Piezoelectric vibration device and method for manufacturing piezoelectric vibration device

Abstract

According to the present invention, a crystal oscillator (100) comprises a second sealing member (30) having: a first through-hole (161) penetrating from a first main surface (301) to a second main surface (302); a conductive member (161d) provided in the first through-hole (161) and closing the first through-hole (161); and an external terminal (32a) covering at least a part of an opening end of the first through-hole (161) on the second main surface (302) side.

Description

Piezoelectric vibration device and method for manufacturing piezoelectric vibration device

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

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

[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, for example, crystal and having 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. And the vibration part (excitation electrode) of the piezoelectric vibration plate 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. Also, 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 solder or the like.

[0004] Japanese Patent Application Laid-Open No. 2010-252051

[0005] However, when mounting a piezoelectric vibrator having a sandwich structure on an external circuit board or the like by soldering, since the solder contains Sn (tin), when the through-hole conduction electrode has an Au film made of Au (gold), the solder may climb up along this Au film and further climb up to the vibration part of the piezoelectric vibration element. The solder that has climbed up into the through-hole diffuses into the conduction electrode and the internal electrode, which may lead to a decrease in the electrical connectivity between the electrode (such as the first excitation electrode and the second excitation electrode) and the external terminal corresponding to the electrode, an inhibition of the vibration of the piezoelectric vibration element, and an airtightness defect due to corrosion of the metal materials of the first sealing member and the second sealing member.

[0006] 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 a second sealing member that joins an external terminal and a mounting pad of a circuit board.

[0007] 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 on the back surface of the first main surface that does not face the vibrating portion, a through hole penetrating from the first main surface to the second main surface, a conductive member provided in the through hole to close the through hole, and an external terminal provided on the second main surface, wherein at least a part of the opening end of the through hole on the second main surface side is covered by the external terminal.

[0008] In other words, the piezoelectric vibration device of the present invention has a conductive member provided in a through hole to close the through hole, and an external terminal provided on a second main surface, wherein at least a portion of the opening end of the through hole on the second main surface side is covered by the external terminal. With this configuration, it is possible to reliably prevent the metal brazing material used to join the external circuit board and the piezoelectric vibration device from creeping up into the through hole. More specifically, with the above configuration, the conductive member that closes the through hole can prevent the metal brazing material from creeping up. Therefore, it is possible to suppress the metal brazing material from creeping up into the through hole. Furthermore, the conductive member that closes the through hole and the external terminal that covers at least a portion of the opening end can improve the electrical characteristics of the piezoelectric vibration device.

[0009] Furthermore, the through-hole may have a conductive electrode on its inner wall surface that electrically connects an internal electrode formed on the first main surface with an external terminal formed on the second main surface, and the external terminal may have a configuration comprising a first external terminal metal layer formed directly on the second main surface and continuously with the conductive electrode, and a second external terminal metal layer that covers at least a portion of the opening end of the through-hole on the second main surface side. With such a configuration, a manufacturing method can be used in which a conductive member is filled into the through-hole and then covered with the second external terminal metal layer. Therefore, the configuration of the present invention, which has a conductive member provided inside the through-hole to seal the through-hole and the opening end of the through-hole on the second main surface side is covered with an external terminal, can be realized, and the creeping up of the metal brazing material into the through-hole can be suppressed.

[0010] Furthermore, the inner wall surface of the through-hole may have 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 the outer terminal may have at least a part of its outermost layer made of gold, with no gold provided over the entire outermost layer in the second inclined portion of the conductive electrode. With such a configuration, the wettability of the surface of the second inclined portion of the through-hole to the metal brazing material can be reduced. In other words, it is possible to further suppress the metal brazing material from creeping up by wetting onto the conductive electrode formed on the inner wall surface of the through-hole.

[0011] Furthermore, the conductive member may contain two or more conductive materials with different shapes and particle sizes dispersed within it. By using a combination of two or more conductive materials in this way, clogging of the nozzle of the coating device used when filling the conductive member can be suppressed, thereby improving productivity.

[0012] Furthermore, the piezoelectric vibration device manufacturing method may also 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 the second sealing member excluding the second external terminal metal layer, a first sealing member joining step for joining the piezoelectric vibration element and the first sealing member, a second sealing member joining step for joining the piezoelectric vibration element and the second sealing member, a conductive member filling step for filling the through hole with a conductive member, and a second external terminal metal layer forming step for forming the second external terminal metal layer so as to cover the opening end on the second main surface side of the through hole, wherein the conductive member filling step is provided after the second sealing member joining step, and the second external terminal metal layer forming step is provided after the conductive member filling step. With such a configuration, the manufacturing method can be such that a conductive member is provided inside the through hole to seal the through hole, and the configuration of the present invention can be realized in which the opening end on the second main surface side of the through hole is covered by an external terminal.

[0013] 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 metal brazing material into through holes formed in a second sealing member that joins an external terminal and a mounting pad of a circuit board.

[0014] Figure 1 is a side view of a quartz crystal oscillator according to the first embodiment. Figure 2 is 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 is 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 is a schematic plan view of the first main surface side of the quartz crystal diaphragm of the quartz crystal oscillator according to the first embodiment. Figure 5 is a schematic plan view of the second main surface side of the quartz crystal diaphragm of the quartz crystal oscillator according to the first embodiment. Figure 6 is 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 is 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 is a schematic cross-sectional view of the first through-hole of the second sealing member of the quartz crystal oscillator according to the first embodiment. Figure 9 is an enlarged view of area A in Figure 8. Figure 10 is a side cross-sectional view of the first through-hole in the conductive paste filling process. Figure 11 is a side cross-sectional view of the first through-hole in the curing process. Figure 12 is a schematic cross-sectional view of the first through-hole of the second sealing member of a quartz crystal oscillator according to the second embodiment.

[0015] Embodiments of the present invention will be described in detail below with reference to the drawings. In the following embodiments, the case in which the piezoelectric vibration device to which the present invention is applied is a quartz crystal oscillator will be described.

[0016] <First Embodiment> First, the basic structure of the crystal oscillator 100 according to this embodiment (first embodiment) will be described. As shown in Figure 1, the crystal oscillator 100 is composed of a crystal diaphragm (piezoelectric vibration element) 10, a first sealing member 20, and a second sealing member 30. In this crystal oscillator 100, the crystal diaphragm 10 and the first sealing member 20 are joined at a sealing portion (seal path) 115, and the crystal diaphragm 10 and the second sealing member 30 are joined at a sealing portion (seal path) 116, thereby forming a roughly rectangular sandwich-structured package. That is, in the crystal oscillator 100, the first sealing member 20 and the second sealing member 30 are joined to each of the two main surfaces of the crystal diaphragm 10 to form an internal space (cavity) of the package, and the vibrating part 11 (see Figures 4 and 5) is hermetically sealed in this internal space.

[0017] Next, the crystal diaphragm 10, the first sealing member 20, and the second sealing member 30 of the crystal oscillator 100 described above will be explained with reference to Figures 1 to 7. Here, we will explain each component as a separate unit that is not joined together. Figures 2 to 7 merely show one example configuration of the crystal diaphragm 10, the first sealing member 20, and the second sealing member 30, and these do not limit the present invention.

[0018] As shown in Figures 4 and 5, in this embodiment, an AT-cut quartz plate (piezoelectric substrate) that performs thickness-sliding vibration is used as the quartz diaphragm 10. In the quartz diaphragm 10 shown in Figures 4 and 5, both main surfaces 101 and 102 of the quartz diaphragm 10 are the XZ' plane. In this XZ' plane, the direction parallel to the short side of the quartz diaphragm 10 is the X-axis direction, and the direction parallel to the long side of the quartz diaphragm 10 is the Z' axis direction. Note that AT cutting is a processing method in which the quartz is cut at an angle of 35°15′ inclined around the X-axis with respect to the Z-axis, one of the three crystal axes of quartz: the electrical axis (X-axis), the mechanical axis (Y-axis), and the optical axis (Z-axis). In an AT-cut quartz plate, the X-axis coincides with the crystal axis of the quartz. The Y' and Z' axes coincide with axes that are approximately 35°15′ inclined from the Y and Z axes of the crystal axis of the quartz (this cutting angle may be slightly changed within the range of adjusting the frequency-temperature characteristics of the AT-cut quartz diaphragm). The Y' and Z' axis directions correspond to the cutting direction when cutting the AT-cut quartz plate. Furthermore, both main surfaces (first main surface 101, second main surface 102) of the quartz diaphragm 10 are formed as flat, smooth surfaces whose surfaces are finished to a mirror-like finish, for example, by polishing.

[0019] The quartz crystal diaphragm 10 has a vibrating portion 11 formed in a substantially rectangular shape, an outer frame portion 12 surrounding the outer circumference of the vibrating portion 11, and a holding portion 13 that holds the vibrating portion 11 by connecting the vibrating portion 11 and the outer frame portion 12. In other words, the quartz crystal diaphragm 10 has a configuration in which the vibrating 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 of the vibrating portion 11 located in the +X direction and the -Z' direction to the outer frame portion 12 in the -Z' direction. A cutout portion 10a formed by cutting out the quartz crystal diaphragm 10 is provided between the vibrating portion 11 and the outer frame portion 12. In this embodiment, the quartz crystal diaphragm 10 is provided with only one holding portion 13 that connects the vibrating portion 11 and the outer frame portion 12, and the cutout portion 10a is formed continuously so as to surround the outer circumference of the vibrating portion 11.

[0020] 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.

[0021] 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-out wiring (first lead-out wiring 113, second lead-out wiring 114) for connecting these excitation electrodes to external terminals is connected to the first excitation electrode 111 and the second excitation electrode 112. The first lead-out wiring 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 wiring 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-out wiring 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.

[0022] Furthermore, as shown in Figures 4 and 5, both main surfaces (first main surface 101 and 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 first bonding pattern 121 is formed as the diaphragm-side sealing portion of the first main surface 101, and a second bonding pattern 122 is formed as the diaphragm-side sealing portion of the second main surface 102. The first bonding pattern 121 and the second bonding 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 first bonding 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.

[0023] 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 surfaces that join 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 is the same as that of the quartz diaphragm 10.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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 provided in a position that overlaps with the outer frame portion 12 of the crystal diaphragm 10 described above.

[0028] 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.

[0029] In the quartz oscillator 100, each internal electrode, including the various bonding patterns and wiring patterns described above, and each excitation electrode are 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.

[0030] 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.

[0031] 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 this embodiment, and Figure 9 is an enlarged view of area A in Figure 8. In Figure 8 and below, the schematic cross-sectional view and details of the first through-hole 161 will be 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.

[0032] The first through-hole 161 has the shape of an hourglass in the side cross-sectional view, with the central area narrowed from both sides. 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.

[0033] 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 to the external terminal 32c formed on the second main surface 302.

[0034] In this embodiment, the conductive electrode 161c is composed of a Cr (chromium) metal layer 161c1, a Ti metal layer 161c2 which is partially laminated on the Cr metal layer 161c1 and the remainder is directly formed on the inner wall surface of the through hole 161, and an Au metal layer 161c3 which is laminated on the Ti metal layer 161c2. In this embodiment, the Ti metal layer 161c2 constituting the conductive electrode 161c is the same layer as the Ti metal layer 31a constituting the sealing member side second bonding pattern 31 and is formed continuously. Furthermore, the Au metal layer 161c3 constituting the conductive electrode 161c is the same layer as the Au metal layer 31b constituting the sealing member side second bonding pattern 31 and is formed continuously. In addition, the Cr metal layer 161c1 and the Cr metal layer 321a1 constituting the external terminal 32a, which will be described later, are the same layer and are formed continuously. Note that the Cr metal layer 161c1 may be a Ti metal layer formed from Ti instead of Cr. Also, the Cr metal layer 161c1 can have a thickness of 500 to 3000 Å. With such a thickness configuration, the creeping of the metal brazing material in the through hole 161 can be suppressed while ensuring sufficiently low conductivity resistance and thus ensuring the electrical characteristics of the quartz oscillator 100. If the Cr metal layer 161c1 is a Ti metal layer, a similar effect can be obtained by setting the thickness to 1000 to 5000 Å.

[0035] Furthermore, the Au metal layer 161c3 is not formed in a part of the first inclined portion 161a and in the second inclined portion 161b. Therefore, the Au metal layer 161c3 is not directly connected to the external terminal 32a. In this embodiment, not only the Au metal layer 161c3 but also the Ti metal layer 161c2 is not formed in a part of the first inclined portion 161a and in the second inclined portion 161b. Therefore, only the Cr metal layer 161c1 is electrically directly connected to the external terminal 32a. In this embodiment, the Au metal layer 161c3 is not formed in the entire second inclined portion 161b, but it is also possible to have a configuration in which the Au metal layer 161c3 is formed in a part of the second inclined portion 161b on the first inclined portion 161a side. For example, it is also possible to have a configuration in which the Au metal layer 161c3 is formed continuously from the first inclined portion 161a to partway up the second inclined portion 161b. In such cases, it is preferable to have a configuration in which the entire Au metal layer 161c3 is covered with a conductive member 161d.

[0036] Furthermore, the first through-hole 161 is blocked by a conductive member 161d provided inside the hole. Here, "blocked" means that the conductive member 161d is filled into the first through-hole 161, so that the other main surface cannot be seen from one main surface side through the first through-hole 161. At this time, the conductive member 161d is positioned to cover the second main surface side end face of the Au metal layer 161c3 and is in contact with the Cr metal layer 161c1 formed on the second inclined portion 161b. The conductive member 161d can be formed from, for example, Ag, Cu, or a conductive resin containing one or more of these. In this embodiment, the conductive member 161d is formed from Ag.

[0037] External terminals 32a, 32b, and 32c have a first external terminal metal layer 321a, 321b, and 321c formed on the second main surface 302, and a second external terminal metal layer 322a, 322b, and 322c formed to cover at least the first through hole 161, the second through hole 162, and the third through hole 163, respectively. External terminal 32d does not have a through hole within its range and is not connected to any of the internal electrodes of the crystal oscillator 100. Therefore, the first external terminal metal layer is not provided for it, and only the second external terminal metal layer 322d is provided for mounting to the external circuit board. The external terminal 32a will be described in detail below with reference to Figures 7, 8, and 9, but external terminals 32b and 32c have the same configuration as external terminal 32a.

[0038] In this embodiment, the first external terminal metal layer 321a is composed of a bottom layer of Cr metal layer 321a1, a Ti metal layer 321a2 formed by laminating on the Cr metal layer 321a1, and an Au metal layer 321a3 formed by laminating on the Ti metal layer 321a2. The Ti metal layer 321a2 and the Au metal layer 321a3 are absent around the through hole 161. Furthermore, the Cr metal layer 321a1 is the same layer as the Cr metal layer 161c1 that constitutes the conductive electrode 161c, and is formed continuously. Note that the bottom layer of Cr metal layer 321a1 may be a Ti metal layer formed of Ti instead of Cr.

[0039] Such a first external terminal metal layer 321a can be formed by vapor deposition or sputtering of a Cr metal layer 321a1, a Ti metal layer 321a2, and an Au metal layer 321a3, or it may be formed by photolithography.

[0040] Then, the Ti metal layer 321a2 and the Au metal layer 321a3 in the region surrounding the through hole 161 in the external terminal 32a are removed by a known method such as etching. At this time, the Ti metal layer and the Au metal layer of the conductive electrode in the second inclined portion 161b of the first through hole 161 are also removed. In this embodiment, as shown in Figure 8, the Au metal layer 161c3 is not formed in the second inclined portion 161b on the inner wall surface of the first through hole 161, but is formed in the first inclined portion 161a continuously from the first main surface 301 side up to a certain point.

[0041] In this embodiment, the first external terminal metal layer 321a is covered by the second external terminal metal layer 322a on the quartz oscillator 100 and is not exposed to the outside. The first external terminal metal layer 321a functions as a connection terminal for ion partials, which are performed to fine-tune the frequency of the quartz oscillator 100 before the second external terminal metal layer 322a is formed. Therefore, the configuration in which the first external terminal metal layer 321a is present allows for fine-tuning of the frequency of the quartz oscillator 100.

[0042] In this embodiment, the second external terminal metal layer 322a is composed of a Ti metal layer 322a1 which is the bottom layer, a Ni metal layer 322a2 which is laminated on the Ti metal layer 322a1 and has Ni as its main component, and an Au metal layer 322a3 which is laminated on the Ni metal layer 322a2. In this embodiment, the Ni metal layer 322a2 is a NiTi alloy with Ni as the main component and containing Ti. The Ni metal layer 322a2 is not limited to a NiTi alloy as in this embodiment, but can be an alloy with Ni as the main component or pure Ni.

[0043] In this embodiment, the second external terminal metal layer 322a is formed so as to cover the first external terminal metal layer 321a and the opening end of the through hole 161. Further, the second external terminal metal layer 322a is in contact with the conductive member 161d at least in part. Therefore, the second external terminal metal layer 322a is electrically connected to the first external terminal metal layer 321a and the conductive member 161d. At this time, the second external terminal metal layer 322a does not need to cover the entire opening of the through hole 161, and it is sufficient to cover at least a part thereof. For example, in a state where the second external terminal metal layer 322a and the conductive member 161d are in contact with each other, due to the unevenness of the contact surface of the conductive member 161d, a part of the second external terminal metal layer 322a, which is a thin film, may be broken, and a part of the conductive member 161d may be exposed. Note that the second external terminal metal layer 322a is preferably provided so as to block the entire opening on the second main surface 302 side in the through hole 161.

[0044] Such a second external terminal metal layer 322a can be formed by depositing or sputtering a Ti metal layer 322a1, a Ni metal layer 322a2, and an Au metal layer 322a3.

[0045] In the crystal oscillator 100 including the crystal plate 10, the first sealing member 20, and the second sealing member 30 having the above configuration, the crystal plate 10 and the first sealing member 20 are diffusion-bonded in a state where the first bonding pattern 121 on the plate side and the first bonding pattern 24 on the sealing member side are overlapped, and the crystal plate 10 and the second sealing member 30 are diffusion-bonded in a state where the second bonding pattern 122 on the plate side and the second bonding pattern 31 on the sealing member side are overlapped, thereby manufacturing a package having a sandwich structure. As a result, the internal space of the package, that is, the vibration part 11 accommodation space is hermetically sealed.

[0046] 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-to-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.

[0047] 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.

[0048] The crystal oscillator 100 as described above can be mounted and used on an external circuit board having mounting pads on its main surface. The mounting pads of the external circuit board can be formed in a form provided at positions corresponding to the external terminals 32a, 32b, 32c, and 32d of the crystal oscillator 100. Then, the corresponding mounting pads and the external terminals are joined by a metal brazing material respectively. As the metal brazing material, for example, solder can be used.

[0049] Further, it can also be a molded crystal oscillator provided with a molded resin covering the crystal oscillator mounted on the external circuit board. As the molded resin, a thermosetting resin such as an epoxy resin can be used. The molded resin can be formed, for example, by impregnating the crystal oscillator in a state mounted on the external circuit board with a liquid resin and performing heat treatment through a reflow furnace by reflow soldering or the like to cure it.

[0050] The manufacturing method of the crystal oscillator 100 as described above includes a crystal vibrating plate manufacturing step of manufacturing the crystal vibrating plate 10, a first sealing member manufacturing step of manufacturing the first sealing member 20, a second sealing member manufacturing step of manufacturing the parts of the second sealing member 30 other than the second external terminal metal layers 322a, 322b, 322c, and 322d, a first sealing member joining step of joining the crystal vibrating plate 10 and the first sealing member 20, a second sealing member joining step of joining the crystal vibrating plate 10 and the second sealing member 30, a conductive member filling step of filling the conductive members into the first, second, and third through holes 161, 162, and 163 of the second sealing member 30, and a second external terminal metal layer forming step of forming the second external terminal metal layers 322a, 322b, and 322c so as to cover the respective opening ends on the second main surface 302 side of the first, second, and third through holes 161, 162, and 163. The conductive member filling step is performed after the second sealing member joining step, and the second external terminal metal layer forming step is performed after the conductive member filling step. Also, either the first sealing member joining step or the second sealing member joining step may be performed first, or they may be performed simultaneously.

[0051] More specifically, after the second sealing member joining process, that is, after joining the crystal diaphragm 10 and the second sealing member 30, the second main surface 102 of the crystal diaphragm 10 becomes the bottom surface in the first, second, and third through holes 161, 162, and 163 of the second sealing member 30. The conductive member filling process includes a conductive paste filling process in which a paste-like conductive paste is filled into each of the first, second, and third through holes 161, 162, and 163, with the second main surface 102 as the bottom surface, and a hardening process in which the filled conductive paste is solidified (hardened) to form a conductive member.

[0052] Figure 10 is a side cross-sectional view of the first through-hole 161 during the conductive paste filling process, and Figure 11 is a side cross-sectional view of the first through-hole 161 during the curing process. The following explanation will use the case where the conductive member 161d is filled into the first through-hole 161 as an example, but the conductive member can be similarly filled into the second through-hole 162 and the third through-hole 164.

[0053] In the conductive paste filling process, conductive paste 401 is filled into the first through-hole 161. At this time, the filling method can be done using a dispensing device 400. After removing the conductive paste adhering to the area around the through-hole 161, pressure is applied using an inert gas or the like to fill the conductive paste 401 to the deepest part of the first through-hole 161, so as not to create any gaps between the conductive paste 401 and the crystal diaphragm 10 and between the through-hole 161.

[0054] As the conductive paste 401, a conductive material dispersed in a dispersion solvent can be used. The conductive material does not need to contain at least Au, but for example, spherical nanoparticles of Ag or Cu can be used. As the dispersion solvent, for example, butyl carbitol can be used. When a filling method using a dispensing device is used, as in this embodiment, it is preferable that the viscosity of the conductive paste 401 be 10 to 100 Pa·s. In this embodiment, a filling method using a dispensing device 400 is used, but a filling method using a squeegee can also be used. Alternatively, the conductive paste 401 may be filled into the first through hole 161 by jet coating using a jet coating device, for example. When a jet coating device is used, raising and lowering the nozzle is unnecessary, so productivity can be improved compared to when a dispensing device is used, and contact of the nozzle with the second sealing member 30 can be suppressed.

[0055] Preferably, the conductive member 401 described above contains two or more conductive materials with different shapes and particle sizes (average particle sizes). For example, it is possible to use two types of conductive materials, such as spherical fine particles of Ag with a particle size of 1 to 2 μm and flake-shaped fine particles of Ag with an average particle size of 3 to 4 μm. As the conductive material, Ag or Cu can be used, and either Ag or Cu alone may be used, or Ag and Cu may be used in combination. The particle size (average particle size) of the conductive material can be a combination of two or more particles within the range of 1 to 4 μm. The shape of the conductive material can be a combination of two or more shapes from various shapes such as spherical, hemispherical, elliptical, needle-shaped, flat, and flake-shaped. In this case, it is preferable to combine a conductive material with a conductive material of a similar shape to a conductive material of another shape. By using two or more conductive materials in combination in this way, aggregation of the conductive paste 401 can be suppressed, clogging of the nozzle of the coating device into which the conductive paste 401 is filled can be suppressed, and productivity can be improved. The average particle size referred to here is the average particle size measured for approximately 20 particles randomly selected from images captured by SEM.

[0056] Alternatively, a manufacturing method may be used in which a large number of crystal oscillators 100 are formed by stacking and bonding crystal wafers, each containing a large number of crystal diaphragms 10, first sealing members 20, and second sealing members 30, and conductive paste 401 is continuously dispensed into all of the large number of through holes contained in the crystal wafers, and then cured.

[0057] In the curing process, the conductive paste 401 filled into the first through-hole 161 is solidified (cured) to form a conductive member 161d. At this time, the curing process can be a heating process in which heat S is applied to the conductive paste 401 to cure it. The temperature and time of the heat S can be appropriately set depending on the conductive material, dispersion solution, their mixing ratio, and other physical properties such as viscosity that constitute the conductive paste 401. Furthermore, the conductive member 161d after curing may contain the substances that constitute the raw material conductive paste 401. That is, in addition to the conductive material, the conductive member 161d after curing may contain residual components of the dispersion solvent that could not be completely removed by the heating process.

[0058] Then, after the conductive member 161d has hardened and filled, a second external terminal metal layer formation process is carried out to form a second external terminal metal layer 322a so as to cover the open end of the through hole 161 on the second main surface 302 side. As a result, the through hole 161 is sealed in a double-sealed state, with the inside sealed by the conductive member 161d and the open end on the second main surface 302 side covered by the second external terminal metal layer 322a.

[0059] Alternatively, a plurality of crystal oscillators 100 may be formed by stacking and bonding crystal wafers containing a plurality of each of the crystal diaphragm 10, the first sealing member 20, and the second sealing member 30, and a second external terminal metal layer may be formed simultaneously for all of the plurality of crystal oscillators 100.

[0060] With the above configuration, it is possible to provide a piezoelectric vibration device and a method for manufacturing a piezoelectric vibration device that can suppress the metal brazing material, which joins the external terminals and the mounting pads of the substrate, from crawling up into the through holes formed in the second sealing member.

[0061] The crystal oscillator 100 of the present invention has a conductive member 161d provided in the through hole 161 to close the through hole 161, and an external terminal 32a provided on the second main surface 302 of the second sealing member 30, wherein at least a part of the opening end of the through hole 161 on the second main surface 302 side is covered by the second external terminal metal layer 322a that constitutes the external terminal 32a. With this configuration, when the 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 crystal oscillator 100 from creeping up into the first through hole 161. More specifically, with the above configuration, the conductive member 161d that closes the through hole 161 can prevent the metal brazing material from creeping up, thereby suppressing the metal brazing material from creeping up into the through hole. Furthermore, the conductive member 161d and the second external terminal metal layer 322a covering the open end on the second main surface 302 side reduce the conductivity resistance around the through hole 161, thereby improving the electrical characteristics of the crystal oscillator 100.

[0062] Furthermore, especially when the crystal oscillator 100 is mounted on an external circuit board and covered with molding resin, if the flux contained in the metal brazing material has not completely evaporated during the initial melting (melting during joining), it may evaporate when the metal brazing material is remelted (when the molding resin hardens). The evaporated flux may then reach the sealing portion (second seal path 116) via the first through hole 161, activating the outermost Au metal layer and potentially destroying the seal. However, with the configuration described above, where the first through hole 161 is blocked by the conductive member 161d, the evaporated flux will not reach the sealing portion (second seal path 116), and a stable seal can be achieved.

[0063] Furthermore, the through-hole 161 has a conductive electrode 161c on its inner wall surface that electrically connects an internal electrode formed on the first main surface 301 with an external terminal 32a formed on the second main surface 302. The external terminal 32a has a configuration in which a first external terminal metal layer 321a is formed directly on the second main surface 302 and is formed continuously with the conductive electrode 161c, and a second external terminal metal layer 322a covers the open end of the through-hole 161 on the second main surface 302 side. With this configuration, a manufacturing method can be implemented in which a conductive member 161d is filled into the through-hole 161 and then covered with the second external terminal metal layer 322a. In other words, a configuration can be realized in which a conductive member 161d is provided inside the through-hole 161 to close the through-hole 161, and the open end of the through-hole 161 on the second main surface 302 side is covered with the external terminal 32a, thereby suppressing the metal brazing material from creeping up into the through-hole.

[0064] Furthermore, the inner wall surface of the through hole 161 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 narrows toward the center in the thickness direction of the second sealing member 30. The external terminal 32a has an Au metal layer 322a3 formed on the outermost layer of the second external terminal metal layer 322a (external terminal 32a), and the entire outermost layer of the second inclined portion 161b of the conductive electrode 161c is not provided with gold. With this configuration, the wettability of the surface of the second inclined portion 161b of the through hole 161 to the metal brazing material can be reduced. In particular, when covering a crystal oscillator 100 mounted on an external circuit board with a molding resin, when the molding resin is hardened by heating to form the structure, pressure is applied from the surroundings by the hardening molding resin to the metal brazing material that has been remelted by heating. As a result, the metal brazing material, surrounded by the hardening molding resin, has nowhere to go and exhibits behavior of crawling up through each through-hole. At this time, if the second external terminal metal layer 322a is incorporated into the metal brazing material, or if the metal brazing material penetrates areas with thinner film thickness, there is a risk that the metal brazing material will wet the conductive electrode 161c and crawl up inside the through-hole 161. However, with a configuration like that of the present invention, the wettability of the surface of the second inclined portion 161b of the through-hole 161 to the metal brazing material can be reduced, and it is possible to suppress the metal brazing material from crawling up by wetting the conductive electrode 161c formed on the inner wall surface of the through-hole 161.

[0065] Furthermore, if Au is not present in a portion of the conductive area, the conductivity resistance of the conductive electrode 161c in the second inclined portion 161b where Au is not provided will increase, which may worsen the electrical characteristics of the crystal oscillator 100. However, with a configuration like that of the present invention, the conductive member 161d reduces the conductivity resistance of the conductive electrode 161c, thereby improving the electrical characteristics of the crystal oscillator 100.

[0066] Furthermore, the conductive member 161d is positioned to cover the second main surface side end face of the Au metal layer 161c3 and is in contact with the Cr metal layer 161c1 formed on the second inclined portion 161b. This configuration prevents the Au metal layer 161c3, which has high wettability to the metal brazing material, from coming into contact with the metal brazing material. In addition, the conductivity resistance of the conductive electrode 161c can be reduced, thereby improving the electrical characteristics of the quartz crystal oscillator 100.

[0067] Furthermore, the manufacturing method of the quartz oscillator 100 includes a conductive member filling step in which a conductive member 161d is filled into the first through hole 161, following the second sealing member joining step in which the quartz diaphragm 10 and the second sealing member 30 are joined, and a second external terminal metal layer forming step in which a second external terminal metal layer 322a is formed to cover the open end of the through hole 161, following the conductive member filling step. With such a configuration, the manufacturing method can be such that the conductive member 161d is filled into the through hole 161 and then covered with the second external terminal metal layer 322a, and the configuration of the present invention, in which the conductive member 161d is provided inside the through hole 161 and closes the through hole 161, and the open end of the through hole 161 on the second main surface 302 side is covered by the external terminal 32a (second external terminal metal layer 322a), can be realized with a simple manufacturing method.

[0068] Furthermore, this invention is not limited to the configuration of the embodiments described above, and many other embodiments can be obtained.

[0069] 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 X-Y 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 X-Y cut quartz crystal.

[0070] 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.

[0071] 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.

[0072] <Second Embodiment> Figure 12 is a schematic cross-sectional view of the first through-hole of the second sealing member of the quartz crystal oscillator according to the second embodiment.

[0073] Furthermore, in the first embodiment, the conductive electrode 161c in the second inclined portion 161b is composed only of a Cr metal layer 161c1, but a Ti metal layer 161c4 and an Au metal layer 161c5 may be provided below the Cr metal layer 161c1. In this case, as shown in Figure 12, it is preferable that the Ti metal layer 161c4 and the Au metal layer 161c5 are provided up to the second main surface 302 and overlap with the Ti metal layer 321a2 and the Au metal layer 321a3 of the first external terminal metal layer 321a. It is also preferable that the Ti metal layer 161c4 and the Au metal layer 161c5 are completely covered by the Cr metal layer 161c1 and not exposed to the outside. With such a configuration, the conductivity resistance in the second inclined portion 161b of the conductive electrode 161c can be reduced, and the electrical characteristics of the crystal oscillator 100 can be improved.

[0074] 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.

[0075] This application claims priority under Japanese Patent Application No. 2024-168419, filed in Japan on 27 September 2024. By reference thereto, all its contents are incorporated into this application.

[0076] 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.

[0077] 10...Quartz diaphragm 100...Quartz oscillator 111...First excitation electrode 112...Second excitation electrode 115...First seal path 116...Second seal path 20...First sealing member 30...Second sealing member 301...First main surface 302...Second main surface 32a, 32b, 32c, 32d...External terminals 321a, 321b, 321c...First external terminal metal layer 322a, 322b, 322c, 322d...Second external terminal metal layer 161...First through hole 161a...First inclined portion 161b...Second inclined portion 161c...Conductive electrode 161c1...Cr metal layer 161c2...Ti metal layer 161c3...Au metal layer 161d...Conductive member 162...Second through hole 163...Third through hole 401...Conductive paste

Claims

1. 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 excitation electrode and the second excitation electrode, is hermetically sealed, wherein the second sealing member has: a first main surface facing the vibrating portion; a second main surface on the back surface of the first main surface that does not face the vibrating portion; a through hole penetrating from the first main surface to the second main surface; a conductive member provided in the through hole to close the through hole; and an external terminal provided on the second main surface, wherein at least a part of the opening end of the through hole on the second main surface side is covered by the external terminal.

2. A piezoelectric vibration device according to claim 1, wherein 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 formed on the second main surface, and the external terminal has a first external terminal metal layer formed directly on the second main surface and continuously formed with the conductive electrode, and a second external terminal metal layer that covers at least a portion of the opening end of the through hole on the second main surface side.

3. A piezoelectric vibration device according to claim 2, wherein 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, and gold is not provided over the entire area of ​​the outermost layer of the second inclined portion of the conductive electrode.

4. A piezoelectric vibration device according to any one of claims 1 to 3, characterized in that two or more conductive materials with different shapes and particle sizes are dispersed in the conductive member.

5. A piezoelectric vibration device manufacturing method for manufacturing the piezoelectric vibration device according to claim 2 or 3, comprising: 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 excluding the second external terminal metal layer; a first sealing member joining step for joining the piezoelectric vibration element and the first sealing member; a second sealing member joining step for joining the piezoelectric vibration element and the second sealing member; a conductive member filling step for filling the through hole with the conductive member; and a second external terminal metal layer forming step for forming the second external terminal metal layer so as to cover the opening end on the second main surface side of the through hole, wherein the conductive member filling step is provided after the second sealing member joining step, and the second external terminal metal layer forming step is provided after the conductive member filling step.

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