Piezoelectric device

Abstract

This piezoelectric device comprises: a package having a recess; a piezoelectric vibration element positioned in the recess; and a lid body with a first surface that faces the open surface of the recess and is joined to the periphery of the recess of the package by a joining member. The lid body has a peripheral edge portion positioned circumferentially along the outer periphery, with the thickness gradually decreasing toward the outer periphery. The peripheral edge portion has a curved shape in a cross-sectional view. Each of a first boundary of the peripheral edge portion of the first surface and a second boundary of the peripheral edge portion of a second surface is located at a position overlapping the recess in a plan view. The joining member extends over the first surface and the second surface of the peripheral edge portion.

Description

Piezoelectric Devices

[0001] The present disclosure relates to piezoelectric devices.

[0002] In response to demands for smaller and thinner piezoelectric devices, the thickness of the lid that seals the piezoelectric vibration element in the package is also being reduced. In JP 2014-236301 A, the thickness of the periphery of the lid is tapered to reduce the thickness of the joining member that joins the upper part of the package frame and the lid.

[0003] a first boundary on the inner edge of the peripheral edge on the first surface and a second boundary on the inner edge of the peripheral edge on a second surface opposite the first surface, the first boundary being a first boundary of the peripheral edge on the first surface, the second boundary being a second boundary of the peripheral edge on the second surface opposite the first surface, the first boundary being a first boundary of the peripheral edge on the second surface opposite the first surface, the first boundary being a first boundary of the peripheral edge on the second surface opposite the first surface, the second boundary being a first boundary of the peripheral edge on the second surface opposite the first surface, the first boundary being a first boundary of the peripheral edge on the second surface opposite the first surface, the second boundary being a first boundary of the peripheral edge on the second surface opposite the first surface, the second boundary being a first boundary of the peripheral edge on the second surface opposite the (3) The piezoelectric device of (1) or (2), wherein at least a portion of the joining member is joined to the first surface of the peripheral edge portion within the recess. (4) The piezoelectric device of (3), wherein the package has an annular frame and a substrate located on the opposite side of the frame from the open surface, an annular metal layer is located on a joining surface of the frame to the lid, and the joining member extends toward the substrate beyond the metal layer in the first direction on at least a portion of the inner surface of the recess. (5) The piezoelectric device of any of (1) to (4), wherein the first boundary and the second boundary are coincident in a plan view. (6) The piezoelectric device of any of (1) to (5), wherein the planar view area of ​​the lid is smaller than the planar view area of ​​the package and is included within the planar view area of ​​the package.

[0004] 1 is a perspective view showing the external configuration of a piezoelectric device; 2 is an exploded perspective view of a piezoelectric device; 3 is a cross-sectional view of a piezoelectric device; 4 is a cross-sectional view of a piezoelectric device of a comparative example; 5 is a diagram showing an example of an enlarged photograph of a joining portion formed by a joining member; and 6 is a diagram showing an example of an enlarged photograph of a joining portion of a joining member in a piezoelectric device of a comparative example.

[0005] An embodiment will now be described with reference to the drawings. FIG. 1 is a perspective view showing the external configuration of a piezoelectric device 1 according to this embodiment. The piezoelectric device 1 has a package 11 and a lid 14. The package 11 is formed by combining a frame 112 and a substrate 111. The package 11 and the lid 14 are joined by a joining member 15. Here, the side to which the lid 14 is joined is the +Z side, or the upper side. A plurality of external electrodes 114 are located on the -Z side, which is the bottom surface of the package 11. The external electrodes 114 are connected to an external substrate or the like by a joining member such as solder, thereby electrically connecting the piezoelectric device 1 to an electrical circuit on the external substrate or the like.

[0006] The piezoelectric device 1 may be substantially rectangular in plan view along the Z-axis direction. The substantially rectangular shape may have some or all of its corners rounded or may have castellations. Here, the X-axis is defined along the long axis direction. The direction perpendicular to the X-axis and Z-axis is the Y-axis direction. The Z-axis direction corresponds to the first direction in this embodiment.

[0007] The package 11 is an insulator, and may be made of, for example, a ceramic material, a semiconductor material, a glass material, or a combination thereof. The frame 112 and the substrate 111 may be made of the same material. The package 11 contains conductive electrical wiring. The conductor may be, for example, molybdenum, copper, silver, tungsten, or the like. Some or all of the signal lines may be plated with nickel, gold, or the like.

[0008] The lid 14 may be a conductor such as a metal. Examples of the metal include iron, copper, nickel, cobalt, molybdenum, or tungsten, or an alloy thereof, such as kovar. The electrical wiring within the package 11 may be exposed from the +Z side surface of the frame 112 and electrically connected to the lid 14 via the bonding member 15. For this purpose, the bonding member 15 may be a conductive bonding member. The conductive bonding member may be, for example, a brazing material or solder.

[0009] The joining member 15 is positioned around the outer periphery of the lid body 14, and joins the lid body 14 and the frame body 112. The size of the lid body 14 in a plan view may be smaller than the size of the package 11 in a plan view. The range of the lid body 14 in a plan view may be included within the range of the package 11 in a plan view.

[0010] 2 is an exploded perspective view of the package 11 and lid 14 of the piezoelectric device 1. The package 11 has an annular frame 112 and a substrate 111 that is positioned to cover one surface of the frame 112, in this case the surface on the -Z side. The +Z side of the frame 112 is an open surface, and a recess 11a surrounded by the frame 112 and the substrate 111 is located therein. In other words, the direction perpendicular to the open surface and facing outward is the +Z direction. In the package 11, the substrate 111 and frame 112 may be integral.

[0011] The lid 14 is joined to the frame 112 around the open surface by a joining member 15, sealing the recess 11a. The lid 14 is flat along the XY plane, but at a peripheral edge 14r along its outer periphery B, the thickness in the Z direction gradually decreases the closer to the outer periphery B. The upper surface on the +Z side of the lid 14 and the lower surface on the -Z side of the lid 14 may have different surface shapes at the peripheral edge 14r, or they may have the same shape. At a central portion 14c surrounded by a boundary Dc, which is the inner edge of the peripheral edge 14r, both the upper and lower surfaces are approximately flat.

[0012] A piezoelectric vibration element 12 is located within the recess 11a. The piezoelectric vibration element 12 may be, for example, a quartz crystal vibration element. The piezoelectric vibration element 12 includes electrodes and wiring related to vibration. The wiring is connected to two connection electrodes 113 located on the bottom surface of the recess 11a by connecting members 13. The piezoelectric vibration element 12 is fixed to the package 11 at its connection portions with the connection electrodes 113 and is supported at a distance from the bottom surface of the recess 11a. The two connection electrodes 113 may be located, for example, side by side in the Y-axis direction near one end of the recess 11a in the X-axis direction, which is the longitudinal direction of the recess 11a. The connection electrodes 113 are connected to external electrodes 114 via conductors that penetrate the substrate 111. An electrical signal supplied to the external electrodes 114 is applied from the connection electrodes 113 to the piezoelectric vibration element 12, and an electrical signal generated in response to the vibration of the piezoelectric vibration element 12 is output from the external electrodes 114 to the outside. The piezoelectric piece of the piezoelectric vibration element 12 may have a flat plate structure, or may have a thick or thin portion. The piezoelectric piece may also have a through hole or a groove.

[0013] The inside of the sealed recess 11a may be substantially vacuum or reduced pressure. This reduces air resistance to the vibration of the piezoelectric vibration element 12. The gas inside the recess 11a may be an inert gas, nitrogen, or ordinary air. The electrical wiring electrically connected to the lid 14 is connected to one of the external electrodes 114. This external electrode 114 may be connected to a ground surface.

[0014] FIG. 3 is a cross-sectional view taken along the XZ plane at the cross-sectional line iii in FIG. 2 . FIG. 4 is a comparative example of a cross-sectional view of the same cross section as FIG. 3 for a comparative piezoelectric device 1R. In one embodiment, as described above, in the peripheral portion 14r of the lid 14, the first surface 14b facing the recess 11a increases in distance from the lower surface 11b, which is the bottom surface of the package 11, as it approaches the outer periphery B. The second surface 14t opposite the first surface 14b decreases in distance from the lower surface 11b of the package 11 as it approaches the outer periphery B. As a result, the thickness of the peripheral portion 14r gradually decreases as it approaches the outer periphery B. At the outer periphery B, the first surface 14b and the second surface 14t are continuously connected in a curved, outwardly convex shape in a cross-sectional view. In other words, the outer periphery B is not a bent, discontinuous shape.

[0015] The boundary Dtl on the +X side of the boundary Dc on the second surface 14t and the boundary Dbl on the +X side of the first surface 14b may be located at the same position in a plan view. Furthermore, the boundary Dtr on the -X side of the boundary Dc on the second surface 14t and the boundary Dbr on the -X side of the boundary Dc on the first surface 14b may be located at the same position in a plan view. Similarly, in a cross section along the YZ plane, the boundary between the curved and flat portions of the first surface 14b may be located at the same position in a plan view as the boundary between the curved and flat portions of the second surface 14t. That is, the second boundary on the second surface 14t, which is the boundary between the peripheral portion 14r and the central portion 14c including the boundaries Dtl and Dtr, may coincide with the first boundary on the first surface 14b, which is the boundary between the peripheral portion 14r and the central portion 14c including the boundaries Dbl and Dbr, in a plan view. The term "coincidence" here may include manufacturing errors and variations. In this case, the boundary Dc is parallel to the Z axis. The central portion 14c has a substantially uniform thickness.

[0016] At the boundary Dc, the first surface 14b and the second surface 14t may be substantially continuously connected with the curved surface of the peripheral portion 14r asymptotically approaching the plane of the central portion 14c, or a discontinuous boundary line may be formed between the curved surface of the peripheral portion 14r and the plane of the central portion 14c.

[0017] On the other hand, the planar position of the first boundary on the first surface 14b and the planar position of the second boundary on the second surface 14t may not coincide at least in part. In this case, the boundary Dc is inclined with respect to the Z axis. The angle of inclination of the boundary Dc with respect to the Z axis may not be constant. In the portion where both the first surface 14b and the second surface 14t are the central portion 14c in plan view, the thickness of the lid 14 is approximately uniform. In the portion where at least one of the first surface 14b and the second surface 14t is the peripheral portion 14r in plan view, the thickness of the lid 14 becomes thinner the closer to the outer periphery B. Within the range described above, the shape and positional relationship of the lid 14 are the same as the central portion 64c and peripheral portion 64r, and the first surface 64b and second surface 64t of the lid 64 of the comparative example based on publicly known technology.

[0018] In contrast, the first boundary of the first surface 14b and the second boundary of the second surface 14t are both positioned so as to overlap the recess 11a in a planar view. That is, the boundary Dc is positioned within the range of the recess 11a in a planar view. This differs from the comparative example of FIG. 4 , in which the boundaries Dbl, Dbr between the central portion 64c and the peripheral portion 64r of the first surface 64b and the boundaries Dtl, Dtr between the central portion 64c and the peripheral portion 64r of the second surface 64t are positioned outside the recess 11a in a planar view. The width of the peripheral portion 14r perpendicular to the circumferential direction of the frame 112 may be wider than the width of the frame 112.

[0019] The joining member 15 may be positioned between the frame 112 and the first surface 14b of the lid 14, and may extend around the outside of the outer periphery B of the lid 14 and even onto the second surface 14t. In this case, the joining member 15 extends continuously across the continuous first surface 14b and second surface 14t. As a result, the joining member 15 is less likely to protrude further toward the +Z direction than the second surface 14t of the central portion 14c. This reduces the possibility of the height of the piezoelectric device 1 increasing due to the protrusion of the joining member 15. Meanwhile, the first surface 14b of the central portion 14c is positioned on the -Z side of the first surface 14b of the peripheral portion 14r that is joined to the frame 112. Depending on the thickness of the joining member 15, the first surface 14b of the central portion 14c may be positioned on the -Z side of the top of the frame 112. This reduces the height of the piezoelectric device 1. 4, the bonding member 40 is located between the central portion 64c, which has a uniform thickness, and the frame body 112, so the thickness of the bonding member 40 directly affects the height of the piezoelectric device 1R. However, reducing the thickness of the bonding member 40 over the entire opposing surface between the central portion 64c and the frame body 112 is likely to lead to a decrease in adhesive strength.

[0020] The lid 14 may also bend toward the -Z side at the central portion 14c. Therefore, the minimum distance hb from the second surface 14t of the lid 14 to the lower surface 11b of the package 11 at the central portion 14c inside the boundary Dc may be smaller than the minimum distance ha from the second surface 14t to the lower surface 11b of the package 11 on the boundary Dc. In other words, the second surface 14t of the central portion 14c may include a point closer to the lower surface 11b than a point on the second surface 14t on the boundary Dc. In particular, when the sealed recess 11a is decompressed, the central portion 14c is likely to bend toward the inside of the recess 11a due to the air pressure difference. Meanwhile, in the comparative example shown in FIG. 4, the central portion 64c has a planar shape along the XY plane.

[0021] An annular metallized layer 1121, i.e., a thin metal layer, may be located at the upper end, which is the end on the +Z side of the frame 112, i.e., on the bonding surface side with the lids 14, 64. The bonding member 15 can bond the metals of the lids 14, 64 and the metallized layer 1121 together more firmly than when bonding the lids 14, 64, which are made of conductive metal, to the frame 112, which is made of an insulator such as ceramic.

[0022] Inner edges Cl and Cr of the area where the bonding member 15 and the first surface 14b are bonded are at least partially located between the frame 112 and the boundary Dc, which includes the boundaries Dbl and Dbr, in a planar view. The shortest distance between the frame 112 and the inner edges Cl and Cr may be smaller than the width of the frame 112 in a planar view. The shortest distance between the frame 112 and the inner edges Cl and Cr may be 0.5 to 4 times the width of the portion where the lid 14 overlaps with the frame 112 in a planar view. The bonding member 15 extends into the recess 11a to a certain extent inside the frame 112 and bonds with the first surface 14b of the peripheral portion 14r, thereby increasing the bonding area with the lid 14 and improving the bonding strength. Meanwhile, the bonding member 15 does not contact the center portion 14c, so it does not get closer to the piezoelectric vibration element 12 than necessary, reducing the possibility of contact between the bonding member 15 and the piezoelectric vibration element 12. In contrast, in the comparative example, the joining member 15 and the central portion 64c are in contact with each other. Note that the inner edges Cl and Cr do not have to be linear, and therefore the shortest distance between each point on the inner edges Cl and Cr and the frame body 112 does not have to be constant.

[0023] FIG. 5 shows an example of a close-up image of the bonded portion formed by the bonding member 15. FIG. 6 shows a comparative example of a close-up image of the bonded portion formed by the bonding member 15 of the piezoelectric device 1R based on the known technology shown in FIG. 4 . Note that the portion below the upper end of the frame 112 is omitted. As described above, the thickness of the lid 14 increases as the first surface 14b and the second surface 14t slope toward the recess 20a, which is located inside the frame 112. In contrast, the boundary Dc of the lid 64 is located at a position overlapping the frame 112, and it can be seen that the thickness is approximately uniform across the frame 112 and the recess 20a. Therefore, the +Z side upper end of the piezoelectric device 1R is located further toward the +Z side from the upper end of the frame 112 by the thickness of the bonding member 15 and the thickness of the lid 64. The first surface 14b of the lid 14 is located inside the recess 20a, further inside the recess 20a than the position where it overlaps with the frame 112. Therefore, the influence of the thickness of the joining member 15 and the lid 14 on the height of the piezoelectric device 1 is reduced.

[0024] In one embodiment of the present disclosure, the bonding member 15 may protrude outside the outer periphery B and onto the second surface 14t of the lid 14 as described above. The bonding member 15 may also protrude into the recess 11a to the extent that it does not interfere with the vibration of the piezoelectric vibration element 12. A larger bonding area between the bonding member 15 and the lid 14 and the frame 112 increases the bonding strength.

[0025] At this time, at least a portion of the bonding member 15 on the inner surface side of the recess 11a may extend beyond the boundary between the metallized layer 1121 and the frame 112 toward the frame 112, i.e., to the -Z side. Furthermore, the bonding member 15 may engage with the gap between the metallized layer 1121 and the frame 112. This allows the bonding member 15 to bond the lid 14 and the package 11 together even more firmly.

[0026] As described above, the piezoelectric device 1 of this embodiment includes a package 11 having a recess 11a, a piezoelectric vibration element 12, and a lid 14 having a first surface 14b. The piezoelectric vibration element 12 is located within the recess 11a. The first surface 14b of the lid 14 faces the open surface of the recess 11a and is bonded to the periphery of the recess 11a of the package 11 with a bonding member 15. The lid 14 has a peripheral edge 14r that is located circumferentially along the outer periphery B and whose thickness in the Z direction perpendicular to the open surface gradually decreases toward the outer periphery B. In a cross-sectional view perpendicular to the open surface, the peripheral edge 14r is curved. A first boundary, which is the inner edge of the peripheral edge 14r on the first surface 14b, and a second boundary, which is the inner edge of the peripheral edge 14r on the second surface 14t opposite the first surface 14b, are both positioned to overlap the recess 11a in a plan view viewed from the Z direction. The bonding member 15 extends across the first surface 14b and the second surface 14t of the peripheral portion 14r. In such a piezoelectric device 1, the bonding member 15 extends continuously over the curved surface of the lid 14. Therefore, the bonding member 15 is less likely to locally protrude from the first surface 14b of the peripheral portion 14r and the package 11, which are the object of bonding. This reduces the local increase in size of the piezoelectric device 1, particularly in the height direction. Furthermore, because the first surface 14b of the lid 14 is easily fixed so as to fit into the recess 11a, the second surface 14t is less likely to be higher than the upper end of the package 11. This also contributes to the low profile of the piezoelectric device 1.

[0027] Furthermore, the second surface 14t may include a point inside the second boundary that is closer to the bottom surface 11b than the minimum distance ha between the second boundary and the bottom surface 11b on the side opposite the open surface of the package 11. In this way, the shape of the central portion 14c that can easily bend and enter the recess 11a further reduces the increase in height of the piezoelectric device 1.

[0028] Furthermore, at least a portion of the bonding member 15 may be bonded to the first surface 14b of the peripheral edge 14r within the recess 11a. That is, the bonding member 15 may be bonded not only between the lid 14 and the upper end of the package 11, but also to the peripheral edge 14r, protruding beyond the frame 112 toward the recess 11a. This allows the piezoelectric device 1 to improve bonding strength while reducing the possibility of adversely affecting the height of the package 11 or the vibration of the piezoelectric vibration element 12.

[0029] The package 11 may also have an annular frame 112 and a substrate 111 located on the opposite side of the open surface of the frame 112. An annular metallized layer 1121 may be located on the bonding surface of the frame 112 with the lid 14. The bonding member 15 may extend toward the substrate 111, i.e., the -Z side, in the Z direction, beyond the metallized layer 1121 on at least a portion of the inner surface of the recess 11a. This further increases the bonding area of ​​the bonding member 15 with the package 11. Therefore, the piezoelectric device 1 can improve bonding strength while reducing the possibility of adversely affecting the height of the package 11 or the vibration of the piezoelectric vibrating element 12.

[0030] The first boundary and the second boundary may coincide in a plan view. That is, the peripheral portion 14r and the central portion 14c may be clearly separated in a plan view. This may make manufacturing easier than if the first boundary and the second boundary were offset in a plan view, and thus may reduce increases in manufacturing effort or cost.

[0031] Furthermore, the planar view range of the lid 14 may be smaller than the planar view range of the package 11, and may be included within the planar view range of the package 11. By having the lid 14 located inside the range of the package 11, the joining member 15 is also less likely to protrude from the planar view range of the package 11. Furthermore, the joining member 15 reliably joins from the upper end of the package 11 to the second surface 14t of the lid 14, thereby increasing the joining strength.

[0032] The above embodiment is merely an example, and various modifications are possible. For example, the width of the peripheral portion 14r perpendicular to the circumferential direction may not be constant. The planar distance between the outer periphery B and the boundary Dbl and the planar distance between the outer periphery B and the boundary Dbr may be different. Furthermore, the planar distance between the outer periphery B and the boundary Dbl or the planar distance between the outer periphery B and the boundary Dbr may not be constant depending on the position of the cross-sectional line iii. Furthermore, the planar distance between the outer periphery B and the boundary in a cross section along the YZ plane may be different from the planar distance between the outer periphery B and the boundary in a cross section along the XZ plane.

[0033] Furthermore, the central portion 14c of the lid 14 does not necessarily have to bend inwardly of the recess 11a. Even if the central portion 14c is bent, the center of gravity of the central portion 14c does not necessarily have to be closest to the bottom surface 11b.

[0034] Furthermore, the joining member 15 does not have to extend into the recess 11 a. Even if the joining member 15 extends into the recess 11 a, it does not have to be in direct contact with the frame body 112.

[0035] Furthermore, in the piezoelectric device 1, the package 11 may not have the metallized layer 1121 on the upper end of the frame 112, and the frame 112 may be directly bonded to the lid 14.

[0036] Furthermore, the lid 14 may have a width in the X direction and / or Y direction that is approximately the same as that of the package 11 in a plan view.

[0037] In addition, the specific details of the structure, configuration, material, size, etc. shown in the above embodiment can be appropriately changed without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention described in the claims and its equivalents.

[0038] The present disclosure can be used in piezoelectric devices.

[0039] 1, 1R Piezoelectric device 11 Package 111 Substrate 112 Frame 1121 Metallized layer 113 Connection electrode 114 External electrode 11a Recess 11b Lower surface 12 Piezoelectric vibration element 13 Connection member 14, 64 Lid 14c, 64c Central portion 14r, 64r Peripheral edge portion 14b, 64b First surface 14t, 64t Second surface 15 Bonding member B Outer periphery

Claims

1. A piezoelectric device comprising: a package having a recess; a piezoelectric vibration element located within the recess; and a lid having a first surface facing the open surface of the recess and joined to the periphery of the recess of the package with a bonding member, wherein the lid has a peripheral edge portion located circumferentially along the outer periphery and whose thickness in a first direction perpendicular to the open surface gradually decreases towards the outer periphery, the peripheral edge portion being curved in a cross section perpendicular to the open surface, a first boundary which is the inner edge of the peripheral edge on the first surface and a second boundary which is the inner edge of the peripheral edge on a second surface opposite to the first surface both being positioned to overlap the recess in a plan view seen from the first direction, and the bonding member extending across the first surface and the second surface of the peripheral edge.

2. A piezoelectric device as described in claim 1, wherein the second surface includes a point inside the second boundary that is closer to the bottom surface than the minimum distance between the second boundary and the bottom surface of the package opposite the open surface.

3. The piezoelectric device according to claim 1 or 2, wherein at least a portion of the joining member is joined to the first surface of the peripheral edge portion within the recess.

4. A piezoelectric device as described in claim 3, wherein the package has an annular frame and a substrate located on the opposite side of the frame from the open surface, an annular metal layer is located on the bonding surface of the frame to the lid, and the bonding material extends toward the substrate beyond the metal layer in the first direction on at least a portion of the inner surface of the recess.

5. A piezoelectric device according to any one of claims 1 to 4, wherein the first boundary and the second boundary coincide in a planar view.

6. A piezoelectric device according to any one of claims 1 to 5, wherein the planar view area of ​​the lid is smaller than the planar view area of ​​the package, and is included within the planar view area of ​​the package.

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