Piezoelectric vibration device
By forming a stepped portion in the package to secure a wide bonding area and using conductive adhesive, the piezoelectric vibration device addresses displacement issues, enhancing reliability and stability while maintaining accurate temperature compensation.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- DAISHINKU CORP
- Filing Date
- 2025-11-28
- Publication Date
- 2026-06-25
Smart Images
Figure JP2025041624_25062026_PF_FP_ABST
Abstract
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, having a concave portion inside, and an upper surface being open, a pedestal blank forming a stepped portion disposed on the inner bottom surface of the concave portion 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 for closing the upper surface opening of the package and hermetically sealing the inside of the package. At this time, the other end opposite to the one end on the cantilever support side of the piezoelectric vibration element 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 is greatly displaced in the direction of the inner bottom surface of the package due to the external shock and contacts the inner bottom surface, which may have an adverse effect on the characteristics of the piezoelectric vibration device.
[0005] Further, in the case of a configuration in which a stepped portion is formed at a position higher than the inner bottom surface of the package and closer to the upper surface opening, and one end of the piezoelectric vibration element is supported in a cantilever state via a substrate on the stepped portion, 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] The present invention has been made in view of the above problems, and aims to form a stepped portion of the package so as to contact the area from near the center of the long side of the substrate to the free end, so that the stepped portion contacts a sufficiently wide area of the substrate, thereby securing a sufficient bonding area between the substrate on which the piezoelectric vibration element is mounted and the package, and 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 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 a pair of connections provided on the stepped portion that are electrically joined to each of the two connection terminals for the piezoelectric vibration element. The electronic component is located 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, with the two piezoelectric vibration element connection terminals being joined to the 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 the fixed end of the substrate, and the edge of the free end of the stepped portion of the substrate extends to a predetermined position in a range from a position spaced apart from the fixed end to the free end, within a region that does not cross a virtual line connecting the centers of a pair of opposing long sides of the outer bottom surface of the substrate in a plan view, and beyond the virtual line.
[0009] In this configuration, within the package, the electronic components are arranged 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 by two piezoelectric vibration element connection terminals being 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 free end of the stepped portion of the substrate in the package extends to a predetermined position within a range from a position spaced apart from the fixed end to a position that crosses the virtual line connecting the centers of a pair of opposing long sides of the outer bottom surface in a plan view, within a region where the virtual line does not cross the virtual line.
[0010] Therefore, when the fixed end of the substrate is joined to the mounting pad of the package using conductive adhesive, the stepped portion can come into contact with the area from near the center of the long side of the substrate to the free end, thereby suppressing displacement of the free end of the substrate due to external impact.
[0011] Furthermore, a sufficient bonding area can be secured between the package and the fixed end of the substrate supported by the stepped portion. This allows the conductive adhesive to be applied over a wider area, thereby improving the bonding strength between the substrate and the package using the conductive adhesive.
[0012] Furthermore, when the free end of the substrate is 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.
[0013] Furthermore, by ensuring a sufficient bonding area between the package and the fixed end of the substrate bonded to the stepped portion, and by applying a wider area of conductive adhesive, heat conducted from the external circuit board to the package is more easily conducted through the conductive adhesive via the piezoelectric vibration element. This suppresses the temperature difference between the temperature detected by the temperature sensor built into the integrated circuit element mounted as an electronic component and the temperature of the piezoelectric vibration element, and as a result, more accurate temperature compensation can be performed in the TCXO (temperature-compensated piezoelectric oscillator).
[0014] Furthermore, if the free-end edge of the stepped portion of the substrate does not extend beyond the virtual straight line, it is preferable that the distance from the free-end edge of the stepped portion of the substrate to the virtual straight line in the direction of the long side be 25% or less of the length of the long side.
[0015] With this configuration, even if the free-end edge of the stepped portion of the substrate does not extend beyond a virtual straight line connecting the centers of opposing long sides on the outer bottom surface of the substrate, if the distance from the free-end edge of the stepped portion of the substrate to the virtual straight line in the direction of the long side is 25% or less of the length of the long side, the stepped portion will contact a sufficiently wide area of the substrate, thus suppressing displacement of the free end of the substrate due to external impact. Conversely, if the above-mentioned distance is 25% or more, the stepped portion will only contact a narrow area of the substrate, making it impossible to secure a sufficiently wide area for the stepped portion to support the substrate. This makes it difficult to suppress displacement of the free end of the substrate due to external impact, meaning there is a risk that the free end of the substrate will be displaced downward and come into contact with electronic components, which is undesirable.
[0016] Furthermore, the package having a rectangular parallelepiped shape is rectangular in plan view, and the edge of the substrate on the free end side of the stepped portion extends to a position that substantially coincides with half the length of the long side in the direction of the long side of the rectangle of the package, or to a nearby position that does not exceed half the length of the long side.
[0017] With this configuration, the free-end edge of the stepped substrate extends to the center or near the center of the long side of the package, thereby improving the rigidity of the package and suppressing package warping. As a result, it becomes possible to suppress the transmission of stress to the joint between the stepped section and the substrate caused by package warping.
[0018] Furthermore, the two connection terminals for the piezoelectric vibration elements are formed on the substrate from the short side on the fixed end side 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.
[0019] With this configuration, the connection terminals for the two piezoelectric vibration elements are formed in the direction of the long side from the short side on the fixed end of the substrate to a length exceeding half the length of the long side. This ensures a sufficiently large bonding area between the fixed end of the substrate supported by the package and the package, thereby increasing the bonding strength between the substrate and the package using conductive adhesive.
[0020] 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 the fixed end side of the substrate.
[0021] With this configuration, the edge of the conductive adhesive on the fixed end side of the substrate extends to the vicinity of the short side of the fixed end side of the substrate, thereby increasing the bonding area of the conductive adhesive and further improving the bonding strength between the substrate and the package.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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 vibration element with more stable characteristics.
[0026] 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.
[0027] 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.
[0028] According to the present invention, a stepped portion of the package is formed so as to contact the area from near the center of the long side of the substrate to the free end, and the stepped portion contacts a sufficiently wide area of the substrate. This ensures a sufficient bonding area between the substrate on which the piezoelectric vibration element is mounted and the package, increases the bonding strength between the substrate and the package, suppresses displacement of the free end of the piezoelectric vibration element due to external impact, and provides a piezoelectric vibration device with stable characteristics.
[0029] 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 cross-sectional view of a piezoelectric vibration device according to the fourth embodiment of the present invention. This is a plan view of the sealing member of the piezoelectric vibration device of Figure 7. This is a bottom view of the sealing member of the piezoelectric vibration device of Figure 7. This is a plan view of the piezoelectric diaphragm of the piezoelectric vibration device of Figure 7. This is a bottom view of the piezoelectric diaphragm of the piezoelectric vibration device of Figure 7. This is a plan view of the substrate of the piezoelectric vibration device of Figure 7. This is a bottom view of the substrate of the piezoelectric vibration device of Figure 7. This is a cross-sectional view of a modified example of the piezoelectric vibration device according to the first embodiment.
[0030] <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.
[0031] (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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] 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.
[0036] 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. In Figures 1 and 3, the dashed line is a virtual straight line L1 indicating the position of the free end edge of the stepped portion 62 on the substrate 2, the dashed line is a virtual straight line L2 connecting the centers of the opposing long sides of the rectangle of the substrate 2, and the dotted line is a virtual straight line L3 connecting the centers of the opposing long sides of the rectangle of the package 6. As shown in Figures 1 and 3, one piezoelectric vibration element connection terminal 21 is formed to be slightly shorter than the length of the long side of the substrate 2, the other piezoelectric vibration element connection terminal 23 is formed to be slightly longer than the imaginary straight line L2 in Figure 3, and 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 to be close to the short side of the free end (left end in Figure 3), which is the other side of the rectangle of the substrate 2, and the length of the ground connection terminal 22 in the long side of the substrate 2 is shorter than that of the piezoelectric vibration element connection terminal 23.
[0037] 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.
[0038] 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.
[0039] Incidentally, the stepped portion 62 of the package 6 is such that the free-end edge of the substrate 2 does not extend beyond the virtual line L2 connecting the centers of the opposing long sides of the substrate 2, as shown by the virtual line L1 in Figures 1 and 3 which represent its position. Therefore, on this stepped portion 62, the free-end edge of the conductive adhesive 65 that joins the piezoelectric vibration element connection terminals 23 and 21 to the piezoelectric vibration element mounting pads 63a and 63b of the stepped portion 62 does not extend beyond the virtual line L2. Consequently, the bonding area of the conductive adhesive 65 is located on the fixed end side (left side in Figure 1, right side in Figure 3) of the virtual line L2 connecting the centers of the opposing long sides of the substrate 2.
[0040] In this case, if the virtual line L1 indicating the position of the free-end edge of the stepped portion 62 on the substrate 2 does not exceed the virtual line L2 connecting the centers of the opposing long sides of the substrate 2, then, as shown in Figure 3, it is desirable that the distance d from the virtual line L1 to the virtual line L2 be 25% or less of the length D of the long side of the substrate 2. Alternatively, the virtual line L1 indicating the position of the free-end edge of the stepped portion 62 may coincide with the virtual line L2, in which case the distance d from the free-end edge of the stepped portion 62 on the substrate 2 to the virtual line L2 is zero. Note that, as shown in Figure 3, the virtual line L1 indicating the position of the free-end edge of the stepped portion 62 on the substrate 2 extends to the vicinity of the virtual line L3 connecting the centers of the opposing long sides of the rectangle of the package 6. Here, the stepped portion 62 may extend until the virtual line L1 indicating the position of the edge of the stepped portion 62 coincides with the virtual line L3 connecting the centers of the long sides of the package 6.
[0041] 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.
[0042] 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 21 and 23 are arranged in parallel on the outer bottom surface along the short side of one end (fixed end) of the substrate 2. At this time, the edge of the stepped portion 62 on the free end side of the substrate 2 (virtual straight line L1) extends to a position that substantially coincides with a virtual straight line L2 connecting the centers of a pair of opposing long sides of the substrate 2 on the outer bottom surface in a plan view. Therefore, when the piezoelectric vibration element connection terminals 23 and 21 of the substrate 2 are conductively bonded to the piezoelectric vibration element mounting pads 63a and 63b of the package 6 using the conductive adhesive 65, the stepped portion 62 can come into contact with the area near the center of the long side of the substrate 2, thereby suppressing displacement of the free end of the substrate 2 due to external impact. Furthermore, a sufficient bonding area can be secured as the bonding area between the fixed end of the substrate 2, which is cantilevered by the stepped portion 62 of the package 6, and the package 6. This allows the conductive adhesive 65 to be applied over a wider area, thereby increasing the bonding strength between the substrate 2 and the package 6 and suppressing displacement of the free end of the substrate 2, on which the piezoelectric vibration element Pv is mounted, due to external impact.
[0043] 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, the stepped portion 62 can contact the region from near the center of the long side of the substrate 2 to the free end side. This suppresses displacement of the free end of the substrate 2 due to external impact, and ensures a sufficient bonding area between the package 6 and the fixed end of the substrate 2 supported by the stepped portion 62. This increases the bonding strength between the substrate 2 and the package 6 by the conductive adhesive 65, and suppresses displacement of the free end of the substrate 2 (right side in Figure 1) due to external impact. Furthermore, 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 providing a highly reliable piezoelectric vibration device 1.
[0044] In addition, since a sufficient bonding area between the package 6 and the fixed end of the substrate 2 joined to the stepped portion 62 can be secured, it becomes possible to arrange a conductive adhesive 65 with a larger area. As a result, heat conducted from the external circuit board to the package 6 can be easily conducted to the piezoelectric vibration element Pv via the conductive adhesive 65. Accordingly, when a temperature sensor is incorporated in the IC chip 4, it becomes possible to suppress the temperature difference between the temperature detected by the temperature sensor and the temperature of the piezoelectric vibration element Pv. As a result, for example, more accurate temperature compensation can be performed in a TCXO.
[0045] Furthermore, by setting the distance d from the virtual straight line L1 indicating the position of the edge on the free end side of the substrate 2 of the stepped portion 62 not to exceed the virtual straight line L2 connecting the centers of the opposing long sides of the substrate 2 and making the distance d 25% or less of the length D of the long side of the substrate 2, a large bonding area between the substrate 2 and the package 6 by the conductive adhesive 65 can be secured and a large bonding strength can be obtained.
[0046] In addition, since the virtual straight line L1 indicating the position of the edge on the free end side of the substrate 2 of the stepped portion 62 extends to the vicinity of the virtual straight line L3 connecting the centers of the opposing long sides of the package 6, the rigidity of the package 6 can be increased and warping of the package 6 can be suppressed. As a result, it becomes possible to suppress the propagation of stress to the joint portion between the stepped portion 62 and the substrate 2 due to warping of the package 6.
[0047] In addition, since the connection terminals 21 and 23 for the piezoelectric vibration element are formed from the short side on the fixed end side of the substrate 2 to a length exceeding half of the long side in the long side direction, a sufficiently large bonding area between the fixed end of the substrate 2 supported by the package 6 and the package 6 can be secured and the bonding strength between the substrate 2 and the package 6 can be increased.
[0048] In addition, 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 2, the bonding area of the conductive adhesive 65 becomes large and the bonding strength between the substrate 2 and the package 6 can be further increased.
[0049] 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 more 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.
[0050] 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.
[0051] <Second Embodiment> A piezoelectric vibration device 1A according to a second embodiment of the present invention will be described with reference to Figure 5. In the second embodiment, the difference from the first embodiment described above is that, as shown in Figure 5, the virtual line L1 indicating the position of the free-end edge of the stepped portion 62A of the package 6 extends beyond the free-end side of the virtual line L2 connecting the centers of the opposing long sides of the substrate 2. Note that the free-end edge of the substrate 2 of the conductive adhesive 65A does not extend beyond the virtual line L2.
[0052] In this case, if the virtual line L1 extends beyond the virtual line L2 towards the free end, the virtual line L1 may extend as far as possible towards the free end (right side in Figure 5), within the range where the other end of the substrate 2 is located above the IC chip 4 or other electronic component as the free end.
[0053] Therefore, according to the second embodiment, the same effects as the first embodiment described above can be obtained, and the virtual line L1 indicating the position of the free end edge of the stepped portion 62A of the package 6 extends beyond the virtual line L2 connecting the centers of the opposing long sides of the substrate 2, thereby making it possible to expand the area in which the substrate 2 and the stepped portion 62A overlap in a plan view. Even if an external force that displaces the substrate 2 in the vertical direction is applied, the stepped portion 62A will be in contact with the substrate 2 over a wide area beyond the center of the long side, thus further suppressing the amount of displacement of the free end of the substrate 2.
[0054] <Third Embodiment> The piezoelectric vibration device 1B according to the third embodiment of the present invention will be described with reference to Figure 6. The following will explain the differences between the piezoelectric vibration device 1B according to the third embodiment and the first embodiment. In the following description, Figures 1 to 4 will also be referenced, and in Figure 6, the same reference numerals as in Figures 1 to 4 indicate the same or equivalent components.
[0055] The piezoelectric vibration device 1B according to the third embodiment differs from the piezoelectric vibration device 1 of the first embodiment in that, as shown in Figure 5, the piezoelectric vibration element 30 comprises a piezoelectric substrate made of quartz, a substantially rectangular vibrating portion in plan view with a pair of excitation electrodes formed on one main surface of the piezoelectric substrate and the other main surface on the opposite side, an outer frame portion having a rectangular inner wall in plan view surrounding the outer peripheral wall of the vibrating portion, a holding portion that holds the vibrating portion by connecting the outer peripheral wall of the vibrating portion and the inner peripheral wall of the outer frame portion, and a cutout portion formed between the vibrating portion and the outer frame portion by cutting out the piezoelectric substrate in the thickness direction. The piezoelectric vibration element 30 with this 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 stacked structure in which the piezoelectric vibration element Pv is mounted on the substrate 2 as in the first embodiment. In Figure 5, 65A is a conductive adhesive that electrically bonds the piezoelectric vibration element connection terminals 21 and 22 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.
[0056] In the piezoelectric vibration device 1B of the third embodiment, similar to the piezoelectric vibration device 1 of the first embodiment, the piezoelectric vibration element connection terminals 21 and 23 of 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 of one side (fixed end) of the substrate 2. As shown in Figure 6, a virtual line L1 indicating the position of the free end edge of the substrate 2 of the stepped portion 62 extends to a position that substantially coincides with a virtual line L2 connecting the centers of a pair of opposing long sides of the substrate 2 on the outer bottom surface in a plan view. 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 using the conductive adhesive 65B, a sufficient bonding area can be secured as the bonding region between the fixed end of the substrate 2, which is cantilevered in the stepped portion 62 of the package 6, and the package 6, thereby increasing the bonding strength with the substrate 2.
[0057] Therefore, according to the third embodiment, the virtual straight line L1 indicating the position of the free-end edge of the substrate 2 of the stepped portion 62 extends to a position that substantially coincides with the virtual straight line L2 connecting the centers of the opposing long sides of the opposing substrates 2 on the outer bottom surface in a plan view, thus achieving the same effects as the first embodiment.
[0058] <Fourth Embodiment> The piezoelectric vibration device 1C according to the fourth embodiment of the present invention will be described with reference to Figures 7 to 13. Below, the differences between the piezoelectric vibration device 1C according to the fourth embodiment and the piezoelectric vibration device 1 of the first embodiment will be described. In the following description, Figures 1 to 4 will also be referenced, and in Figures 7 to 13, the same reference numerals as in Figures 1 to 4 indicate the same or equivalent components.
[0059] As shown in Figure 7, the piezoelectric vibration device 1C according to the fourth embodiment has the same cross-sectional configuration as the piezoelectric vibration device 1 according to the first embodiment (see Figure 1), and differs from the first embodiment in the following respects.
[0060] The piezoelectric vibration element PvC, which constitutes the piezoelectric vibration device 1C shown in Figure 7, comprises a piezoelectric diaphragm 3C to which a substrate 2C serving as a lower sealing member is bonded to the lower surface, and an upper sealing member 4C to which the piezoelectric diaphragm 3C is bonded to the upper surface. As will be described later, vias 272C and 273C are formed in the substrate 2C, which are through holes filled with conductors that penetrate in the thickness direction of the substrate 2C. The second excitation electrode 32Cb of the piezoelectric diaphragm 3C, which will be described later, is connected to the piezoelectric vibration element connection terminal 21C of the substrate 2C via a connecting bonding pattern 26C and via 273C, as shown in Figures 12 and 13. Furthermore, unlike the first embodiment described above, one of the piezoelectric vibration element connection terminals 21C, 23C, and ground connection terminal 22C provided on the outer bottom surface (lower surface) 2Cb of the substrate 2C, extends from one end of the substrate 2C (the left end in Figure 7) in the direction of the long side of the substrate 2C, and a via 273C overlaps its one end, as will be described later.
[0061] The sealing member 4C of the piezoelectric vibrating element PvC is configured as shown in Figures 8 and 9, the piezoelectric diaphragm 3C is configured as shown in Figures 10 and 11, and the substrate 2C is configured as shown in Figures 12 and 13. The sealing member 4C, piezoelectric diaphragm 3C, and substrate 2C will be described below.
[0062] In detail, the piezoelectric diaphragm 3C is a roughly rectangular parallelepiped quartz substrate 31C, as shown in Figures 10 and 11, with the first main surface 3Ca and the second main surface 3Cb formed as flat, smooth surfaces (mirror-finished). An AT-cut quartz plate that performs thickness-sliding vibration is used as the piezoelectric diaphragm 3C. In the piezoelectric diaphragm 3C shown in Figures 10 and 11, the first and second main surfaces 3Ca and 3Cb of the piezoelectric diaphragm 3C are the XZ' plane.
[0063] In this XZ' plane, the direction parallel to the shorter side of the rectangle of the piezoelectric diaphragm 3C is defined as the X-axis direction, and the direction parallel to the longer side of the rectangle of the piezoelectric diaphragm 3C 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 3C may be an SC-cut quartz plate or a tuning fork type vibrator, not limited to the AT-cut quartz plate described above.
[0064] The piezoelectric diaphragm 3C has a substantially rectangular vibrating section 33C on a first main surface 3Ca and a second main surface 3Cb, on which a pair of excitation electrodes, the first excitation electrode 32Ca and the second excitation electrode 32Cb, are formed; an outer frame section 34C having an inner wall that is rectangular in plan view and surrounds the outer wall of the vibrating section 33C; a holding section 35C that holds the vibrating section 33C by connecting the outer wall of the vibrating section 33C and the inner wall of the outer frame section 34C; and a cutout section 36C formed between the vibrating section 33C and the outer frame section 34C by cutting out the piezoelectric diaphragm 3C in the thickness direction. In other words, the piezoelectric diaphragm 3C has a configuration in which the vibrating section 33C, the outer frame section 34C and the holding section 35C are integrally provided.
[0065] The holding portion 35C is provided at only one location between the vibrating portion 33C and the outer frame portion 34C. Furthermore, the vibrating portion 33C and the holding portion 35C are formed thinner than the outer frame portion 34C. Due to this difference in thickness between the outer frame portion 34C and the holding portion 35C, the natural frequencies of the piezoelectric vibrations of the outer frame portion 34C and the holding portion 35C are different, and the propagation of vibrations excited in the vibrating portion 33C is suppressed. In addition, when the sealing member 4C and the substrate 2C are joined to the piezoelectric diaphragm 3C, a gap is formed between the vibrating portion 33C and the sealing member 4C and substrate 2C on the inner side of the inner circumferential wall of the outer frame portion 34C, and this gap is sealed. Furthermore, the outer frame portion 34C of the piezoelectric diaphragm 3C may be formed thicker than the vibrating portion 33C and the holding portion 35C, and a gap may be formed by joining the flat sealing member 4C and the substrate 2C. Alternatively, the outer frame portion 34C may be made the same thickness as the vibrating portion 33C and the holding portion 35C, and a gap may be formed by creating recesses in the sealing member 4C and the substrate 2C and joining them. In addition, the location of the holding portion 35C is not limited to one place, but may be provided in two or more places between the vibrating portion 33C and the outer frame portion 34C.
[0066] The holding portion 35C extends from only one corner of the vibrating portion 33C located in the +X and -Z' directions to the outer frame portion 34C in the -Z' direction. In this way, since the holding portion 35C is provided at the corner of the outer circumference of the vibrating portion 33C where the displacement of piezoelectric vibration is relatively small, it is possible to suppress leakage of piezoelectric vibration to the outer frame portion 34C through the holding portion 35C compared to when the holding portion 35C is provided at a part other than the corner (the center of the side), and the vibrating portion 33C can be vibrated piezoelectrically more efficiently. Furthermore, compared to when two or more holding portions 35C are provided, the stress acting on the vibrating portion 33C 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.
[0067] The first excitation electrode 32Ca is provided on the first main surface 3Ca side of the vibrating section 33C, and the second excitation electrode 32Cb is provided on the second main surface 3Cb side of the vibrating section 33C. The first excitation electrode 32Ca and the second excitation electrode 32Cb are connected to the first and second excitation electrodes 32Ca and 32Cb, respectively, by first lead wiring 37Ca and second lead wiring 37Cb, which connect these first and second excitation electrodes 32Ca and 32Cb to external electrode terminals. The first lead wiring 37Ca is drawn out from the first excitation electrode 32Ca and connected via the holding section 35C to a roughly rectangular connecting joint pattern 381C that is elongated in the X-axis direction and formed at the -Z' side of the outer frame section 34C. The second lead wire 37Cb is led out from the second excitation electrode 32Cb and connected via the holding portion 35C to a substantially circular connecting joint pattern 382C formed in the +X direction and -Z' direction of the outer frame portion 34C. Thus, the first lead wire 37Caa is formed on the first main surface 3Ca side of the holding portion 35C, and the second lead wire 37Cb is formed on the second main surface 3Cb side of the holding portion 35C.
[0068] Furthermore, on the first main surface 3Ca and the second main surface 3Cb of the outer frame portion 34C of the piezoelectric diaphragm 3C, substantially rectangular connecting joint patterns 383C and 384C, which are elongated in the X-axis direction, are formed on the +Z' side, respectively. On the first main surface 3Ca side of the outer frame portion 34C of the piezoelectric diaphragm 3C, a substantially crescent-shaped connecting joint pattern 385B is formed at a position in the +X direction and -Z' direction. In addition, on the opposite side of the connecting joint pattern 381C on the second main surface 3Cb of the outer frame portion 34C of the piezoelectric diaphragm 3C, a substantially rectangular connecting joint pattern 386C, which is elongated in the X-axis direction, is formed.
[0069] The first main surface 3Caa and the second main surface 3Cb of the piezoelectric diaphragm 3C are provided with vibration-side sealing portions for joining the piezoelectric diaphragm 3C to the sealing member 4C and the substrate 2C, respectively. The vibration-side sealing portion of the first main surface 3Caa has a vibration-side first bonding pattern 387Caa formed for joining to the sealing member 4C. The vibration-side sealing portion of the second main surface 3Cb has a vibration-side second bonding pattern 387Cb formed for joining to the substrate 2C. The vibration-side first bonding pattern 387Caa and the vibration-side second bonding pattern 387Cb are provided on the outer frame portion 34C and are formed in an annular shape in plan view. The first excitation electrode 32Caa and the second excitation electrode 32Cb are not electrically connected to the vibration-side first bonding pattern 387Caa and the vibration-side second bonding pattern 387Cb.
[0070] Furthermore, as shown in Figures 10 and 11, the piezoelectric diaphragm 3C has a connecting bonding pattern 381C that is connected to a connecting bonding pattern 386C formed on the second main surface 3Cb side of the outer frame 34C via internal wiring 39C formed on the inner wall surface of the outer frame 34C. The internal wiring 39C is provided on the inner wall surface of the outer frame 34C that is aligned with the X-axis direction and on the -Z' side. In this case, the internal wiring 39C is formed in a V-shaped recess in plan view provided on the inner wall surface of the outer frame 34C. The first excitation electrode 32Ca is then connected to the piezoelectric vibration element connection terminal 23C via the connecting bonding pattern 381C, internal wiring 39C, connecting bonding pattern 386C, and the connecting bonding pattern 25C and via 272C of the substrate 2C, which will be described later.
[0071] The sealing member 4C is, for example, a rectangular substrate formed from a single quartz substrate 41C. As shown in Figure 8, nothing is formed on the first main surface (upper surface) 4Ba of the sealing member 4B that does not face the piezoelectric diaphragm 3B. The second main surface (lower surface) 4Cb of the sealing member 4C that is joined to the piezoelectric diaphragm 3C is formed as a flat, smooth surface (mirror finish). It is preferable to use AT-cut quartz for the sealing member 4C, similar to the piezoelectric diaphragm 3C, 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.
[0072] As shown in Figure 9, a first sealing-side bonding pattern 42C is formed on the second main surface 4Cb of the sealing member 4C, serving as a first sealing portion for bonding to the upper surface of the piezoelectric diaphragm 3C. This first sealing-side bonding pattern 42C is formed in an annular shape in plan view, similar to the first bonding pattern 387Caa on the vibration side of the piezoelectric diaphragm 3C.
[0073] Furthermore, connection bonding patterns 43C, 44C, and 45C are formed on the second main surface 4Cb of the sealing member 4C at positions facing the connection bonding patterns 381C, 383C, and 385C of the piezoelectric diaphragm 3C, respectively. The connection bonding patterns 43C, 44C, and 45C have substantially the same shape as the connection bonding patterns 381C, 383C, and 385C of the piezoelectric diaphragm 3C, respectively.
[0074] As shown in Figures 12 and 13, the substrate 2C is a rectangular parallelepiped substrate formed from, for example, a single quartz substrate 20C, and the first main surface 2Ca of this substrate 2C (the upper surface that is joined to the piezoelectric diaphragm 3C) is formed as a flat, smooth surface (mirror finish). It is desirable to use AT-cut quartz for the substrate 2C as well as the piezoelectric diaphragm 3C 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.
[0075] As shown in Figure 12, a second sealing side bonding pattern 24C is formed on the first main surface 2Ca of the substrate 2C, serving as a second sealing side sealing portion for bonding to the piezoelectric diaphragm 3C. The second sealing side bonding pattern 24C is formed in an annular shape in plan view, similar to the first and second bonding patterns 387Ca and 387Cb on the vibration side of the piezoelectric diaphragm 3C and the first sealing side bonding pattern 42C of the sealing member 4C.
[0076] Furthermore, a connecting bonding pattern 25C is formed on the first main surface 2Ca of the substrate 2C at a position opposite to the connecting bonding pattern 386C for the piezoelectric diaphragm 3C. This connecting bonding pattern 25C 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 26C is formed on the first main surface 2Ca of the substrate 2C at a position opposite to the connecting bonding pattern 384C for the piezoelectric diaphragm 3C. This connecting bonding pattern 26C has a shape that extends along the long side on the B2 side from the A2 side towards the A1 side.
[0077] Furthermore, as shown in Figure 13, the second main surface 2Cb, which is the outer bottom surface of the substrate 2C, is provided with three connection terminals 21C, 22C, and 23C, similar to those of the substrate 2 in the first embodiment. Two of these connection terminals, 23C and 21C, are connection terminals for piezoelectric vibration elements, which are connected to the first and second excitation electrodes 32Ca and 32Cb of the piezoelectric diaphragm 3C, respectively, while the remaining connection terminal 23C is a ground connection terminal. Hereinafter, these will be referred to as the connection terminals 21C and 23C for piezoelectric vibration elements and the ground connection terminal 22C.
[0078] The two piezoelectric vibration element connection terminals 21C and 23C are arranged in parallel along the short side of one side (the right side in Figure 13) of the rectangle of the substrate 2C. Similar to the first embodiment, the dashed line in Figures 7 and 13 is a virtual straight line L1 indicating the position of the free-end edge of the stepped portion 62 on the substrate 2C, the dashed line is a virtual straight line L2 connecting the centers of the opposing long sides of the rectangle of the substrate 2C, and the dotted line is a virtual straight line L3 connecting the centers of the opposing long sides of the package 6. As shown in Figure 13, the piezoelectric vibration element connection terminal 21C is formed to be slightly shorter than the length of the long side of the substrate 2C, the piezoelectric vibration element connection terminal 23C is formed to be slightly longer than the imaginary straight line L2 representing the center of the long side of the substrate 2C, and the ground connection terminal 22C is formed to be longer from a position slightly to the left of the left end of the piezoelectric vibration element connection terminal 23C to near the short side of the other rectangular side of the substrate 2C (the left side in Figure 13), and the length of the ground connection terminal 23C in the long side direction of the substrate 2B is shorter than the piezoelectric vibration element connection terminal 23C. Also, as shown in Figure 13, the corner portion 21Ca in the A1-B2 direction of the piezoelectric vibration element connection terminal 21C is cut out at an angle.
[0079] Furthermore, as shown in Figure 13, vias 272C and 273C are formed by filling through holes drilled through the substrate 2C with conductors. Via 273C penetrates the connection bonding pattern 26C and the piezoelectric vibration element connection terminal 21C, while via 272C penetrates the connection bonding pattern 25C on the A2 side and also penetrates the piezoelectric vibration element connection terminal 23C, as shown in Figure 12.
[0080] 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 23C and 21C, respectively, by conductive adhesive 65C, as shown by the dashed circle in Figure 13. After the conductive adhesive 65C is applied in a substantially circular shape to the piezoelectric vibration element mounting pads 63a and 63b or the piezoelectric vibration element connection terminals 23C and 21C, the piezoelectric vibration element PvC is pressed against the stepped portion 62 of the package 6 with a predetermined pressure. As a result, the piezoelectric vibration element PvC's connection terminals 23C and 21C are joined to the piezoelectric vibration element mounting pads 63a and 63b on the stepped portion 62, respectively, with the conductive adhesive 65C slightly spread.
[0081] In this case, as in the first embodiment, as shown in Figures 7 and 13, the virtual line L1 indicating the free end edge of the substrate 2C of the stepped portion 62 extends to a position that substantially coincides with the virtual line L2 connecting the centers of the opposing long sides of the substrate 2C, and the virtual line L1 is located on the fixed end side of the substrate 2B (left side in Figure 7, right side in Figure 13) without crossing the virtual line L2. In this case, when the virtual line L1 does not cross the virtual line L2 to the free end side of the substrate 2C, it is desirable that the distance d from the virtual line L1 to the virtual line L2 shown in Figure 13 is 25% or less of the length D of the long side of the substrate 2C.
[0082] In addition, in the fourth embodiment, as in the first embodiment, the virtual line L1 may coincide with the virtual line L2, and in this case, the distance d from the virtual line L1 to the virtual line L2 is zero. Also, as in the second embodiment, the virtual line L1 indicating the position of the free end edge of the substrate 2C of the stepped portion 62 may extend beyond the virtual line L2 connecting the centers of the long sides of the substrate 2C to the free end side of the substrate 2C, and in this case, the virtual line L1 may reach as far as possible to the free end side (right side in Figure 7) within the range where the other end of the substrate 2C is located above the electronic component such as the IC chip 4 as the free end.
[0083] Thus, as in the first embodiment, the free-end edge (virtual straight line L1) of the substrate 2C of the stepped portion 62 extends to a position that substantially coincides with a virtual straight line L2 connecting the centers of a pair of opposing long sides of the opposing substrates 2C on the outer bottom surface in a plan view. Therefore, when conductively bonding the piezoelectric vibration element connection terminals 23C and 21C of the substrate 2C 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 2C, which is cantilevered in the stepped portion 62 of the package 6, and the package 6, thereby increasing the bonding strength with the substrate 2.
[0084] Furthermore, similar to the piezoelectric vibration device 1 of the first embodiment, the piezoelectric vibration element connection terminals 23C and 21C on the second main surface 2Cb, which is the outer bottom surface of the substrate 2C, are formed to a length exceeding a virtual straight line L2 connecting the centers of the corresponding long sides of the substrate 2C, 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 21C may be shortened to the position shown by the dashed line in Figure 13, which reduces the risk of contact with the IC 5 located below the free end of the substrate 2C (the left end in Figure 13) even if it is displaced by an impact.
[0085] At this time, of the first and second excitation electrodes 32Ca and 32Cb of the piezoelectric diaphragm 3C, the first excitation electrode 32Ca is connected to the piezoelectric vibration element connection terminal 23C on the second main surface 2Cb of the substrate 2C via a connecting bonding pattern 381C, internal wiring 39C, connecting bonding pattern 386C, connecting bonding pattern 25C, and via 272C. The second excitation electrode 32Cb is led out to the other end of the substrate 2C (the right side in Figure 13) via a connecting bonding pattern 382C, connecting bonding pattern 26C, and via 273C, and is connected to the A2 side end of the piezoelectric vibration element connection terminal 21C on the second main surface 2Cb of the substrate 2C.
[0086] Therefore, as shown in Figure 12, the position where the first excitation electrode 32Ca of the piezoelectric diaphragm 3C is led out onto the first main surface 2Ca of the substrate 2C is via 272C, and similarly, the position where the second excitation electrode 32Cb is led out is the A2 side end of the connecting bonding pattern 26C. Furthermore, the position where the second excitation electrode 32Cb is led out onto the first main surface 2Ca extends through the connecting bonding pattern 26C and to via 273C. The positions where the first and second excitation electrodes 32Ca and 32Cb are led out onto the second main surface 2Cb of the substrate 2C become vias 272C and via 273C of the substrate 2C, and are electrically connected to the piezoelectric vibration element connection terminals 23C and 21C, respectively.
[0087] Therefore, according to the fourth embodiment, since the virtual straight line L1 indicating the position of the free-end edge of the stepped portion 62 on the substrate 2C extends to a position near which it substantially coincides with the virtual straight line L2 connecting the centers of the opposing long sides of the substrate 2C, similar to the first embodiment, the stepped portion 62 can come into contact with the region from near the center of the long side of the substrate 2C to the free-end side, thereby suppressing displacement of the free end of the substrate 2C due to external impacts, and ensuring a sufficient area for bonding with the conductive adhesive 65C, thereby increasing the bonding strength between the substrate 2C and the package 6.
[0088] Furthermore, as described above, the positions from which the first and second excitation electrodes 32Ca and 32Cb are derived on the substrate 2C are vias 272C and 273C on the substrate 2C, respectively. By forming the piezoelectric vibration element connection terminal 21C to be approximately the same length as the long side of the substrate 2C, it becomes possible to connect the first and second excitation electrodes 32Ca and 32Cb 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 1C.
[0089] Furthermore, as shown in Figure 13, by obliquely cutting out the corner portion 21Ca of the piezoelectric vibration element connection terminal 21C in the A1-B2 direction, 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 2C in Figure 13 is displaced by an impact, thereby further improving reliability.
[0090] 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.
[0091] 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 14 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 14) of one main surface (bottom surface in Figure 14) 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 14) 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.
[0092] 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.
[0093] 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).
[0094] Alternatively, instead of the vias 272C and 273C in the fourth embodiment described above, through-holes with conductors attached to their interiors may be formed.
[0095] Furthermore, in piezoelectric vibration devices 1, 1A, 1B, and 1C, the materials used for the piezoelectric vibration elements Pv, 30, and PvC are not limited to quartz, as long as they perform piezoelectric vibration.
[0096] Furthermore, the above-described embodiment is applicable to both temperature sensor-integrated oscillators, SPXOs (Simple Packaged Crystal Oscillators), and TCXOs (Temperature Compensated Crystal Oscillators).
[0097] 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.
[0098] 1, 1A, 1B, 1C... Piezoelectric vibration device 2, 2C... Substrate 2a... Outer bottom surface 2Cb... Second main surface (outer bottom surface) 21, 23, 21C, 23C... Connection terminals for piezoelectric vibration element 3, 3C... Piezoelectric diaphragm 32Ca, 32Cb... First and second excitation electrodes 33C... Vibrating part 272C, 273C... Via 4, 4C... Sealing material Pv, PvC, 30... Piezoelectric vibration element 5... IC (Electronic component / integrated circuit element) 5T... Thermistor (Electronic component) 6... Package 61... Recess 62, 62A... Step 63a, 63b... Piezoelectric vibration element mounting pad (mounting pad) 65, 65A, 65B, 65C... Conductive adhesive L1, L2, L3... 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 the piezoelectric vibration element are arranged in parallel on the outer bottom surface along the short side of the fixed end of the substrate, and the edge of the stepped portion of the substrate on the free end side extends to a predetermined position in a range from a position spaced apart from the fixed end to the free end, within a region that does not cross a virtual line connecting the centers of a pair of opposing long sides of the outer bottom surface of the substrate in a plan view, and beyond the virtual line.
2. The piezoelectric vibration device according to claim 1, characterized in that, if the free-end edge of the substrate of the stepped portion 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 stepped portion to the virtual straight line is 25% or less of the length of the long side.
3. The piezoelectric vibration device according to claim 1, characterized in that the package having a rectangular parallelepiped shape is rectangular in plan view, and the free-end edge of the substrate of the stepped portion extends to a position that substantially coincides with half the length of the long side in the direction of the long side of the rectangle of the package, or to a nearby position that does not exceed half the length of the long side.
4. The piezoelectric vibration device according to claim 1, characterized in that the two connection terminals for piezoelectric vibration elements are formed on the substrate from the short side on the fixed end side 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.
5. 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 the fixed end side of the substrate.
6. 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.
7. 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.
8. 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.