Piezoelectric vibration plate and piezoelectric vibration device

Abstract

Provided is a crystal vibration plate 10, wherein a first excitation electrode 111 and a second excitation electrode 112 of a vibration part 11 are provided with: central parts 111g, 112g which are portions between first parallel sides 111a, 112a and second parallel sides 111b, 112b and in which width dimensions W1, W2 along a second specific crystal axis direction reach a maximum; and a pair of reduced width parts 111h, 112h which are provided adjacent to both sides of the central parts 111g, 112g and in which the width dimensions W1, W2 become smaller as a distance from a first virtual straight line L1 becomes greater. The following are provided: a first extraction electrode 113 extending along the first virtual straight line L1 from the first parallel side 111a of the first excitation electrode 111; and a second extraction electrode 114 extending along the first virtual straight line L1 from the second parallel side 112b of the second excitation electrode 112. The vibration part 11, a holding part 13, the first excitation electrode 111, and the second excitation electrode 112 are formed line-symmetrically with respect to the first virtual straight line L1 and a second virtual straight line L2.

Description

Piezoelectric Vibrating Plate and Piezoelectric Vibration Device

[0001] The present invention relates to a piezoelectric vibrating plate and a piezoelectric vibration device including the same.

[0002] Conventionally, a so-called sandwich-structured piezoelectric vibration device is known as a piezoelectric vibration device suitable for size reduction and thickness reduction. In the sandwich-structured piezoelectric vibration device, the housing thereof is formed of a substantially rectangular parallelepiped package. This package includes a first sealing member and a second sealing member made of, for example, glass or quartz, and a piezoelectric vibrating plate having excitation electrodes formed on both main surfaces thereof, wherein the first sealing member and the second sealing member are laminated and bonded together with the piezoelectric vibrating plate interposed therebetween. Then, the vibrating portion of the piezoelectric vibrating plate disposed inside the package (internal space) is hermetically sealed by the first sealing member and the second sealing member (see, for example, Patent Document 1).

[0003] In the piezoelectric vibration device described in Patent Document 1, the piezoelectric vibrating plate includes: a vibrating portion having an excitation electrode formed on a main surface thereof; an outer frame portion surrounding an outer peripheral wall of the vibrating portion; a holding portion connecting the outer peripheral wall of the vibrating portion and an inner peripheral wall of the outer frame portion; and a cutout portion formed by cutting out a space between the vibrating portion and the outer frame portion in a thickness direction. By providing only one holding portion, the configuration is less susceptible to the influence of external stress transmitted from the outer frame portion and the influence of vibration leakage of vibration energy of the vibrating portion while coping with size reduction.

[0004] Japanese Unexamined Patent Publication No. 2020-141358

[0005] By the way, in the above-described piezoelectric vibrating plate, spurious vibration occurs due to various factors such as the peripheral shape of the excitation electrode of the vibrating portion, and when the influence of the spurious vibration becomes large, it becomes difficult to stably oscillate the main vibration.

[0006] The present invention has been made in consideration of the above-described circumstances, and an object of the present invention is to provide a piezoelectric vibrating plate capable of stabilizing main vibration while suppressing spurious vibration, and a piezoelectric vibration device including the same.

[0007] The present invention provides the following means for solving the above-mentioned problems. That is, the present invention provides a piezoelectric diaphragm that vibrates with thickness shear, wherein the piezoelectric diaphragm is a quartz diaphragm, and both main surfaces are planes including a first specific crystal axis and a second specific crystal axis perpendicular to the first specific crystal axis, and the thickness direction is parallel to a third specific crystal axis perpendicular to the first specific crystal axis and the second specific crystal axis, and a pair of excitation electrodes facing the two main surfaces are formed on the vibrating part, an outer frame part surrounding the vibrating part, a holding part connecting the vibrating part and the outer frame part, and the vibrating part and the outer frame The structure includes a cutout portion formed by cutting out the space between the parts in the thickness direction, a first virtual straight line passing through the center point of the vibrating portion in a plan view along the second specific crystal axis, a second virtual straight line passing through the center point of the vibrating portion in a plan view along the first specific crystal axis, the excitation electrode on one of the two main surfaces of the vibrating portion being the first excitation electrode, and the excitation electrode on the other of the two main surfaces of the vibrating portion being the second excitation electrode, and the first and second excitation electrodes are in the direction of the first specific crystal axis The first excitation electrode and the second excitation electrode have a pair of opposing first and second parallel sides along the first and second parallel sides, and the first excitation electrode and the second excitation electrode are provided with a central portion between the first and second parallel sides where the width dimension along the second specific crystal axis direction is maximum, and a pair of narrowed portions provided adjacent to both sides of the central portion in the direction of the first specific crystal axis direction, wherein the width dimension along the second specific crystal axis direction decreases as the distance from the first virtual line increases, and the vibrating portion is provided with a first extraction electrode extending from the first parallel side of the first excitation electrode along the first virtual line, and a second extraction electrode extending from the second parallel side of the second excitation electrode along the first virtual line in the direction opposite to the extension direction of the first extraction electrode, and the first extraction electrode and the second extraction electrode are formed symmetrically with respect to the first virtual line, and the vibrating portion, holding portion, first excitation electrode, and second excitation electrode are formed symmetrically with respect to the first virtual line and the second virtual line.

[0008] According to the above configuration, the principal vibration can be stabilized while suppressing spurious vibrations. Specifically, with respect to spurious vibrations caused by the surrounding shape of the first and second excitation electrodes of the vibrating part, compared to the principal vibration, the vibration displacement region of spurious vibrations extending in the first specific crystal axis direction and the second specific crystal axis direction can be narrowed more reliably and efficiently by a pair of narrowing sections formed symmetrically with respect to the first and second virtual lines. This makes it possible to suppress spurious vibrations extending in the first specific crystal axis direction and the second specific crystal axis direction of the vibrating part. On the other hand, a stable vibration region of the principal vibration can be secured by the central part where the width dimension in the second specific crystal axis direction between the first and second parallel sides is maximum. Furthermore, by providing a pair of narrowing sections on both sides of the central part in the direction of the first specific crystal axis, where the width dimension along the second specific crystal axis direction decreases as the distance from the first virtual line increases, the vibration region can be further secured without hindering the excitation of the principal vibration.

[0009] Furthermore, the vibrating section has no unnecessary electrodes for external connections other than the first and second excitation electrodes and the first and second extraction electrodes, and is mechanically supported by the outer frame only via the holding section. As a result, the vibrating section is not mechanically connected in any additional way, eliminating the post-manufacturing weighting of the piezoelectric vibration device and the imbalance in the vibration region relative to the main vibration and spurious vibration. This allows for stable oscillation of the main vibration and suppression of spurious vibration, thereby stabilizing the characteristics. In other words, by increasing the resistance value of the spurious vibration, the spurious vibration can be suppressed and the main vibration stabilized, based on the CI ratio, which is the comparison between the CI value of the main vibration (a value indicating the ease of oscillation of the main vibration and the equivalent series resistance value that results in vibration loss) and the resistance value (CI value) of the spurious vibration.

[0010] In the piezoelectric diaphragm with the above configuration, it is preferable that the piezoelectric diaphragm is an AT-cut quartz diaphragm, with one of the X-axis and Z'-axis directions of the AT cut being the first specific crystal axis, the other being the second specific crystal axis, and the Y'-axis direction of the AT cut being the third specific crystal axis. With this configuration, compared to the main vibration, spurious vibrations caused by the surrounding shape of the first and second excitation electrodes of the vibrating part can be narrowed more reliably and efficiently by a pair of narrowed width sections formed symmetrically with respect to the first and second virtual lines, respectively, which narrow the vibration displacement region of spurious vibrations extending in the X-axis and Z'-axis directions. This makes it possible to suppress spurious vibrations extending in the X-axis and Z'-axis directions of the vibrating part. On the other hand, a stable vibration region of the main vibration can be secured by the central part where the width dimension in the second specific crystal axis direction between the first and second parallel sides is maximum. Furthermore, by providing a pair of narrowed sections on both sides of the first specific crystal axis direction in the central part, the width dimension along the second specific crystal axis direction decreases as the distance from the first virtual line increases, it is possible to further secure the vibration region without hindering the excitation of the main vibration.

[0011] In the piezoelectric diaphragm with the above configuration, it is preferable that, at the connection portion between the first excitation electrode and the first extraction electrode, the width dimension of the first extraction electrode along the first specific crystal axis direction is at least half the length of the first parallel side of the first excitation electrode, and at the connection portion between the second excitation electrode and the second extraction electrode, the width dimension of the second extraction electrode along the first specific crystal axis direction is at least half the length of the second parallel side of the second excitation electrode. With this configuration, by providing the first and second extraction electrodes which are formed symmetrically with respect to the first and second virtual lines and have a width dimension of at least half the length of the first and second parallel sides of the first and second excitation electrodes, the conductivity performance of the first and second excitation electrodes by the first and second extraction electrodes can be improved, the CI value of the main vibration can be reduced, and the main vibration can be stabilized.

[0012] In the piezoelectric diaphragm with the above configuration, the holding portion preferably has a pair of vibration holding portions aligned with the first virtual straight line and a pair of outer frame holding portions extending in a direction different from the second specific crystal axis direction and connecting each vibration holding portion to two locations on the inner circumferential wall of the outer frame portion, with each vibration holding portion connected to the outer circumferential wall of the vibrating portion and the outer frame holding portion, and the outer frame holding portions connected to four locations on the inner circumferential wall of the outer frame portion. With this configuration, the influence on the vibrating portion due to the formation of the first and second extraction electrodes on the holding portion can be reduced, and the characteristics of the main vibration can be stabilized without subsequently hindering the stable oscillation of the main vibration or hindering the suppression of spurious vibrations. Furthermore, it has a pair of vibration-holding parts along a first virtual straight line, and a pair of outer frame holding parts that extend in a direction different from the second specific crystal axis direction and connect each vibration-holding part to two locations on the inner circumferential wall of the outer frame. Each vibration-holding part is connected to the outer circumferential wall of the vibrating part and to the outer frame holding part, and the outer frame holding part is connected to four locations on the inner circumferential wall of the outer frame. This makes it possible to make the stress transmitted from the outer frame to the vibrating part via the outer frame holding part and vibration-holding part uniform, and to suppress the influence of external stresses, etc. The deflection in the thickness direction of the piezoelectric diaphragm can be suppressed with the fewest possible points.

[0013] In the piezoelectric diaphragm with the above configuration, it is preferable that the vibrating portion is formed in a rectangular shape having a pair of parallel sides along the first specific crystal axis direction and a pair of parallel sides along the second specific crystal axis direction, and that the first excitation electrode and the second excitation electrode have a pair of parallel sides along the second specific crystal axis direction. With this configuration, it is possible to secure a gap dimension between the end (parallel side) of the excitation electrode and the outer peripheral end of the vibrating portion, thereby further improving spurious suppression while confining the energy of the main vibration and stabilizing the main vibration.

[0014] In the piezoelectric diaphragm with the above configuration, it is preferable that the thickness of the vibrating portion is thinner in the central part inward than in the outer part. This configuration makes it possible to realize a piezoelectric diaphragm that can handle high frequencies. Furthermore, by ensuring a gap dimension between the end (parallel side) of the excitation electrode and the thick wall portion provided on the outer periphery of the vibrating portion, it is possible to further improve spurious suppression while confining the energy of the main vibration and stabilizing the main vibration.

[0015] In the piezoelectric diaphragm with the above configuration, it is preferable that the first specific crystal axis direction is the X axis direction and the second specific crystal axis direction is the Z' axis direction. With this configuration, in a quartz diaphragm which is an AT-cut quartz diaphragm, by providing a pair of narrowed width sections in which the width dimension along the Z' axis direction gradually narrows in a direction that moves away from each other along the longer X axis direction of the vibration displacement distribution of the main vibration, it is possible to further secure the vibration region without hindering the excitation of the main vibration.

[0016] Furthermore, the present invention relates to a piezoelectric vibration device comprising a piezoelectric diaphragm as described above, characterized in that an upper sealing plate covering the upper surface of the piezoelectric diaphragm and a lower sealing plate covering the lower surface of the piezoelectric diaphragm are joined to the piezoelectric diaphragm. The piezoelectric vibration device with the above configuration provides the same effects as the piezoelectric diaphragm described above.

[0017] According to the piezoelectric diaphragm and piezoelectric vibration device of the present invention, it is possible to stabilize the principal vibration while suppressing spurious vibrations.

[0018] Figure 1 is a schematic diagram illustrating the crystal oscillator according to this embodiment. Figure 2 is a schematic plan view of the first main surface side of the first sealing member of the crystal oscillator. Figure 3 is a schematic plan view of the second main surface side of the first sealing member of the crystal oscillator. Figure 4 is a schematic plan view of the first main surface side of the crystal diaphragm according to this embodiment. Figure 5 is a schematic plan view of the second main surface side of the crystal diaphragm according to this embodiment. Figure 6 is a schematic plan view of the first main surface side of the second sealing member of the crystal oscillator. Figure 7 is a schematic plan view of the second main surface side of the second sealing member of the crystal oscillator. Figure 8 is a diagram corresponding to Figure 4 of a crystal diaphragm according to another embodiment 1. Figure 9 is a diagram corresponding to Figure 4 of a crystal diaphragm according to another embodiment 2. Figure 10 is a diagram corresponding to Figure 5 of a crystal diaphragm according to another embodiment 2. Figure 11 is a diagram corresponding to Figure 4 of a crystal diaphragm according to another embodiment 3.

[0019] 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.

[0020] First, the basic structure of the crystal oscillator 100 according to this embodiment will be described. As shown in Figure 1, the crystal oscillator 100 is composed of a crystal diaphragm (piezoelectric diaphragm) 10, a first sealing member (upper sealing plate) 20, and a second sealing member (lower sealing plate) 30. In this crystal oscillator 100, the crystal diaphragm 10 and the first sealing member 20 are joined together, and the crystal diaphragm 10 and the second sealing member 30 are joined together to form 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.

[0021] The crystal oscillator 100 in this embodiment has a package size of, for example, 1.0 × 0.8 mm, achieving miniaturization and a low profile. The crystal oscillator 100 is electrically connected to an external circuit board (not shown) via solder or the like.

[0022] 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.

[0023] As shown in Figures 4 and 5, the quartz diaphragm 10 is a piezoelectric substrate made of quartz, and both of its main surfaces (first main surface 101, second main surface 102) are formed as flat, smooth surfaces (mirror-finished). In the quartz diaphragm 10, both main surfaces (first main surface 101, second main surface 102) are planes that include a first specific crystal axis and a second specific crystal axis perpendicular to this first specific crystal axis, and the thickness direction is parallel to a third specific crystal axis perpendicular to these first and second specific crystal axes.

[0024] In this embodiment, an AT-cut quartz plate 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 longitudinal direction (long side direction) of the quartz diaphragm 10 is defined as the X-axis direction, and the direction parallel to the short side (short side direction) of the quartz diaphragm 10 is defined as the Z' axis direction. One of the X-axis direction and Z' axis direction of the AT cut (in this case, the X-axis direction) is defined as the first specific crystal axis, the other (in this case, the Z' axis direction) is defined as the second specific crystal axis direction, and the Y' axis direction of the AT cut is defined as the third specific crystal axis. Note that AT cutting is a processing method in which artificial quartz is cut at an angle of approximately 35°15′ tilted around the X axis with respect to the Z axis, which is one of the three crystal axes of artificial 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 tilted approximately 35°15′ from the Y and Z axes of the quartz crystal axis, respectively (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. Note that the cutting angle may be slightly shifted depending on the characteristics.

[0025] 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 crystal diaphragm 10. The quartz crystal diaphragm 10 has a configuration comprising a substantially rectangular vibrating section 11, an outer frame section 12 surrounding the outer peripheral wall of the vibrating section 11, a holding section 13 connecting the outer peripheral wall of the vibrating section 11 and the inner peripheral wall of the outer frame section 12, and cutout sections 14a and 14b formed by cutting out the space between the vibrating section 11 and the outer frame section 12 in the thickness direction. Both the inner peripheral wall of the outer frame section 12 and the outer peripheral wall of the vibrating section 11 are formed in a rectangular shape in plan view. Furthermore, the direction of the long side of the quartz crystal diaphragm 10 in plan view and the direction of the long side of the inner peripheral wall of the outer frame section 12 in plan view are perpendicular to each other, and the direction of the long side of the inner peripheral wall of the outer frame section 12 in plan view and the direction of the long side of the vibrating section 11 in plan view are perpendicular to each other. The long side direction in a plan view of the quartz crystal diaphragm 10 and the long side direction in a plan view of the vibrating section 11 are arranged in the same direction. In this embodiment, the outer frame 12 of the quartz crystal diaphragm 10 is configured without through holes or castellations. The outer peripheral portion 11b side of the vibrating section 11, where the first excitation electrode 111 and the second excitation electrode 112 are not formed, is formed to be thicker than the central portion 11a side where the first excitation electrode 111 and the second excitation electrode 112 are formed, and annular steps 11c are formed on both main surfaces of the vibrating section 11. One holding section 13 is provided on both the +Z' direction side and the +Z' direction side of the vibrating section 11. The holding section 13 is composed of a vibration holding section 13a on the vibrating section 11 side and an outer frame holding section 13b on the outer frame 12 side. Details of the holding section 13 will be described later.

[0026] 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 electrodes (lead-out wiring) for connecting these excitation electrodes to external electrode terminals are connected to the first excitation electrode 111 and the second excitation electrode 112. The first lead-out electrode 113 is led out from the first excitation electrode 111 in the +Z' direction and is connected to a connecting joint pattern 12b formed on the first main surface 101 side of the outer frame section 12 via a holding section 13 provided on the +Z' direction side of the vibrating section 11. The outer frame section 12 is formed to be thicker than the holding section 13, and a step is formed between the outer frame section 12 and the holding section 13. For this reason, the first lead-out electrode 113 is connected to the connecting joint pattern 12b via internal wiring 17 formed on the inner circumferential wall of the outer frame section 12. The connecting joint pattern 12b is also connected to the connecting joint pattern 12f formed on the second main surface 102 side of the outer frame 12 via internal wiring 17 formed on the inner circumferential wall of the outer frame 12. The internal wiring 17 is provided on the inner circumferential wall of the outer frame 12, specifically on the inner circumferential wall in the +X direction, along the Z' axis direction.

[0027] The second lead electrode 114 is led out from the second excitation electrode 112 toward the -Z' direction and connected to a connecting joint pattern 12e formed on the second main surface 102 side of the outer frame 12 via a holding portion 13 provided on the -Z' side of the vibrating portion 11. As described above, a step is formed between the outer frame 12 and the holding portion 13, and the second lead electrode 114 is connected to the connecting joint pattern 12e via internal wiring 18 formed on the inner circumferential wall of the outer frame 12. The internal wiring 18 is provided on the inner circumferential wall of the outer frame 12, specifically on the inner circumferential wall along the Z' axis direction, and on the -X side. In this embodiment, since the first lead electrode 113 and the second lead electrode 114 are led out in different directions, the lead electrodes of each other are not positioned facing each other across the vibrating portion 11. Therefore, unnecessary excitation by the lead electrodes in the vibrating portion 11 is eliminated, and the stability of the characteristics can be improved.

[0028] 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 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 joining pattern 122 is provided close to the outer edge of the second main surface 102 of the crystal diaphragm 10 (outer frame portion 12). The diaphragm-side first bonding pattern 121 and the diaphragm-side second bonding pattern 122 are connected via internal wiring 19 formed on the inner circumferential wall of the outer frame portion 12. The internal wiring 19 is provided on the inner circumferential wall of the outer frame portion 12 that is aligned with the X-axis direction and on the -Z' side, and is provided on the inner circumferential wall perpendicular to the inner circumferential wall on which the aforementioned internal wirings 17 and 18 are provided. A connecting bonding pattern 12a is formed on the first main surface 101 side of the outer frame portion 12.

[0029] As shown in Figures 2 and 3, the first sealing member 20 is a rectangular substrate formed from a single AT-cut quartz plate, and the second main surface 202 of the first sealing member 20 (the surface that joins to the quartz diaphragm 10) is formed as a flat, smooth surface (mirror finish). Although the first sealing member 20 does not have a vibrating part, by using an AT-cut quartz plate similar to the quartz diaphragm 10, the thermal expansion coefficients of the quartz diaphragm 10 and the first sealing member 20 can be made the same, thereby suppressing thermal deformation in the quartz resonator 100. Furthermore, 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 this embodiment, since the first sealing member 20 does not have through holes or castellations, the manufacturing process of the first sealing member 20 can be significantly shortened. In addition, by eliminating the path for moisture to enter the internal space of the package from the first main surface 201 side of the first sealing member 20, corrosion resistance can be improved.

[0030] A first sealing member side bonding pattern 24 is formed on the second main surface 202 of the first sealing member 20, serving as the first sealing portion on the sealing member side for bonding to the crystal diaphragm 10. The first sealing member side bonding pattern 24 is formed in an annular shape in plan view. The outer edge of the first sealing member side bonding pattern 24 is provided close to the outer edge of the second main surface 202 of the first sealing member 20. In addition, connecting bonding patterns 22a and 22b are formed on the second main surface 202 of the first sealing member 20 for bonding to the connecting bonding patterns 12a and 12b formed on the first main surface 101 of the outer frame portion 12 of the crystal diaphragm 10.

[0031] As shown in Figures 6 and 7, the second sealing member 30 is a rectangular substrate formed from a single AT-cut quartz plate, and the first main surface 301 of this second sealing member 30 (the surface that joins to the quartz diaphragm 10) is formed as a flat, smooth surface (mirror finish). It is desirable 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.

[0032] The first main surface 301 of the second sealing member 30 has a second sealing pattern 31 on the sealing member side, which serves as a second sealing portion on the sealing member side for joining to the crystal diaphragm 10. The second sealing pattern 31 on the sealing member side is formed in an annular shape in plan view. The outer edge of the second sealing pattern 31 on the sealing member side is provided close to the outer edge of the first main surface 301 of the second sealing member 30. In addition, the first main surface 301 of the second sealing member 30 has connecting patterns 34a and 34b formed for joining to connecting patterns 12e and 12f formed on the second main surface 102 of the outer frame portion 12 of the crystal diaphragm 10.

[0033] 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 electrode terminals 32 that are electrically connected to an external circuit board provided outside the crystal oscillator 100. The external electrode terminals 32 are formed in a substantially rectangular shape and are located at the four corners (corners) of the second main surface 302 of the second sealing member 30. In a plan view, the external electrode terminals 32 are provided in a position that overlaps with the outer frame portion 12 of the crystal diaphragm 10 described above.

[0034] As shown in Figures 6 and 7, the second sealing member 30 has three through-holes 33a, 33b, and 33c that penetrate between the first main surface 301 and the second main surface 302. The through-holes 33a, 33b, and 33c are provided in the four corner (corner) regions of the second sealing member 30. Through electrodes are formed along the inner wall surfaces of the through-holes 33a, 33b, and 33c to ensure electrical conductivity between the electrodes formed on the first main surface 301 and the second main surface 302. The through electrodes formed on the inner wall surfaces of the through-holes 33a, 33b, and 33c provide electrical conductivity between the electrode (connection pattern) formed on the first main surface 301 and the external electrode terminal 32 formed on the second main surface 302. Furthermore, the central portions of each through-hole 33a, 33b, and 33c are hollow through-holes that penetrate between the first main surface 301 and the second main surface 302.

[0035] In the quartz crystal oscillator 100, which includes the quartz crystal diaphragm 10, the first sealing member 20, and the second sealing member 30 as described above, the quartz crystal diaphragm 10 and the first sealing member 20 are diffusion-bonded with the diaphragm-side first bonding pattern 121 and the sealing member-side first bonding pattern 24 overlapping, and the quartz crystal diaphragm 10 and the second sealing member 30 are diffusion-bonded with the diaphragm-side second bonding pattern 122 and the sealing member-side second bonding pattern 31 overlapping, thereby manufacturing a sandwich-structured package as shown in Figure 1. As a result, the internal space of the package, that is, the space housing the vibrating part 11, is hermetically sealed.

[0036] In this process, the aforementioned connection patterns are also superimposed and diffusely bonded. Through the bonding of the connection patterns, electrical conductivity is achieved between the first excitation electrode 111, the second excitation electrode 112, and the external electrode terminals 32, 32 in the quartz oscillator 100. Specifically, the first excitation electrode 111 is connected to the external electrode terminal 32 via the first lead electrode 113, internal wiring 17, connection pattern 12f, connection pattern 34b, and through-hole 33b in that order. The second excitation electrode 112 is connected to the external electrode terminal 32 via the second lead electrode 114, internal wiring 18, connection pattern 12e, connection pattern 34a, and through-hole 33a in that order.

[0037] In the quartz oscillator 100, it is preferable that the various bonding patterns consist of multiple layers stacked on a quartz plate, with the Ti (titanium) layer and Au (gold) layer formed from the bottom layer by vapor deposition or sputtering. Furthermore, if the other wiring and electrodes formed on the quartz oscillator 100 have the same configuration as the bonding patterns, the bonding patterns, wiring, and electrodes can be patterned simultaneously, which is preferable.

[0038] In the crystal oscillator 100 configured as described above, the sealing portions (seal paths) 15 and 16 that hermetically seal the vibrating portion 11 of the crystal diaphragm 10 are formed in annular shape in plan view. The seal path 15 is formed by diffusion bonding (Au-Au bonding) of the diaphragm-side first bonding pattern 121 and the sealing member-side first bonding pattern 24 described above. The outer edge shape of the seal path 15 is formed to be substantially rectangular, and the outer edge of the seal path 15 is positioned close to the outer edge of the package. Similarly, the seal path 16 is formed by diffusion bonding (Au-Au bonding) of the diaphragm-side second bonding pattern 122 and the sealing member-side second bonding pattern 31 described above. The outer edge shape of the seal path 16 is formed to be substantially rectangular, and the outer edge of the seal path 16 is positioned close to the outer edge of the package. The seal paths 15 and 16 are not electrically connected to the electrical conduction path between the first and second excitation electrodes 111 and 112 and the external electrode terminals 32 and 32. Specifically, the seal path 15 is connected to the seal path 16 via internal wiring 19, and the seal path 16 is further connected to earth (ground connection, utilizing a portion of the external electrode terminal 32) via the through-hole electrode 33c.

[0039] In the quartz crystal oscillator 100 in which seal paths 15 and 16 are formed by diffusion bonding as described above, the gap between the first sealing member 20 and the quartz crystal diaphragm 10 is 1.00 μm or less, and the gap between the second sealing member 30 and the quartz crystal diaphragm 10 is 1.00 μm or less. In other words, the thickness of the seal path 15 between the first sealing member 20 and the quartz crystal diaphragm 10 is 1.00 μm or less, and the thickness of the seal path 16 between the second sealing member 30 and the quartz crystal diaphragm 10 is 1.00 μm or less (specifically, 0.15 μm to 1.00 μm in the Au-Au bonding of this embodiment). For comparison, in conventional metal paste sealing materials using Sn, the gap is 5 μm to 20 μm.

[0040] In this embodiment, in the crystal diaphragm 10 with the above configuration, the first excitation electrode 111 and the second excitation electrode 112 are formed symmetrically with respect to a first virtual line L1 that passes through the center point (centroid) C1 of the vibrating part 11 in a plan view and along the second specific crystal axis direction (here, the Z' axis direction), and are also formed symmetrically with respect to a second virtual line L2 that passes through the center point C1 of the vibrating part 11 in a plan view and along the first specific crystal axis direction (here, the X axis direction). The first excitation electrode 111 and the second excitation electrode 112 have a pair of first parallel sides 111a, 112a and second parallel sides 111b, 112b that face each other along the first specific crystal axis direction. The first excitation electrode 111 and the second excitation electrode 112 are provided with central portions 111g, 112g, which are between the first parallel sides 111a, 112a and the second parallel sides 111b, 112b, and where the width dimensions W1, W2 along the second specific crystal axis direction are maximum, and a pair of narrowed width portions 111h, 112h, which are provided adjacent to both sides of the central portions 111g, 112g along the first specific crystal axis direction, and where the width dimensions W1, W2 along the second specific crystal axis direction decrease as the distance from the first virtual straight line L1 increases. This point will be explained with reference to Figures 4 and 5.

[0041] As shown in Figures 4 and 5, the +Z' and -Z' directions of the rectangular vibrating section 11 in plan view are provided with holding sections 13 that are roughly T-shaped in plan view, respectively, and the holding sections 13 are arranged symmetrically with respect to the first virtual line L1 and the second virtual line L2. Specifically, the holding section 13 has a configuration in which a vibration holding section 13a extending linearly from the outer peripheral wall of the vibrating section 11 along the first virtual line L1 and an outer frame holding section 13b extending linearly parallel to the second virtual line L2 are integrally formed.

[0042] The vibration holding portion 13a and the outer frame holding portion 13b are connected to each other in directions orthogonal to each other. The vibration holding portion 13a extends toward the outer frame holding portion 13b along the long side direction of the inner peripheral wall of the outer frame portion 12 in plan view, and the outer frame holding portion 13b extends toward the inner peripheral wall side of the outer frame portion 12 along the short side direction of the inner peripheral wall of the outer frame portion 12 in plan view. One end of the vibration holding portion 13a is connected to a central portion of the vibrating portion 11 in the X-axis direction, and the other end of the vibration holding portion 13a is connected to a central portion of the outer frame holding portion 13b in the X-axis direction. The outer frame holding portions 13b are connected to regions at four corners of the inner peripheral wall of the outer frame portion 12 in plan view. One end of the outer frame holding portion 13b is connected to the inner peripheral wall on the +X direction side among the inner peripheral walls of the outer frame portion 12, and the other end of the outer frame holding portion 13b is connected to the inner peripheral wall on the -X direction side among the inner peripheral walls of the outer frame portion 12.

[0043] Both the vibration holding portion 13a and the outer frame holding portion 13b are formed in a linear shape in plan view. The vibration holding portion 13a is formed to be wider in plan view and shorter in length than the outer frame holding portion 13b. Specifically, the length of the vibration holding portion 13a along the Z'-axis direction is shorter than the length of the outer frame holding portion 13b along the X-axis direction. The width of the vibration holding portion 13a along the X-axis direction is wider than the width of the outer frame holding portion 13b along the Z'-axis direction.

[0044] By the holding portion 13 having the above configuration, a cutout portion formed between the outer peripheral wall of the vibrating portion 11 and the inner peripheral wall of the outer frame portion 12 is divided into a plurality of (in this case, four) portions in plan view. Specifically, the cutout portion 14a is a portion surrounded by the outer peripheral wall of the vibrating portion 11, the inner peripheral wall of the outer frame portion 12, and the vibration holding portion 13a and the outer frame holding portion 13b of the holding portion 13, and is formed in a substantially U-shape in plan view. The cutout portion 14b is a portion surrounded by the inner peripheral wall of the outer frame portion 12 and the outer frame holding portion 13b of the holding portion 13, and is formed in a linear shape extending along the X-axis direction in plan view.

[0045] As shown in Figures 4 and 5, the first excitation electrode 111 and the second excitation electrode 112 are formed in an octagonal shape in plan view, and are formed symmetrically with respect to the first virtual line L1 and the second virtual line L2. The first excitation electrode 111 and the second excitation electrode 112 are formed in the same shape and dimensions, and are located at positions where their center points in plan view coincide. In detail, the first excitation electrode 111 has a pair of opposing first parallel sides 111a and second parallel sides 111b along the first specific crystal axis direction (X axis direction). The first parallel side 111a is located on the +Z' side, and the second parallel side 111b is located on the -Z' side. The first excitation electrode 111 also has a pair of opposing third parallel sides 111c and fourth parallel sides 111d along the second specific crystal axis direction (Z' axis direction). The third parallel side 111c is located on the +X direction side, and the fourth parallel side 111d is located on the -X direction side.

[0046] Inclined sides 111e, 111e are provided between the first parallel side 111a and the third parallel side 111c, and between the second parallel side 111b and the third parallel side 111c, respectively. Inclined sides 111f, 111f are provided between the first parallel side 111a and the fourth parallel side 111d, and between the second parallel side 111b and the fourth parallel side 111d, respectively. As described above, the first excitation electrode 111 is formed symmetrically with respect to the first virtual line L1 and the second virtual line L2, so the third parallel side 111c and the fourth parallel side 111d, which face each other, are arranged parallel to each other.

[0047] Similarly, the second excitation electrode 112 has a pair of first parallel sides 112a and second parallel sides 112b that face each other along the first specific crystal axis direction (X axis direction). The first parallel side 112a is provided on the +Z' direction side, and the second parallel side 112b is provided on the -Z' direction side. The second excitation electrode 112 also has a pair of third parallel sides 112c and fourth parallel sides 112d that face each other along the second specific crystal axis direction (Z' axis direction). The third parallel side 112c is provided on the +X direction side, and the fourth parallel side 112d is provided on the -X direction side.

[0048] Inclined sides 112e and 112e are respectively provided between the first parallel side 112a and the third parallel side 112c, and between the second parallel side 112b and the third parallel side 112c. Inclined sides 112f and 112f are respectively provided between the first parallel side 112a and the fourth parallel side 112d, and between the second parallel side 112b and the fourth parallel side 112d. As described above, the second excitation electrode 112 is formed line-symmetrically with respect to the first virtual straight line L1 and the second virtual straight line L2, so the third parallel side 112c and the fourth parallel side 112d that face each other are provided parallel to each other.

[0049] The central portions 111g and 112g between the first parallel sides 111a, 112a and the second parallel sides 111b, 112b of the first excitation electrode 111 and the second excitation electrode 112 are formed in a rectangular shape in plan view, and the width dimensions W1 and W2 along the second specific crystal axis direction between the first parallel sides 111a, 112a and the second parallel sides 111b, 112b are maximum. A pair of width-reduced portions 111h and 112h formed in a trapezoidal shape in plan view are provided on both sides of the central portions 111g and 112g in the first specific crystal axis direction. The width-reduced portions 111h and 112h are provided adjacent to the central portions 111g and 112g. In the width-reduced portions 111h and 112h, the width dimensions W1 and W2 along the second specific crystal axis direction become smaller (narrower) as the distance from the first virtual straight line L1 (the distance along the first specific crystal axis direction) increases.

[0050] As shown in Figures 4 and 5, the vibrating section 11 has a first extraction electrode 113 and a second extraction electrode 114 that extend from the first excitation electrode 111 and the second excitation electrode 112 to the holding section 13. The first extraction electrode 113 extends from the first parallel side 111a of the first excitation electrode 111 along the second specific crystal axis direction (Z' axis direction) and is connected to the first extraction electrode 113 formed in the holding section 13. The first extraction electrode 113 is formed in a substantially L-shape in plan view and is formed to be approximately the same width. The second extraction electrode 114 extends from the second parallel side 112b of the second excitation electrode 112 along the second specific crystal axis direction, extends in the direction opposite to the first extraction electrode 113, and is connected to the second extraction electrode 114 formed in the holding section 13. The second extraction electrode 114 is formed in a substantially L-shape in plan view and is formed to be approximately the same width. Although the first and second extraction electrodes 113 and 114 of the holding portion 13 are provided point-symmetrically with respect to the center point C1 in a plan view of the vibrating portion 11, the first and second extraction electrodes 113 and 114 of the holding portion 13 may also be provided line-symmetrically with respect to the second virtual line L2.

[0051] At the connection point between the first excitation electrode 111 and the first extraction electrode 113, the width dimension of the first extraction electrode 113 along the first specific crystal axis direction (X-axis direction) is at least half the length of the first parallel side 111a of the first excitation electrode 111. Similarly, at the connection point between the second excitation electrode 112 and the second extraction electrode 114, the width dimension of the second extraction electrode 114 along the first specific crystal axis direction is at least half the length of the second parallel side 112b of the second excitation electrode 112. Within the vibrating section 11, the first extraction electrode 113 and the second extraction electrode 114 are formed along a first virtual line L1 and are formed symmetrically with respect to the first virtual line L1.

[0052] According to this embodiment, in the quartz diaphragm 10, the principal vibration can be stabilized while suppressing spurious vibrations. Specifically, with respect to spurious vibrations caused by the surrounding shapes of the first excitation electrode 111 and the second excitation electrode 112 of the vibrating section 11 compared to the principal vibration, the vibration displacement region of spurious vibrations extending in the X-axis direction and the Z'-axis direction can be narrowed more reliably and efficiently by a pair of narrowed width sections 111h and 112h formed symmetrically with respect to the first virtual line L1 and the second virtual line L2. This makes it possible to suppress spurious vibrations extending in the X-axis direction and the Z'-axis direction of the vibrating section 11. On the other hand, a stable vibration region of the principal vibration can be secured by the central sections 111g and 112g, where the width dimension in the second specific crystal axis direction (Z'-axis direction) between the first parallel sides 111a and 112a and the second parallel sides 111b and 112b of the first excitation electrode 111 and the second excitation electrode 112 is maximized. Furthermore, by providing a pair of narrowed width sections 111h and 112h on both sides of the central sections 111g and 112g in the direction of the first specific crystal axis (X axis), where the width dimensions W1 and W2 along the second specific crystal axis become smaller as the distance from the first virtual straight line L1 increases, it is possible to further secure the vibration region without hindering the excitation of the main vibration.

[0053] Furthermore, the vibrating section 11 has no unnecessary electrodes for external connection other than the first and second excitation electrodes 111, 112 and the first and second extraction electrodes 113, 114, and is mechanically supported by the outer frame 12 only via the holding section 13. As a result, the vibrating section 11 is not mechanically connected in any additional way, eliminating the need for post-manufacturing weighting of the quartz crystal oscillator 100 with respect to the main vibration and spurious vibration, and preventing imbalances in the vibration region. This allows for stable oscillation of the main vibration and suppression of spurious vibration, thereby stabilizing the characteristics. In other words, by increasing the resistance value of the spurious vibration, the spurious vibration can be suppressed and the main vibration stabilized, based on the CI ratio, which is the comparison between the CI value of the main vibration (a value indicating the ease of oscillation of the main vibration, and the equivalent series resistance value that results in vibration loss) and the resistance value (CI value) of the spurious vibration.

[0054] Furthermore, a first extraction electrode 113 and a second extraction electrode 114 are provided, which are formed symmetrically with respect to the first virtual line L1 and the second virtual line L2, and have a width dimension of more than half the length of the first parallel side 111a and the second parallel side 111b of the first and second excitation electrodes 111 and 112. This improves the conductivity performance of the first and second excitation electrodes 111 and 112 by the first extraction electrode 113 and the second extraction electrode 114, thereby reducing the CI value of the main vibration and stabilizing the main vibration.

[0055] In this embodiment, the holding portion 13 has a pair of vibration holding portions 13a along a first virtual straight line L1, and a pair of outer frame holding portions 13b that extend in a direction different from the second specific crystal axis direction (Z' axis direction) and connect each vibration holding portion 13a to two locations on the inner circumferential wall of the outer frame portion 12. Each vibration holding portion 13a is connected to the outer circumferential wall of the vibrating portion 11 and the outer frame holding portion 13b, and the outer frame holding portions 13b are connected to four locations on the inner circumferential wall of the outer frame portion 12. This reduces the influence on the vibrating portion 11 due to the formation of the first and second extraction electrodes 113 and 114 on the holding portion 13, and does not hinder the stable oscillation of the main vibration afterward or hinder the suppression of spurious vibrations, thereby stabilizing the characteristics of the main vibration. In addition, the stress transmitted from the outer frame portion 12 to the vibrating portion 11 via the outer frame holding portions 13b and vibration holding portions 13a can be made uniform, and the influence of external stresses can be suppressed. The deflection of the crystal diaphragm 10 in the thickness direction can be suppressed with as few points as possible.

[0056] Furthermore, the vibrating section 11 is formed in a rectangular shape having a pair of parallel sides along the first specific crystal axis direction (X axis direction) and a pair of parallel sides along the second specific crystal axis direction, and the first excitation electrode 111 and the second excitation electrode 112 have a pair of third parallel sides 111c, 112c and a fourth parallel side 111d, 112d along the second specific crystal axis direction (Z' axis direction). This ensures a gap dimension between the ends of the first excitation electrode 111 and the second excitation electrode 112 (the pair of third parallel sides 111c, 112c and the fourth parallel sides 111d, 112d) and the outer peripheral end of the vibrating section 11, thereby further improving spurious suppression while confining the energy of the main vibration and stabilizing the main vibration. Moreover, the length of the vibrating section 11 in the X axis direction is greater than or equal to the length in the Z' axis direction, and both the long side direction in the plan view of the quartz diaphragm 10 and the long side direction in the plan view of the vibrating section 11 are parallel to the X axis direction. This makes it possible to minimize the planar area of ​​the cutout portion 14a formed between the vibrating portion 11, the outer frame portion 12, and the holding portion 13, and maximize the planar area of ​​the vibrating portion 11, thereby ensuring that the vibration region of the vibrating portion 11 is as wide as possible.

[0057] In this embodiment, the vibrating portion 11 is formed with a thicker outer periphery 11b side compared to the central portion 11a side, resulting in an inverted mesa shape. In this case, the thickness of the vibrating portion 11, the outer frame portion 12, and the holding portion 13 are in the following order: outer frame portion 12 > outer periphery 11b of the vibrating portion 11 > holding portion 13 > central portion 11a of the vibrating portion 11. The holding portion 13 is connected to the outer frame portion 12 and the central portion of the vibrating portion 11 in the thickness direction. This makes it possible to realize a crystal diaphragm 10 that can handle high frequencies of, for example, 100 MHz or higher (more preferably 300 MHz or higher). Furthermore, by ensuring a gap between the ends of the first excitation electrode 111 and the second excitation electrode 112 (a pair of third parallel sides 111c, 112c and fourth parallel sides 111d, 112d) and the thick wall portion provided on the outer periphery 11b of the vibrating portion 11, it is possible to further improve spurious suppression while confining the energy of the main vibration and stabilizing the main vibration. Here, when such an inverted mesa-shaped vibrating portion 11 is formed by wet etching, a difference in thickness tends to occur in the central portion 11a of the vibrating portion 11, and there is a concern that spurious vibrations may occur as a result. However, according to this embodiment, it is also effective in suppressing such spurious vibrations.

[0058] In this embodiment, the first specific crystal axis direction is the X-axis direction, and the second specific crystal axis direction is the Z'-axis direction. As a result, in the quartz diaphragm 10, which is an AT-cut quartz diaphragm, a pair of narrowed width sections 111h and 112h are provided, in which the width dimension along the Z'-axis direction gradually narrows in a direction away from each other along the longer X-axis direction of the vibration displacement distribution of the main vibration, thereby further securing the vibration region without hindering the excitation of the main vibration. In addition, the center points in the plan view of the first and second excitation electrodes 111 and 112 are superimposed on the center point C1 of the vibrating section 11. As a result, the first and second excitation electrodes 111 and 112 are provided in a region where the thickness variation of the vibrating section 11 of the quartz diaphragm 10 is relatively small, so spurious vibrations can be suppressed and the main vibration can be oscillated stably.

[0059] Furthermore, in this embodiment, the first extraction electrode 113 and the second extraction electrode 114 are formed on the holding portion 13 of the quartz diaphragm 10, and no extraction electrodes are formed on the first sealing member 20 or the second sealing member 30. Therefore, it is possible to route the first extraction electrode 113 and the second extraction electrode 114 along the shortest possible path. This makes it possible to shorten the length of the first extraction electrode 113 and the second extraction electrode 114, thereby reducing the parasitic capacitance caused by this.

[0060] Even with a quartz oscillator 10 equipped with the quartz diaphragm 10 described above, the same effects and advantages as those of the quartz diaphragm 10 described above can be obtained. That is, the principal vibration can be stabilized while spurious vibrations are suppressed. Furthermore, the quartz oscillator 100 can be easily miniaturized.

[0061] 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.

[0062] The shapes and numbers of the vibration-holding portion 13a and outer frame holding portion 13b described above are examples and can be changed in various ways. For example, the vibration-holding portion 13a may be trapezoidal, with the width on the vibration portion 11 side being narrower than the width on the outer frame holding portion 13b side. Also, as shown in Figure 8, for example, the outer frame holding portion 13b may be V-shaped with a bend at a predetermined angle, or it may be an arc shape or an elliptical arc shape. In the example in Figure 8, the end of the outer frame holding portion 13b is connected to the corner of the inner circumferential wall of the outer frame portion 12, and the holding portion 13 is formed in a roughly Y shape. It is preferable that the number of connection points (connection points) of the vibration-holding portion 13a and the outer frame holding portion 13b is even, and that the number of connection points of the outer frame holding portion 13b is a multiple of the number of connection points of the vibration-holding portion 13a.

[0063] Furthermore, in the above embodiment, the width dimension between the first parallel sides 111a, 112a and the second parallel sides 111b, 112b of the first excitation electrode 111 and the second excitation electrode 112 (width dimension in the X-axis direction) and the width dimension between the third parallel sides 111c, 112c and the fourth parallel sides 111d, 112d (width dimension in the Z'-axis direction) were made approximately the same. However, as shown in Figure 8, for example, the width dimension between the first parallel sides 111a, 112a and the second parallel sides 111b, 112b of the first excitation electrode 111 and the second excitation electrode 112 may be made larger than the width dimension between the third parallel sides 111c, 112c and the fourth parallel sides 111d, 112d. In this way, by making the first excitation electrode 111 and the second excitation electrode 112 elongated horizontally in the X-axis direction, the vibration region of the main vibration can be further secured.

[0064] Furthermore, in the above embodiment, the lengths of the first parallel sides 111a, 112a and the second parallel sides 111b, 112b of the first excitation electrode 111 and the second excitation electrode 112 (length in the X-axis direction) and the lengths of the third parallel sides 111c, 112c and the fourth parallel sides 111d, 112d (length in the Z'-axis direction) were made approximately the same. However, the embodiment is not limited to this, and the lengths of the first parallel sides 111a, 112a and the second parallel sides 111b, 112b of the first excitation electrode 111 and the second excitation electrode 112 and the lengths of the third parallel sides 111c, 112c and the fourth parallel sides 111d, 112d may be different.

[0065] In the above embodiment, the outer frame portion 12 of the crystal diaphragm 10 was not provided with through holes. However, through holes may be provided in the outer frame portion 12, and electrical connections may be made using through electrodes within the through holes. Alternatively, a part of the side surface of the crystal diaphragm 10 may be cut out, and a castellation may be formed in which electrodes are attached to the inner wall surface of the cut-out area to make electrical connections. For example, as shown in Figures 9 and 10, five through holes 12g, 12h may be formed in the crystal diaphragm 10, penetrating between the first main surface 101 and the second main surface 102. In the example of Figures 9 and 10, four through holes 12g are provided in the four corner (corner) regions of the outer frame portion 12, and the four through holes 12g are located on the extension line of the outer frame holding portion 13b of the holding portion 13. In addition, one through hole 12h is provided in the outer frame portion 12, on one side in the X-axis direction of the vibrating portion 11 (the -X direction side in Figures 9 and 10). Around each of the four through-holes 12g, a connecting pattern 12i is formed on the first main surface 101 side, and a connecting pattern 12j is formed on the second main surface 102 side. Similarly, around the through-hole 12h, a connecting pattern 12a is formed on the first main surface 101 side, and a connecting pattern 12e is formed on the second main surface 102 side. Through electrodes are formed along the inner walls of the five through-holes 12g and 12h to ensure conductivity between the electrodes formed on the first main surface 101 and the second main surface 102. The central portion of each of the five through-holes 12g and 12h is a hollow through-hole that penetrates between the first main surface 101 and the second main surface 102.

[0066] In the above embodiment, the first excitation electrode 111 and the second excitation electrode 112 are octagonal in plan view, but other shapes are also possible. In this case, it is preferable that the first excitation electrode 111 and the second excitation electrode 112 have a configuration similar to the above embodiment, comprising a central portion 111g, 112g and a pair of narrowed portions 111h, 112h. The first excitation electrode 111 and the second excitation electrode 112 may be, for example, polygons with five or more sides in plan view, or ovals, etc. For example, as shown in Figure 11, the first excitation electrode 111 and the second excitation electrode 112 may be hexagonal in plan view. In this case, the first excitation electrode 111 and the second excitation electrode 112 do not have a pair of third parallel sides 111c, 112c and fourth parallel sides 111d, 112d that face each other along the second specific crystal axis direction (Z' axis direction). The first excitation electrode 111 and the second excitation electrode 112 have a central portion 111g, 112g that is rectangular in shape when viewed from above, and a pair of narrowed portions 111h, 112h that are triangular in shape when viewed from above, adjacent to both sides of the central portion 111g, 112g.

[0067] In the above embodiment, the width dimension of the first extraction electrode 113 along the first specific crystal axis direction (X axis direction) is set to be at least half the length of the first parallel side 111a of the first excitation electrode 111, and the width dimension of the second extraction electrode 114 along the first specific crystal axis direction is set to be at least half the length of the second parallel side 112b of the second excitation electrode 112. However, the width dimension of the first extraction electrode 113 along the first specific crystal axis direction may be set to be the same as the length of the first parallel side 111a of the first excitation electrode 111, and the width dimension of the second extraction electrode 114 along the first specific crystal axis direction may be set to be the same as the length of the second parallel side 112b of the second excitation electrode 112. Alternatively, the width dimension of the first extraction electrode 113 along the first specific crystal axis direction may be set to be greater than the length of the first parallel side 111a of the first excitation electrode 111, and the width dimension of the second extraction electrode 114 along the first specific crystal axis direction may be set to be greater than the length of the second parallel side 112b of the second excitation electrode 112. In these cases, since no stepped portion is formed at the connection between the first and second excitation electrodes 111, 112 and the first and second extraction electrodes 113, 114, stable vibration of the first and second excitation electrodes 111, 112 can be ensured. Furthermore, although the holding portion 13 is configured to be approximately T-shaped in plan view with a vibration holding portion 13a and an outer frame holding portion 13b, the outer frame holding portion 13b may be omitted, and the linear vibration holding portion 13a may be extended to the inner circumferential wall of the outer frame portion 12.

[0068] In the above embodiment, the X-axis direction of the AT cut was designated as the first specific crystal axis and the Z'-axis direction as the second specific crystal axis. However, the Z'-axis direction of the AT cut may be designated as the first specific crystal axis and the X-axis direction as the second specific crystal axis.

[0069] In the above embodiment, the case where the quartz crystal diaphragm 10 is an AT-cut quartz crystal diaphragm was described. However, the present invention is not limited to AT-cut quartz crystal diaphragms, but can also be applied to a two-axis rotating quartz crystal diaphragm (for example, an SC-cut quartz crystal diaphragm) obtained by further rotating the AT-cut quartz crystal diaphragm by a predetermined angle around the Z-axis.

[0070] In the above embodiment, the first sealing member 20 and the second sealing member 30 were formed from quartz plates, but the invention is not limited to this, and the first sealing member 20 and the second sealing member 30 may be formed from, for example, glass or resin. Furthermore, in the above embodiment, an example of applying the present invention to a piezoelectric vibration device with a sandwich structure (three-layer structure) in which the quartz diaphragm 10 is sandwiched between the first sealing member 20 and the second sealing member 30 was described, but the invention is not limited to this, and the present invention may also be applied to a piezoelectric vibration device with a structure in which the quartz diaphragm 10 is mounted inside a base made of ceramic or the like.

[0071] In the above embodiment, the number of external electrode terminals 32 on the second main surface 302 of the second sealing member 30 is set to four, but it is not limited to this, and the number of external electrode terminals 32 may be, for example, two, six, or eight. Furthermore, although the present invention has been described in the case where it is applied to a quartz crystal oscillator 100, it is not limited to this, and the present invention may also be applied to piezoelectric oscillators such as quartz oscillators. In the case of a piezoelectric oscillator, as described above, by routing the first extraction electrode 113 and the second extraction electrode 114 in the piezoelectric diaphragm along the shortest possible path, parasitic capacitance can be reduced, thereby securing a larger variable frequency range for the piezoelectric oscillator and improving the performance of the piezoelectric oscillator, which is particularly effective in VCXOs (voltage-controlled piezoelectric oscillators).

[0072] This application claims priority under Japanese Patent Application No. 2025-056285, filed in Japan on 28 March 2025. By reference thereto, all its contents are incorporated into this application.

[0073] 10 Crystal diaphragm (piezoelectric diaphragm) 11 Vibration section 12 Outer frame section 13 Holding section 13a Vibration holding section 13b Outer frame holding section 14a, 14b Cut-out section 20 First sealing member (upper sealing plate) 30 Second sealing member (lower sealing plate) 100 Crystal oscillator (piezoelectric vibration device) 111 First excitation electrode 111a First parallel side 111b Second parallel side 111g Center section 111h Reduced width section 112 Second excitation electrode 112a First parallel side 112b Second parallel side 112g Center section 112h Reduced width section C1 Center point L1 First virtual line L2 Second virtual line W1, W2 Width dimensions

Claims

1. A piezoelectric diaphragm that vibrates with thickness shear, wherein the piezoelectric diaphragm is a quartz diaphragm, and both main surfaces are planes including a first specific crystal axis and a second specific crystal axis perpendicular to the first specific crystal axis, and the thickness direction is parallel to the first specific crystal axis and a third specific crystal axis perpendicular to the second specific crystal axis, and comprises a vibrating part on which a pair of excitation electrodes facing the two main surfaces are formed, an outer frame surrounding the vibrating part, a holding part connecting the vibrating part and the outer frame, and a cutout formed by cutting out the space between the vibrating part and the outer frame in the thickness direction, wherein a straight line passing through the center point of the vibrating part in a plan view along the second specific crystal axis is defined as the first virtual straight line, and a straight line passing through the center point of the vibrating part in a plan view along the first specific crystal axis is defined as the second virtual straight line, The excitation electrode on one of the two main surfaces of the vibrating part is designated as the first excitation electrode, and the excitation electrode on the other main surface of the vibrating part is designated as the second excitation electrode. The first excitation electrode and the second excitation electrode have a pair of first and second parallel sides that face each other along the first specific crystal axis direction. The first and second excitation electrodes are provided with a central portion between the first and second parallel sides where the width dimension along the second specific crystal axis direction is maximum, and a pair of reduced width portions provided adjacent to both sides of the central portion in the direction of the first specific crystal axis direction, where the width dimension along the second specific crystal axis direction decreases as the distance from the first virtual line increases. The vibrating portion is provided with a first extraction electrode extending from a first parallel side of the first excitation electrode along a first virtual line, and a second extraction electrode extending from a second parallel side of the second excitation electrode along the first virtual line in a direction opposite to the extension direction of the first extraction electrode, wherein the first extraction electrode and the second extraction electrode are formed symmetrically with respect to the first virtual line, and the vibrating portion, holding portion, first excitation electrode, and second excitation electrode are formed symmetrically with respect to the first virtual line and the second virtual line, respectively, characterized in that the piezoelectric diaphragm is provided with respect to the vibrating portion, holding portion, first excitation electrode, and second excitation electrode.

2. A piezoelectric diaphragm according to claim 1, wherein the piezoelectric diaphragm is an AT-cut quartz diaphragm, and one of the X-axis direction and Z'-axis direction of the AT cut is the first specific crystal axis, the other is the second specific crystal axis, and the Y'-axis direction of the AT cut is the third specific crystal axis.

3. A piezoelectric diaphragm according to claim 1 or 2, characterized in that, at the connection portion between the first excitation electrode and the first extraction electrode, the width dimension of the first extraction electrode along the first specific crystal axis direction is half or more the length of the first parallel side of the first excitation electrode, and at the connection portion between the second excitation electrode and the second extraction electrode, the width dimension of the second extraction electrode along the first specific crystal axis direction is half or more the length of the second parallel side of the second excitation electrode.

4. A piezoelectric diaphragm according to claim 1 or 2, wherein the holding portion comprises a pair of vibration holding portions along the first virtual straight line and a pair of outer frame holding portions extending in a direction different from the second specific crystal axis direction and connecting each vibration holding portion to two locations on the inner circumferential wall of the outer frame portion, wherein each vibration holding portion is connected to the outer circumferential wall of the vibration portion and the outer frame holding portion, and the outer frame holding portions are connected to four locations on the inner circumferential wall of the outer frame portion.

5. A piezoelectric diaphragm according to claim 1 or 2, wherein the vibrating portion is formed in a rectangular shape having a pair of parallel sides along the first specific crystal axis direction and a pair of parallel sides along the second specific crystal axis direction, and the first excitation electrode and the second excitation electrode each have a pair of parallel sides along the second specific crystal axis direction.

6. A piezoelectric diaphragm according to claim 1 or 2, characterized in that the vibrating portion is formed with a thinner thickness in the central portion inward than in the outer portion.

7. A piezoelectric diaphragm according to claim 2, characterized in that the first specific crystal axis direction is the X axis direction and the second specific crystal axis direction is the Z' axis direction.

8. A piezoelectric vibration device comprising a piezoelectric diaphragm according to claim 1 or 2, characterized in that an upper sealing plate covering the upper side of the piezoelectric diaphragm and a lower sealing plate covering the lower side of the piezoelectric diaphragm are joined to the piezoelectric diaphragm.

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