Piezoelectric vibration device
Patent Information
- Application Number
- PCT/JP2026/006141
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-26
- Filing Date
- 2026-02-19
- Publication Date
- 2026-10-01
Smart Images
Figure JP2026006141_01102026_PF_FP_ABST
Abstract
Description
Piezoelectric vibration device
[0001] The present invention relates to a piezoelectric vibration device.
[0002] Conventionally, as a piezoelectric vibration device in which a piezoelectric vibration element is hermetically sealed inside a package, there is one described in Patent Document 1. The piezoelectric vibration device described in Patent Document 1 includes: a substantially rectangular substrate in plan view having at least two connection terminals on an outer bottom surface; a piezoelectric vibrating plate having a pair of excitation electrodes and mounted on a surface opposite to the outer bottom surface of the substrate; and a package that houses the substrate and the piezoelectric vibrating plate mounted on the substrate therein and hermetically seals them. Two mounting pads provided on the package are each bonded to the two connection terminals of the substrate via a conductive adhesive.
[0003] Published Japanese translation of PCT international publication No. 2018 / 092572
[0004] By the way, in the case of the piezoelectric vibration device described in Patent Document 1, since it has a configuration in which the substrate and the piezoelectric vibrating plate mounted on the substrate are housed and mounted in the package, compared to a configuration in which the piezoelectric vibrating plate is directly bonded to the package with a conductive adhesive without being mounted on the substrate, the weight of the object mounted on the package is increased by the weight of the substrate. Moreover, since the conductive adhesive does not have wettability like solder, the self-weight of the mounted object easily causes the conductive adhesive to protrude outside the mounting pads of the package.
[0005] The protruding conductive adhesive is prone to causing problems such as making electrical contact with the piezoelectric vibrating plate, conductors on the substrate (inner vias, wiring patterns, etc.), or contacting the inner wall of the package. When such problems occur, there is a risk that the accuracy of the vibration characteristics of the piezoelectric vibrating plate may be degraded, or defects such as wiring short circuits may occur.
[0006] The present invention has been made in view of the above problems. An object of the present invention is to, in a configuration in which a substrate and a piezoelectric vibrating plate mounted on the substrate are housed and mounted in a package, prevent the conductive adhesive interposed between the mounting pads on the package side and the connection terminals on the substrate side from protruding to the outside of the mounting pads of the package.
[0007] 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 diaphragm mounted on the side of the substrate opposite to the outer bottom surface, and a package that houses the substrate and the piezoelectric diaphragm mounted on the substrate and seals them hermetically, wherein the piezoelectric diaphragm has a pair of excitation electrodes, the package has two mounting pads that are joined to each of the two connection terminals by a conductive adhesive, the two connection terminals are arranged side by side along one side of the substantially rectangular substrate and extend toward the opposite side opposite to that side, with the edges of the extended sides of the substantially rectangular substrate located beyond or near the center, and the conductive adhesive is arranged in a region enclosed by the outer edge of the rectangle of the substrate in plan view when the piezoelectric diaphragm and the substrate are housed in the package.
[0008] In this configuration, the two connection terminals of the substrate are arranged side by side along one side of the roughly rectangular substrate and extend toward the opposite side. The extended edges of the two connection terminals are located beyond or near the center of the substrate, and the two connection terminals are positioned within the area enclosed by the outer edge of the substrate in a plan view. This allows for greater flexibility in adjusting the amount and position of the conductive adhesive applied. It prevents the conductive adhesive applied between the connection terminals of the substrate and the mounting pad of the package from overflowing from the area enclosed by the outer edge of the substrate in a plan view due to the weight of the substrate and the piezoelectric diaphragm mounted on it. This prevents defects such as a decrease in the accuracy of the piezoelectric diaphragm's vibration characteristics or short circuits in the wiring caused by conductive adhesive overflowing beyond the outer edge of the substrate electrically contacting the piezoelectric diaphragm or the conductors of the substrate, or contacting the inner wall of the package.
[0009] Furthermore, the substrate has two additional connection terminals arranged side by side along the opposite side to the side on which the two connection terminals are arranged side by side, and the two connection terminals arranged side by side along the opposite side extend in the direction of the side, with the extended edges extending beyond or near the center of the substantially rectangular substrate, and the package further has two mounting pads which are joined to each of the two connection terminals arranged side by side along the opposite side by a conductive adhesive, and each of the four mounting pads has a larger area than the connection terminals to which they are joined in a plan view, and each of the four connection terminals is located within the region enclosed by the outer edge of the mounting pad to which it is joined.
[0010] With this configuration, four mounting pads are provided on the package, each of which is joined to one of the four connection terminals on the substrate. Each of the four mounting pads has a larger area than the connection terminal to which it is joined in a plan view, and the connection terminal is located within the area enclosed by the outer edge of the mounting pad. Therefore, even if there is variation in the mounting position of the substrate on the package, each connection terminal of the substrate can be positioned within the area enclosed by the outer edge of each mounting pad on the package, and the conductive adhesive applied between the connection terminal of the substrate and the mounting pad of the package can be prevented from protruding beyond the area enclosed by the outer edge of the substrate in a plan view.
[0011] Furthermore, by providing four mounting pads on the package, each of which is bonded to one of the four connection terminals on the substrate, it becomes possible to efficiently transfer heat conducted from the external circuit board to the piezoelectric vibration device to the piezoelectric diaphragm. Compared to a case where the piezoelectric diaphragm is configured alone without being mounted on a substrate, the piezoelectric diaphragm mounted on the substrate has a larger heat capacity, and the four mounting pads are effective in that they increase the heat conduction path.
[0012] Furthermore, it is preferable that each of the aforementioned connection terminals be positioned spaced inward from the rectangular outer edge of the substrate when viewed from above.
[0013] With this configuration, in a plan view, the conductive adhesive can be positioned neatly within the area of the substrate so that it does not extend beyond the outer edge of the substrate.
[0014] Furthermore, the mounting pads have a substantially rectangular shape in plan view, and the conductive adhesive used to bond each connection terminal to each mounting pad is preferably located within the rectangular area of the mounting pad, away from the center of the substantially rectangular substrate.
[0015] With this configuration, if the conductive adhesive is located within the rectangular area of the mounting pad and close to the center of the roughly rectangular substrate, there is a risk that the substrate will be joined to the package at an angle. Therefore, by positioning the conductive adhesive within the rectangular area of the mounting pad and away from the center of the roughly rectangular substrate, it is possible to prevent the substrate from being joined to the package at an angle.
[0016] Furthermore, it is preferable to further provide a sealing member that is superimposed on the side of the piezoelectric diaphragm opposite to the mounting surface on the substrate, and that hermetically seals the vibrating portion of the piezoelectric diaphragm together with the substrate.
[0017] This configuration has a three-layer laminated structure consisting of a sealing member corresponding to the top plate, a piezoelectric diaphragm, and a substrate. Since the piezoelectric diaphragm is further hermetically sealed inside the package, it is possible to provide a piezoelectric vibration device with a double sealing structure. Such double sealing makes it less susceptible to changes in the external environment and allows for the provision of a smaller piezoelectric vibration device with more stable characteristics.
[0018] Furthermore, the package may contain electronic components in addition to the substrate and the piezoelectric diaphragm mounted on the substrate.
[0019] This configuration provides a piezoelectric vibration device with good and stable characteristics, even when accommodating electronic components such as temperature sensors and oscillator integrated circuits, while preventing conductive adhesive from overflowing onto the mounting pads of the package.
[0020] Furthermore, in a piezoelectric vibration device comprising a substrate that is substantially rectangular in plan view and has four connection terminals on its outer bottom surface, a piezoelectric diaphragm mounted on the side of the substrate opposite to the outer bottom surface, and a package that houses the substrate and the piezoelectric diaphragm mounted on the substrate and seals them hermetically, the piezoelectric diaphragm has a pair of excitation electrodes, the package has four mounting pads which are joined to each of the four connection terminals by conductive adhesive, two of the four connection terminals are arranged side by side along one side of the substantially rectangular substrate and are formed to extend toward the opposite side opposite to that side, with the edges of the extended side of each being located near the center of the substantially rectangular substrate, and the remaining two of the four connection terminals The connection terminals are arranged side by side along the opposing sides of the substrate and extend toward the side opposite to the opposing side, with the edges of each extension located near the center of the substantially rectangular substrate; the conductive adhesive is arranged in a region enclosed by the rectangular outer edge of the substrate in a plan view when the piezoelectric diaphragm and the substrate are housed in the package; each of the four mounting pads has a larger area than the connection terminals to be joined in a plan view; each of the four connection terminals is located in a region enclosed by the outer edge of the mounting pad to which the connection terminal is joined; and the package may contain electronic components in addition to the substrate and the piezoelectric diaphragm mounted on the substrate.
[0021] In this case as well, it is possible to provide a piezoelectric vibration device with good and stable characteristics, while preventing conductive adhesive from overflowing onto the outside of the package's mounting pads.
[0022] According to the present invention, in a configuration in which a substrate and a piezoelectric diaphragm mounted on the substrate are housed and mounted in a package, it is possible to prevent the conductive adhesive interposed between the mounting pad on the package side and the connection terminal on the substrate side from protruding outside the mounting pad on the package, thereby providing a piezoelectric vibration device with good and stable characteristics.
[0023] 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 in Figure 1 with the cover removed. This is a plan view of the piezoelectric vibration device in Figure 1 with the cover, piezoelectric vibration element, and electronic components removed. This is a plan view of the top plate of the piezoelectric vibration device in Figure 1. This is a bottom view of the top plate of the piezoelectric vibration device in Figure 1. This is a plan view of the piezoelectric diaphragm of the piezoelectric vibration device in Figure 1. This is a bottom view of the piezoelectric diaphragm of the piezoelectric vibration device in Figure 1. This is a plan view of the bottom plate of the piezoelectric vibration device in Figure 1. This is a bottom view of the bottom plate of the piezoelectric vibration device in 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 top wall of the package of the piezoelectric vibration device in Figure 11. This is a plan view of the base plate of the package of the piezoelectric vibration device in Figure 11. This is a bottom view of the base plate of the package of the piezoelectric vibration device in Figure 11. This is a bottom view of the package of the piezoelectric vibration device in Figure 11. This is a plan view showing the bonding state between the substrate (bottom plate) and the package by conductive adhesive in the piezoelectric vibration device in Figure 11. This is a plan view showing the positional relationship between the conductive adhesive and the electronic components in the piezoelectric vibration device in Figure 11. This shows a modified example of the piezoelectric vibration device according to the third embodiment, and is a plan view showing the bonding state between the substrate (bottom plate) and the package using conductive adhesive in the piezoelectric vibration device. This shows a modified example of the piezoelectric vibration device according to the first embodiment, and is a plan view of the piezoelectric vibration device with the cover removed. This shows another modified example of the piezoelectric vibration device according to the first embodiment, and is a plan view of the piezoelectric diaphragm.
[0024] <First Embodiment> A piezoelectric vibration device 1 according to the first embodiment of the present invention will be described with reference to Figures 1 to 9.
[0025] As shown in Figure 1, the piezoelectric vibration device 1 in the first embodiment comprises a piezoelectric vibration element Pv consisting of a substantially rectangular lower plate 2 having at least two connection terminals on its lower surface, a piezoelectric diaphragm 3, and an upper plate 4, an integrated circuit element (hereinafter referred to as IC) 5 which is an electronic component, and a ceramic package 6 that hermetically seals the lower plate 2, the piezoelectric vibration element Pv mounted on the lower plate 2, and the IC 5. Here, the piezoelectric vibration element Pv has a piezoelectric diaphragm 3 mounted on the upper surface, which is the surface opposite to the lower surface of the lower plate 2, and an upper plate 4 superimposed on the upper surface of the piezoelectric diaphragm 3. A lid 7 made of a metal plate is seam-welded to the upper surface of the package 6 by a substantially rectangular metal member 8, thereby sealing the package 6.
[0026] As shown in Figure 1, the package 6 is formed by stacking multiple ceramic plates and has an overall rectangular parallelepiped shape with an open top surface. Inside, a recess 61 is formed off-center 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 two mounting pads that are electrically connected to the two piezoelectric vibration element connection terminals of the lower plate 2, which will be described later, and the IC 5 is positioned on the inner bottom surface 61a of the recess 61.
[0027] Figure 2 is a plan view showing the package 6 without its lid 7, and Figure 3 is a plan view showing the state before the bottom plate 2, piezoelectric vibration element Pv, and IC 5 are housed inside the package 6. As shown in Figure 2, the stepped portion 62, which is the mounting portion for the piezoelectric vibration element Pv inside the package 6, is provided with a pair of piezoelectric vibration element mounting pads 63a and 63b that are electrically connected to the two piezoelectric vibration element connection terminals 23 and 21 (see Figure 9) on the bottom plate 2, respectively. Furthermore, the recess 61 is provided with first to sixth IC mounting pads 64a, 64b, 64c, 64d, 64e, and 64f. The bottom surface 6a of the package 6 is provided with a plurality of external connection terminals 70. Here, the piezoelectric vibration element mounting pads 63a and 63b correspond to the "mounting pads" in the present invention.
[0028] These piezoelectric vibration element mounting pads 63a and 63b are electrically connected to the piezoelectric vibration element connection terminals 23 and 21, respectively, by a conductive adhesive 65 made of silicone resin (hereinafter sometimes simply referred to as "adhesive"). The first to sixth IC mounting pads 64a to 64f are also electrically connected to the six connection terminals of IC 5, respectively, by a conductive adhesive 66 similar to adhesive 65. Here, the conductive adhesives 65 and 66 may be made of epoxy resin.
[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 lower plate 2 is superimposed and joined, and an upper plate 4 superimposed on the side of the piezoelectric diaphragm 3 opposite to the mounting surface on the lower plate 2, and together with the lower plate 2, hermetically sealing the vibrating portion of the piezoelectric diaphragm 3. In this piezoelectric vibration element Pv, a sandwich structure is formed by joining the piezoelectric diaphragm 3, the upper plate 4, and the lower plate 2, creating a space inside, and the vibrating portion of the piezoelectric diaphragm 3 is hermetically sealed in this internal space. Here, the lower plate 2 corresponds to the "substrate" in this invention.
[0030] As shown in Figures 6 and 7, the piezoelectric diaphragm 3 is a roughly rectangular parallelepiped quartz substrate 31, with the first main surface 3a and the second main surface 3b formed as flat, smooth surfaces (mirror-finished). An AT-cut quartz plate that performs thickness-sliding vibration is used as the piezoelectric diaphragm 3. In the piezoelectric diaphragm 3 shown in Figures 6 and 7, the first and second main surfaces 3a and 3b of the piezoelectric diaphragm 3 are the XZ' plane.
[0031] In this XZ' plane, the direction parallel to the shorter side of the rectangle of the piezoelectric diaphragm 3 is defined as the X-axis direction, and the direction parallel to the longer side of the rectangle of the piezoelectric diaphragm 3 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 3 may be an SC-cut quartz plate or a tuning fork type vibrator, not limited to the AT-cut quartz plate described above.
[0032] The piezoelectric diaphragm 3 has a substantially rectangular vibrating section 33 on its first main surface 3a and second main surface 3b, respectively, on which a pair of excitation electrodes in the present invention, namely the first excitation electrode 32a and the second excitation electrode 32b, are formed; an outer frame section 34 having an inner wall that is rectangular in plan view and surrounds the outer wall of the vibrating section 33; a holding section 35 that holds the vibrating section 33 by connecting the outer wall of the vibrating section 33 to the inner wall of the outer frame section 34; and a cutout section 36 formed between the vibrating section 33 and the outer frame section 34 by cutting out the piezoelectric diaphragm 3 in the thickness direction. In other words, the piezoelectric diaphragm 3 has a configuration in which the vibrating section 33, the outer frame section 34 and the holding section 35 are integrally provided.
[0033] The holding portion 35 is provided at only one location between the vibrating portion 33 and the outer frame portion 34. Furthermore, the vibrating portion 33 and the holding portion 35 are formed thinner than the outer frame portion 34. Due to this difference in thickness between the outer frame portion 34 and the holding portion 35, the natural frequencies of the piezoelectric vibrations of the outer frame portion 34 and the holding portion 35 are different, and the propagation of vibrations excited by the vibrating portion 33 is suppressed. In addition, when the upper plate 4 and the lower plate 2 are joined to the piezoelectric diaphragm 3, a gap is formed between the vibrating portion 33 and the upper plate 4 and the lower plate 2 on the inner side of the inner circumferential wall of the outer frame portion 34, and this gap is sealed. Alternatively, the outer frame portion 34 of the piezoelectric diaphragm 3 may be formed thicker than the vibrating portion 33 and the holding portion 35, and the gap may be formed by joining the flat upper plate 4 and the lower plate 2, or the outer frame portion 34 may be made the same thickness as the vibrating portion 33 and the holding portion 35, and the gap may be formed by creating recesses in the upper plate 4 and the lower plate 2 and joining them.
[0034] The holding portion 35 is formed parallel to the Z' axis, extending from only one corner of the vibrating portion 33 located in the -X direction and +Z' direction, toward the outer frame portion 34 in the +Z' direction. In this way, since the holding portion 35 is provided at the corner of the outer circumference of the vibrating portion 33 where the displacement of piezoelectric vibration is relatively small, it is possible to suppress leakage of piezoelectric vibration to the outer frame portion 34 through the holding portion 35 compared to when the holding portion 35 is provided at a part other than the corner (the center of the side), and the vibrating portion 33 can be vibrated piezoelectrically more efficiently. Furthermore, compared to when two or more holding portions 35 are provided, the stress acting on the vibrating portion 33 can be reduced, and the frequency shift of piezoelectric vibration caused by such stress can be reduced, thereby improving the stability of piezoelectric vibration.
[0035] The first excitation electrode 32a is provided on the first main surface 3a side of the vibrating section 33, and the second excitation electrode 32b is provided on the second main surface 3b side of the vibrating section 33. The first excitation electrode 32a and the second excitation electrode 32b are connected to the first and second excitation electrodes 32a and 32b, respectively, by first lead wiring 37a and second lead wiring 37b for connecting these first and second excitation electrodes 32a and 32b to external electrode terminals. The first lead wiring 37a is drawn out from the first excitation electrode 32a and connected via the holding section 35 to a roughly rectangular connection joint pattern 381 that is elongated in the X-axis direction and formed on the +Z' side of the outer frame section 34. The second lead wiring 37b is drawn out from the second excitation electrode 32b and connected via the holding section 35 to a roughly circular connection joint pattern 382 that is formed on the -X direction and +Z' direction of the outer frame section 34. As described above, the first lead wire 37a is formed on the first main surface 3a side of the holding portion 35, and the second lead wire 37b is formed on the second main surface 3b side of the holding portion 35.
[0036] Furthermore, on the first main surface 3a and the second main surface 3b of the outer frame portion 34 of the piezoelectric diaphragm 3, substantially rectangular connecting joint patterns 383 and 384, which are elongated in the X-axis direction, are formed on the -Z' side, respectively. On the first main surface 3a of the outer frame portion 34 of the piezoelectric diaphragm 3, a substantially crescent-shaped connecting joint pattern 385 is formed at a position in the -X direction and +Z' direction. Additionally, on the second main surface 3b of the outer frame portion 34 of the piezoelectric diaphragm 3, a substantially rectangular connecting joint pattern 386, which is elongated in the X-axis direction, is formed on the opposite side of the connecting joint pattern 381.
[0037] The first main surface 3a and the second main surface 3b of the piezoelectric diaphragm 3 are provided with vibration-side sealing portions for joining the piezoelectric diaphragm 3 to the upper plate 4 and the lower plate 2, respectively. The vibration-side sealing portion of the first main surface 3a has a vibration-side first joining pattern 387a formed for joining to the upper plate 4. The vibration-side sealing portion of the second main surface 3b has a vibration-side second joining pattern 387b formed for joining to the lower plate 2. The vibration-side first joining pattern 387a and the vibration-side second joining pattern 387b are provided on the outer frame portion 34 and are formed in an annular shape in plan view. The first excitation electrode 32a and the second excitation electrode 32b are not electrically connected to the vibration-side first joining pattern 387a and the vibration-side second joining pattern 387b.
[0038] Furthermore, as shown in Figures 6 and 7, the connecting joint pattern 381 of the piezoelectric diaphragm 3 is connected to the connecting joint pattern 386 formed on the second main surface 3b side of the outer frame 34 via internal wiring 39 formed on the inner wall surface of the outer frame 34. The internal wiring 39 is provided on the inner wall surface of the outer frame 34 that is aligned with the X-axis direction and on the +Z' side. In this case, the internal wiring 39 is formed in a V-shaped recess in plan view provided on the inner wall surface of the outer frame 34. The first excitation electrode 32a is connected to the piezoelectric vibration element connection terminal 23 via the connecting joint pattern 381, internal wiring 39, connecting joint pattern 386, the connecting joint pattern 25 of the lower plate 2 (described later), and via 272. The second excitation electrode 32b is connected to the piezoelectric vibration element connection terminal 21 via the connecting joint pattern 382, the connecting joint pattern 26 (described later), and via 273.
[0039] The upper plate 4 corresponds to the "sealing member" in the present invention, and is, for example, a rectangular parallelepiped substrate formed from a single quartz substrate 41. As shown in Figure 4, nothing is formed on the first main surface (upper surface) 4a of the upper plate 4 that does not face the piezoelectric diaphragm 3, and as shown in Figure 5, the second main surface (lower surface) 4b of the upper plate 4 that is joined to the piezoelectric diaphragm 3 is formed as a flat, smooth surface (mirror finish). It is preferable to use AT-cut quartz for the upper plate 4, similar to that used for the piezoelectric diaphragm 3, 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.
[0040] As shown in Figure 5, a sealing-side first bonding pattern 42 is formed on the second main surface 4b of the upper plate 4, serving as a sealing-side first sealing portion for bonding to the upper surface of the piezoelectric diaphragm 3. This sealing-side first bonding pattern 42 is formed in an annular shape in plan view, similar to the vibration-side first bonding pattern 387a of the piezoelectric diaphragm 3.
[0041] Further, connection bonding patterns 43, 44, 45 are formed on the second main surface 4b of the upper plate 4 at positions respectively facing the connection bonding patterns 381, 383, 385 of the piezoelectric vibrating plate 3. The connection bonding patterns 43, 44, 45 have substantially the same shapes as the respective connection bonding patterns 381, 383, 385 of the piezoelectric vibrating plate 3.
[0042] The lower plate corresponds to the "substrate" in the present invention, and as shown in Figs. 8 and 9, it is a rectangular parallelepiped substrate formed of, for example, a single quartz substrate 20. The first main surface 2a of the lower plate 2 (the upper surface bonded to the piezoelectric vibrating plate 3) is formed as a flat and smooth surface (mirror-finished). It is desirable that the lower plate also uses AT-cut quartz similar to that of the piezoelectric vibrating plate 3, since this allows the mutual thermal expansion coefficients to be the same, but other quartz-cut plates, piezoelectric substrates, glass substrates or the like may also be used.
[0043] As shown in Fig. 8, a sealing-side second bonding pattern 24 serving as a sealing-side second sealing portion for bonding to the piezoelectric vibrating plate 3 is formed on the first main surface 2a of the lower plate 2. Similar to the vibrating-side first and second bonding patterns 387a, 387b of the piezoelectric vibrating plate 3 and the sealing-side first bonding pattern 42 of the upper plate 4, the sealing-side second bonding pattern 24 is formed in an annular shape in plan view.
[0044] Further, on the first main surface 2a of the lower plate 2, a connection bonding pattern 25 is formed in substantially the same shape at a position facing the connection bonding pattern 386 of the piezoelectric vibrating plate 3. A connection bonding pattern 26 is formed at a position on the first main surface 2a of the lower plate 2 facing the connection bonding pattern 384 of the piezoelectric vibrating plate 3, and the connection bonding pattern 26 has a shape extending from the A1 side in the A2 direction along the long side on the B1 side.
[0045] As shown in Fig. 9, three connection terminals 21, 22, 23 are provided on the second main surface 2b that is the lower surface of the lower plate 2. Among them, two connection terminals 23 and 21 are piezoelectric vibrating element connection terminals respectively connected to the first and second excitation electrodes 32a, 32b of the piezoelectric vibrating plate 3, and the remaining one connection terminal 22 is a non-connection terminal that is not electrically connected to any terminal. Hereinafter, these are referred to as the piezoelectric vibrating element connection terminals 21, 23 and the non-connection terminal 22.
[0046] The two connecting terminals 21 and 23 for piezoelectric vibrating elements are juxtaposed along the short side on the A2 side of the lower plate 2. The connecting terminal 21 for a piezoelectric vibrating element extends to near the short side on the A1 side and has an elongated rectangular shape, and the connecting terminal 23 for a piezoelectric vibrating element extends toward the short side on the A1 side, and the edge on the extending side thereof slightly exceeds a center P of the lower plate 2 indicated by the "x" mark in FIG. 2 and FIG. 9 and is positioned near the center P. Further, the non-connection terminal 22 extends toward the short side on the A1 side of the lower plate 2 from a position slightly separated in the A1 direction from the edge on the extending side of the connecting terminal 23 for a piezoelectric vibrating element.
[0047] Further, as shown in FIG. 8 and FIG. 9, a conductor is filled into through holes penetrating the lower plate 2 to form vias 271, 272, and 273. As shown in FIG. 8, the via 271 penetrates the sealing-side second bonding pattern 24 slightly offset toward the B2 direction on the A1 side and also penetrates the non-connection terminal 22; the via 272 penetrates the connection bonding pattern 25 and the connecting terminal 23 for a piezoelectric vibrating element; and the via 273 penetrates the connection bonding pattern 26 and the connecting terminal 21 for a piezoelectric vibrating element.
[0048] Note that the connecting terminals 21 and 23 for piezoelectric vibrating elements on the second main surface 2b, which is the lower surface of the lower plate 2, are respectively superimposed on piezoelectric vibrating element mounting pads 63a and 63b provided on the stepped portion 62 of the package 6, and are bonded by a conductive adhesive 65 as will be described later.
[0049] Thus, as described above, among the first and second excitation electrodes 32a and 32b of the piezoelectric diaphragm 3, the first excitation electrode 32a is connected to the connecting terminal 23 for a piezoelectric vibrating element on the second main surface 2b of the lower plate 2 via the connection bonding pattern 381, the internal wiring 39, the connection bonding pattern 386, the connection bonding pattern 25, and the via 272. Further, the second excitation electrode 32b is led out to the A1 side of the lower plate 2 via the connection bonding pattern 382, the connection bonding pattern 26, and the via 273, and is connected to the end on the A1 side of the connecting terminal 21 for a piezoelectric vibrating element on the second main surface 2b of the lower plate 2.
[0050] Therefore, as shown in Figure 8, the position where the first excitation electrode 32a of the piezoelectric diaphragm 3 is led out onto the first main surface 2a of the lower plate 2 becomes via 272, and similarly, the position where the second excitation electrode 32b is led out becomes the A2 side end of the connecting bonding pattern 26. Furthermore, the position where the second excitation electrode 32b is led out onto the first main surface 2a extends through the connecting bonding pattern 26 to via 273. The positions where the first and second excitation electrodes 32a and 32b are led out onto the second main surface 2b of the lower plate 2 become vias 272 and via 273, which are located approximately diagonally opposite each other in the rectangle of the lower plate 2, and are electrically connected to the piezoelectric vibration element connection terminals 23 and 21, respectively. Here, the piezoelectric vibration element connection terminals 23 and 21 correspond to the "connection terminals" of the lower plate 2 in this invention.
[0051] Then, the two piezoelectric vibration element mounting pads 63a and 63b on the package 6 and the two piezoelectric vibration element connection terminals 21 and 23 on the lower plate 2 are joined together with a conductive adhesive 65, such as silicone resin, as shown in Figure 9. At this time, the conductive adhesive 65 is positioned within the area enclosed by the rectangular outer edge of the lower plate 2 in a plan view, when the piezoelectric vibration element Pv and the lower plate 2 are housed in the package 6, and within the rectangular areas of the two piezoelectric vibration element mounting pads 63a and 63b on the package 6, away from the center P of the lower plate 2. The A2 side end of the piezoelectric vibration element Pv becomes a fixed end fixed to the package 6 by the adhesive 65, and the A1 side end of the piezoelectric vibration element Pv becomes a free end that is not fixed.
[0052] Therefore, according to the first embodiment, the two piezoelectric vibration element connection terminals 21 and 23 of the lower plate 2 are arranged side by side along the short side on the A2 side of the rectangle of the lower plate 2, and are formed to extend toward the short side on the A1 side opposite to the short side, and the extended ends of the piezoelectric vibration element connection terminals 21 and 23 extend to a position beyond the center P of the lower plate 2, and the piezoelectric vibration element connection terminals 21 and 23 are arranged within the area enclosed by the outer edge of the rectangle of the lower plate 2 in a plan view, so that the degree of freedom when adjusting the amount and position of application of the conductive adhesive 65 can be greatly increased, and the piezoelectric vibration element connection terminals of the lower plate 2 The conductive adhesive 65 applied between 21, 23 and the piezoelectric vibration element mounting pads 63a, 63b of package 6 can be prevented from overflowing from the area enclosed by the rectangular outer edge of the lower plate 2 in a plan view due to the weight of the lower plate 2 and the piezoelectric vibration element Pv mounted thereon. This prevents defects such as a decrease in the accuracy of the vibration characteristics of the piezoelectric vibration element Pv or short circuits in the wiring caused by the conductive adhesive 65 overflowing beyond the outer edge of the lower plate 2 making electrical contact with the piezoelectric vibration element Pv or the conductor of the lower plate 2, or making contact with the inner wall of package 6.
[0053] Furthermore, since the piezoelectric vibration element connection terminals 21 and 23 are provided spaced inward from the rectangular outer edge of the lower plate 2 in a plan view, the conductive adhesive 65 can be positioned neatly within the area of the lower plate 2 so that it does not protrude beyond the outer edge of the lower plate 2 in a plan view, thereby more reliably preventing problems caused by the conductive adhesive 65 protruding beyond the outer edge of the lower plate 2.
[0054] Furthermore, since the conductive adhesive 65 is located within the rectangular area of the piezoelectric vibration element mounting pads 63a and 63b of the package 6, and away from the center P of the substantially rectangular lower plate 2, it prevents the lower plate 2 from being joined to the package 6 at an angle, as would occur if the conductive adhesive 65 were located near the center P of the lower plate 2.
[0055] Furthermore, the piezoelectric vibration element Pv has a three-layer laminated structure in which a piezoelectric diaphragm 3 has a vibrating section 33 including a pair of excitation electrodes 32a and 32b, and a lower plate 2 and an upper plate 4 are bonded to the lower and upper surfaces of the piezoelectric diaphragm 3, respectively. Since the vibrating section 33 is further hermetically sealed inside the package 6, it becomes 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 allows for the provision of a smaller piezoelectric vibration device 1 with more stable characteristics.
[0056] Furthermore, since silicone resin is used as the conductive adhesive 65, the stress and strain are smaller compared to when epoxy resin is used, making it possible to minimize the stress and strain transmitted to the vibrating part 33 of the piezoelectric vibration element Pv due to the adhesive.
[0057] <Second Embodiment> A piezoelectric vibration device 1A according to the second embodiment of the present invention will be described with reference to Figure 10. The following will explain the differences between the piezoelectric vibration device 1A according to the second embodiment and the first embodiment. In the following description, Figures 1 to 9 will also be referenced, and in Figure 10, the same reference numerals as in Figures 1 to 9 indicate the same or equivalent components.
[0058] The piezoelectric vibration device 1A according to the second embodiment differs from that of the first embodiment in that, instead of a three-layer laminated structure like the piezoelectric vibration device 1 of the first embodiment, it uses a piezoelectric vibration element PvA having a laminated structure in which a piezoelectric diaphragm 30 is laminated on a lower plate 2, as shown in Figure 10.
[0059] Although not shown in Figure 10, the piezoelectric diaphragm 30 comprises a piezoelectric substrate made of quartz, a substantially rectangular vibrating section in plan view on which a pair of excitation electrodes are formed on one main surface and the other main surface opposite to it, an outer frame section having an inner wall in plan view that is rectangular in shape and surrounds the outer wall of the vibrating section, a holding section that holds the vibrating section by connecting the outer wall of the vibrating section and the inner wall of the outer frame section, and a cutout section formed between the vibrating section and the outer frame section by cutting out the piezoelectric substrate in the thickness direction.
[0060] The piezoelectric diaphragm 30, having this configuration, is joined to the upper surface of the lower plate 2, for example, by Au-Au diffusion bonding, so that the piezoelectric diaphragm 30 is mounted on the upper surface of the lower plate 2. As shown in Figure 10, the piezoelectric vibration element connection terminals 21 and 23 (see Figure 9) on the lower surface of the lower plate 2 on which the piezoelectric diaphragm 30 is mounted are joined to the piezoelectric vibration element mounting pads 63a and 63b of the package 6, respectively, using a conductive adhesive 65 made of silicone resin, similar to that of the first embodiment.
[0061] Therefore, according to the second embodiment, the same effects as the first embodiment described above can be obtained. Furthermore, because of the lower plate (substrate) 2, compared to the case where the outer edge of a single piezoelectric diaphragm 30 is directly fixed to the package 6 without the lower plate 2, the connection terminals that join to the piezoelectric vibration element mounting pads 63a and 63b of the package 6 can be formed to a position inside the piezoelectric diaphragm 30, thereby increasing the bonding strength of the adhesive 65.
[0062] <Third Embodiment> The piezoelectric vibration device 1B according to the third embodiment of the present invention will be described with reference to Figures 11 to 17. The piezoelectric vibration device 1B according to the third embodiment is a piezoelectric vibration device with a thermistor (TSX: Temperature Sensor Xtal), and the differences between the piezoelectric vibration device 1B according to the third embodiment and the first embodiment will be described below. In the following description, Figures 1 to 9 will also be referenced, and in Figures 11 to 17, the same reference numerals as in Figures 1 to 9 indicate the same or equivalent components.
[0063] The piezoelectric vibration device 1B in the third embodiment differs from the first embodiment in that, as shown in Figure 11, the package 6B, which is roughly rectangular in plan view, has an H-shaped vertical cross-section, and the piezoelectric vibration element PvB, which has a piezoelectric diaphragm 3B mounted on the upper surface opposite to the lower surface of the lower plate 2B and an upper plate 4B superimposed on the upper surface of the piezoelectric diaphragm 3B, is housed in the upper recess 61Ba of the package 6B, while the thermistor 5B, which is an electronic component, is housed in the lower recess 61Bb of the package 6B.
[0064] Furthermore, as shown in Figure 16, four piezoelectric vibration element connection terminals 28Ba, 28Bb, 28Bc, and 28Bd, which are rectangular in plan view, are provided on the outer bottom surface of the lower plate 2B. On the upper surface of the base plate 6B1 of the package 6B, four piezoelectric vibration element mounting pads 63Ba, 63Bb, 63Bc, and 63Bd, which are rectangular in plan view, are provided at positions opposite each of the piezoelectric vibration element connection terminals 28Ba, 28Bb, 28Bc, and 28Bd. The piezoelectric vibration element connection terminals 28Ba, 28Bb, 28Bc, and 28Bd are joined to the piezoelectric vibration element mounting pads 63Ba, 63Bb, 63Bc, and 63Bd, respectively, by conductive adhesive 65B. The lower plate (substrate) 2B and the package 6B are joined at four points by conductive adhesive 65B, which is also different from the first embodiment. Here, of the four piezoelectric vibration element connection terminals 28Ba, 28Bb, 28Bc, and 28Bd, for example, the piezoelectric vibration element connection terminals 28Bb and 28Bd are electrically connected to a pair of excitation electrodes, while the piezoelectric vibration element connection terminals 28Ba and 28Bc are connection terminals that are not electrically connected to either the excitation electrodes or the thermistor.
[0065] As shown in Figure 11, the H-shaped package 6B comprises a ceramic base plate 6B1 which is roughly rectangular in plan view, a ceramic upper wall 6B2 laminated on the upper side of the base plate 6B1, and a ceramic lower wall 6B3 laminated on the lower side of the base plate 6B1.
[0066] As shown in Figure 13, on the upper surface 6B1a of the base plate 6B1, piezoelectric vibration element mounting pads 63Ba, 63Bb, 63Bc, and 63Bd are formed on the upper surface of the base plate 6B1 of the package 6B, at positions facing the piezoelectric vibration element connection terminals 28Ba, 28Bb, 28Bc, and 28Bd on the outer bottom surface of the lower plate 2B. These pads have a larger area than each of the piezoelectric vibration element connection terminals 28Ba to 28Bd on the lower plate 2B when viewed from above, and the piezoelectric vibration element connection terminals 28Ba to 28Bd are joined to the piezoelectric vibration element mounting pads 63Ba to 63Bd by conductive adhesive 65B. Here, the piezoelectric vibration element connection terminals 28Ba to 28Bd are each located within the region enclosed by the outer edges of the piezoelectric vibration element mounting pads 63B to 63Bd that are joined. The sides of the four corners of the base plate 6B1 are cut out in an arc shape in the vertical direction. Furthermore, vias Va, Vb, Vc, and Vd are formed on each piezoelectric vibration element mounting pad 63Ba to 63Bd, respectively.
[0067] As shown in Figure 14, via receivers VRa, VRb, VRc, and VRd corresponding to vias Va, Vb, Vc, and Vd on the upper surface are formed on the lower surface 6B1b of the base plate 6B1. Inside the dotted rectangle in Figure 14 that shows the inner wall of the recess 61Bb, T-shaped thermistor mounting pads 9a and 9b are formed in the B1-B2 direction and connected to terminals 5B1 and 5B2 on the B1 and B2 sides of the thermistor 5B. Via receivers VRb and VRd are electrically connected to castellations C2 and C4, which will be described later, via hook-shaped lead electrodes 10a and 10b, respectively, and thermistor mounting pads 9a and 9b are electrically connected to castellations C1 and C3, which will be described later, via L-shaped lead electrodes 11a and 11b, respectively.
[0068] As shown in Figure 12, the upper wall 6B2 is laminated to the periphery of the base plate 6B1 so as to form an upward-facing upper wall surface, and a recess 61Ba for housing the piezoelectric vibration element PvB mounted on the lower plate 2 is formed on the upper surface side of the base plate 6B1. The sides of the four corners of the upper wall 6B2 are cut out in an arc shape in the vertical direction.
[0069] As shown in Figure 15, the lower wall 6B3 has a wall surface that is generally thicker than the upper wall 6B2, and the thickness of the wall surfaces on sides A1 and A2 of the lower wall 6B3 is formed to be thicker than the wall surfaces on sides B1 and B2. It is laminated to the peripheral edge of the lower surface of the base plate 6B1 so as to form a lower wall surface that extends downward, and a recess 61Bb for housing the thermistor 5B is formed on the lower surface of the base plate 6B1. Castellations C1, C2, C3, and C4 are formed on the sides of the four corners of the lower wall 6B3 by being cut out in an arc shape in the vertical direction and metallized, and external connection terminals 12a, 12b, 12c, and 12d provided at the four corners of the bottom surface (lower surface) of the lower wall 6B3 are electrically connected to the castellations C1, C2, C3, and C4, respectively.
[0070] In addition, the top surface of the package 6B is sealed by seam welding a lid 7B made of a metal plate to the top surface of the package 6B using a substantially rectangular metal member 8B, similar to the first embodiment.
[0071] Here, the piezoelectric vibration element mounting pads 63Bb and 63Bd on the upper surface 6B1a of the base plate 6B1 are connected to the pair of first and second excitation electrodes of the piezoelectric diaphragm 3B of the piezoelectric vibration element PvB, respectively. The piezoelectric vibration element mounting pad 63Bb is electrically connected to the external connection terminal 12b via via Vb, via receiver VRb, lead electrode 10a, and castellation C2. The piezoelectric vibration element mounting pad 63Bd is electrically connected to the external connection terminal 12d via via Vd, via receiver VRd, lead electrode 10b, and castellation C4.
[0072] Furthermore, the thermistor-mounted pad 9a on the lower surface 6B1b of the base plate 6B1 is electrically connected to the external connection terminal 12a via the lead electrode 11a and castellation C1, and the thermistor-mounted pad 9b on the lower surface 6B1b of the base plate 6B1 is electrically connected to the external connection terminal 12c via the lead electrode 11b and castellation C3.
[0073] As shown in Figure 16, the piezoelectric vibration element connection terminals 28Ba to 28Bd of the lower plate 2B are superimposed on the piezoelectric vibration element mounting pads 63Ba to 63Bd and joined by conductive adhesive 65B, and the terminals 5B1 on the B1 side and 5B2 on the B2 side of the thermistor 5B are joined to the thermistor mounting pads 9a and 9b of the base plate 6B1, for example by solder, so that the piezoelectric vibration element PvB mounted on the lower plate 2B is on the upper side of the package 6B. The thermistor 5B is housed in the recess 61Ba, and the thermistor 5B is housed in the recess 61Bb on the lower side of the package 6B. As described above, one excitation electrode of the piezoelectric diaphragm 3B is electrically connected to the external connection terminal 12b, and the other excitation electrode of the piezoelectric diaphragm 3B is electrically connected to the external connection terminal 12d. The terminal 5B1 on the B1 side of the thermistor 5B is connected to the external connection terminal 12a, and the terminal 5B2 on the B2 side of the thermistor 5B is connected to the external connection terminal 12c. The top surface of the package 6B is then sealed by the lid 7B, and the recess 61Ba is hermetically sealed.
[0074] At this time, as shown in Figure 16, the connection terminals 28Ba to 28Bd for each piezoelectric vibration element on the lower plate 2B are spaced inward from the outer rectangular edge of the lower plate 2B in a plan view, and the conductive adhesive 65B is positioned inside the area enclosed by the outer rectangular edge of the lower plate 2B, and within the rectangular area of each piezoelectric vibration element mounting pad 63Ba to 63Bd on the base plate 6B1, away from the center P of the rectangle of the lower plate 2B (marked with an "x" in Figure 16).
[0075] In this way, the connection terminals 28Ba to 28Bd for each piezoelectric vibration element are positioned spaced inward from the outer edge of the rectangle of the lower plate 2B in a plan view, and the conductive adhesive 65B is positioned within the rectangular area of each piezoelectric vibration element mounting pad 63Ba to 63Bd, away from the center P of the rectangle of the lower plate 2B. As a result, in a plan view, the conductive adhesive 65B can be neatly positioned within the area of the lower plate 2B without protruding beyond the outer edge of the substrate.
[0076] Incidentally, as shown in Figure 17, the width D in the A1-A2 direction of the terminals 5B1 and 5B2 of the thermistor 5B (cross-hatched portion in the figure) is set to be approximately the same as the distance between adjacent piezoelectric vibration element mounting pads 63Ba and 63Bd on the base plate 6B1 and between piezoelectric vibration element mounting pads 63Bb and 63Bc in the A1-A2 direction. Furthermore, when the piezoelectric vibration element PvB mounted on the lower plate 2B and the thermistor 5B are housed in the recesses 61Ba and 61Bb of the package 6B, as shown in Figure 17, the conductive adhesive 65B that joins the respective piezoelectric vibration element connection terminals 28Ba to 28Bd on the lower plate 2B and the respective piezoelectric vibration element mounting pads 63Ba to 63Bd on the base plate 6B1 is set so as not to overlap with the terminals 5B1 and 5B2 of the thermistor 5B.
[0077] Therefore, according to the third embodiment, even when the lower plate 2B on which the piezoelectric vibration element PvB is mounted is joined to the H-type package 6B at four points using a conductive adhesive 65B, the same effects as those of the first embodiment described above can be obtained.
[0078] Furthermore, each piezoelectric vibration element mounting pad 63Ba to 63Bd of package 6B has a larger area than each piezoelectric vibration element connection terminal 28Ba to 28Bd that is joined in a plan view, and each piezoelectric vibration element connection terminal 28Ba to 28Bd is positioned within the region enclosed by the rectangular outer edges of each piezoelectric vibration element mounting pad 63Ba to 63Bd, and away from the center P of the diameter of the lower plate 2B. As a result, even if there is variation in the mounting position of the lower plate 2B on which the piezoelectric vibration element PvB is mounted on package 6B, each piezoelectric vibration element connection terminal 28Ba to 28Bd of the lower plate 2B can be positioned within the region enclosed by the rectangular outer edges of each piezoelectric vibration element mounting pad 63Ba to 63Bd of package 6B, thereby preventing the conductive adhesive 65B from overflowing from the region enclosed by the outer edges of the lower plate 2B in a plan view.
[0079] Furthermore, as shown in Figure 17, the width D of the terminals 5B1 and 5B2 of the thermistor 5B in the A1-A2 direction is set to be approximately the same as the distance between adjacent piezoelectric vibration element mounting pads 63Ba and 63Bd on the base plate 6B1 and between piezoelectric vibration element mounting pads 63Bb and 63Bc in the A1-A2 direction. This ensures that the conductive adhesive 65B that joins the connection terminals 28Ba to 28Bd for each piezoelectric vibration element on the lower plate 2B to the piezoelectric vibration element mounting pads 63Ba to 63Bd on the base plate 6B1 does not overlap with the terminals 5B1 and 5B2 of the thermistor 5B. Therefore, when the terminals 5B1 and 5B2 of the thermistor 5B are soldered to the thermistor mounting pads 9a and 9b on the base plate 6B1 of the package 6B, the influence of the soldering stress on the package 6B and the deterioration of the characteristics of the piezoelectric vibration device 1B can be more reliably prevented.
[0080] Furthermore, in the TSX, since four piezoelectric vibration element mounting pads 63Ba to 63Bd are provided on the package 6B, the heat conducted from the external substrate to the piezoelectric vibration device 1B can be efficiently conducted to the piezoelectric vibration element PvB. This reduces the difference between the temperature detected by the thermistor 5B and the temperature of the piezoelectric diaphragm 3B, thereby preventing a deterioration in the characteristics of the piezoelectric vibration device.
[0081] 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.
[0082] For example, as a modification of the third embodiment described above, as shown in Figure 18, the conductive adhesive 65B may be placed within the rectangular area of each piezoelectric vibration element mounting pad 63Ba to 63Bd of the base plate 6B1, and closer to the center P of the rectangle of the lower plate 2B (marked with an "x" in Figure 18) compared to the position shown in Figure 16. Here, the conductive adhesive 65B is located away from the center P of the rectangle of the lower plate 2B (marked with an "x" in Figure 18), just as in the third embodiment. In this case, since the four conductive adhesives 65B are closer to the center P of the rectangle of the lower plate 2 (see Figure 16) compared to the third embodiment, it becomes possible to reduce the amount of displacement of the piezoelectric diaphragm 3B (see Figure 11) with respect to the tensile stress caused by the four conductive adhesives 65B, and an improvement in the hysteresis of the piezoelectric vibration device 1B (see Figure 11) can be expected. In this context, hysteresis refers to the difference in frequency between heating and cooling in the frequency-temperature characteristics of a piezoelectric vibration device, that is, the shift in frequency during temperature changes. The smaller this shift in frequency, the better the characteristics.
[0083] Furthermore, as a modification of the first embodiment described above, as shown in Figure 19, the conductive adhesive 65 may be placed in a position closer to each other than the position shown in Figure 2, within the region where the piezoelectric vibration element mounting pads 63a, 63b of the package 6 and the connection terminals 21, 23 for the piezoelectric vibration element overlap. Here, the conductive adhesive 65 is located away from the center P of the rectangle of the lower plate 2 (marked with an "x" in Figure 19), just as in the first embodiment. In this case as well, since the two conductive adhesives 65 are closer to the center P of the rectangle of the lower plate 2 (see Figure 2) compared to the first embodiment, it becomes possible to reduce the amount of displacement of the piezoelectric diaphragm 3 (see Figure 1) with respect to the tensile stress caused by the two conductive adhesives 65, and an improvement in the hysteresis of the piezoelectric vibration device 1 (see Figure 1) can be expected.
[0084] Furthermore, as another modification of the first embodiment described above, conductive adhesive 5 may be placed in three locations as shown in Figure 20. Specifically, for example, in the piezoelectric vibration device shown in Figure 1, if the piezoelectric vibration element Pv is positioned above the stepped portion 62 of the package 6, including the free end, and the IC 5 is not positioned below the free end, in addition to the two conductive adhesives 65 lined up on the fixed end side in the A2 direction of Figure 9 (the -Z' side in Figure 20) that join the piezoelectric vibration element connection terminals 21, 23 on the second main surface 2b, which is the lower surface of the lower plate 2, to the piezoelectric vibration element mounting pads 63a, 63b provided on the stepped portion 62 of the package 6, a conductive adhesive 651 may also be placed at the position on the +Z' and +X side of Figure 20 that joins the unconnected terminal 22 (see Figure 9) to the stepped portion 62. In this case, the conductive adhesive 651 does not overlap the holding portion 35 that connects the outer peripheral wall of the vibrating portion 33 and the inner peripheral wall of the outer frame portion 34 to hold the vibrating portion 33, thus suppressing the effect of stress transmitted to the holding portion 35. Therefore, it does not adversely affect the vibration characteristics of the vibrating portion 33.
[0085] Furthermore, among the four piezoelectric vibration element connection terminals 28Ba, 28Bb, 28Bc, and 28Bd in the third embodiment, the piezoelectric vibration element connection terminals 28Bb and 28Bd are electrically connected to a pair of excitation electrodes, while the piezoelectric vibration element connection terminals 28Ba and 28Bc are connection terminals that are not electrically connected to either the excitation electrodes or the thermistor, and either one or both of them may be connected to ground.
[0086] Furthermore, in the above-described embodiment, the lid 7 is seam-welded to the package 6 to close the top opening of the package 6, but the lid 7 may also be bonded to the package 6 with a resin-based adhesive to close the top opening. This would reduce manufacturing costs compared to seam welding, which is usually expensive as it uses gold. The resin-based adhesive may or may not contain a conductive filler. In the case of a resin-based adhesive containing a conductive filler, grounding becomes possible by making the lid 7 out of metal, which can shield against electromagnetic noise from the outside.
[0087] Furthermore, the thermistor 5B in the third embodiment described above may have the following configurations. For example, a pair of thermistor electrodes may be arranged opposite each other on a substrate such as alumina ceramic via a resistive film and covered with a protective film. Another example is a configuration in which a pair of electrodes are formed on the surface of a single ceramic plate (resistive plate), in which case the pair of electrodes may be formed on the front and back surfaces of the ceramic plate, or they may be formed side by side on one side, for example.
[0088] Furthermore, although the conductive adhesives 65, 65B, and 651 are shown as circular in each of the embodiments described above, the shape of the conductive adhesives 65, 65B, and 651 is not necessarily limited to a circle, and may be, for example, elliptical.
[0089] Furthermore, in the piezoelectric vibration devices 1 and 1A of the first and second embodiments described above, a concave space is formed inside the package 6 for arranging piezoelectric vibration elements Pv, PvA, etc., and the top surface of the package 6 is closed with a flat plate-shaped lid 7. However, the piezoelectric vibration elements, etc., may be arranged in the package without a concave space, and a cup-shaped lid having a U-shaped cross-section may be placed over the top surface of the package to close it.
[0090] Furthermore, although the vibrating part of the piezoelectric diaphragm 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 even tuning fork shaped.
[0091] Furthermore, in the above-described embodiment, the piezoelectric vibration element mounting pads 63a and 63b were described as being electrically connected to the piezoelectric vibration element connection terminals 23 and 21 of the lower plate 2, respectively, by an adhesive 65 made of silicone resin, for example. However, the adhesive may be a conductive adhesive made of epoxy resin, or an insulating adhesive and wire may be combined.
[0092] Furthermore, in piezoelectric vibration devices 1, 1A, and 1B, the materials used for the piezoelectric vibration elements Pv, PvA, and PvB are not limited to quartz, as long as they perform piezoelectric vibration.
[0093] Furthermore, the electronic components housed within packages 6 and 6B are not limited to the IC 5 and thermistor 5B mentioned above. Note that electronic components are not required.
[0094] Furthermore, the above-described embodiment is applicable to temperature sensor-integrated oscillators, as well as SPXO (Simple Packaged Crystal Oscillator), TCXO (Temperature Compensated Crystal Oscillator), and OCXO (Oven Controlled Crystal Oscillator).
[0095] The present invention is widely applicable to a package that houses and hermetically seals a substrate, which has a substantially rectangular shape in plan view and has at least two connection terminals on its outer bottom surface, a piezoelectric diaphragm mounted on the side of the substrate opposite to its outer bottom surface, and the substrate and the piezoelectric diaphragm mounted on the substrate.
[0096] 1, 1A, 1B... Piezoelectric vibration device 2, 2B... Bottom plate (substrate) 21, 23, 28a-28d... Connection terminals for piezoelectric vibration element 3, 30, 3B... Piezoelectric diaphragm 32a, 32b... First and second excitation electrodes 33... Vibration section Pv, PvA, PvB... Piezoelectric vibration element 4, 4B... Top plate (sealing member) Pv, 30... Piezoelectric vibration element 5... IC (electronic component) 5B... Thermistor (electronic component) 6... Package 6a... Outer bottom surface 62... Step section (mounting section) 63a, 63b, 63Ba-63Bd... Piezoelectric vibration element mounting pad (mounting pad) 65, 65B, 651... Conductive adhesive P... Center of bottom plate (substrate)
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 diaphragm mounted on the side of the substrate opposite to the outer bottom surface, and a package that houses the substrate and the piezoelectric diaphragm mounted on the substrate and seals them hermetically, wherein the piezoelectric diaphragm has a pair of excitation electrodes, the package has two mounting pads that are joined to each of the two connection terminals by a conductive adhesive, the two connection terminals are arranged side by side along one side of the substantially rectangular substrate and extend toward the opposite side opposite to that side, the edges of the extended sides of the substantially rectangular substrate are located beyond or near the center, and the conductive adhesive is arranged in a region enclosed by the outer edge of the rectangle of the substrate in plan view when the piezoelectric diaphragm and the substrate are housed in the package.
2. The piezoelectric vibration device according to claim 1, wherein the substrate has two additional connection terminals arranged along the opposite side to the side on which the two connection terminals are arranged side by side, the two connection terminals arranged side by side along the opposite side extend toward the direction of the side, and the extended edges are located beyond or near the center of the substantially rectangular substrate, the package further has two mounting pads which are joined to each of the two connection terminals arranged side by side along the opposite side by a conductive adhesive, each of the four mounting pads has a larger area than the connection terminals to which they are joined in a plan view, and each of the four connection terminals is located within the region enclosed by the outer edge of the mounting pad to which it is joined.
3. The piezoelectric vibration device according to claim 1 or 2, characterized in that each of the connection terminals is arranged spaced inward from the rectangular outer edge of the substrate in a plan view.
4. The piezoelectric vibration device according to claim 1 or 2, characterized in that the mounting pad has a substantially rectangular shape in plan view, and the conductive adhesive used to bond each connection terminal to each mounting pad is located within the rectangular area of the mounting pad and away from the center of the substantially rectangular substrate.
5. The piezoelectric vibration device according to claim 1 or 2, further comprising 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.
6. The piezoelectric vibration device according to claim 1, claim 2, or claim 5 dependent on claim 1, characterized in that the package contains electronic components in addition to the substrate and the piezoelectric diaphragm mounted on the substrate.
7. A piezoelectric vibration device comprising a substrate that is substantially rectangular in plan view and has four connection terminals on its outer bottom surface, a piezoelectric diaphragm mounted on the side of the substrate opposite to the outer bottom surface, and a package that houses the substrate and the piezoelectric diaphragm mounted on the substrate and seals them hermetically, wherein the piezoelectric diaphragm has a pair of excitation electrodes, the package has four mounting pads that are joined to each of the four connection terminals by a conductive adhesive, two of the four connection terminals are arranged side by side along one side of the substantially rectangular substrate and extend toward the opposite side, with the edges of the extended side of each being located near the center of the substantially rectangular substrate, the remaining two of the four connection terminals are arranged side by side along the opposite side of the substrate and extend toward the opposite side, with the edges of the extended side of each being located near the center of the substantially rectangular substrate, The piezoelectric vibration device is characterized in that the conductive adhesive is arranged in a region enclosed by the rectangular outer edge of the substrate in a plan view when the piezoelectric diaphragm and the substrate are housed in the package, each of the four mounting pads has a larger area than the connection terminals to which they are joined in a plan view, each of the four connection terminals is located in a region enclosed by the outer edge of the mounting pad to which it is joined, and the package houses electronic components in addition to the substrate and the piezoelectric diaphragm mounted on the substrate.