JP2008160332A - Piezoelectric vibration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel chip-type piezoelectric vibration device capable of reliably holding and hermetically sealing a piezoelectric vibration element even when it is miniaturized and has a high frequency.
[Solution]
The quartz diaphragm 1 is formed with a thin portion 1a at the center and a thick portion 1b around it, and has an inverted mesa (biconcave) configuration as a whole. Excitation electrodes 11 and 12 are formed opposite to each other on the front and back of the thin portion 1a, and these excitation electrodes are led out to the thick portion 1b by extraction electrodes 11a and 12a, respectively. The thin part of the quartz diaphragm 1 is hermetically sealed by the lids 21 and 22. Lead electrodes 11a and 12a extend on the side surface (end surface) 1c of the short side of the crystal diaphragm 1, and terminal portions 31 and 32 are joined to both side surfaces 1c, respectively.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric vibration device such as a crystal resonator used in an electronic apparatus.

  Piezoelectric vibration devices such as surface-mount type crystal resonators that are currently widely used use a ceramic package having a region for accommodating the crystal vibration element. After mounting the crystal vibration element on the ceramic package, the lid is hermetically sealed with a lid. Many configurations are adopted. For example, Japanese Patent Laid-Open No. 2000-236035 (Patent Document 1) is a prior art showing an example.

  In the configuration using such a ceramic package, when the piezoelectric vibration device is further reduced in size, there is a possibility that the ceramic package cannot cope with the reduction in size. For example, a ceramic body constituted by using a ceramic lamination technique by firing always varies in dimensional accuracy. When the ceramic body is miniaturized, it becomes difficult to ensure desired dimensional accuracy due to the variation. In addition, when a reduction in height is required, sufficient package strength may not be ensured by ceramic lamination. In such a case, environmental resistance performance such as airtightness required as an electronic component may not be satisfied.

  Furthermore, in order to mount the crystal resonator element on the package, a mounting device and a jig are required. However, there is a problem that it becomes difficult to mount the crystal unit due to the jig interfering with the package. It was.

  If the piezoelectric vibration device is further miniaturized in this way, it may not be possible to cope with the configuration using a ceramic package that is currently popular, and a piezoelectric vibration device configuration suitable for ultra miniaturization has been demanded. .

JP 2000-236035 A

  The present invention has been made in view of the above points, and is a novel chip-type piezoelectric vibration device that can reliably hold and hermetically seal the piezoelectric vibration element even when the size is reduced to a high frequency. The purpose is to provide.

  In order to achieve the above object, the present inventor aims at a configuration in which the piezoelectric vibrating plate can be easily held and the package can be easily chipped even when the piezoelectric vibrating device is miniaturized and the frequency is increased. Invented a configuration that uses a piezoelectric diaphragm with a reverse mesa structure and has a thin-walled part, and sealed the thin-walled part. Also, by providing a terminal part on the side of the piezoelectric diaphragm, a package that was conventionally required should be used. In this way, a chip-type piezoelectric vibration device is obtained, which is realized by the following configuration.

  That is, as shown in claim 1, the thin portion is formed in the central portion, the thick portion is formed around the thin portion, the excitation electrode is formed facing the front and back of the thin portion, and the excitation The electrode is connected to the piezoelectric diaphragm drawn to the thick part by the extraction electrode, a lid that is joined to the thick part and hermetically seals the thin part, and is joined to the side surface of the piezoelectric diaphragm, and is electrically connected to the extraction electrode. A piezoelectric vibration device including a terminal portion to be joined.

According to the configuration of the first aspect, by using the inverted mesa type piezoelectric diaphragm, it is possible to cope with the higher frequency of the piezoelectric diaphragm, and the lid is thicker so as to cover the concave portion formed by the thin portion. By thinly bonding the front and back surfaces of the meat part, the thin part serving as the excitation region can be hermetically sealed. The terminal portion is made of, for example, a metal block body, and at least the surface thereof is made of a conductor, whereby the lead electrode formed on the thick portion around the piezoelectric diaphragm can be led out to the outside through the terminal portion. it can. The terminal portion must be thicker than the thickness of the integral component of the piezoelectric diaphragm that is hermetically joined by the lid, and such a terminal portion is conductively joined to the side surface of the thick portion of the piezoelectric diaphragm. Thus, when mounted on the mounting substrate, the terminal portion can be joined to the mounting substrate without the lid or the piezoelectric diaphragm contacting the mounting substrate. Therefore, an ultra-miniaturized chip-type piezoelectric vibration device can be obtained without using a conventionally required ceramic package or the like.

  The piezoelectric diaphragm is a so-called reverse mesa type piezoelectric diaphragm having a thin portion at the center and a thick portion around the thin portion, but an intermediate thickness is provided between the thin portion and the thick portion. One or a plurality of middle thickness portions may be provided stepwise. In this case, a configuration in which the lid body is fitted to the inner wall portion may be adopted, and the lid body is arranged in such a manner that the lid body is regulated in the formation region of the inner meat portion. And the bondability of the lid to the piezoelectric diaphragm is improved.

  Moreover, the structure which has a taper-shaped inclined surface between a thin part and a thick part may be sufficient. In this case, the strength between the thin wall portion and the thick wall portion is improved, the strength of the piezoelectric diaphragm is improved, and the distortion stress generated in the thick wall portion is buffered and transmitted to the thin wall portion, thereby suppressing the distortion of the thin wall portion. The characteristics can be stabilized.

  Although the excitation electrode and the extraction electrode are composed of a single layer or a multilayer metal film, according to the present invention, since the extraction electrode is directly exposed to the outside, at least the uppermost layer that touches the outside air of the extraction electrode is It is preferable to use a material having excellent corrosion resistance such as gold.

  For example, a sealing glass material may be used for joining the thick portion and the lid. In the case of using a sealing glass material, the sealing glass material is formed in advance on the upper surface of the thick part, or the sealing glass material is formed in advance on the lid side, or the sealing glass is preliminarily formed on both. A material may be formed. Examples of the sealing glass material include borosilicate glass, tin phosphate glass, bismuth glass, and vanadium oxide glass.

  Moreover, you may use a metal brazing material for the joining of the said thick part and a cover body. For example, as shown in claim 2, there can be mentioned a configuration in which a circumferential metal film surrounding the thin part is formed in the thick part, and the metal film and the lid are joined by a metal brazing material. . In this case, the circumferential metal film may be formed simultaneously with the formation of the excitation electrode and the extraction electrode formed in the thin part or the thick part. In addition, a metal layer suitable for joining a metal brazing material may be formed on the circumferential metal film. The metal film may be formed by a vacuum deposition method or a sputtering method using a masking means in which only the metal film formation portion is opened, or by an electrode film formation using a photolithography technique.

  Alternatively, a metal brazing material may be formed on the lid in advance, and the lid with the metal brazing material may be joined to the piezoelectric diaphragm so as to cover the recess formed by the thin portion. The metal brazing material previously formed on the lid may be formed on the entire surface of the lid, or may be formed corresponding to the circumferential metal film.

  According to the second aspect of the present invention, since the thin portion serving as the excitation region is hermetically sealed by the lid by joining with the metal brazing material, a piezoelectric vibration device having excellent air tightness and stable characteristics can be obtained.

  According to a third aspect of the present invention, the lead electrode may be extended to a side surface of the piezoelectric diaphragm, and the side surface and the terminal portion may be joined by a metal brazing material. Since the side surface of the piezoelectric diaphragm is a thick portion, a relatively wide bonding region can be obtained by forming the extraction electrode on the side surface of the thick portion. By using the joining region to join the terminal portion and the metal brazing material, strong conductive joining can be performed. The metal brazing material can be, for example, gold-tin alloy, gold-germanium alloy, lead-free solder, etc., but the bonding temperature environment to the mounting substrate and the bonding temperature environment at the time of hermetic sealing by the lid body can be set. It is necessary to determine the metal brazing material in consideration, for example, it is necessary to apply a metal brazing material having heat resistance to the bonding temperature in the subsequent process.

  Furthermore, as shown in claim 4, the lid may have a plurality of configurations, and a part or all of the plurality of configurations may employ a material or a configuration excellent in buffering properties. When a stress is applied to the thick part of the piezoelectric diaphragm, a part of the stress is transmitted to the thin part, which may adversely affect the characteristics of the piezoelectric diaphragm. In this case, it is possible to suppress the propagation of stress to the thin wall portion by joining the lid and the thick wall portion, and further to suppress the deformation of the entire piezoelectric diaphragm by forming a plurality of this. This stress propagation suppressing action can be further obtained. Further, by using a material having excellent buffering property or a buffering structure having a plurality of bent portions for the lid, it is possible to suppress stress propagation to the thin wall portion which is the vibration region, which contributes to improvement of characteristics.

  According to a fifth aspect of the present invention, the lid body and the terminal portion may be integrated. For example, a configuration in which an integrated component having an L-shaped cross section is joined to the piezoelectric diaphragm may be employed. With such a configuration, the thin-walled portion can be hermetically sealed by the lid and the external lead-out terminal can be joined to the piezoelectric diaphragm at the same time. The bonding can be performed on a plurality of surfaces because the integral component has many bonding points with the piezoelectric diaphragm, and the bonding strength is increased. Further, by making at least the outer size of the terminal portion larger than the outer size of the piezoelectric diaphragm, the piezoelectric diaphragm can be conductively bonded without directly contacting a mounting board such as a printed wiring board.

  As described above, according to the present invention, it is possible to obtain a surface-mount type piezoelectric vibration device that can cope with miniaturization or high frequency without using a special package.

  Hereinafter, a first embodiment according to the present invention will be described with reference to the drawings. In the present embodiment, an AT-cut quartz crystal diaphragm that operates by thickness shear vibration will be described as an example of a piezoelectric diaphragm.

  FIG. 1 is an exploded perspective view of the piezoelectric vibration device according to the first embodiment, and FIG. 2 is a cross-sectional view taken along line AA in a state where FIG. 1 is assembled.

  The quartz vibrating plate 1 is made of an AT-cut quartz vibrating element, and is a rectangular plate having a long side (X axis), a short side (Z axis), and a thickness (Y axis) as a whole. The quartz diaphragm 1 is formed with a thin portion 1a at the center and a thick portion 1b around it, and has an inverted mesa (biconcave) configuration as a whole. The thin portion 1a is dug in the thickness direction from the front and back surfaces, and the quartz diaphragm 1 is thinned from the front and back surfaces. Excitation electrodes 11 and 12 are formed opposite to each other on the front and back of the thin portion 1a, and these excitation electrodes are led out to the thick portion 1b by extraction electrodes 11a and 12a, respectively. The extraction electrodes 11a and 12a are extracted to the thick portion side surface 1c.

The thick portion 1b is configured in a frame shape around the thin portion 1a, and circumferential metal films 13 and 14 are formed on the front and back surfaces of the thick portion 1b so as to surround the thin portion 1a. Is formed. In the present embodiment, the metal films 13 and 14, the excitation electrode, and the extraction electrode are formed by the same material and the same process. Specifically, a chrome layer is formed in contact with the quartz crystal plate, and a gold layer is formed on the chrome layer. In the multilayer film configuration, a metal film may be separately formed only on the metal films 13 and 14. For example, a silver or nickel-tin layer may be further formed on the chrome-gold multilayer film, and the metal films 13 and 14 may be made of a material different from that of the excitation electrode and the extraction electrode.

The metal film (electrode film) may be formed by a vacuum deposition method or a sputtering method using a masking means in which only the metal film formation portion is opened, or by an electrode film formation using a photolithography technique.

The electrode configuration is not limited to the above example. For example, a base layer of a chromium layer or a nickel layer may be formed in contact with the quartz diaphragm, and a silver layer may be formed on the base layer. A gold layer may be further formed on the silver layer. In addition, it is preferable that the electrode part outside the recess that is not hermetically sealed has a gold layer or the like excellent in corrosion resistance in the uppermost layer.

  The thin part of the quartz diaphragm 1 is hermetically sealed by the lids 21 and 22. The lids 21 and 22 use a Kovar material as a core material, and a nickel layer is formed on the surface (not shown in detail). Further, a gold germanium (AuGe) layer is formed on the surface to be bonded to the quartz crystal plate 1 in a circumferential shape corresponding to the circumferential metal films 13 and 14 as the metal brazing materials 21a and 22a. In the present embodiment, a metal brazing material 22a is formed in a circumferential shape in the vicinity of the outer periphery of the back surface of the lid (joint surface with the crystal diaphragm).

The nickel layer is formed by a technique such as plating, vacuum deposition or rolling, and the gold germanium layer (metal brazing material) is formed by pressing a sheet-like metal film preformed in a frame shape. The layer may be formed by other methods. It should be noted that the outer dimensions of the lid bodies 21 and 22 need to be designed so as not to contact the terminal bodies because the terminal bodies 31 and 32 described later are joined.

  The lids 21 and 22 are joined to the circumferential metal films 13 and 14 of the crystal diaphragm by metal brazing materials 21a and 22a, respectively. As described above, in this embodiment, a gold germanium layer is used as the metal brazing material. The metal brazing material is melted by heating the entire piezoelectric vibrating device in a heating furnace, or an energy beam such as a laser beam or an electron beam is applied to the outer peripheral portion of the lid corresponding to the metal brazing material directly or the metal brazing material forming region. By locally heating and melting by the method, the quartz diaphragm and the lid can be brazed.

  The lids 21 and 22 may be made of a material such as ceramic, glass, or quartz.

  In this embodiment, the concave portion formed in the quartz diaphragm is hermetically sealed with a lid, but the airtight atmosphere in the concave portion uses a vacuum or an inert gas atmosphere. Each airtight atmosphere can be determined by the atmosphere at the time of airtight sealing. Note that the hermetic sealing of the recesses does not need to be performed simultaneously at the top and bottom. For example, after one recess is bonded in a nitrogen gas atmosphere, and after adjusting characteristics such as frequency adjustment to the excitation electrode of the other recess, Hermetic sealing may be performed in a gas atmosphere.

  As described above, the extraction electrodes 11a and 12a extend on the side surface (end surface) 1c of the short side of the quartz crystal diaphragm 1, and the terminal portions 31 and 32 are joined to both side surfaces 1c, respectively. The terminal portions 31 and 32 are, for example, a block or thick plate made of metal and have a rectangular parallelepiped shape as a whole, and one side surface of each of the terminal portions 31 and 32 is joined to the side surface of the crystal diaphragm. When the terminal portion is made of metal, for example, an alloy such as Kovar or 42 alloy is used for the core material, and nickel plating or the like is formed on the surface thereof. Metal brazing materials 31a and 32a are used for joining the crystal diaphragm and the terminal portion, and the metal brazing material is formed in advance as a metal brazing layer in the joining region of the terminal portion, for example. The metal brazing material portion is brought into contact with the extraction electrodes 11a and 12a on the side surfaces of the quartz diaphragm, and fusion bonding is performed by overall heating by a heating furnace as described above or local heating by an energy beam. The metal brazing material used here is a gold-tin brazing material, and a metal brazing material having a melting point lower than that of the gold germanium used for joining the lid is used.

  The piezoelectric vibration device according to the present embodiment has the above-described configuration. As shown in FIG. 2, the height of the terminal portions 31 and 32 is an integrated product of the crystal vibration plate 1 and the lids 21 and 22. The upper and lower lids are arranged so as to be located inside the upper and lower ends of the terminal portions 31 and 32 in the height direction. With this arrangement, when placed on the mounting board, the terminal part does not come into contact with the mounting board, and the lid or quartz diaphragm does not come into direct contact with the front or back surface of the piezoelectric vibration device. The problem of short circuit between terminals does not occur, and the characteristics can be stabilized.

  In the present embodiment, two types of melting point metal brazing materials are used in consideration of the heating environment during assembly, but by simultaneously joining the lid and the terminal part to the crystal diaphragm, Only one type of metal brazing material may be used. In this case, for example, by using a jig that brings the upper and lower lids and the left and right terminal portions into close contact with a predetermined position of the crystal diaphragm, collective joining processing can be performed.

  Moreover, you may comprise the structure of the thin part and thick part of a quartz-crystal diaphragm by joining a some quartz plate. For example, a frame-shaped quartz diaphragm that forms a thick part is tightly bonded to a quartz diaphragm that forms the central part in the vertical direction, forming a thin part and a thick part, and an excitation electrode or lead on the surface. An electrode may be formed.

  Further, although an AT-cut quartz plate is used as the quartz plate, for example, a quartz plate having a short side on the X axis and a long side on the Z axis may be used, or a tuning fork type quartz plate with a frame. But you can. As is well known, the tuning-fork type quartz diaphragm needs to be formed with electrodes so that the vibrating arms can bend and vibrate, but it is preferable to finally draw out electrodes of the respective electrodes on the front and back surfaces. And it joins with a terminal part with a frame. In addition, another piezoelectric diaphragm may be used instead of the quartz diaphragm, or may be applied to a piezoelectric vibration device such as SAW (surface acoustic wave).

  Moreover, although the terminal part illustrated the block-shaped or thick plate-shaped rectangular parallelepiped structure which consists of metals, the metal of the rectangular parallelepiped shape of a hollow structure may be sufficient, and the metal of a cross-section may be sufficient as a cross section. Moreover, the structure by which the conductor was formed in the surface of insulators, such as a ceramic, may be sufficient.

  By the way, when the lid and the crystal diaphragm are joined with a joining material such as a metal brazing material or a sealing glass material, the molten sealing material can flow out into the thin-walled portion and hinder the excitation operation of the piezoelectric vibration device. There is sex. In order to suppress such a problem, for example, an insulating film such as silicon oxide is provided on the thin portion side (inner region intersecting the circumferential metal film 13) of the extraction electrode 11a formed in the thick portion 1b in FIG. The bank portion may be formed by forming or forming a metal film. It is possible to prevent the sealing material melted by the bank from flowing out into the thin wall portion.

  With the above configuration, a simple configuration can be obtained without using a ceramic package as in the prior art, and a chip-type piezoelectric vibration device in which the terminal portion contacts the mounting substrate can be obtained.

  A second embodiment according to the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view showing the internal structure of the piezoelectric vibration device. In the present embodiment, compared to the first embodiment, the configuration of the thick portion, the metal brazing material used for bonding, the mechanical bonding configuration of the crystal diaphragm and the terminal body are different. Note that the same components as those in the first embodiment are described with the same reference numerals, and a part of the description is omitted.

  The quartz vibrating plate 1 is made of an AT cut quartz vibrating element, and is a rectangular plate having a long side, a short side, and a thickness as a whole. The quartz diaphragm 1 is formed with a thin portion 1a at the center and a thick portion 1b around it, and has an inverted mesa (biconcave) configuration as a whole. The thin portion 1a is dug in the thickness direction from the front and back surfaces, and the quartz diaphragm 1 is thinned from the front and back surfaces. Excitation electrodes 11 and 12 are formed opposite to each other on the front and back of the thin portion 1a, and these excitation electrodes are led out to the thick portion 1b by extraction electrodes 11a and 12a, respectively. The extraction electrodes 11a and 12a are extracted to the side surface of the thick portion 1b.

The thick portion 1b is configured in a frame shape around the thin portion 1a, and circumferential metal films 13 and 14 are formed on the front and back surfaces of the thick portion 1b so as to surround the thin portion 1a. Is formed. In the present embodiment, the metal films 13 and 14, the excitation electrode, and the extraction electrode are formed by the same material and the same process. Specifically, a chromium layer is formed in contact with the quartz diaphragm, and a gold layer is formed on the chromium layer, and the metal film (electrode film) is formed by a metal film forming portion. Alternatively, it may be formed by a vacuum vapor deposition method or a sputtering method using a masking means having only an opening, or by an electrode film formation using a photolithography technique.

In the thick portion 1b, a step portion 1d is formed on the upper surface on one side of a short side to which a terminal body described later is joined. On the lower surface side, a step portion 1e is formed on the lower surface on the other short side to which a terminal body described later is joined. Each of the step portions 1d and 1e may be formed at one place on a part of the short side or at a plurality of places. Moreover, you may form over the whole.

  The thin part of the quartz diaphragm 1 is hermetically sealed by the lids 21 and 22. The lids 21 and 22 use a Kovar material as a core material, and a nickel layer is formed on the surface (not shown in detail). Further, a gold tin (AuSn) layer is formed in a circumferential shape corresponding to the metal films 13 and 14 as the metal brazing materials 21 a and 22 a on the surface to be bonded to the quartz crystal plate 1. In the present embodiment, a metal brazing material 22a is formed in a circumferential shape in the vicinity of the outer periphery of the back surface of the lid (joint surface with the crystal diaphragm).

The nickel layer is formed by a technique such as plating, vacuum deposition or rolling, and the gold germanium layer (metal brazing material) is formed by pressing a sheet-like metal film preformed in a frame shape. The layer may be formed by other methods. It should be noted that the outer dimensions of the lid bodies 21 and 22 need to be designed so as not to contact the terminal bodies because the terminal bodies 31 and 32 described later are joined.

  The lids 21 and 22 are joined to the circumferential metal films 13 and 14 of the crystal diaphragm by metal brazing materials 21a and 22a, respectively. The metal brazing material is melted by heating the entire piezoelectric vibration device in a heating furnace, or the outer peripheral portion of the lid corresponding to the metal brazing material forming region is locally heated by an energy beam such as a laser beam or an electron beam. Then, the quartz diaphragm and the lid can be brazed by melting.

  In the present embodiment, the concave portion formed in the quartz diaphragm is hermetically sealed with a lid, and the inert gas atmosphere is used as the airtight atmosphere in the concave portion, but a vacuum atmosphere may be used. . In addition, each airtight atmosphere can be determined by the atmosphere at the time of airtight sealing. Further, the hermetic sealing of the recesses does not need to be performed simultaneously at the top and bottom. For example, one recess is bonded in a vacuum atmosphere, and after adjusting characteristics such as frequency adjustment to the excitation electrode of the other recess, the vacuum atmosphere May be hermetically sealed.

  As described above, the extraction electrodes 11a and 12a extend on the side surface (end surface) 1c of the short side of the quartz crystal diaphragm 1, and the terminal portions 31 and 32 are joined to both side surfaces 1c, respectively. The terminal portions 31 and 32 have a configuration in which at least the surface thereof is electrically conductive, are block-shaped or thick-plate-shaped, and have a rectangular parallelepiped shape as a whole. Each side surface of the terminal portions 31 and 32 is joined to the side surface of the crystal diaphragm. Metal brazing materials 31a and 32a are used for joining, and the metal brazing material is formed in advance as a metal brazing layer in the joining region of the terminal portion, for example. The metal brazing material portion is brought into contact with the extraction electrodes 11a and 12a on the side surfaces of the quartz diaphragm, and fusion bonding is performed by overall heating by a heating furnace as described above or local heating by an energy beam. The metal brazing material used here is a gold-tin brazing material, which is the same as the metal brazing material used for hermetic sealing.

The terminal portion is formed with recesses 31a and 32a corresponding to the stepped portion formed in the thick portion on the joint surface with the crystal diaphragm. A part of the thick part is fitted by the concave part, and the joint strength between the two is remarkably improved.

  Furthermore, in the present embodiment, the integrated body of the crystal vibrating plate 1 and the lid and the terminal portions 31 and 32 are additionally bonded by the insulating bonding material S. As shown in FIG. 3, the insulating bonding material S may be formed so as to cover the crystal diaphragm 1, the terminal body, and the lid, or may extend only to the crystal diaphragm 1 and the terminal portions 31 and 32. It may be formed. By forming so as to cover the crystal diaphragm 1, the terminal body, and the lid body, the mechanical strength in an integrated state of each of these components is improved, and the handling as a chip-type component is simplified. In addition, as an example of the insulating bonding material, an epoxy resin bonding material and a silicone resin bonding material can be exemplified. However, since the silicone resin bonding material is flexible, for example, the stress propagation to the thin portion is reduced. Can be preferable.

  According to the present embodiment, the mechanical strength is greatly improved by the fitting configuration of the stepped portion of the thick wall portion and the concave portion of the terminal portion, and the additional bonding by the resin bonding material, the handling property is improved and the characteristics are improved. A stable chip-type piezoelectric vibration device can be obtained. The mechanical strength can be improved even with only the above-described fitting configuration or a configuration in which any of the additional bonding using the resin bonding material is applied.

  A third embodiment according to the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view showing the internal structure of the piezoelectric vibration device. In the present embodiment, as compared with the first embodiment, the configuration of the concave portion of the crystal diaphragm, the configuration of the lid, and the junction configuration of the crystal diaphragm and the lid are different. Note that the same components as those in the first embodiment are described with the same reference numerals, and a part of the description is omitted.

  The quartz vibrating plate 1 is made of an AT cut quartz vibrating element, and is a rectangular plate having a long side, a short side, and a thickness as a whole. The quartz diaphragm 1 is formed with a thin portion 1a at the center and a thick portion 1b around it, and has an inverted mesa (biconcave) configuration as a whole. The thin portion 1a is dug in the thickness direction from the front and back surfaces, and the quartz diaphragm 1 is thinned from the front and back surfaces. Excitation electrodes 11 and 12 are formed opposite to each other on the front and back of the thin portion 1a, and these excitation electrodes are led out to the thick portion 1b by extraction electrodes 11a and 12a, respectively. The extraction electrodes 11a and 12a are extracted to the side surface of the thick portion 1b.

  A tapered inclined surface 1f is formed at the boundary between the thin portion 1a and the thick portion 1b. For example, the inclined surface 1f may be formed between the thick part and the thin part of the short side, or may be formed over the entire short side and the long side. These inclined surfaces improve the mechanical strength of the quartz diaphragm, and the strain stress generated in the thick part is buffered and transmitted to the thin part, so that the distortion of the thin part can be suppressed and the characteristics can be stabilized. Further, by forming the inclined surface on the side where the extraction electrode is formed, it is possible to solve the problem of the electrode disconnection of the extraction electrode. The extraction electrode is formed of a single layer or a multilayer metal film, but by providing an inclined surface between the thin part and the thick part, these metal films can be formed reliably, and there is a problem of electrode breakage due to the boundary part. Is solved.

The thick portion 1b is configured to have a frame shape around the thin portion 1a. However, unlike the above two embodiments, the thick portion 1b does not have a circumferential metal film, and the extraction electrode has the inclined portion and the thickness. It is only drawn out to the side surface (end surface) through the main surface of the meat part.

In the present embodiment, the excitation electrode and the extraction electrode are formed by the same material and the same process. Specifically, a chromium layer is formed in contact with the quartz diaphragm, and a gold layer is formed on the chromium layer, and the metal film (electrode film) is formed by a metal film forming portion. Alternatively, it may be formed by a vacuum vapor deposition method or a sputtering method using a masking means having only an opening, or by an electrode film formation using a photolithography technique.

  The thin part of the quartz diaphragm 1 is hermetically sealed by the lids 21 and 22. The lid body 21 is formed of a lower lid body 211 in contact with the crystal diaphragm and an upper lid body 212 joined to the upper portion of the lower lid body, and the lid body 22 is similarly formed from the lower lid body 221 and the upper lid body 222. Is formed. Each of the lower cover plates 211 and 221 has a function of a buffer plate using a material having excellent buffering properties. For example, a material mainly composed of copper is used to relieve strain stress generated at the time of joining with the crystal diaphragm. It has a function.

  The upper lid plates 212 and 222 on the upper surface of the lower lid plate are preferably made of a material having a temperature coefficient similar to that of the lower lid plate, and a metal material or a ceramic material can be used. For example, when both of the upper and lower cover plates are metal, a clad material structure by rolling may be used, or a structure in which both are bonded by a bonding material may be used. The bonding material can be, for example, a resin bonding material, but the buffering function is improved by interposing the bonding material between the upper and lower cover plates.

  In the third embodiment, the lids 21 and 22 are joined to the thick part of the crystal diaphragm by a sealing glass material to hermetically seal the recess. For example, the sealing glass material is formed in advance on the quartz vibration plate side, the lid plate side, or both, and melt-bonded by heating. Examples of the sealing glass include borosilicate glass having excellent hermeticity, but it is not limited to this material.

  In this embodiment, the concave portion formed in the quartz diaphragm is hermetically sealed with a lid, but the airtight atmosphere in the concave portion uses a vacuum or an inert gas atmosphere. Each airtight atmosphere can be determined by the atmosphere at the time of airtight sealing. Note that the hermetic sealing of the recesses does not need to be performed simultaneously at the top and bottom. For example, after one recess is bonded in a nitrogen gas atmosphere, and after adjusting characteristics such as frequency adjustment to the excitation electrode of the other recess, Hermetic sealing may be performed in a gas atmosphere.

  As described above, the extraction electrodes 11a and 12a extend on the side surface (end surface) 1c of the short side of the quartz crystal diaphragm 1, and the terminal portions 31 and 32 are joined to both side surfaces, respectively. The terminal portions 31 and 32 are block-shaped or thick plate-shaped, and have a rectangular parallelepiped shape as a whole, and one side surface of each of the terminal portions 31 and 32 is joined to the side surface of the crystal diaphragm. Metal brazing materials 31a and 32a are used for joining, and the metal brazing material is formed in advance as a metal brazing layer in the joining region of the terminal portion, for example. The metal brazing material portion is brought into contact with the extraction electrodes 11a and 12a on the side surfaces of the quartz diaphragm, and fusion bonding is performed by overall heating by a heating furnace as described above or local heating by an energy beam.

In the present embodiment, relatively deep recesses 33a and 34a are formed in the terminal portion. The concave portion is for fitting a part of the thick portion 1b, and a concave portion having a size corresponding to the thickness dimension of the thick portion where the extraction electrode is formed is formed. Such a fitting configuration can improve the bonding strength.

  According to the present embodiment, since the lid has a multi-layer structure, the stress acting on the crystal resonator can be relaxed and deformation of the vibration region formed in the thin portion can be suppressed. Moreover, the problem of electrode breakage is solved by providing an inclined portion between the thin portion and the thick portion of the quartz diaphragm. Further, since the lid body is joined to the quartz crystal vibrating plate by a sealing glass material, practical and hermetic sealing can be performed at a relatively low cost, and a practical piezoelectric vibration device can be obtained.

  The terminal portion may have not only the rectangular parallelepiped shape shown in FIG. 1 but also an L-shaped configuration in a plan view partially extending to the long side or a U-shaped configuration. FIG. 5 shows a modification of the terminal portion disclosed as the fourth embodiment. The basic configuration of the fourth embodiment is the same as that of the first embodiment, but the configuration of the terminal portion is different. U-shaped terminal portions 51 and 52 are conductively joined to the short side of the quartz crystal plate 1 hermetically sealed by the lids 21 and 22. The terminal portions 51 and 52 are formed with bent portions 51a and 52a, respectively, and have a U-shaped configuration as a whole. Even in the bent portion, the bonding strength between the crystal vibrating plate and the terminal portion is improved by bonding to the end surface of the long side of the crystal vibrating plate.

  A fifth embodiment of the present invention will be described with reference to the drawings. 6 is a perspective view showing a state in which the piezoelectric vibration device is mounted on the mounting substrate P, and FIG. 7 is a cross-sectional view taken along the line BB in FIG. In this embodiment, compared to the first embodiment, the configuration of the lid, the bonding configuration of the crystal diaphragm and the lid, and the mounting configuration on the mounting substrate are different. Note that the same components as those in the first embodiment are described with the same reference numerals, and a part of the description is omitted.

  The quartz vibrating plate 1 is made of an AT cut quartz vibrating element, and is a rectangular plate having a long side, a short side, and a thickness as a whole. The quartz diaphragm 1 is formed with a thin portion 1a at a central portion and a thick portion 1b around the central portion, and has a reverse mesa (concave) configuration as a whole. The thin portion 1a is dug in the thickness direction from the front and back surfaces, and the quartz diaphragm 1 is thinned from the front and back surfaces. Excitation electrodes 11 and 12 are formed opposite to each other on the front and back of the thin portion 1a, and these excitation electrodes are led out to the thick portion 1b by extraction electrodes 11a and 12a, respectively. The extraction electrodes 11a and 12a are extracted to the side surface of the thick portion 1b.

Although the thick part 1b is a structure formed in the frame shape around the thin part 1a, it does not have a circumferential metal film, and the lead electrode passes through the main surface in the thick part, and the side surface (end face). It has only been drawn to.

In the present embodiment, the excitation electrode and the extraction electrode are formed by the same material and the same process. Specifically, a chromium layer is formed in contact with the quartz diaphragm, and a gold layer is formed on the chromium layer, and the metal film (electrode film) is formed by a metal film forming portion. Alternatively, it may be formed by a vacuum vapor deposition method or a sputtering method using a masking means having only an opening, or by an electrode film formation using a photolithography technique.

  The thin part of the quartz diaphragm 1 is hermetically sealed by lids 61 and 62. The lids 61 and 62 have a configuration in which a terminal portion joined to the short side of the crystal diaphragm is integrated, and has an L shape in plan view as shown in FIG. The L-shaped lid has sealing portions 61b and 62b that hermetically seal the concave portion formed by the thin portion and the thick portion, and terminal portions 61c and 62c in which one end of the sealing portion is bent. is doing. The terminal portions 61c and 62c are joined to the end surface of the short side of the crystal diaphragm. In the L-shaped configuration, one metal plate may be formed into an L shape having a sealing portion and a terminal portion by press molding, or a metal block is attached to the metal plate and the sealing portion and the terminal are formed. You may form in the L shape which has a part. Furthermore, a thin part and a thick part may be formed by an etching technique and used as a sealing part and a terminal part, respectively.

Moreover, you may use a ceramic for the base material of a cover body. In this case, since the terminal portion needs to have a function of drawing out the electrode, an electrode pattern is formed on the surface of the ceramic, and conductive bonding with the mounting substrate is performed by the electrode pattern. In the fifth embodiment, as shown in FIG. 6, a quartz diaphragm is erected with respect to the mounting substrate. Therefore, when an insulator such as ceramic is used for the base material of the lid, it is necessary to form an electrode pattern on the lid so that the extraction electrode drawn out on the side surface of the crystal diaphragm is drawn to the mounting substrate. In the configuration as shown in FIG. 6, it is preferable that the longitudinal dimension of the lid is increased so that the crystal diaphragm does not contact the mounting substrate.

  In the fifth embodiment, the lids 61 and 62 are bonded by a resin bonding material. It is necessary to use an insulating resin bonding material in order to avoid a short circuit between the electrodes in the bonding between the sealing portion and the crystal diaphragm. In addition, since the lead electrode is led out to the outside as described above for joining the terminal portion and the crystal diaphragm, it is necessary to use a conductive resin bonding material containing a conductive filler. Further, the sealing part and the crystal diaphragm may be joined with a sealing glass material to improve airtightness, and the terminal part and the crystal diaphragm may be joined using a conductive resin bonding material, or The sealing portion and the crystal vibration plate, and the terminal portion and the crystal vibration plate may be joined by a sealing glass material.

  In this embodiment, the concave portion formed in the quartz diaphragm is hermetically sealed with a lid, but the airtight atmosphere in the concave portion uses a vacuum or an inert gas atmosphere. Each airtight atmosphere can be determined by the atmosphere at the time of airtight sealing. Note that the hermetic sealing of the recesses does not need to be performed simultaneously at the top and bottom. For example, after one recess is bonded in a nitrogen gas atmosphere, and after adjusting characteristics such as frequency adjustment to the excitation electrode of the other recess, Hermetic sealing may be performed in a gas atmosphere.

  According to the present embodiment, since the lid has a structure in which the sealing portion and the joining portion are integrated, the airtight sealing of the reverse mesa region (recessed portion) can be achieved by simply joining the lid to the crystal diaphragm. The electrode can be derived. Further, for example, by adopting an L-shaped configuration when viewed from the long side by the sealing portion and the joining portion, it is possible to have a standing configuration that is mounted substantially perpendicular to the mounting substrate as shown in FIG. Since each lid can be used as a terminal, a piezoelectric vibration device having a small projected area can be obtained.

  The present invention is not limited to the above-described embodiment, and for example, the crystal resonator element and the excitation electrode may be circular or oval, and various modifications can be applied. The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The scope of the present invention is indicated by the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

  Applicable for mass production of crystal units.

It is a disassembled perspective view which shows 1st Embodiment by this invention. It is AA sectional drawing at the time of assembling FIG. It is an internal sectional view showing a 2nd embodiment by the present invention. It is an internal sectional view showing a 3rd embodiment by the present invention. It is a perspective view which shows 4th Embodiment by this invention. It is a perspective view which shows 5th Embodiment by this invention. It is BB sectional drawing of FIG.

Explanation of symbols

1 Quartz diaphragm 1a Thin part 1b Thick part
11, 12 Excitation electrodes 11a, 12a Extraction electrodes 21, 22, 61, 62 Lids 31, 32, 33, 34 Terminal portions

Claims (5)

It has a thin part at the center, a thick part around the thin part, an excitation electrode is formed opposite to the front and back of the thin part, and the excitation electrode is drawn out to the thick part by the extraction electrode. Piezoelectric vibration comprising a piezoelectric diaphragm, a lid that is joined to the thick part and hermetically seals the thin part, and a terminal part that is joined to the side surface of the piezoelectric diaphragm and is conductively joined to the extraction electrode device. The piezoelectric vibration device according to claim 1, wherein a circumferential metal film surrounding the thin-walled portion is formed on the thick-walled portion, and the metal film and the lid are joined by a metal brazing material. The piezoelectric vibration device according to claim 1 or 2, wherein the extraction electrode is extended to a side surface of the piezoelectric vibration plate, and the side surface and the terminal portion are joined by a metal brazing material. The piezoelectric vibrating device according to claim 1, wherein the lid has a plurality of sheets. 5. The piezoelectric vibration device according to claim 1, wherein the lid and the terminal portion are integrally configured.

Images