Piezoelectric vibration device

Abstract

In this piezoelectric vibration device, a sufficient bonding region is ensured between a package and a substrate on which a piezoelectric vibration element is mounted, thereby making it possible to suppress displacement of a free end of the piezoelectric vibration element due to external impacts.　Piezoelectric vibration element connection terminals 21, 22 are formed and disposed in parallel along a short side on a fixed end side, which is one side of a rectangular substrate 2, on the outer bottom surface 2a of the substrate 2. When an IC 5 and a piezoelectric vibration element Pv mounted on the substrate 2 are disposed at prescribed positions in a package 6 and are conductively bonded to each other, a conductive adhesive 65 is provided such that an edge portion of the conductive adhesive 65 on a free end (opposite side to the fixed end) of the substrate 2 extends to a region near a virtual straight line L1 connecting the centers of the long sides, of the substrate 2, that face each other on the outer bottom surface in a plan view.

Description

Piezoelectric vibration device

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

[0002] Conventionally, there is a piezoelectric vibration device described in Patent Document 1 in which a piezoelectric vibration element is hermetically sealed inside a package. As shown in FIG. 8 of Patent Document 1, this type of piezoelectric vibration device includes, for example, a ceramic package having a rectangular parallelepiped outer shape, a recess inside, and an open upper surface, a pedestal blank forming a stepped portion disposed on the inner bottom surface of the recess of the package, a piezoelectric vibration element having one end joined and fixed to the upper surface of the pedestal blank in a cantilever state, and a lid member that closes the upper surface opening of the package and hermetically seals the inside of the package. At this time, the other end of the piezoelectric vibration element opposite to the one end on the cantilever support side is a free end that can be displaced.

[0003] Japanese Patent Application Laid-Open No. 2016-15757

[0004] In the case of a piezoelectric vibration device configured to support a piezoelectric vibration element in a cantilever state via a substrate inside a conventional package, when an external shock is applied to the device, the free end side opposite to the cantilever support side of the substrate on which the piezoelectric vibration element is mounted may be greatly displaced in the direction of the inner bottom surface of the package due to the external shock and contact the inner bottom surface, which may have an adverse effect on the characteristics of the piezoelectric vibration device.

[0005] Further, in a configuration in which a stepped portion is formed at a position higher than the inner bottom surface of the package near the upper surface opening, one end of the piezoelectric vibration element is supported in a cantilever manner via a substrate, and an integrated circuit element having an oscillation amplification circuit is disposed on the inner bottom surface of the package, when the free end of the substrate on which the piezoelectric vibration element is mounted is greatly displaced due to an external shock, the free end of the substrate may contact the integrated circuit element.

[0006] Therefore, in order to suppress the displacement of the free end side of the piezoelectric vibration element due to an external shock, it is conceivable to increase the bonding strength by expanding the bonding region between the cantilever support side of one end of the substrate and the package. However, in the face of strong demands for miniaturization and thinning (low profile) of recent piezoelectric vibration devices, it is difficult to secure a sufficient bonding region between the substrate on which the piezoelectric vibration element is mounted and the package due to space constraints, and an effective countermeasure is desired.

[0007] This invention has been made in view of the above problems, and aims to ensure a sufficient bonding area between the substrate on which the piezoelectric vibration element is mounted and the package, thereby suppressing displacement of the free end of the piezoelectric vibration element due to external impact.

[0008] To achieve the above objective, the piezoelectric vibration device according to the present invention comprises a substrate that is substantially rectangular in plan view and has at least two connection terminals on its outer bottom surface, a piezoelectric vibration element mounted on the side of the substrate opposite to the outer bottom surface, an electronic component, and a package that hermetically seals the substrate, the piezoelectric vibration element mounted on the substrate, and the electronic component, wherein the piezoelectric vibration element has a pair of excitation electrodes, the two connection terminals on the substrate are connection terminals for the piezoelectric vibration element that are respectively connected to the pair of excitation electrodes, and the package has a rectangular parallelepiped outer shape with an open top surface, a recess formed off-center to one side, a stepped portion formed above the inner bottom surface of the recess, and the two provided on the stepped portion The device has internally a pair of mounting pads that are conductively bonded to each of two piezoelectric vibration element connection terminals, the electronic component is positioned on the inner bottom surface of the recess, the substrate is supported at one end as a fixed end and positioned above the electronic component as a free end, with the two piezoelectric vibration element connection terminals being bonded to the pair of mounting pads via a conductive adhesive, the two piezoelectric vibration element connection terminals are arranged in parallel on the outer bottom surface along the short side of one end of the substrate, and the edge of the conductive adhesive on the free end side of the substrate extends to a region containing a virtual line connecting the centers of a pair of opposing long sides of the outer bottom surface in a plan view, or to a region near the virtual line.

[0009] In this configuration, within the package, the electronic components are placed on the inner bottom surface of the recess, and the substrate is supported at one end as a fixed end and at the other end as a free end above the electronic components, with two piezoelectric vibration element connection terminals bonded to a pair of mounting pads via conductive adhesive. The two piezoelectric vibration element connection terminals are arranged in parallel on the outer bottom surface along the short side of one end of the substrate, and the edge of the conductive adhesive on the free end side of the substrate extends to a region containing a virtual line connecting the centers of a pair of opposing long sides of the outer bottom surface in a plan view, or to a region near such a virtual line.

[0010] Therefore, when bonding the substrate to the mounting pad of the package using a conductive adhesive, a sufficient bonding area can be secured between the package and one end of the substrate supported by the stepped portion, thereby increasing the bonding strength between the substrate and the package using the conductive adhesive, and suppressing displacement of the free end of the piezoelectric vibration element due to external impact. Furthermore, when the fixed end of one end of the substrate and the free end on the opposite side are positioned above the electronic component, it is possible to suppress large displacement of the free end of the substrate towards the inner bottom surface of the package due to external impact, thereby preventing contact with the electronic component and providing a highly reliable piezoelectric vibration device.

[0011] Furthermore, the two connection terminals for the piezoelectric vibration elements are formed on the substrate from the short side at one end to the long side, extending for a length exceeding half the length of the long side, and are preferably superimposed on the pair of mounting pads in a plan view.

[0012] With this configuration, the connection terminals for the two piezoelectric vibration elements are formed from the short side of one end of the substrate to a length exceeding half the length of the long side in the direction of the long side. This ensures a sufficiently large bonding area between one end of the substrate (fixed end) supported by the package and the package, thereby increasing the bonding strength between the substrate and the package using conductive adhesive.

[0013] Furthermore, if the free-end edge of the substrate of the conductive adhesive does not extend beyond the virtual straight line, the distance in the direction of the long side from the free-end edge of the substrate of the conductive adhesive to the virtual straight line is 25% or less of the length of the long side. If the free-end edge of the substrate of the conductive adhesive extends beyond the virtual straight line, the distance in the direction of the long side from the free-end edge of the substrate of the conductive adhesive to the virtual straight line is 20% or less of the length of the long side.

[0014] With this configuration, even if the free edge of the conductive adhesive substrate does not extend beyond a virtual straight line connecting the centers of a pair of opposing long sides on the outer bottom surface of the substrate, a high bonding strength between the substrate and the package can be obtained using the conductive adhesive if the distance from the free edge of the conductive adhesive substrate to the virtual straight line in the direction of the long side is 25% or less of the length of the long side.

[0015] Furthermore, even if the free edge of the conductive adhesive substrate extends beyond a virtual straight line connecting the centers of two opposing long sides on the outer bottom surface of the substrate, a strong bond strength between the substrate and the package can be obtained using the conductive adhesive if the distance from the free edge of the conductive adhesive substrate to the virtual straight line in the direction of the long side is 20% or less of the length of the long side.

[0016] Furthermore, it is preferable that the edge of the conductive adhesive on the fixed end side of the substrate extends to the vicinity of the short side on one end of the substrate.

[0017] With this configuration, the edge of the conductive adhesive on one end (fixed end) of the substrate extends to the vicinity of the short side on the same end (fixed end) of the substrate. This increases the bonding area of ​​the conductive adhesive, further improving the bonding strength between the substrate and the package.

[0018] Furthermore, the piezoelectric vibration element has a vibrating section including the pair of excitation electrodes, and the vibrating section is preferably hermetically sealed inside the package by a sealing member.

[0019] This configuration makes it possible to provide a piezoelectric vibration device with a double-sealed structure. The double sealing makes it less susceptible to changes in the external environment, resulting in a piezoelectric vibration device with stable characteristics.

[0020] Furthermore, the piezoelectric vibration element may further include a piezoelectric diaphragm having a vibrating portion including the pair of excitation electrodes and the substrate being superimposed and joined to it, and a sealing member superimposed on the side of the piezoelectric diaphragm opposite to the mounting surface on the substrate, which hermetically seals the vibrating portion of the piezoelectric diaphragm together with the substrate.

[0021] This configuration provides a three-layer laminated structure consisting of a sealing member, a piezoelectric diaphragm, and a substrate, making it possible to provide a smaller piezoelectric vibrator with more stable characteristics.

[0022] Furthermore, the electronic component may be an integrated circuit element that forms an oscillation circuit together with the piezoelectric vibration element, or a temperature sensor.

[0023] This configuration makes it possible to provide a piezoelectric vibration device in which integrated circuit elements that constitute an oscillation circuit together with the piezoelectric vibration element, as well as electronic components such as a temperature sensor, are sealed within a package.

[0024] According to the present invention, it is possible to secure a sufficient bonding area between the substrate on which the piezoelectric vibration element is mounted and the package, thereby increasing the bonding strength between the substrate and the package, suppressing displacement of the free end of the piezoelectric vibration element due to external impact, and providing a piezoelectric vibration device with stable characteristics.

[0025] This is a cross-sectional view of a piezoelectric vibration device according to the first embodiment of the present invention. This is a plan view of the piezoelectric vibration device of Figure 1 with the lid member, piezoelectric vibration element, and IC removed. This is a bottom view of the substrate on which the piezoelectric vibration element of the piezoelectric vibration device of Figure 1 is mounted. This is a bottom view of the IC of the piezoelectric vibration device of Figure 1. This is a cross-sectional view of a piezoelectric vibration device according to the second embodiment of the present invention. This is a cross-sectional view of a piezoelectric vibration device according to the third embodiment of the present invention. This is a plan view of the sealing member of the piezoelectric vibration device of Figure 6. This is a bottom view of the sealing member of the piezoelectric vibration device of Figure 6. This is a plan view of the piezoelectric diaphragm of the piezoelectric vibration device of Figure 6. This is a bottom view of the piezoelectric diaphragm of the piezoelectric vibration device of Figure 6. This is a plan view of the substrate of the piezoelectric vibration device of Figure 6. This is a bottom view of the substrate of the piezoelectric vibration device of Figure 6. This is a cross-sectional view of a piezoelectric vibration device according to the fourth embodiment of the present invention. This is a bottom view of the substrate on which the piezoelectric vibration element of the piezoelectric vibration device of Figure 13 is mounted. This is a cross-sectional view of a modified example of the piezoelectric vibration device according to the first embodiment.

[0026] <First Embodiment> A piezoelectric vibration device according to the first embodiment of the present invention will be described with reference to Figures 1 to 4.

[0027] (Configuration) As shown in Figure 1, the piezoelectric vibration device 1 in the first embodiment comprises a substrate 2 that is substantially rectangular in plan view and has at least two connection terminals on its outer bottom surface (lower surface) 2a, a piezoelectric vibration element Pv, an integrated circuit element (hereinafter referred to as IC) 5 which is an electronic component, and a ceramic package 6 that hermetically seals the substrate 2, the piezoelectric vibration element Pv mounted on the substrate 2, and the IC 5. Here, the piezoelectric vibration element Pv has a piezoelectric diaphragm 3 mounted on the upper surface of the substrate 2, which is the surface opposite to the outer bottom surface 2a, and a sealing member 4 joined to the upper surface of the piezoelectric diaphragm 3. A metal lid member 7 is seam-welded to the upper surface of the package 6 by a substantially rectangular metal member 8, thereby sealing the package 6.

[0028] As shown in Figure 1, the package 6 has a rectangular parallelepiped shape with an open top surface. Inside, a recess 61 is formed, offset to one side (the right side in Figure 1), and a stepped portion 62 is formed above the inner bottom surface 61a of the recess 61, protruding to approximately the center in a plan view. The stepped portion 62 is provided with a pair of mounting pads that are electrically connected to the two piezoelectric vibration element connection terminals of the substrate 2, which will be described later, and the IC 5 is positioned on the inner bottom surface 61a of the recess 61.

[0029] The piezoelectric vibration element Pv comprises a piezoelectric diaphragm 3 having a vibrating portion (not shown) including a pair of excitation electrodes, to which a substrate 2 is superimposed and joined, and a sealing member 4 superimposed on the side of the piezoelectric diaphragm 3 opposite to the mounting surface (upper surface) on the substrate 2, and hermetically sealing the vibrating portion of the piezoelectric diaphragm 3 together with the substrate 2. In the piezoelectric vibration element Pv, a sandwich structure is formed by joining the piezoelectric diaphragm 3, the sealing member 4 and the substrate 2, creating a space inside, and the vibrating portion of the piezoelectric diaphragm 3 is hermetically sealed in this internal space.

[0030] Here, the piezoelectric diaphragm 3 is made of an AT-cut quartz plate that has a roughly rectangular parallelepiped shape formed from a single quartz plate and performs thickness-sliding vibration, and has a roughly rectangular vibrating section in which one and the other excitation electrodes are formed at opposing positions on the upper main surface and the lower main surface. Furthermore, an AT-cut quartz plate is used as the sealing member 4 and the substrate 2, on which the surface joined to the piezoelectric diaphragm 3 is formed as a flat, smooth surface (mirror finish). Here, one and the other excitation electrodes correspond to the "pair of excitation electrodes" in the present invention.

[0031] Incidentally, as shown in Figure 3, the substrate 2 is provided with three connection terminals on its outer bottom surface 2a side. Two of these are connection terminals 21 and 23 for piezoelectric vibration elements, which are connected to a pair of excitation electrodes of the piezoelectric diaphragm 3, respectively, and the remaining one is a ground connection terminal 22.

[0032] The two piezoelectric vibration element connection terminals 21 and 23 are arranged in parallel along the short side of the fixed end (right end in Figure 3), which is one side of the rectangle of the substrate 2. The dashed line in Figure 3 is a virtual straight line L1 connecting the centers of the opposing long sides of the rectangle of the substrate 2. One piezoelectric vibration element connection terminal 21 is formed to be slightly shorter than the length of the long side of the substrate 2, and the other piezoelectric vibration element connection terminal 23 is formed to be slightly longer than the virtual straight line L1 in Figure 3. The ground connection terminal 22 is formed to be slightly to the left of the left end of the piezoelectric vibration element connection terminal 23 and extends to near the short side of the free end (left end in Figure 3), which is the other side of the rectangle of the substrate 2. The length of the ground connection terminal 22 in the long side direction of the substrate 2 is shorter than that of the piezoelectric vibration element connection terminal 23.

[0033] Figure 2 is a plan view showing the state of the package 6 before the lid member 7 is removed and the substrate 2, piezoelectric vibration element Pv, and IC 5 are housed inside the package 6. The dotted rectangle R1 represents the plan view outline of the substrate 2 and piezoelectric vibration element Pv, and the double dotted rectangle R2 represents the plan view outline of IC 5. As shown in Figure 2, the stepped portion 62 inside the package 6 is provided with a pair of piezoelectric vibration element mounting pads 63a and 63b, which are electrically connected to the two piezoelectric vibration element connection terminals 23 and 21 on the substrate 2, respectively. Furthermore, the recess 61 is provided with first to sixth IC mounting pads 64a, 64b, 64c, 64d, 64e, and 64f. Here, the piezoelectric vibration element mounting pads 63a and 63b correspond to the "mounting pads" in the present invention.

[0034] These piezoelectric vibration element mounting pads 63a and 63b are electrically and mechanically joined to the piezoelectric vibration element connection terminals 23 and 21, respectively, by conductive adhesive 65, as shown by the dashed circles in Figures 2 and 3. For example, silicone adhesive or epoxy adhesive can be used as the conductive adhesive 65. After the conductive adhesive 65 is applied in a roughly circular shape to the piezoelectric vibration element mounting pads 63a and 63b or the piezoelectric vibration element connection terminals 23 and 21, the piezoelectric vibration element Pv is pressed against the stepped portion 62 with a predetermined pressure, and the piezoelectric vibration element Pv's piezoelectric vibration element connection terminals 23 and 21 and the piezoelectric vibration element mounting pads 63a and 63b of the stepped portion 62 are joined, respectively, with the conductive adhesive 65 slightly spread.

[0035] Incidentally, when the piezoelectric vibration element connection terminals 23, 21 and the piezoelectric vibration element mounting pads 63a, 63b of the stepped portion 62 are joined, the free-end edge of the conductive adhesive 65 on the substrate 2 extends to the vicinity of a virtual straight line L1 connecting the centers of the opposing long sides of the substrate 2, as shown in Figures 1 to 3. Specifically, if the position of the free-end edge of the conductive adhesive 65 on the substrate 2 is shown by the dashed line L2 in Figures 1 and 3, the free-end edge of the conductive adhesive 65 on the substrate 2 is located on the fixed end side of the substrate 2 (left side in Figure 1, right side in Figure 3) without crossing the virtual straight line L1. Furthermore, when the free-end edge of the conductive adhesive 65 on the substrate 2 does not cross the virtual straight line L1 on the free-end side of the substrate 2, it is desirable that the distance d from the line L2 shown in Figure 3 to the virtual straight line L1 be 25% or less of the length D of the long side of the substrate 2. Here, the free-end edges of the two conductive adhesives 65 on the substrate 2 do not necessarily have to be aligned like a straight line L2, and it is sufficient that the distance d from the virtual straight line L1 to the free-end edge of the conductive adhesive 65 on the substrate 2 that is further away is 25% or less of the length D of the long side of the substrate 2.

[0036] Furthermore, the free-end edge of the substrate 2 on which the conductive adhesive 65 is applied may coincide with the virtual line L1. In this case, the distance d from the virtual line L1 to the free-end edge of the substrate 2 on which the conductive adhesive 65 is applied is zero. Also, the free-end edge of the substrate 2 on which the conductive adhesive 65 is applied may extend beyond the virtual line L1 to the free-end side of the substrate 2. If it does, the distance d from the virtual line L1 to the free-end edge of the substrate 2 on which the conductive adhesive 65 is applied should be 20% or less of the length D of the long side of the substrate 2.

[0037] As shown in Figure 4, the outer bottom surface (lower surface) of IC 5 is provided with first to sixth connection terminals 5a, 5b, 5c, 5d, 5e, and 5f. The first connection terminal 5a is, for example, a power terminal, the second connection terminal 5b is an output terminal, the third and fourth connection terminals 5c and 5d are connection terminals for two piezoelectric vibration elements, and the fifth and sixth connection terminals 5e and 5f are ground connection terminals. The first to sixth IC mounting pads 64a to 64f on the package 6 side are electrically connected to the first to sixth connection terminals 5a to 5f of IC 5, respectively, by metal bumps 66.

[0038] Then, when the piezoelectric vibration element Pv and IC 5 mounted on the substrate 2 are placed in predetermined positions within the package 6 and conductively bonded, one end of the substrate 2 (left side in Figure 1, right side in Figure 3) is supported as a fixed end, and the other end (right side in Figure 1, left side in Figure 3) is positioned above the IC 5 as a free end. The two piezoelectric vibration element connection terminals 23 and 21 are arranged in parallel on the outer bottom surface along the short side of one end of the substrate 2, and the edge of the conductive adhesive 65 on the free end side of the substrate 2 extends to the vicinity of a virtual straight line L1 connecting the centers of a pair of opposing long sides of the substrate 2 on the outer bottom surface in a plan view, or to the region including the virtual straight line L1. As a result, when conductively bonding the piezoelectric vibration element connection terminals 23 and 21 of the substrate 2 to the piezoelectric vibration element mounting pads 63a and 63b of the package 6, a sufficient bonding area can be secured as the bonding region between the fixed end of the substrate 2, which is cantilevered at the stepped portion 62 of the package 6, and the package 6. This increases the bonding strength with the substrate 2 and suppresses displacement of the free end of the substrate 2, on which the piezoelectric vibration element Pv is mounted, due to external impact.

[0039] Therefore, according to the first embodiment, when the substrate 2 is joined to the piezoelectric vibration element mounting pads 63a and 63b of the package 6 with the conductive adhesive 65, a sufficient bonding area can be secured between the package 6 and the fixed end of the substrate 2 supported by the stepped portion 62, thereby increasing the bonding strength between the substrate 2 and the package 6 by the conductive adhesive 65, and suppressing displacement of the free end (right side in Figure 1) of the piezoelectric vibration element Pv due to external impact. Furthermore, when the free end of the substrate 2 opposite to the fixed end is positioned above the IC 5, it is possible to suppress large displacement of the free end side of the substrate 2 towards the inner bottom surface of the package 6 due to external impact, thereby preventing contact with the IC 5, and a highly reliable piezoelectric vibration device 1 can be provided.

[0040] Furthermore, by ensuring that the free-end edge of the conductive adhesive 65 on the substrate 2 does not extend beyond the virtual straight line L1 connecting the centers of a pair of opposing long sides on the outer bottom surface (lower surface) 2a of the substrate 2, and that the distance d in the direction of the long side from the line L2 indicating the position of the free-end edge of the conductive adhesive 65 on the substrate 2 to the virtual line L1 is 25% or less of the length of the long side of the substrate 2, a high bonding strength between the substrate 2 and the package 6 can be obtained using the conductive adhesive 65.

[0041] Furthermore, since the piezoelectric vibration element connection terminals 21 and 23 are formed to extend from the short side on the fixed end of the substrate 2 to the long side in a length exceeding half the length of the long side, a sufficiently large bonding area can be secured between the fixed end of the substrate 2 supported by the package 6 and the package 6, thereby increasing the bonding strength between the substrate 2 and the package 6.

[0042] Furthermore, since the edge of the conductive adhesive 65 on the fixed end side of the substrate 2 extends to the vicinity of the short side on the fixed end side of the substrate, the bonding area of ​​the conductive adhesive 65 is enlarged, and the bonding strength between the substrate 2 and the package 6 can be further increased.

[0043] Furthermore, by joining the piezoelectric vibration element connection terminals 23 and 21 of the substrate 2 to the piezoelectric vibration element mounting pads 63a and 63b using conductive adhesive 65, the shrinkage force of the conductive adhesive 65 during curing acts to lift the free end side of the substrate 2, making it easier to maintain the substrate 2 in a horizontal position. In addition, while solder used with conductive adhesive 65 may spread to unintended areas of the metal piezoelectric vibration element connection terminals, conductive adhesive 65 does not spread to metal, making it easy to control the bonding area.

[0044] Furthermore, the piezoelectric vibration element Pv has a three-layer laminated structure in which a piezoelectric diaphragm 3 having a vibrating section including a pair of excitation electrodes is bonded to the lower and upper surfaces of the piezoelectric diaphragm 3, respectively, and the vibrating section is further hermetically sealed inside the package 6, making it possible to provide a piezoelectric vibration device 1 with a double-sealed structure. Such double sealing makes it less susceptible to changes in the external environment and makes it possible to provide a smaller piezoelectric vibration device 1 with more stable characteristics.

[0045] <Second Embodiment> A piezoelectric vibration device according to the second embodiment of the present invention will be described while referring to FIG. 5. Hereinafter, differences between the piezoelectric vibration device 1A according to the second embodiment and the first embodiment will be described. In the following description, FIGS. 1 to 4 are also referred to, and in FIG. 5, the same reference numerals as those in FIGS. 1 to 4 indicate the same or corresponding parts.

[0046] The piezoelectric vibration device 1A according to the second embodiment is different from the piezoelectric vibration device 1 of the first embodiment in that, as shown in FIG. 5, the piezoelectric vibration element 30 includes a piezoelectric substrate made of quartz, a vibration portion having a substantially rectangular planar shape in which a pair of excitation electrodes are formed on one main surface and the other main surface on the opposite side of the piezoelectric substrate, an outer frame portion having an inner peripheral wall in a rectangular shape in plan view surrounding the outer peripheral wall of the vibration portion, a holding portion that holds the vibration portion by connecting the outer peripheral wall of the vibration portion and the inner peripheral wall of the outer frame portion, and a cutout portion formed by cutting out the piezoelectric substrate in the plate thickness direction between the vibration portion and the outer frame portion. The piezoelectric vibration element 30 having such a configuration is bonded to the upper surface of the substrate 2 by, for example, Au-Au diffusion bonding, and the piezoelectric vibration element 30 is mounted on the upper surface of the substrate 2, which is different from the three-layer laminated structure in which the piezoelectric vibration element Pv is mounted on the substrate 2 as in the first embodiment. In FIG. 5, 65A is a conductive adhesive that conducts and bonds the connection terminals 21 and 22 for the piezoelectric vibration element on the outer bottom surface of the substrate 2 on which the piezoelectric vibration element 30 is mounted to the piezoelectric vibration element mounting pads 63a and 63b of the package 6, respectively.

[0047] The piezoelectric vibration device 1A of the second embodiment has the same cross-sectional structure as the piezoelectric vibration device 1 of the first embodiment. The connection terminals 21 and 23 for the piezoelectric vibration element on the substrate 2 on which the piezoelectric vibration element 30 is mounted are arranged in parallel on the outer bottom surface along the short side on one (fixed end) side of the substrate 2. As shown in FIG. 5, the straight line L2 indicating the position of the edge on the free end side of the substrate 2 of the conductive adhesive 65A extends into the region near the virtual straight line L1 connecting the centers of a pair of long sides of the opposing substrate 2 on the outer bottom surface in a plan view, and the edge on the opposite side of the edge indicated by the straight line L2 of the conductive adhesive 65A extends in the direction of the fixed end of the substrate 2. When the connection terminals 23 and 21 for the piezoelectric vibration element of the substrate 2 are conductively joined to the piezoelectric vibration element mounting pads 63a and 63b of the package 6 respectively, a bonding area wider than that of the first embodiment can be ensured as the bonding area between the fixed end of the substrate 2 supported in a cantilever state at the step portion 62 of the package 6 and the package 6, and the bonding strength with the substrate 2 can be increased. Note that the straight line L2 indicating the position of the edge on the free end side of the substrate 2 of the conductive adhesive 65A may coincide with the virtual straight line L1.

[0048] Therefore, according to the second embodiment, since the edge on the free end side of the substrate 2 of the conductive adhesive 65A extends into the region near the virtual straight line L1 connecting the centers of the opposing long sides of the opposing substrate 2 on the outer bottom surface in a plan view, or the region including the virtual straight line L1, the same effects as those of the first embodiment can be obtained.

[0049] <Third Embodiment> The piezoelectric vibration device according to the third embodiment of the present invention will be described with reference to FIGS. 6 to 12. Hereinafter, the differences between the piezoelectric vibration device 1B according to the third embodiment and the piezoelectric vibration device 1 of the first embodiment will be described. In the following description, FIGS. 1 to 4 will also be referred to, and in FIGS. 6 to 12, the same reference numerals as those in FIGS. 1 to 4 denote the same or corresponding components.

[0050] As shown in FIG. 6, the piezoelectric vibration device 1B according to the third embodiment has the same cross-sectional structure as the piezoelectric vibration device 1 according to the first embodiment (see FIG. 1), and is different from the first embodiment in the following points.

[0051] The piezoelectric vibration element PvB constituting the piezoelectric vibration device 1B shown in Figure 6 comprises a piezoelectric diaphragm 3B to which a substrate 2B serving as a lower sealing member is bonded to the lower surface, and an upper sealing member 4B bonded to the upper surface of the piezoelectric diaphragm 3B. As will be described later, vias 272B and 273B are formed in the substrate 2B, which are through holes filled with conductors that penetrate in the thickness direction of the substrate 2B. The second excitation electrode 32Bb of the piezoelectric diaphragm 3B, which will be described later, is connected to the right end of the piezoelectric vibration element connection terminal 21B of the substrate 2B via a connecting bonding pattern 26B and via 273B, which will be described later, as shown in Figures 11 and 12. Furthermore, unlike the first embodiment described above, one of the piezoelectric vibration element connection terminals 21B, 23B, and ground connection terminal 22B provided on the outer bottom surface (lower surface) 2Bb of the substrate 2B, the piezoelectric vibration element connection terminal 21B extends from one end of the substrate 2B (the left end in Figure 6) in the direction of the long side of the substrate 2B, and a via 273B overlaps its one end, as will be described later.

[0052] The sealing member 4B of the piezoelectric vibrating element PvB is configured as shown in Figures 7 and 8, the piezoelectric diaphragm 3B is configured as shown in Figures 9 and 10, and the substrate 2B is configured as shown in Figures 11 and 12. The sealing member 4B, piezoelectric diaphragm 3B, and substrate 2B will be described below.

[0053] In detail, the piezoelectric diaphragm 3B is a roughly rectangular parallelepiped quartz substrate 31B, as shown in Figures 9 and 10, with the first main surface 3Ba and the second main surface 3Bb formed as flat, smooth surfaces (mirror-finished). An AT-cut quartz plate that performs thickness-sliding vibration is used as the piezoelectric diaphragm 3B. In the piezoelectric diaphragm 3B shown in Figures 9 and 10, the first and second main surfaces 3Ba and 3Bb of the piezoelectric diaphragm 3B are the XZ' plane.

[0054] In this XZ' plane, the direction parallel to the shorter side of the rectangle of the piezoelectric diaphragm 3B is defined as the X-axis direction, and the direction parallel to the longer side of the rectangle of the piezoelectric diaphragm 3B is defined as the Z'-axis direction. AT cutting is a processing method in which artificial quartz is cut at an angle of 35°15′ around the X-axis with respect to the Z-axis, one of the three crystal axes of 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'-axis and Z'-axis coincide with axes that are 35°15′ inclined from the Y-axis and Z-axis of the quartz crystal axis, respectively. The Y'-axis and Z'-axis directions correspond to the cutting direction when cutting the AT-cut quartz plate. Note that the piezoelectric diaphragm 3B may be an SC-cut quartz plate or a tuning fork type vibrator, not limited to the AT-cut quartz plate described above.

[0055] The piezoelectric diaphragm 3B has a substantially rectangular vibrating section 33B on a first main surface 3Ba and a second main surface 3Bb, on which a pair of excitation electrodes, the first excitation electrode 32Ba and the second excitation electrode 32Bb, are formed; an outer frame section 34B having an inner wall that is rectangular in plan view and surrounds the outer wall of the vibrating section 33B; a holding section 35B that holds the vibrating section 33B by connecting the outer wall of the vibrating section 33B and the inner wall of the outer frame section 34B; and a cutout section 36B formed between the vibrating section 33B and the outer frame section 34B by cutting out the piezoelectric diaphragm 3B in the thickness direction. In other words, the piezoelectric diaphragm 3B has a configuration in which the vibrating section 33B, the outer frame section 34B and the holding section 35B are integrally provided.

[0056] The holding portion 35B is provided at only one location between the vibrating portion 33B and the outer frame portion 34B. Furthermore, the vibrating portion 33B and the holding portion 35B are formed thinner than the outer frame portion 34B. Due to this difference in thickness between the outer frame portion 34B and the holding portion 35B, the natural frequencies of the piezoelectric vibrations of the outer frame portion 34B and the holding portion 35B are different, and the propagation of vibrations excited in the vibrating portion 33B is suppressed. In addition, when the sealing member 4B and the substrate 2B are joined to the piezoelectric diaphragm 3B, a gap is formed between the vibrating portion 33B and the sealing member 4B and substrate 2B on the inner side of the inner circumferential wall of the outer frame portion 34B, and this gap is sealed. Furthermore, the outer frame portion 34B of the piezoelectric diaphragm 3B may be formed thicker than the vibrating portion 33B and the holding portion 35B, and a gap may be formed by joining the flat sealing member 4B and the substrate 2B. Alternatively, the outer frame portion 34B may be made the same thickness as the vibrating portion 33B and the holding portion 35B, and a gap may be formed by creating recesses in the sealing member 4B and the substrate 2B and joining them together. In addition, the location of the holding portion 35B is not limited to one place, but may be provided in two or more places between the vibrating portion 33B and the outer frame portion 34B.

[0057] The holding portion 35B extends from only one corner of the vibrating portion 33B located in the +X and -Z' directions to the outer frame portion 34B in the -Z' direction. In this way, since the holding portion 35B is provided at the corner of the outer circumference of the vibrating portion 33B where the displacement of piezoelectric vibration is relatively small, it is possible to suppress leakage of piezoelectric vibration to the outer frame portion 34B through the holding portion 35B compared to when the holding portion 35B is provided at a part other than the corner (the center of the side), and the vibrating portion 33B can be vibrated piezoelectrically more efficiently. Furthermore, compared to when two or more holding portions 35B are provided, the stress acting on the vibrating portion 33B can be reduced, and the frequency shift of the piezoelectric vibration caused by such stress can be reduced, thereby improving the stability of the piezoelectric vibration.

[0058] The first excitation electrode 32Ba is provided on the first main surface 3Ba side of the vibrating section 33B, and the second excitation electrode 32Bb is provided on the second main surface 3Bb side of the vibrating section 33B. The first excitation electrode 32Ba and the second excitation electrode 32Bb are connected to the first and second excitation electrodes 32Ba and 32Bb, respectively, by first lead wiring 37Ba and second lead wiring 37Bb, which connect these first and second excitation electrodes 32Ba and 32Bb to external electrode terminals. The first lead wiring 37Ba is drawn out from the first excitation electrode 32Ba and connected via the holding section 35B to a roughly rectangular connecting joint pattern 381B that is elongated in the X-axis direction and formed at the -Z' side of the outer frame section 34B. The second lead wire 37Bb is led out from the second excitation electrode 32Bb and connected via the holding portion 35B to a substantially circular connecting joint pattern 382B formed in the +X direction and -Z' direction of the outer frame portion 34B. Thus, the first lead wire 37Ba is formed on the first main surface 3Ba side of the holding portion 35B, and the second lead wire 37Bb is formed on the second main surface 3Bb side of the holding portion 35B.

[0059] Furthermore, on the first main surface 3Ba side and the second main surface 3Bb side of the outer frame portion 34B of the piezoelectric diaphragm 3B, substantially rectangular connecting joint patterns 383B and 384B, respectively, are formed on the +Z' side, and a substantially crescent-shaped connecting joint pattern 385B is formed at a position in the +X direction and -Z' direction on the first main surface 3Ba side of the outer frame portion 34B of the piezoelectric diaphragm 3B. In addition, on the opposite side of the connecting joint pattern 381B on the second main surface 3Bb of the outer frame portion 34B of the piezoelectric diaphragm 3B, a substantially rectangular connecting joint pattern 386B, which is long in the X direction, is formed.

[0060] The first main surface 3Ba and the second main surface 3Bb of the piezoelectric diaphragm 3B are provided with vibration-side sealing portions for joining the piezoelectric diaphragm 3B to the sealing member 4B and the substrate 2B, respectively. The vibration-side sealing portion of the first main surface 3Ba has a vibration-side first bonding pattern 387Ba formed for joining to the sealing member 4B. The vibration-side sealing portion of the second main surface 3Bb has a vibration-side second bonding pattern 387Bb formed for joining to the substrate 2B. The vibration-side first bonding pattern 387Ba and the vibration-side second bonding pattern 387Bb are provided on the outer frame portion 34B and are formed in an annular shape in plan view. The first excitation electrode 32Ba and the second excitation electrode 32Bb are not electrically connected to the vibration-side first bonding pattern 387Ba and the vibration-side second bonding pattern 387Bb.

[0061] Furthermore, as shown in Figures 9 and 10, the piezoelectric diaphragm 3B has a connecting bonding pattern 381B that is connected to a connecting bonding pattern 386B formed on the second main surface 3Bb side of the outer frame 34B via internal wiring 39B formed on the inner wall surface of the outer frame 34B. The internal wiring 39B is provided on the inner wall surface of the outer frame 34B that is aligned with the X-axis direction and on the -Z' side. In this case, the internal wiring 39B is formed in a V-shaped recess in plan view provided on the inner wall surface of the outer frame 34B. The first excitation electrode 32Ba is then connected to the piezoelectric vibration element connection terminal 23B via the connecting bonding pattern 381B, the internal wiring 39B, the connecting bonding pattern 386B, and the connecting bonding pattern 25B and via 272B of the substrate 2B, which will be described later.

[0062] The sealing member 4B is, for example, a rectangular parallelepiped substrate formed from a single quartz substrate 41B. As shown in Figure 7, nothing is formed on the first main surface (upper surface) 4Ba of the sealing member 4B that does not face the piezoelectric diaphragm 3B, as shown in Figure 8. The second main surface (lower surface) 4Bb of the sealing member 4B that is joined to the piezoelectric diaphragm 3B is formed as a flat, smooth surface (mirror finish). It is preferable to use AT-cut quartz for the sealing member 4B, similar to the piezoelectric diaphragm 3B, in order to ensure that their thermal expansion coefficients are the same. However, other quartz cut plates, piezoelectric substrates, glass substrates, etc., may also be used.

[0063] As shown in Figure 8, a first sealing-side bonding pattern 42B is formed on the second main surface 4Bb of the sealing member 4B, serving as a first sealing portion for bonding to the upper surface of the piezoelectric diaphragm 3B. This first sealing-side bonding pattern 42B is formed in an annular shape in plan view, similar to the first bonding pattern 387Ba on the vibration side of the piezoelectric diaphragm 3B.

[0064] Furthermore, connection bonding patterns 43B, 44B, and 45B are formed on the second main surface 4Bb of the sealing member 4B at positions facing the connection bonding patterns 381B, 383B, and 385B of the piezoelectric diaphragm 3B, respectively. The connection bonding patterns 43B, 44B, and 45B have substantially the same shape as the connection bonding patterns 381B, 383B, and 385B of the piezoelectric diaphragm 3B, respectively.

[0065] As shown in Figures 11 and 12, the substrate 2B is a rectangular parallelepiped substrate formed from, for example, a single quartz substrate 20B, and the first main surface 2Ba of this substrate 2B (the upper surface that is joined to the piezoelectric diaphragm 3B) is formed as a flat, smooth surface (mirror finish). It is preferable to use AT-cut quartz for the substrate 2B as well as the piezoelectric diaphragm 3B in order to ensure that their thermal expansion coefficients are the same, but other quartz cut plates, piezoelectric substrates, glass substrates, etc. may also be used.

[0066] As shown in Figure 11, a second sealing side bonding pattern 24B is formed on the first main surface 2Ba of the substrate 2B, serving as a second sealing side sealing portion for bonding to the piezoelectric diaphragm 3B. The second sealing side bonding pattern 24B is formed in an annular shape in plan view, similar to the first and second bonding patterns 387Ba and 387Bb on the vibration side of the piezoelectric diaphragm 3B and the first sealing side bonding pattern 42B of the sealing member 4B.

[0067] Furthermore, a connecting bonding pattern 25B is formed on the first main surface 2Ba of the substrate 2B at a position opposite to the connecting bonding pattern 386B for the piezoelectric diaphragm 3B. This connecting bonding pattern 25B extends along the long side on the B1 side from the A1 side towards the A2 side and has a U-shape in plan view. A connecting bonding pattern 26B is formed on the first main surface 2Ba of the substrate 2B at a position opposite to the connecting bonding pattern 384B for the piezoelectric diaphragm 3B. This connecting bonding pattern 26B has a shape that extends along the long side on the B2 side from the A2 side towards the A1 side.

[0068] Furthermore, as shown in Figure 12, the second main surface 2Bb, which is the outer bottom surface of the substrate 2B, is provided with three connection terminals 21B, 22B, and 23B, similar to the substrate 2 of the first embodiment. Two of these connection terminals, 23B and 21B, are connection terminals for piezoelectric vibration elements that are connected to the first and second excitation electrodes 32Ba and 32Bb of the piezoelectric diaphragm 3B, respectively, while the remaining connection terminal 22B is a ground connection terminal. Hereinafter, these will be referred to as the connection terminals 21B and 23B for piezoelectric vibration elements and the ground connection terminal 22B.

[0069] The two piezoelectric vibration element connection terminals 21B and 23B are arranged in parallel along the short side of one side (the right side in Figure 12) of the rectangle of the substrate 2B. The dashed line in Figure 12 is a virtual straight line L1 connecting the centers of the opposing long sides of the rectangle of the substrate 2B. The piezoelectric vibration element connection terminal 21B is formed to be slightly shorter than the length of the long side of the substrate 2B, the piezoelectric vibration element connection terminal 23B is formed to be slightly longer than the virtual straight line L1 representing the center of the long side of the substrate 2B, and the ground connection terminal 22B is formed to be extended from a position slightly to the left of the left end of the piezoelectric vibration element connection terminal 23B to near the short side of the other side (the left side in Figure 12) of the rectangle of the substrate 2B. The length of the ground connection terminal 22B in the direction of the long side of the substrate 2B is shorter than that of the piezoelectric vibration element connection terminal 23B. As shown in Figure 12, the corner portion 21Ba of the piezoelectric vibration element connection terminal 21B in the A1-B2 direction is cut at an angle.

[0070] Furthermore, as shown in Figure 12, vias 272B and 273B are formed by filling the through-holes in the substrate 2B with conductors. Via 273B passes through the connection bonding pattern 26B and the piezoelectric vibration element connection terminal 21B, while via 272B passes through the connection bonding pattern 25B on the A2 side and also passes through the piezoelectric vibration element connection terminal 23B, as shown in Figure 11.

[0071] Furthermore, the stepped portion 62 of the package 6 is provided with piezoelectric vibration element mounting pads 63a and 63b, similar to those in the first embodiment. These piezoelectric vibration element mounting pads 63a and 63b are electrically and mechanically joined to the piezoelectric vibration element connection terminals 23B and 21B, respectively, by conductive adhesive 65B, as shown by the dashed circle in Figure 12. After the conductive adhesive 65B is applied in a roughly circular shape to the piezoelectric vibration element mounting pads 63a and 63b or the piezoelectric vibration element connection terminals 23B and 21B, the piezoelectric vibration element PvB is pressed against the stepped portion 62 of the package 6 with a predetermined pressure. As a result, the piezoelectric vibration element PvB's connection terminals 23B and 21B are joined to the piezoelectric vibration element mounting pads 63a and 63b on the stepped portion 62, respectively, with the conductive adhesive 65B slightly spread.

[0072] In this case, as in the first embodiment, when the piezoelectric vibration element connection terminals 23B, 21B and the piezoelectric vibration element mounting pads 63a, 63b of the stepped portion 62 are joined, the free-end edge of the conductive adhesive 65B on the substrate 2 extends to the vicinity of a virtual straight line L1 connecting the centers of the opposing long sides of the substrate 2B, as shown in Figures 6 and 12. Specifically, if the position of the free-end edge of the conductive adhesive 65B on the substrate 2 is shown by the dashed line L2 in Figures 6 and 12, the free-end edge of the conductive adhesive 65B on the substrate 2B is located on the fixed end side of the substrate 2B (left side in Figure 6, right side in Figure 12) without crossing the virtual straight line L1. Furthermore, if the free-end edge of the substrate 2B of the conductive adhesive 65B does not extend beyond the virtual line L1 to the free-end side of the substrate 2B, it is desirable that the distance d from the line L2 shown in Figure 12 to the virtual line L1 be 25% or less of the length D of the long side of the substrate 2. Here, the free-end edges of the substrate 2B of the two conductive adhesives 65B do not necessarily have to be aligned as shown by the line L2, and it is sufficient that the distance d from the virtual line L1 to the free-end edge of the substrate 2B of the conductive adhesive 65B that is further away is 25% or less of the length D of the long side of the substrate 2.

[0073] In the third embodiment, as in the first embodiment, the free-end edge of the substrate 2B of the conductive adhesive 65B may coincide with the virtual line L1, and in this case, the distance d from the virtual line L1 to the free-end edge of the substrate 2B of the conductive adhesive 65B is zero. Also, the free-end edge of the substrate 2B of the conductive adhesive 65B may extend beyond the virtual line L1 to the free-end side of the substrate 2B, and if it does, the distance d from the virtual line L1 to the free-end edge of the substrate 2B of the conductive adhesive 65B that is further away should be 20% or less of the length D of the long side of the substrate 2.

[0074] Thus, the straight line L2 indicating the position of the free-end edge of the substrate 2B of the conductive adhesive 65B extends to the vicinity of the virtual straight line L1 connecting the centers of a pair of opposing long sides of the substrate 2 on the second main surface (outer bottom surface) 2Bb in a plan view, or to the region including the virtual straight line L1. Therefore, when conductively bonding the piezoelectric vibration element connection terminals 23B and 21B of the substrate 2B to the piezoelectric vibration element mounting pads 63a and 63b of the package 6, a sufficient bonding area can be secured as the bonding area between the fixed end of the substrate 2B, which is cantilevered at the stepped portion 62 of the package 6, and the package 6, thereby increasing the bonding strength with the substrate 2.

[0075] Furthermore, similar to the piezoelectric vibration device 1 of the first embodiment, the piezoelectric vibration element connection terminals 23B and 21B on the second main surface 2Bb, which is the outer bottom surface of the substrate 2B, are formed to a length exceeding the imaginary straight line L connecting the centers of the corresponding long sides of the substrate 2B, and are superimposed on the piezoelectric vibration element mounting pads 63a and 63b provided on the stepped portion 62 of the package 6, respectively. Here, the length of the piezoelectric vibration element connection terminal 21B may be shortened to the position shown by the dashed line in Figure 12, which reduces the risk of contact with the IC 5 located below the free end of the substrate 2B (the left end in Figure 12) even if it is displaced by an impact.

[0076] At this time, of the first and second excitation electrodes 32Ba and 32Bb of the piezoelectric diaphragm 3B, the first excitation electrode 32Ba is connected to the piezoelectric vibration element connection terminal 23B on the second main surface 2Bb of the substrate 2B via a connecting bonding pattern 381B, internal wiring 39B, connecting bonding pattern 386B, connecting bonding pattern 25B, and via 272B. The second excitation electrode 32Bb is led out to the other end of the substrate 2B (the right side in Figure 12) via a connecting bonding pattern 382B, connecting bonding pattern 26B, and via 273B, and is connected to the A2 side end of the piezoelectric vibration element connection terminal 21B on the second main surface 2Bb of the substrate 2B.

[0077] Therefore, as shown in Figure 11, the position where the first excitation electrode 32Ba of the piezoelectric diaphragm 3B is led out onto the first main surface 2Ba of the substrate 2B is via 272B, and similarly, the position where the second excitation electrode 32Bb is led out is the A2 side end of the connecting bonding pattern 26B. Furthermore, the position where the second excitation electrode 32Bb is led out onto the first main surface 2Ba extends through the connecting bonding pattern 26B and to via 273B. The positions where the first and second excitation electrodes 32Ba and 32Bb are led out onto the second main surface 2Bb of the substrate 2B become vias 272B and via 273B of the substrate 2B, and are electrically connected to the piezoelectric vibration element connection terminals 23B and 21B, respectively.

[0078] Therefore, according to the third embodiment, the free-end edge of the substrate 2B on which the conductive adhesive 65B is applied extends to a region near the virtual straight line L1 connecting the centers of opposing long sides of the substrate 2B on the second main surface (outer bottom surface) 2Bb in a plan view, or to a region including the virtual straight line L1, thus achieving the same effects as the first embodiment.

[0079] Furthermore, as described above, the positions from which the first and second excitation electrodes 32Ba and 32Bb are derived on the substrate 2B are vias 272B and 273B on the substrate 2B, respectively. By forming the piezoelectric vibration element connection terminal 21B to be approximately the same length as the long side of the substrate 2B, it becomes possible to connect the first and second excitation electrodes 32Ba and 32Bb to the outside via piezoelectric vibration element mounting pads 63a and 63b provided on the stepped portion 62 of the package 6 without changing the internal wiring or internal structure of the package 6, thereby suppressing the cost increase associated with changes to the internal wiring or internal structure of the piezoelectric vibration device 1B.

[0080] Furthermore, as shown in Figure 12, by cutting the corner portion 21Ba in the A1-B2 direction of the piezoelectric vibration element connection terminal 21B at an angle, the probability of contact with the IC 5 located below it can be reduced even if the free end on the left side of the substrate 2B in Figure 12 is displaced by an impact, thereby further improving reliability.

[0081] <Fourth Embodiment> The piezoelectric vibration device according to the fourth embodiment of the present invention will be described with reference to Figures 13 and 14. Below, the differences between the piezoelectric vibration device 1C according to the fourth embodiment and the first embodiment will be described. In the following description, Figures 1 to 4 will also be referenced, and in Figures 13 and 14, the same reference numerals as in Figures 1 to 4 indicate the same or equivalent components.

[0082] The piezoelectric vibration device 1C according to the fourth embodiment differs from the piezoelectric vibration device 1 of the first embodiment in that, as shown in Figures 13 and 14, the stepped portion 62C of the package 6 is formed such that the free-end edge of the stepped portion 62C of the package 6 extends beyond a virtual straight line L1 connecting the centers of a pair of long sides of the substrate 2, the piezoelectric vibration element mounting pads 63a and 63b are provided on the stepped portion 62C such that the free-end edges of the substrate 2 of the piezoelectric vibration element mounting pads 63a and 63b extend beyond the virtual straight line L1, and the conductive adhesive 65C is arranged such that the straight line L2 indicating the position of the free-end edge of the substrate 2 of the conductive adhesive 65C extends beyond the virtual straight line L1. In this case, it is desirable that the distance d between the straight line L2 and the virtual straight line L1 be 20% or less of the length D of the long side of the substrate 2. If it is greater than 20%, the stepped portion 62C of the package 6 will become too large, making it difficult to secure the recess 61 for arranging the IC 5, which may make it difficult to miniaturize the piezoelectric vibration device. Note that the elliptical shape of the conductive adhesive 65C shown in Figure 14 is just one example, and the shape of the conductive adhesive 65C is not limited to an ellipse.

[0083] Therefore, according to the fourth embodiment, even if the free-end edge of the substrate 2 with the conductive adhesive 65C exceeds a virtual straight line L1 connecting the centers of a pair of long sides of the substrate 2, a high bonding strength between the substrate 2 and the package 6 can be obtained by making the distance d in the direction of the long side from the free-end edge of the substrate 2 with the conductive adhesive 65C to the virtual straight line L1 20% or less of the length D of the long side.

[0084] It should be noted that the present invention is not limited to the above-described configuration, and various design modifications can be made within the scope of the matters described in the claims.

[0085] For example, the electronic component housed in the package 6 is not limited to the IC 5 described above, but may be a temperature sensor. Specifically, as a modification of the first embodiment, a thin, single-plate NTC thermistor 5T shown in Figure 15 may be housed in the package as an electronic component instead of IC 5. Here, the single-plate thermistor 5T comprises a rectangular thermistor substrate 5T1, a pair of rectangular operating electrodes 5T21 and 5T22 provided at predetermined intervals at both ends (left and right ends in Figure 15) of one main surface (bottom surface in Figure 15) of the thermistor substrate 5T1, and a rectangular relay electrode 5T3 provided over the entire surface of the other main surface (top surface in Figure 15) of the thermistor substrate 5T1, and the pair of operating electrodes 5T21 and 5T22 are electrically connected to pads 64g and 64h provided in recesses 61 of the package 6 by conductive adhesive 66T.

[0086] In addition to the single-plate thermistor 5T described above, a so-called chip-type thermistor having electrodes at both ends may also be used as a temperature sensor.

[0087] Furthermore, although the vibrating part of the piezoelectric vibration element is described as rectangular (AT cut) in the above-described embodiment, it is not limited to this, and may be rectangular (SC cut, etc.) or tuning fork shaped (BT cut).

[0088] Alternatively, instead of the vias 272B and 273B in the third embodiment described above, through-holes with conductors attached to their interiors may be formed.

[0089] Furthermore, in piezoelectric vibration devices 1, 1A, 1B, and 1C, the materials used for the piezoelectric vibration elements Pv, 30, and PvB are not limited to quartz, as long as they perform piezoelectric vibration.

[0090] Furthermore, the above-described embodiment is applicable to both temperature sensor-integrated oscillators, SPXOs (Simple Packaged Crystal Oscillators), and TCXOs (Temperature Compensated Crystal Oscillators).

[0091] The present invention is widely applicable to piezoelectric vibration devices comprising a substrate that is substantially rectangular in plan view and has at least two connection terminals on its outer bottom surface, a piezoelectric vibration element mounted on the side of the substrate opposite to the outer bottom surface, an electronic component, and a package that hermetically seals the substrate, the piezoelectric vibration element mounted on the substrate, and the electronic component.

[0092] 1, 1A, 1B, 1C... Piezoelectric vibration device 2, 2B... Substrate 2a... Outer bottom surface 2Bb... Second main surface (outer bottom surface) 21, 23, 21B, 23B... Connection terminals for piezoelectric vibration element 3, 3B... Piezoelectric diaphragm 32Ba, 32Bb... First and second excitation electrodes 33B... Vibrating part 272B, 273B... Via 4, 4B... Sealing material Pv, PvB, 30... Piezoelectric vibration element 5... IC (Electronic component / integrated circuit element) 5T... Thermistor (Electronic component) 6... Package 61... Recess 62, 62C... Step 63a, 63b... Piezoelectric vibration element mounting pad (mounting pad) 65, 65A, 65B, 65C... Conductive adhesive L1... Imaginary straight line

Claims

1. A piezoelectric vibration device comprising: a substrate that is substantially rectangular in plan view and has at least two connection terminals on its outer bottom surface; a piezoelectric vibration element mounted on the side of the substrate opposite to the outer bottom surface; an electronic component; and a package that hermetically seals the substrate, the piezoelectric vibration element mounted on the substrate, and the electronic component, wherein the piezoelectric vibration element has a pair of excitation electrodes; the two connection terminals on the substrate are connection terminals for the piezoelectric vibration element that are connected to the pair of excitation electrodes, respectively; the package has a rectangular parallelepiped outer shape with an open top surface, and includes a recess formed off-center to one side, a stepped portion formed above the inner bottom surface of the recess, and a pair of mounting pads provided on the stepped portion that are electrically bonded to each of the two connection terminals for the piezoelectric vibration element; the electronic component is arranged on the inner bottom surface of the recess; and the substrate is positioned above the electronic component with one end supported as a fixed end and the other end as a free end, by the two connection terminals for the piezoelectric vibration element being bonded to the pair of mounting pads via a conductive adhesive. The piezoelectric vibration device is characterized in that the two connection terminals for piezoelectric vibration elements are arranged in parallel on the outer bottom surface along the short side of one end of the substrate, and the edge of the conductive adhesive on the free end side of the substrate extends to a region that includes a virtual straight line connecting the centers of a pair of opposing long sides of the outer bottom surface in a plan view, or to a region near the virtual straight line.

2. The piezoelectric vibration device according to claim 1, characterized in that the two connection terminals for piezoelectric vibration elements are formed from the short side on one end of the substrate to a length exceeding half the length of the long side in the direction of the long side, and are superimposed on the pair of mounting pads in a plan view.

3. The piezoelectric vibration device according to claim 2, characterized in that, if the free-end edge of the substrate of the conductive adhesive does not exceed the virtual straight line, the distance in the direction of the long side from the free-end edge of the substrate of the conductive adhesive to the virtual straight line is 25% or less of the length of the long side, and if the free-end edge of the substrate of the conductive adhesive exceeds the virtual straight line, the distance in the direction of the long side from the free-end edge of the substrate of the conductive adhesive to the virtual straight line is 20% or less of the length of the long side.

4. The piezoelectric vibration device according to claim 1, characterized in that the edge of the conductive adhesive on the fixed end side of the substrate extends to the vicinity of the short side on one end side of the substrate.

5. The piezoelectric vibration device according to claim 1, wherein the piezoelectric vibration element has a vibrating portion including the pair of excitation electrodes, and the vibrating portion is hermetically sealed inside the package by a sealing member.

6. The piezoelectric vibration device according to claim 1, further comprising: a piezoelectric diaphragm having a vibrating portion including the pair of excitation electrodes and the substrate being superimposed and joined; and a sealing member superimposed on the side of the piezoelectric diaphragm opposite to the mounting surface on the substrate, which hermetically seals the vibrating portion of the piezoelectric diaphragm together with the substrate.

7. The piezoelectric vibration device according to claim 1, characterized in that the electronic component is an integrated circuit element that constitutes an oscillation circuit together with the piezoelectric vibration element, or a temperature sensor.

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