20 does not have a vibrating part, it is preferable to use an AT-cut quartz plate, similar to the quartz diaphragm 10. Furthermore, in this embodiment, the orientation of the X, Y, and Z' axes of the first sealing member 20 is the same as that of the quartz diaphragm 10. In addition, it is preferable that the thickness of the first sealing member 20 be the same as that of the quartz diaphragm 10.

[0025] 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 oscillator 100) in this embodiment is a smooth surface in which the quartz forming the substrate of the first sealing member 20 is fully exposed.

[0026] As shown in Figure 3, a first sealing pattern 24 on the second main surface 202 of the first sealing member 20 is formed as a first sealing portion on the sealing member side for joining to the crystal diaphragm 10. The first sealing pattern 24 on the sealing member side is formed in an annular shape in plan view. The outer edge of the first sealing pattern 24 on the sealing member side is provided close to the outer edge of the second main surface 202 of the first sealing member 20. In addition, the second main surface 202 of the first sealing member 20 has a connecting joining pattern 22a for joining to a connecting joining pattern 12a formed on the first main surface 101 of the outer frame portion 12 of the crystal diaphragm 10, a connecting joining pattern 22b for joining to a connecting joining pattern 12b formed on the first main surface 101 of the outer frame portion 12 of the crystal diaphragm 10, and a connecting joining pattern 22c for joining to a connecting joining pattern 12c formed on the first main surface 101 of the outer frame portion 12 of the crystal diaphragm 10.

[0027] As shown in Figures 6 and 7, the second sealing member 30 is formed from a rectangular substrate made from a single AT-cut quartz plate. The first main surface 301 (the surface that joins to the quartz diaphragm 10) and the second main surface 302 (the bottom surface of the quartz oscillator 100) of the second sealing member 30 are formed as flat, smooth surfaces (mirror-finished). It is preferable that the second sealing member 30 also uses an AT-cut quartz plate, similar to the quartz diaphragm 10, and that the orientation of the X, Y, and Z' axes is the same as that of the quartz diaphragm 10. Furthermore, it is preferable that the thickness of the second sealing member 30 is the same as that of the quartz diaphragm 10 and the first sealing member 20.

[0028] As shown in Figure 7, the second main surface 302 of the second sealing member 30 (the outer main surface not facing the crystal diaphragm 10) is provided with four external terminals 32a, 32b, 32c, and 32d that are electrically connected to an external circuit board provided outside the crystal oscillator 100. Each external terminal 32a, 32b, 32c, and 32d is formed in a substantially rectangular shape and is located at the four corners (corners) of the second main surface 302 of the second sealing member 30. In a plan view, each external terminal 32a, 32b, 32c, and 32d is located in a position that overlaps with the outer frame portion 12 of the crystal diaphragm 10 described above.

[0029] A second sealing member side bonding pattern 31 is formed on the first main surface 301 of the second sealing member 30, which serves as a second sealing portion on the sealing member side for bonding to the crystal diaphragm 10. The second sealing member side bonding pattern 31 is formed in an annular shape in plan view. The outer edge of the second sealing member side bonding pattern 31 is provided close to the outer edge of the first main surface 301 of the second sealing member 30. Furthermore, the first main surface 301 of the second sealing member 30 has a connecting bonding pattern 33a for bonding to a connecting bonding pattern 12e formed on the second main surface 102 of the crystal diaphragm 10, a connecting bonding pattern 33b for bonding to a connecting bonding pattern 12f formed on the second main surface 102 of the crystal diaphragm 10, and a connecting bonding pattern 33c for bonding to a connecting bonding pattern 12d formed on the second main surface 102 of the crystal diaphragm 10. In addition, the connecting bonding pattern 33b and the connecting bonding pattern 33c are connected by a wiring pattern 34.

[0030] In the quartz oscillator 100, each internal electrode, including the various bonding patterns and wiring patterns described above, and each excitation electrode may be formed by stacking multiple layers on the main surface of each quartz substrate, with a Ti (titanium) metal layer and an Au (gold) metal layer formed from the bottom layer side by vapor deposition or sputtering. The various bonding patterns, wiring patterns, and electrodes described above may also be formed by photolithography.

[0031] The second sealing member 30 has three through holes that penetrate between the first main surface 301 and the second main surface 302. Specifically, the first through hole 161, the second through hole 162, and the third through hole 163 are provided in the second sealing member 30, respectively. The first, second, and third through holes 161, 162, and 163 are formed so that, in a plan view from the second main surface 302 side, each falls within one of the three external terminals 32a, 32b, and 32c.

[0032] Figure 8 is a schematic cross-sectional view of the first through-hole 161 of the second sealing member 30 of the quartz oscillator 100 according to the first embodiment. In Figure 8 and below, a schematic cross-sectional view and details of the first through-hole 161 are described as an example, but the second through-hole 162 and the third through-hole 163 have the same configuration as the first through-hole 161.

[0033] The first through-hole 161 has the shape of an hourglass, with the central area narrowed from both sides in a side cross-sectional view. That is, the inner wall surface of the first through-hole 161 has a first inclined portion 161a formed toward the central axis from the first main surface 301 side, and a second inclined portion 161b formed toward the central axis from the second main surface 302 side.

[0034] A conductive electrode 161c is formed along the inner wall surface of the first through-hole 161 to ensure electrical connection between the sealing member side second bonding pattern 31 formed on the first main surface 301 and the external terminal 32a formed on the second main surface 302. In other words, the conductive electrode 161c of the first through-hole 161 is electrically connected to the sealing member side second bonding pattern 31 formed on the first main surface 301 of the second sealing member 30 and the external terminal 32a formed on the second main surface 302. Similarly, conductive electrodes are formed along the inner wall surfaces of the second and third through-holes 162 and 163. The conductive electrode of the second through-hole 162 is electrically connected to the connecting bonding pattern 33a formed on the first main surface 301 of the second sealing member 30 and the external terminal 32b formed on the second main surface 302. The conductive electrode of the third through-hole 163 is electrically connected to the connecting bonding pattern 33b formed on the first main surface 301 of the second sealing member 30 and the external terminal 32c formed on the second main surface 302.

[0035] In this embodiment, the conductive electrode 161c is composed of a Ti metal layer 161c1 and an Au metal layer 161c2 formed by laminating it on the Ti metal layer 161c1. In this embodiment, the Ti metal layer 161c1 constituting the conductive electrode 161c is the same layer as the Ti metal layer 31a constituting the second bonding pattern 31 on the sealing member side and is formed continuously. Furthermore, the Au metal layer 161c2 constituting the conductive electrode 161c is the same layer as the Au metal layer 31b constituting the second bonding pattern 31 on the sealing member side and is formed continuously. In addition, the Ti metal layer 161c1 and the Ti metal layer 321a1 constituting the external terminal 32a, which will be described later, are the same layer and are formed continuously.

[0036] Furthermore, the Au metal layer 161c2 is not formed on a portion of the first inclined portion 161a and the second inclined portion 161b. Therefore, the Au metal layer 161c2 is not directly connected to the external terminal 32a, and only the Ti metal layer 161c1 is electrically directly connected to the external terminal 32a.

[0037] Furthermore, the first through-hole 161 is provided with an embedded metal layer 161d, which is formed along the inner wall surface of the first through-hole 161 at least in the second inclined portion 161b and covered by a conductive electrode 161c. In this embodiment, the embedded metal layer 161d is provided continuously from the second inclined portion 161b to the periphery of the first through-hole 161 on the second main surface 302. In this embodiment, the embedded metal layer 161d is completely covered by the conductive electrode 161c in the second inclined portion 161b and completely covered by the external terminal 32a on the second main surface 302. In this embodiment, the embedded metal layer 161d is formed only in the second inclined portion 161b of the through-hole 161, but the embedded metal layer 161d may also be formed continuously from the second inclined portion 161b to the first inclined portion 161a. In this configuration, it is preferable that the embedded metal layer 161d is superimposed on the Au metal layer 161c2 that constitutes the conductive electrode 161c. With this configuration, the conductivity resistance in the through hole 161 of the quartz oscillator 100 can be reduced.

[0038] In this embodiment, the embedded metal layer 161d is composed of a Ti metal layer 161d1 directly formed on the second inclined portion 161b and the second main surface 302, and an Au metal layer 161d2 formed by laminating on the Ti metal layer 161d1. Therefore, in the second inclined portion of the through hole 161, the embedded metal layer 161d including the Au metal layer 161d2 has a lower conductivity resistance compared to the conductive electrode 161c consisting only of the Ti metal layer 161c1 laminated on the embedded metal layer 161d. In this embodiment, the embedded metal layer 161d is composed of two layers, the Ti metal layer 161d1 and the Au metal layer 161d2, but for example, a Ni metal layer may be provided as an intermediate layer. Also, in this embodiment, the metal layer directly formed on the second inclined portion 161b and the second main surface 302 is an example of a Ti metal layer 161d1 mainly composed of Ti, but a Cr metal layer mainly composed of Cr (chromium) may also be used.

[0039] The four external terminals 32a, 32b, 32c, and 32d each have, in a plan view, a first region 32a1, 32b1, 32c1, and 32d1, and a second region 32a2, 32b2, 32c2, and 32d2, respectively. Within the second region 32a2, 32b2, and 32c2, through holes 161, 162, and 163 are formed, respectively. Furthermore, beneath the external terminals 32a, 32b, and 32c, embedded metal layers 161d, 162d, and 163d are formed, respectively. The external terminal 32a will be described in detail below with reference to Figures 7 and 8, but the external terminals 32b, 32c, and 32d have a similar configuration to external terminal 32a. However, external terminal 32d does not have through holes or embedded metal layers within its range. Therefore, the configuration related to the through-hole and embedded metal layer is limited to the external terminal 32d, but not limited to that.

[0040] In the first region 32a1, a Ni metal layer 321a2, mainly composed of Ni, is laminated on a Ti metal layer 321a1 which serves as the underlying layer, and an Au metal layer 321a3 is further laminated on the Ni metal layer 321a2. That is, the surface layer of the first region 32a1 is the Au metal layer 321a3. In this embodiment, the Ni metal layer 321a2 is a NiTi alloy mainly composed of Ni and containing Ti. Furthermore, the Ti metal layer 321a1 is the same layer as the Ti metal layer 161c1 that constitutes the conductive electrode 161c, and is formed continuously.

[0041] The second region 32a2 is provided around the through hole 161 and consists of a Ti metal layer 321a1 and an embedded metal layer 161d. That is, the outermost layer of the second region 32a2 is a Ti metal layer 321a1, with Ti as the main component. Such a second region 32a2 can be formed, for example, by forming a Ti metal layer 321a, a Ni metal layer 321b, and an Au metal layer 321c at the external terminal 32a by photolithography, and then removing the Ni metal layer 321b and Au metal layer 321c in a predetermined area around the through hole 161 by etching.

[0042] In this embodiment, the embedded metal layer 161d formed on the second main surface 302 is covered by the Ti metal layer 321a. At least a portion of the first region 32a1 and the embedded metal layer 161d are superimposed in a plan view. In this embodiment, the embedded metal layer 161d is configured to superimpose in a plan view on at least a portion of all the metal layers constituting the external terminal 32a: the Ti metal layer 321a, the Ni metal layer 321b, and the Au metal layer 321c, but the embodiment is not limited to this configuration. For example, the embedded metal layer 161d may be configured to superimpose in a plan view only on the Ti metal layer 321a constituting the external terminal 32a on the second main surface 302.

[0043] In the crystal oscillator 100, which includes the crystal diaphragm 10, first sealing member 20, and second sealing member 30 as described above, the crystal diaphragm 10 and the first sealing member 20 are diffusion-bonded with the first bonding pattern 121 on the diaphragm side and the first bonding pattern 24 on the sealing member side overlapping, and the crystal diaphragm 10 and the second sealing member 30 are diffusion-bonded with the second bonding pattern 122 on the diaphragm side and the second bonding pattern 31 on the sealing member side overlapping, thereby manufacturing a sandwich-structure package. As a result, the internal space of the package, that is, the space housing the vibrating part 11, is hermetically sealed.

[0044] Furthermore, at this time, the aforementioned connection patterns are also diffusely bonded while superimposed. Through the bonding of the connection patterns, electrical conductivity is obtained between the first excitation electrode 111 and the external terminal 32c, and between the second excitation electrode 112 and the external terminal 32b in the crystal oscillator 100. Specifically, the first excitation electrode 111 is connected to the external terminal 32c via the first lead wiring 113, connection pattern 12a, second front / back routing wiring 18, connection pattern 12e, connection pattern 33a, and the conductive electrode of the third through hole 163 in that order. The second excitation electrode 112 is connected to the external terminal 32b via the second lead wiring 114, connection pattern 12d, connection pattern 33c, wiring pattern 34, connection pattern 33b, and the conductive electrode of the second through hole 162 in that order.

[0045] Furthermore, in the crystal oscillator 100 of this embodiment, a sealing portion (seal path) is formed to hermetically seal the vibrating portion 11 of the crystal diaphragm 10. The seal path consists of a first seal path 115 formed by diffusion bonding (Au-Au bonding) of the first bonding pattern 121 on the diaphragm side and the first bonding pattern 24 on the sealing member side, and a second seal path 116 formed by diffusion bonding (Au-Au bonding) of the second bonding pattern 122 on the diaphragm side and the second bonding pattern 31 on the sealing member side. The first and second seal paths 115 and 116 are not electrically connected to the electrical conduction path between the first and second excitation electrodes 111 and 112 and the external terminals 32b and 32c. 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 connected to the external terminal 32a via the conductive electrode 161c of the first through hole 161. In this embodiment, the external terminal 32a is connected to earth (ground). In other words, the external terminal 32a in this embodiment functions as a ground terminal.

[0046] The crystal oscillator 100 described above can be used by mounting it on an external circuit board that has mounting pads on its main surface. The mounting pads on the external circuit board can be provided at positions corresponding to the external terminals 32a, 32b, 32c, and 32d of the crystal oscillator 100. The corresponding mounting pads and external terminals are then joined together with a metal brazing material. For example, solder can be used as the metal brazing material.

[0047] Furthermore, a molded quartz crystal oscillator can be provided, which includes a molding resin covering the quartz crystal oscillator mounted on an external circuit board. Thermosetting resins such as epoxy resin can be used as the molding resin. The molding resin can be formed, for example, by impregnating the quartz crystal oscillator, while mounted on the external circuit board, with liquid resin and then curing it by heat treatment through a reflow oven using reflow soldering.

[0048] The method for manufacturing the quartz oscillator 100 as described above includes a quartz diaphragm manufacturing step for manufacturing a quartz diaphragm 10, a first sealing member manufacturing step for manufacturing a first sealing member 20, a second sealing member manufacturing step for manufacturing a second sealing member 30, a first sealing member joining step for joining the quartz diaphragm 10 and the first sealing member 20, and a second sealing member joining step for joining the quartz diaphragm 10 and the second sealing member 30. Furthermore, the first sealing member joining step and the second sealing member joining step may be performed in either order or simultaneously.

[0049] The second sealing member manufacturing step further includes a buried metal layer forming step for forming a buried metal layer 161d, a conductive electrode forming step for forming a conductive electrode 161c, and an external terminal forming step for forming an external terminal 32a. In this case, the conductive electrode forming step and the external terminal forming step are performed after the buried metal layer forming step. That is, after forming the buried metal layer 161d around the second inclined portion 161b of the through hole 161 and the through hole 161 of the second main surface 302, the conductive electrode 161c and the external terminal 32a are formed so as to cover the buried metal layer 161d. Each metal layer can be formed by photolithography. In this case, it is preferable that the Ti metal layer 161c1 of the conductive electrode 161c and the Ti metal layer 321a of the external terminal 32a are formed simultaneously. With such a manufacturing method, the number of steps in manufacturing can be reduced and manufacturing efficiency can be improved.

[0050] With the above configuration, it is possible to provide a piezoelectric vibration device and a method for manufacturing a piezoelectric vibration device that suppresses the crawling up of the metal brazing material into the through hole formed in the second sealing member and improves its electrical characteristics. The quartz crystal oscillator 100 of the present invention has an embedded metal layer 161d embedded in the second inclined portion 161b of the through hole 161 as a layer below the conductive electrode 161c. The conductive electrode 161c does not have an Au metal layer 161c2 at least on the outermost layer in the second inclined portion 161b, and the embedded metal layer 161d has a smaller conductivity resistance than the conductive electrode 161c laminated on the embedded metal layer 161d. With this configuration, when the quartz crystal oscillator 100 of the present invention is mounted on an external circuit board, it is possible to suppress the metal brazing material that joins the external circuit board and the quartz crystal oscillator 100 from creeping up into the first through hole 161. More specifically, with the above configuration, the outermost layer of the inclined portion (second inclined portion 161b) on the second main surface 302 side that is joined with the metal brazing material in the through hole 161 does not have metal which has high wettability with the metal brazing material, thus suppressing the metal brazing material from creeping up into the through hole 161.

[0051] Furthermore, in the second inclined portion 161b, which does not have gold on its outermost layer, the conductivity resistance of the conductive electrode 161c increases, which may worsen the electrical characteristics of the crystal oscillator 100. However, with the configuration of the present invention, the conductivity resistance of the embedded metal layer 161d provided in the second inclined portion 161b is smaller than that of the conductive electrode 161c laminated on the embedded metal layer 161d, thus improving the electrical characteristics of the crystal oscillator 100. In other words, it is possible to suppress the creeping of metal brazing material into the through hole 161 and achieve good electrical characteristics of the crystal oscillator 100 by reducing conductivity resistance.

[0052] Furthermore, the embedded metal layer 161d is provided from the second inclined portion 161b to the second main surface 302 and is superimposed on at least a portion of all the metal layers constituting the external terminal 32a (Ti metal layer 321a1, Ni metal layer 321a2, and Au metal layer 321a3). With this configuration, the conductivity resistance not only in the second inclined portion 161b but also in the second main surface 302 can be reduced, thereby improving the electrical characteristics of the crystal oscillator 100.

[0053] Furthermore, the embedded metal layer 161d has a Ti metal layer 161d1 (first metal layer) made of titanium and an Au metal layer 161d2 (second metal layer) made of gold, with the Au metal layer 161d2 being covered by a conductive electrode 161c and an external terminal 32a. With this configuration, gold, which has low conductivity, is embedded as the Au metal layer 161d2 of the embedded metal layer 161d, which makes it possible to further reduce the conductivity resistance in the second inclined portion 161b and the second main surface 302, thereby improving the electrical characteristics of the crystal oscillator 100. In addition, because the Au metal layer 161d2 is covered by a conductive electrode 161c and an external terminal 32a, the gold, which has high wettability with metal brazing material, does not come into contact with the metal brazing material, and the metal brazing material does not creep up inside the through hole 161.

[0054] Furthermore, the manufacturing method of the quartz oscillator 100 includes a second sealing member manufacturing step which comprises an embedded metal layer forming step for forming an embedded metal layer 161d and a conductive electrode forming step for forming a conductive electrode 161c, with the embedded metal layer forming step being performed before the conductive electrode forming step. With this configuration, the manufacturing method can be such that an embedded metal layer 161d is formed in the second inclined portion 161b of the through hole 161, and then the embedded metal layer 161d is covered with a conductive electrode 161c, thus easily realizing the configuration of the present invention in which an embedded metal layer 161d is embedded in the second inclined portion 161b as a layer below the conductive electrode 161c.

[0055] Furthermore, this invention is not limited to the configuration of the embodiments described above, and many other embodiments can be obtained. For example, in this embodiment, the vibrating part 11 is configured to be substantially rectangular in shape, with 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 part 11 may also be shaped like a tuning fork, with a pair of protruding vibrating arms (corresponding to the vibrating part in each embodiment) having a first excitation electrode 111 and a second excitation electrode 112 on each main surface. In such a case, the quartz diaphragm 10 equipped with the vibrating part 11 is formed from an XY-cut quartz crystal. Furthermore, it is preferable that the substrates of the first sealing member 20 and the second sealing member 30 are also formed from an XY-cut quartz crystal.

[0056] Furthermore, in this embodiment, the quartz diaphragm 10 and the first sealing member 20 and the second sealing member 30 are joined by diffusion bonding (Au-Au bonding), but they may also be joined by a brazing material such as AuSn brazing.

[0057] Furthermore, in this embodiment, the substrates of the first sealing member 20 and the second sealing member 30 are formed of quartz, but for example, at least one of the substrates of the first sealing member 20 and the second sealing member 30 may be formed of one selected from glass and silicon. In addition, in this embodiment, the substrate of the quartz diaphragm 10 is formed of AT-cut quartz, but it may be formed of quartz 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 that are joined to the quartz diaphragm 10 are formed of quartz obtained in the same cutting direction as the quartz diaphragm 10.

[0058] Furthermore, although the through-hole 161 is hollow in this embodiment, it may be filled with one of the following: metal paste, conductive resin, and insulating resin. With such a configuration, the creeping up of the metal brazing material into the through-hole 161 can be further suppressed.

[0059] The embodiments disclosed herein are illustrative in all respects and are not intended to be restrictive. Therefore, the technical scope of the present invention is not construed solely by the embodiments described above, but is defined by the claims. This includes all modifications within the meaning and scope of the equivalents of the claims. [Industrial applicability]

[0060] The piezoelectric vibration device of the present invention can be used in the industry for manufacturing and selling piezoelectric vibration devices having a sandwich structure. [Explanation of symbols]

[0061] 10...Crystal diaphragm 100...Crystal resonator 111...First excitation electrode 112...Second excitation electrode 115...1st Seal Pass 116...Second Seal Pass 20...First sealing member 30...Second sealing member 301...First main surface 302...Second main surface 32a, 32b, 32c, 32d...external terminal 161...First through hole 161a...first slope part 161b…Second slope part 161c...Conducting electrode 161c1…Ti metal layer 161c2…Au metal layer 161d…Buried metal layer 161d1…Ti metal layer 161d2…Au metal layer 162...Second through hole 163...Third through hole

Claims

1. A piezoelectric vibration element having a first excitation electrode formed on one main surface of a piezoelectric substrate and a second excitation electrode paired with the first excitation electrode, The piezoelectric vibration element comprises a first sealing member and a second sealing member that cover both main surfaces of the piezoelectric vibration element, In a piezoelectric vibration device in which the first sealing member and the piezoelectric vibration element are joined together, and the second sealing member and the piezoelectric vibration element are joined together, thereby providing an internal space in which the vibrating portion of the piezoelectric vibration element, including the first excitation electrode and the second excitation electrode, is hermetically sealed, The second sealing member is The first main surface facing the vibrating part, The back surface of the first main surface, which is a second main surface that does not face the vibrating part, A through hole extending from the first main surface to the second main surface, The second main surface has an external terminal, The through hole has a conductive electrode on its inner wall surface that electrically connects the internal electrode formed on the first main surface with the external terminal. The inner wall surface has a first inclined portion on the first main surface side and a second inclined portion on the second main surface side such that the through hole becomes narrower toward the center in the thickness direction of the second sealing member. At least the second inclined portion has an embedded metal layer embedded as a layer beneath the conductive electrode, The conductive electrode does not have gold in at least the outermost layer of the second inclined portion. The embedded metal layer has a lower conductivity resistance than the conductive electrodes laminated on top of the embedded metal layer. Piezoelectric vibration device.

2. The aforementioned external terminal is composed of multiple external terminal metal layers, The embedded metal layer is provided on the second main surface and, in a plan view, overlaps with a portion of the outer terminal metal layer that forms at least the lowest layer of the plurality of outer terminal metal layers constituting the outer terminal. The piezoelectric vibration device according to claim 1.

3. The buried metal layer comprises a first metal layer made of titanium or chromium and a second metal layer made of gold. The second metal layer is covered by the conductive electrode and the external terminal. A piezoelectric vibration device according to claim 1 or 2.

4. A piezoelectric vibration element manufacturing step for manufacturing the piezoelectric vibration element, A first sealing member manufacturing step for manufacturing the first sealing member, A second sealing member manufacturing step for manufacturing the second sealing member, A first sealing member joining step of joining the piezoelectric vibration element and the first sealing member, The process includes a second sealing member joining step for joining the piezoelectric vibration element and the second sealing member, The second sealing member manufacturing step comprises an embedded metal layer forming step for forming the embedded metal layer and a conductive electrode forming step for forming the conductive electrode, The embedded metal layer formation step is performed before the conductive electrode formation step. A method for manufacturing a piezoelectric vibration device according to claim 1 or 2.

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