Package, piezoelectric device, and method for manufacturing piezoelectric device

Abstract

This package comprises: a substrate having a first surface; a frame body that is annularly positioned at a peripheral edge on the first surface and surrounds a first region on the first surface; and an annular bonding layer that is positioned on a second surface of the frame body on the opposite side from the first surface. The bonding layer has a first bonding layer and a second bonding layer spaced apart from the first bonding layer and positioned outside the first bonding layer. Either the first bonding layer or the second bonding layer has a self-heating layer. The first bonding layer may have the self-heating layer. The self-heating layer may have either a structure in which nickel layers and aluminum layers are alternately stacked and the outermost layer farthest from the first surface is a nickel layer, or a structure in which titanium layers and silicon layers are alternately stacked and the outermost layer is a titanium layer.

Description

Package, piezoelectric device, and method for manufacturing a piezoelectric device

[0001] This disclosure relates to a package, a piezoelectric device, and a method for manufacturing a piezoelectric device.

[0002] Packages housing piezoelectric vibration elements are becoming smaller in line with the miniaturization of the piezoelectric vibration elements themselves. Consequently, it is necessary to reduce the adverse effects on other parts, such as the piezoelectric vibration elements, caused by heating of the bonding members when sealing the package containing the piezoelectric vibration elements. Japanese Patent Application Publication No. 2021-127274 discloses a bonding technology that can be performed at room temperature.

[0003] One aspect of the present disclosure is a package comprising: [1] a substrate having a first surface; a frame positioned annularly on the periphery of the first surface and surrounding a first region on the first surface; and an annular bonding layer positioned on a second surface of the frame opposite to the first surface, wherein the bonding layer comprises a first bonding layer and a second bonding layer positioned outside the first bonding layer at a distance from the first bonding layer, and either the first bonding layer or the second bonding layer has a self-heating layer. [2] The package of [1], wherein the first bonding layer has the self-heating layer. [3] The package of [1] or [2], wherein the self-heating layer has a structure in which nickel layers and aluminum layers are alternately stacked and the outermost layer furthest from the first surface is a nickel layer, or a structure in which titanium layers and silicon layers are alternately stacked and the outermost layer is a titanium layer. [4] The package of [2], wherein the second bonding layer is brazing material or solder. [5] A piezoelectric device comprising: a package according to any one of [1] to [3]; a piezoelectric vibrating element located in the first region; and a lid joined to the package by the bonding layer. [6] A piezoelectric device comprising: a substrate having a first surface and being rectangular in plan view; a frame located on the periphery of the first surface and surrounding a first region located on the first surface; and an annular bonding layer located on a second surface of the frame opposite to the first surface; a piezoelectric vibrating element located in the first region; and a lid joined to the package by the bonding layer, wherein the bonding layer comprises: a first bonding layer of a first component located on the inside in plan view; and a second bonding layer of a second component located on the outside of the first bonding layer; and either the first bonding layer or the second bonding layer is a self-heating layer; and the first component and the second component are mixed in the contact portion of the first bonding layer and the second bonding layer. [7] The piezoelectric device of [6] wherein the component ratio of the first component and the second component changes continuously in the contact portion.[8] A piezoelectric device manufacturing method, comprising: joining a piezoelectric vibration element to a first region of a package including a substrate having a first surface, a frame body annularly located at a periphery on the first surface and surrounding a first region on the first surface, and an annular bonding layer located on a second surface opposite to the first surface of the frame body; having a first bonding layer and a second bonding layer spaced apart from the first bonding layer and located outside the first bonding layer, and mounting a lid on the second surface with a bonding layer having a self-heating layer sandwiched between any one of the first bonding layer and the second bonding layer; applying a predetermined stimulus to the self-heating layer to cause the self-heating layer to generate heat, and bonding the package and the lid by the bonding layer to seal the first region.

[0004] It is a perspective view of a piezoelectric device. It is a cross-sectional view of a piezoelectric device. It is a plan view of a package. It is a cross-sectional view of a package. It is a diagram for explaining a bonding layer. It is a diagram for explaining a bonding layer during heat generation. It is a diagram for explaining a bonding layer during heat generation. It is a diagram for explaining a manufacturing process of a piezoelectric device.

[0005] Hereinafter, embodiments will be described based on the drawings. In the following figures, for the sake of explanation, the ratio of the lengths in the three-axis directions and the ratio of the sizes between members may differ from the actual values.

[0006] FIG. 1 is a perspective view showing a piezoelectric device 1 including a package 20 of the present embodiment. The piezoelectric device 1 includes a package 20, a lid 10, and a bonding layer 30. The lid 10 is located on the +Z side of the package 20. The lid 10 is bonded to the package 20 by the bonding layer 30. The lid 10 may be a flat plate. The lid 10 may be made of a metal having electrical conductivity. Examples of the metal material include metals containing iron, copper, nickel, cobalt, molybdenum or tungsten, or alloys thereof, such as kovar. The package 20 has a rectangular shape in a plan view as viewed from the +Z side. The plan view shape of the lid 10 may be the same as that of the package 20. The bonding layer 30 will be described later, but it has electrical conductivity.

[0007] Figure 2 is a cross-sectional view of the piezoelectric device 1 cut along the cross-sectional line ii. The package 20 of the piezoelectric device 1 has a substrate 21 and a frame 22. The substrate 21 may be a flat plate extending along the XY plane. The frame 22 is located on the periphery of the first surface 21a on the +Z side of the substrate 21 and surrounds the first region S, which is the central part on the substrate 21. That is, the first region S is a recess surrounded by the first surface 21a of the substrate 21 and the inner wall surface of the frame 22. The substrate 21 and the frame 22 may be an integral structure. The substrate 21 and the frame 22 may be made of, for example, a ceramic material, a semiconductor material, or a glass material, or a combination thereof. In addition, wiring made of metal conductors may be located inside and on the surface of the substrate 21 and the frame 22.

[0008] A piezoelectric vibration element 40, bonded to the first surface 21a, is located in the first region S. The piezoelectric vibration element 40 may be a quartz vibration element of an appropriate structure, for example, using a quartz crystal piece such as an AT cut. The electrode positions and support positions of the piezoelectric vibration element 40 may be determined as appropriate as needed. Depending on the electrode positions of the piezoelectric vibration element 40, the positions of the electrode pads 23 and wiring of the package 20 may also be arbitrarily determined. The electrodes and wiring may be made of metal, such as molybdenum, copper, silver, or tungsten. Part or all of the wiring may have layers of nickel plating and gold plating laminated on its surface. The resonant frequency of the piezoelectric vibration element 40 may be 20 MHz or higher, 50 MHz or higher, or 100 MHz or higher. The planar size of the piezoelectric vibration element 40 may be, for example, 1000 μm or less on each side.

[0009] The piezoelectric vibration element 40 may have its mounted electrodes 41, used for bonding with the package 20, bonded to the electrode pads 23 on the first surface 21a by a conductive bonding member 50 or the like. The conductive bonding member 50 may be a conductive adhesive. Alternatively, the conductive bonding material 50 may be solder, such as gold-tin solder or silver-copper-tin solder. Furthermore, if the piezoelectric vibration element 40 is fixed and supported at locations other than the electrodes, these fixed locations may be bonded by an insulating bonding member.

[0010] The bonding layer 30 is located in an annular shape on the second surface 22a of the frame 22, opposite to the first surface 21a, i.e., on the +Z side. The bonding layer 30 seals the first region S by bonding the lid 10 to the package 20. The sealed first region S may be under reduced pressure below atmospheric pressure, or it may be filled with an inert gas such as argon or nitrogen. Alternatively, the inside of the first region S may contain air that is approximately the same as the outside air.

[0011] Figure 3 is a plan view of the package 20. Figure 4 is a cross-sectional view of the package 20 along cross-sectional line iv. When the lid 10 is not joined to the package 20, the joining layer 30 in the package 20 has a double annular structure. The inner first joining layer 31 and the second joining layer 32, which is outside the first joining layer 31, are located apart from each other. The annular structure here may have a discontinuous portion and may not be circumferentially connected, but when joined, it is possible to ultimately seal the first region S without interruption.

[0012] The second bonding layer 32 may be a layer of bonding material containing metal, such as solder or brazing material. The second bonding layer 32 melts upon heating and bonds to the lid 10.

[0013] The first bonding layer 31 may have a self-heating layer. The self-heating layer is a layer in which layers of different elements are alternately stacked, as described in Japanese Patent Application Publication No. 2021-127274 as a self-propagating exothermic reaction, and a reaction occurs in which a compound of the different elements is produced by an electrical, thermal, or mechanical external stimulus or a combination thereof, and the layer generates heat instantaneously in response to the reaction. Here, instantaneous means may be less than 0.1 seconds. One of the elements may be a transition metal. The first bonding layer 31 may also contain a brazing material or the like in the self-heating layer. In this case, the amount of brazing material or the like included may be in a proportion that does not cause the splash described later. An electrical stimulus may be applied, for example, by passing an electric current through the lid 10. A mechanical stimulus may be applied, for example, by applying an impact from the top of the lid 10.

[0014] Figure 5 is an enlarged view of the bonding layer 30 in a cross-sectional view of the package 20. As described above, the first bonding layer 31 and the second bonding layer 32 are located on the second surface 22a of the frame 22, with the first bonding layer 31 and the second bonding layer 32 separated from each other.

[0015] The self-heating layer contained in the inner first bonding layer 31 may be a laminated structure in which, for example, the first layer 311 and the second layer 312 are alternately positioned. For example, the first layer 311 may be a nickel layer and the second layer 312 may be an aluminum layer. The aluminum referred to here may be an aluminum alloy. The first layer 311 and the second layer 312 may each be thin film layers of about 10 to 100 nm. Although eight layers are shown in the diagram for illustrative purposes, in reality, more thin film layers may be laminated. The outermost layer 310 of the first bonding layer 31, furthest from the second surface 22a, may be a nickel layer. Alternatively, the self-heating layer may be a laminated structure in which silicon layers and titanium layers are alternately positioned. In this case, the titanium layer may be the outermost layer 310. As described above, the components of the first layer 311 and the second layer 312 should be a combination that generates heat instantaneously by forming compounds in response to electrical stimulation, thermal stimulation, and / or mechanical pressure. The outermost layer 310 primarily bonds with the lid 10 during the compound formation reaction, allowing the lid 10 to be stably bonded to the package 20 over a long period of time.

[0016] The heat generated in the self-heating layer is quickly transferred to the nearest second bonding layer 32, raising its temperature. This melts the bonding material in the second bonding layer 32, allowing the lid 10 to be bonded to the package 20. In other words, the first bonding layer 31 only needs to generate enough heat through the compound formation reaction to melt the bonding material in the second bonding layer 32. This reduces the amount of heat transferred to other parts of the piezoelectric device 1. For example, the amount of heat may be sufficient to raise the temperature of the second bonding layer 32 to 300°C or higher. Therefore, since the temperature rise in other parts of the piezoelectric device 1 is reduced, adverse effects on each part due to the temperature rise are reduced.

[0017] Figures 6A and 6B illustrate the changes in the bonding layer 30 when the first bonding layer 31 is heated. As shown in Figure 6A, the first bonding layer 31 is heated by stimulation and changes into a nickel-aluminum compound layer. At this time, the first bonding layer 31 may melt and spread. The second bonding layer 32 is heated by the heat generated by the first bonding layer 31 and melts. As a result, the melted first bonding layer 31 and the second bonding layer 32 may come into contact.

[0018] As shown in Figure 6B, at the contact portion 33 between the first bonding layer 31 and the second bonding layer 32, the first component of the first bonding layer and the second component of the second bonding layer 32 may be mixed. The degree of this mixing may be such that the first component is more abundant closer to the first bonding layer 31 and relatively decreases as you move closer to the second bonding layer 32. In other words, the ratio of the second component to the first component may change continuously from the side of the first bonding layer 31 to the side of the second bonding layer 32. The state in which the first and second components are mixed can be determined by observation using a scanning electron microscope (SEM) with an energy-dispersive X-ray spectrometer (EDS) or a transmission electron microscope (TEM).

[0019] Conventionally, seam welding is used as a joining method by localized heating, but there is a problem in that molten metal splatter, i.e., splash occurs and adheres to the first region S, especially to the piezoelectric vibration element 40. Also, even with localized heating, the heating temperature is high, so cracks may occur in the lid 10 and package 20 that are to be joined. On the other hand, in joining using solder or brazing material, although the heating temperature is lower than that of seam welding, localized heating is difficult for the size of the piezoelectric device 1, and the entire device is heated to join it, causing other parts of the piezoelectric device 1 to rise to a similar temperature. In this embodiment, since the inner first joining layer 31 of the joining layer 30 is a self-heating layer, splash does not occur from the first joining layer 31, and the risk of molten metal splatter adhering to the first region S, especially to the piezoelectric vibration element 40 and adversely affecting vibration is reduced. Meanwhile, the second joining layer 32 melts due to localized heating by the self-heating layer and joins the lid 10 to the package 20, so the temperature rise of other parts is reduced. Furthermore, the first bonding layer 31 acts as a barrier, making it difficult for the components of the second bonding layer 32 to scatter into the first region S.

[0020] The first bonding layer 31 may be a bonding member, and the second bonding layer 32 may be a self-heating layer. In this case as well, the heat generated from the second bonding layer 32 is limited to melting the bonding member of the first bonding layer 31, thus reducing the adverse effects of raising the temperature of the piezoelectric vibration element 40, etc. If the self-heating layer is electrically stimulated, the self-heating layer must have a structure through which current flows throughout.

[0021] Furthermore, the amount of heat generated by the joining of the lid 10 and the package 20 and reaching the piezoelectric vibration element 40 may be less than the curing condition of the conductive adhesive which is the conductive bonding member 50. If the amount of heat reaching the piezoelectric vibration element 40 rises above the curing condition, the curing of the conductive bonding member 50 will progress further, causing tensile stress on the piezoelectric vibration element 40 and resulting in a change in the resonant frequency. However, since the heat generated by the self-heating layer is localized, the amount of heat reaching the piezoelectric vibration element 40 can be kept low. Therefore, the above problem is less likely to occur.

[0022] Figure 7 illustrates the manufacturing process of the piezoelectric device 1. In this manufacturing process, the piezoelectric vibration element 40 is bonded to the bottom surface of the first region S of the package 20 (P1). The bonding may be performed using a conductive bonding member, i.e., a conductive adhesive as described above.

[0023] Aligned with the package 20, the lid 10 is mounted on the second surface 22a with the bonding layer 30 in between (P2). The lid 10 may simply be placed on the package 20, or the lid 10 and / or the package 20 may be fixed by a support member.

[0024] A predetermined stimulus is applied to the first bonding layer 31 (P3). As a result, the first bonding layer 31 generates heat as the compound is formed. The heat generated melts the first bonding layer 31 and the second bonding layer 32, bonding them to the lid 10 and sealing the first region S. Also, the first bonding layer 31 and the second bonding layer 32 come into contact, and the first component and the second component mix at the contact portion 33. Thus, a piezoelectric device 1 is obtained.

[0025] As described above, the package 20 of this embodiment comprises a substrate 21, a frame 22, and a bonding layer 30. The substrate 21 has a first surface 21a and is rectangular in plan view. The frame 22 is located annularly on the periphery of the first surface 21a and surrounds the first region S on the first surface 21a. The bonding layer 30 is located annularly on the second surface 22a of the frame 22, opposite to the first surface 21a. The bonding layer 30 has a first bonding layer 31 and a second bonding layer 32 located outside the first bonding layer 31, separated from it. Either the first bonding layer 31 or the second bonding layer 32 has a self-heating layer. In sealing, it is necessary for the members to be firmly joined together without gaps. In this way, by having the bonding layer 30 have a self-heating layer and a layer of normal bonding members in parallel, localized heat is obtained from the self-heating layer, which heats the normal bonding members and is used for joining with the lid 10. Therefore, the package 20 does not generate excessive heat, and heat is not easily transferred over a wide area, thus reducing the adverse thermal effects on the piezoelectric device 1 in which the package 20 is used. On the other hand, since both the first bonding layer 31 and the second bonding layer 32 are bonded to the lid 10, the package 20 can be firmly bonded to the lid 10.

[0026] The package 20 may have a self-heating layer in the first bonding layer 31. Having the inner bonding layer of the double bonding layer be a self-heating layer allows the first bonding layer 31 to act as a barrier against the outer second bonding layer 32. Therefore, the possibility of droplets scattering into the first region S when the bonding material melts in the second bonding layer 32 can be reduced. As a result, the risk of scattered bonding material adhering to the piezoelectric vibration element 40, leading to unstable coaxial frequencies or deterioration of crystal impedance, is reduced. Consequently, the reliability of the performance of the piezoelectric device 1 using the package 20 is improved.

[0027] The self-heating layer may have a structure in which nickel layers and aluminum layers are alternately stacked, with the outermost layer 310, which is furthest from the first surface 21a, being a nickel layer. Alternatively, the self-heating layer may have a structure in which titanium layers and silicon layers are alternately stacked, with the outermost layer 310 being a titanium layer. These structures can be expected to generate an appropriate amount of heat, allowing the joining member to be stably melted and joined to the lid 10.

[0028] The second bonding layer 32 may be brazing material or solder. By making the bonding member a conductive bonding member containing these metals, it can be stably melted at a desired temperature and bonded to the lid 10.

[0029] Furthermore, the piezoelectric device 1 of this embodiment may also include the package 20 described above, a piezoelectric vibration element 40 located in the first region S, and a lid 10 joined to the package 20 by a bonding layer 30. With this piezoelectric device 1, the package 20 and the lid 10 are firmly joined in parallel by the self-heating layer and the bonding member. On the other hand, the heat generated by the self-heating layer is limited to the amount necessary for melting the bonding member, and the heat does not spread widely and cause a temperature rise to the point where problems occur in other parts, so the piezoelectric device 1 is less likely to be adversely affected by heating during sealing.

[0030] Alternatively, the piezoelectric device 1 comprises a package 20, a piezoelectric vibration element 40, and a cover 10. The package 20 may comprise a substrate 21, a frame 22, and a bonding layer 30. The substrate 21 has a first surface 21a. The frame 22 is located on the periphery of the first surface 21a and surrounds a first region S located on the first surface 21a. The bonding layer 30 is located on a second surface 22a of the frame 22 opposite to the first surface 21a and is annular in shape. The piezoelectric vibration element 40 is located in the first region S. The cover 10 is bonded to the package 20 by the bonding layer 30. The bonding layer 30 has a first bonding layer 31 of a first component located on the inside in a plan view, and a second bonding layer 32 of a second component located on the outside of the first bonding layer 31. Either the first bonding layer 31 or the second bonding layer 32 is a self-heating layer. At the contact portion between the first bonding layer 31 and the second bonding layer 32, the first component and the second component may be mixed. In this way, since the piezoelectric device 1 has the first bonding layer 31 and the second bonding layer 32 connected by the contact portion 33, the bonding strength of the bonding layer 30 is increased, and the first region S can be sealed more firmly.

[0031] In the contact portion 33, the ratio of the first component to the second component may change continuously. By continuously bonding the first bonding layer 31 and the second bonding layer 32, the bond can be made stronger.

[0032] Furthermore, the manufacturing method of the piezoelectric device 1 of this embodiment using the package 20 includes the following steps: (1) Bonding the piezoelectric vibration element 40 to the first region S of the package 20. (2) Mounting the lid 10 on the second surface 22a with the bonding layer 30 in between. (3) Applying a predetermined stimulus to the self-heating layer in the bonding layer 30 to heat the self-heating layer, thereby bonding the package 20 and the lid 10 with the bonding layer 30 and sealing the first region S. According to this manufacturing method, the bonding member can be locally heated by the self-heating layer to bond the package 20 and the lid 10. Also, since the self-heating layer itself is involved in the bonding, the piezoelectric device 1 can be sealed more firmly while reducing adverse effects on the piezoelectric device 1.

[0033] It should be noted that the above embodiments are illustrative and can be modified in various ways. For example, although the above description assumes that the package 20 has a bonding layer 30, the piezoelectric device 1 is not limited to this. The lid 10 may have a bonding layer 30 and be aligned with the package 20 so that the lid 10 and the package 20 are bonded together.

[0034] In addition to the piezoelectric vibration element 40, other elements or electronic components may be located within the first region S. The first region S may also have other shapes, such as more complex shapes.

[0035] The package 20 does not have to be rectangular in plan view. Also, the lid 10 does not have to be flat. For example, the lid 10 may have a frame corresponding to the package 20, and the frame 22 of the package 20 and the frame of the lid 10 may be joined by a bonding layer 30.

[0036] In the piezoelectric device 1, the first bonding layer 31 and the second bonding layer 32 do not necessarily have to be in contact, and do not necessarily have a contact portion 33. It is sufficient that the heat generated by the self-heating layer melts the bonding member, and the lid 10 and the package 20 are joined by the bonding member.

[0037] Even if the bonding layer 30 has a contact portion 33, the ratio of the second component to the first component does not need to change continuously in the contact portion 33.

[0038] Furthermore, the specific details such as structure, configuration, materials, and size shown in the above embodiments may be modified as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention as described in the claims and its equivalents.

[0039] This disclosure can be used for packages, piezoelectric devices, and methods for manufacturing piezoelectric devices.

[0040] 1 Piezoelectric device 10 Cover 20 Package 21 Substrate 21a First surface 22 Frame 22a Second surface 23 Electrode pad 30 Bonding layer 31 First bonding layer 310 Outermost layer 311 First layer 312 Second layer 32 Second bonding layer 33 Contact portion 40 Piezoelectric vibration element 41 Mounted electrode 50 Conductive bonding member S First region

Claims

1. A package comprising: a substrate having a first surface; a frame positioned annularly on the periphery of the first surface and enclosing a first region on the first surface; and an annular bonding layer positioned on a second surface of the frame opposite to the first surface, wherein the bonding layer comprises a first bonding layer and a second bonding layer positioned outside the first bonding layer at a distance from it, and either the first bonding layer or the second bonding layer has a self-heating layer.

2. The package according to claim 1, wherein the first bonding layer has the self-heating layer.

3. The package according to claim 1 or 2, wherein the self-heating layer has a structure in which nickel layers and aluminum layers are alternately stacked, and the outermost layer furthest from the first surface is a nickel layer, or a structure in which titanium layers and silicon layers are alternately stacked, and the outermost layer is a titanium layer.

4. The package according to claim 2, wherein the second bonding layer is a brazing material or solder.

5. A piezoelectric device comprising: a package according to any one of claims 1 to 3; a piezoelectric vibrating element located in the first region; and a lid joined to the package by the bonding layer.

6. A piezoelectric device comprising: a substrate having a first surface; a frame located at the periphery of the first surface and surrounding a first region located on the first surface; an annular bonding layer located on a second surface of the frame opposite to the first surface; a piezoelectric vibration element located in the first region; and a lid bonded to the package by the bonding layer, wherein the bonding layer comprises a first bonding layer of a first component located on the inside in a plan view, and a second bonding layer of a second component located on the outside of the first bonding layer, and either the first bonding layer or the second bonding layer is a self-heating layer, and the first component and the second component are mixed at the contact portion of the first bonding layer and the second bonding layer.

7. The piezoelectric device according to claim 6, wherein the ratio of the first component to the second component changes continuously in the contact portion.

8. A method for manufacturing a piezoelectric device, comprising: a substrate having a first surface; a frame positioned annularly on the periphery of the first surface and surrounding a first region on the first surface; and an annular bonding layer positioned on a second surface of the frame opposite to the first surface; a piezoelectric vibrating element being bonded to the first region of the package; a cover being mounted on the second surface with a bonding layer having a first bonding layer and a second bonding layer positioned outside the first bonding layer and separated from the first bonding layer, wherein either the first bonding layer or the second bonding layer has a self-heating layer; and a predetermined stimulus being applied to the self-heating layer to heat the self-heating layer, thereby bonding the package and the cover with the bonding layer and sealing the first region.

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