JP6364970B2 - Method for manufacturing piezoelectric device - Google Patents

Description

  The present invention relates to a method for manufacturing a piezoelectric device.

Conventionally, there has been known a laser welding method in which a workpiece including an element such as a crystal element or a semiconductor element or an electronic component such as a piezoelectric body is irradiated with a laser beam to weld a lid and a package.
In such a welding method, for example, as disclosed in Patent Document 1, when the laser beam passes near the corner of the lid, the lid is heated by greatly reducing the irradiation output of the laser beam. By adjusting the temperature, it was possible to suppress the occurrence of defects such as welding near the corners of the lid becoming stronger or heat being accumulated near the corners, resulting in deep welding marks and holes. Further, it was possible to suppress welding variations between the corners of the lid and other regions, to prevent a large temperature distribution on the workpiece, and to perform uniform welding.

JP 2007-31544 A

  However, in the process of sealing the package by irradiating the energy beam (laser beam) and welding the lid (lid) and the base substrate (package) on which the piezoelectric element (electronic component) is mounted, the production efficiency In order to increase the energy beam scanning speed, the energy beam scanning speed tends to increase, and in the welding method described in Patent Document 1, the energy beam irradiation output (laser output) is controlled with respect to the energy beam scanning speed. It will not catch up, causing a shift. In addition, due to the recent downsizing of products, the effect is remarkable.

  Therefore, it is difficult to accurately reduce the irradiation output of the energy beam as set at the corner (near the corner) of the lid that is set to reduce the irradiation output of the energy beam in advance. Welding has become stronger compared to the area. As a result, there has been a problem that the welding strength of the package of the piezoelectric device (work) varies and the yield of the product decreases.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following application examples or forms.

  [Application Example 1] A method of manufacturing a piezoelectric device according to the application example includes a base substrate on which a piezoelectric element is mounted, and a bonding portion is disposed so as to surround the piezoelectric element in a plan view of the piezoelectric element; A step of preparing a lid body having a corner portion, a step of placing the lid body on the joint portion so as to accommodate the piezoelectric element between the base substrate and the lid body, Irradiating a portion of the lid that overlaps the joint with an energy beam while scanning the base substrate and the lid, and in the welding step, scanning the energy The irradiation of the energy beam is stopped in front of the corner portion.

  According to the piezoelectric device manufacturing method of this application example, when the base substrate and the lid are welded, the irradiation of the energy beam is stopped before the corner portion of the lid. However, as soon as irradiation of the energy beam is started on the lid, the lid and the base substrate are heated and the temperature rises. Therefore, irradiation of the energy beam is performed before the corner portion of the lid to be welded. Even if it is stopped, there is heat generated and accumulated in the lid that has already been irradiated and heated before stopping. Since this heat is transmitted to the corner portion of the lid body to be welded from now on, the corner portion of the lid body and the base substrate can be welded to such an extent that airtightness is ensured.

  That is, according to the method for manufacturing a piezoelectric device of this application example, it is possible to reduce the intensity of welding of the corner portion of the lid body by irradiation of the energy beam, and to equalize the welding strength in the welded portion of the lid body. It becomes possible. Therefore, the heat accumulated in the lid body is prevented from staying without being released, and the distortion caused by the accumulated heat is reduced, so that damage to the base substrate can be reduced.

  Further, it is possible to reduce the case where the corner portion of the lid body becomes high temperature, the lid body is melted excessively, a leak path is formed between the lid body and the base substrate, and sealing is not completed without ensuring airtightness. . Therefore, it is possible to reliably weld the lid and the base substrate, and it is possible to reduce a decrease in product yield.

  Application Example 2 In the piezoelectric device manufacturing method according to the application example, in the preparing step, the lid body has a brazing material on one surface, and in the arranging step, the one surface It arrange | positions toward the said junction part side, It is characterized by the above-mentioned.

  According to the method for manufacturing a piezoelectric device of this application example, it is possible to lower the welding temperature as compared to the case of welding without using a brazing material. As a result, welding of the base substrate and the lid can be facilitated, and damage to the base substrate can be reduced.

  Application Example 3 In the piezoelectric device manufacturing method according to the application example described above, in the preparing step, the base substrate has a concave cavity, and the lid has a flat plate shape.

  According to the piezoelectric device manufacturing method of this application example, electronic components such as piezoelectric elements and ICs can be accommodated in the concave cavity (internal space) of the base substrate. Therefore, a piezoelectric device having a function as a timing device or a sensor device can be obtained.

  Application Example 4 In the piezoelectric device manufacturing method according to the application example described above, in the step of preparing, the base substrate has a flat plate shape, and the lid body has a cap shape.

  According to the method for manufacturing a piezoelectric device of this application example, if a piezoelectric device is manufactured using a flat base substrate and a cap-shaped lid, the piezoelectric element can be accommodated by the swelling of the lid. Thus, an internal space in which the piezoelectric element can vibrate can be secured. Further, the base substrate can be formed into a flat plate shape, and the base substrate can be easily manufactured and the cost can be reduced as compared with the case where the concave recess is provided.

  Application Example 5 In the piezoelectric device manufacturing method according to the application example described above, in the welding step, a length of 1% or more and 30% or less with respect to the length of the joint in the scanning direction of the energy beam. The irradiation with the energy beam is stopped while leaving a portion corresponding to.

  According to the method for manufacturing a piezoelectric device of this application example, when the length of the portion not irradiated with the energy beam is longer than 30% with respect to the length of the joint portion in the scanning direction of the energy beam, welding will be performed from now on. Heat is not sufficiently transmitted to the corner portion of the lid body, and the corner portion is heated and melted, and heat necessary for welding to such an extent that airtightness is ensured is insufficient.

  Further, when the length of the portion not irradiated with the energy beam is shorter than 1% with respect to the length of the joining portion in the scanning direction of the energy beam, the corner portion of the lid to be welded is melted too much. A leak path is formed between the lid and the base substrate, and airtightness is not ensured and sealing becomes incomplete.

  Application Example 6 In the method of manufacturing a piezoelectric device according to the application example, the energy beam is a laser beam in the welding step.

According to the manufacturing method of the piezoelectric device of this application example, the beam scanning speed can be increased as compared with an electron beam or the like. Therefore, the time for which the lid is exposed to high temperature can be shortened by irradiating the beam, so that the base substrate that receives heat from the lid can be reduced from being damaged by the influence of high temperature, and a highly reliable piezoelectric device is manufactured. It becomes possible to do.
Moreover, since the processing time required for welding can be shortened, manufacturing cost can be reduced.

  Application Example 7 In the piezoelectric device manufacturing method according to the application example described above, in the welding step, at least one of the corner portions is not welded but left as an unwelded portion, and the remaining corner portions are welded first. A welding step; and a second welding step of welding the unwelded portion in a reduced-pressure atmosphere.

  According to the piezoelectric device manufacturing method of this application example, in the second welding step, the portion where the lid and the base substrate are welded by irradiating the energy beam is left unwelded in the first welding step. In the second welding step, the distance to be welded is short and the heating time is also short. Therefore, as compared with the case where the outer circumference of the lid is welded in one step, the distortion due to the thermal stress generated in the lid and the base substrate during welding is reduced, so that the damage to the piezoelectric device is reduced. Can be reduced. As a result, a highly reliable piezoelectric device can be manufactured.

  Further, in the first welding step, since there is a partial region that is not welded, in the first welding step, the generated outgas is discharged outside without stagnation inside the piezoelectric device, and the degree of vacuum is reduced in the second welding step. High piezoelectric device sealing becomes possible.

Schematic which shows the structure of the laser welding apparatus used for the manufacturing method of the crystal oscillator which concerns on 1st Embodiment of this invention. The perspective view which shows the scanning locus | trajectory of the laser beam which concerns on 1st Embodiment of this invention. 1 is a cross-sectional view showing the structure of a crystal resonator according to a first embodiment of the invention. 3 is a flowchart showing a manufacturing process of the crystal resonator according to the first embodiment of the invention. Sectional drawing which shows the structure of the crystal oscillator based on the modification 1 of this invention. Explanatory drawing of the cover body sheet | seat and base board sheet | seat in the manufacture process of the crystal oscillator which concerns on the modification 2 of this invention. The perspective view which shows the scanning locus | trajectory of the laser beam which concerns on 2nd Embodiment of this invention. 9 is a flowchart showing a manufacturing process of a crystal resonator according to a second embodiment of the invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each layer and each member is made different from the actual scale so that each layer and each member can be recognized.

<First Embodiment>
A method of sealing the package of the piezoelectric device will be described along with the method of manufacturing the crystal resonator as the piezoelectric device according to the first embodiment.
In the following drawings, the same or similar components are denoted by the same or similar reference numerals. For convenience of explanation, in the plan view when seen from the direction in which the base substrate 31 and the lid 35 overlap, the surface on the lid 35 side is described as the upper surface and the surface on the base substrate 31 side is described as the lower surface.

FIG. 1 is a schematic view showing the configuration of a laser welding apparatus used in the method for manufacturing a crystal resonator according to the first embodiment of the present invention. That is, the configuration of a package welding apparatus suitable for use in the piezoelectric device manufacturing method of the present embodiment is shown.
Hereinafter, a package welding apparatus in which a package of a crystal resonator is sealed by being irradiated with a laser beam as an energy beam will be described.

<Package welding equipment>
First, referring to FIG. 1, a laser welding apparatus 10 suitable for sealing a package 30 of a crystal resonator 20 will be described as an example of a package welding apparatus.
As shown in FIG. 1, the laser welding apparatus 10 includes a laser beam source 11 as an energy beam source, a chamber 13 having a transmission part 12, and a processing stage 14. A package 30 of the crystal resonator 20 is disposed inside the chamber 13.

  Furthermore, the laser welding apparatus 10 has a compressor 17 capable of making the atmospheric pressure of the internal space 19 of the chamber 13 higher than the atmospheric pressure via the vent pipe 16a connected to the chamber 13, and the vent pipe 16b. And a vacuum pump 18 that can lower the atmospheric pressure of the internal space 19 below atmospheric pressure.

Thus, since the chamber 13 is sealed so that the atmospheric pressure of the internal space 19 can be adjusted, for example, it is higher than the atmospheric pressure while changing the atmosphere by filling with an inert gas such as N ₂ or Ar. The pressure and atmosphere of the internal space 29 of the quartz crystal resonator 20 can be freely changed by selecting the pressure to be welded if desired to be welded and the pressure being reduced to be lower than the atmospheric pressure for welding. The package 30 can be welded.

  The laser beam source 11 may be a pulse wave such as a YAG laser, but in this embodiment, a continuous wave laser capable of welding the package 30 with high reliability even when the irradiation output is lowered. A semiconductor laser oscillator from which the beam L is emitted is used.

  In the present embodiment, by selecting the laser beam L as the energy beam, the beam scanning speed can be increased as compared with an electron beam or the like. As a result, the time during which the lid 35 is heated by the beam can be shortened, so that damage to the package 30 due to the influence of heat can be reduced. Therefore, the crystal resonator 20 with high reliability can be manufactured. In addition, since the processing time is shortened, the manufacturing cost can be reduced.

  The transmission part 12 is provided on a part of the upper surface of the chamber 13, and can transmit the laser beam L emitted from the upper surface side outside the chamber 13 into the chamber 13. From this, the material of the transmitting portion 12 is at least selected from materials that transmit the laser beam L, for example, soda glass, quartz glass, polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS resin). Glass or plastic made of a material including one kind can be used.

  The chamber 13 is a member that does not deform so that the internal space 19 can be maintained at a constant pressure and a constant atmosphere, and a member that generates little gas even when heat is applied, such as iron (Fe), steel, stainless steel ( Metals such as SUS, copper (Cu), aluminum (Al), tungsten (W), molybdenum (Mo), and titanium (Ti) can be used.

<Laser sealing>
Next, an outline of laser sealing will be described. As shown in FIG. 1, the laser beam L emitted from the laser beam source 11 provided outside the chamber 13 passes through the transmission part 12 provided in the chamber 13 and is sealed in the chamber 13. The lid 35 of the crystal unit 20 placed on the processing stage 14 in the internal space 19 is irradiated.

  The lid 35 and the seam ring 34 are melted and joined to each other by transferring heat from the lid 35 that is irradiated and heated to the laser beam L to the seam ring 34 disposed on the upper surface of the base substrate 31. . Here, a portion where the base substrate 31 is bonded to the lid body 35 is referred to as a bonded portion. In this way, the base substrate 31 and the lid 35 are welded to seal the package 30 of the crystal unit 20.

The internal space 29 of the crystal unit 20 depends on the atmosphere of the internal space 19 of the chamber 13 at the time of welding. In this embodiment, the internal space 19 of the chamber 13 is depressurized to an atmosphere lower than atmospheric pressure. The internal space 29 of the crystal unit 20 is also sealed in a reduced pressure state.
Alternatively, the internal space 19 of the chamber 13 may be filled with an inert gas or the like. In that case, the internal space 29 of the crystal unit 20 is also filled with an inert gas and sealed.

  FIG. 2 is a perspective view showing the scanning trajectory of the laser beam according to the first embodiment of the present invention. As soon as the irradiation of the laser beam L is started, the temperature of the lid 35 rises. In particular, as shown in FIG. 2, the corner portions 78 located at the four corners of the lid body 35 are irradiated with the laser beam L, so that the direction in which heat is released compared to the straight portion 77. limited.

  For this reason, heat easily accumulates at the corner portion 78 of the lid 35, the temperature rises locally, the lid 35 melts too much, and a leak path occurs between the lid 35 and the base substrate 31. As a result, sealing of the package 30 may be incomplete.

  Furthermore, recently, in order to increase the production efficiency, the scanning speed of the laser beam tends to increase year by year, and the control for changing the irradiation output of the laser beam L is delayed without catching up with the scanning speed of the laser beam L. End up.

  That is, in order to adjust the temperature at which the lid 35 is heated, the irradiation output of the laser beam L is accurately controlled at the corner portion 78 of the lid 35 that is set in advance to reduce the irradiation output of the laser beam L. It is difficult to reduce. As a result, the welding strength of the crystal unit 20 varies, and the yield of the product is reduced.

  However, according to the manufacturing method of the crystal unit 20 of the present embodiment, the length of the straight portion 77 as a joint portion in the scanning direction of the laser beam L, for example, before the corner portion 78 of the lid 35 is as follows. The irradiation of the laser beam L is stopped before a portion corresponding to a length of 1% or more and 30% or less.

  As described above, the temperature of the lid 35 rises as soon as the irradiation of the laser beam L is started. Therefore, the irradiation of the laser beam L is stopped before the corner portion 78 of the lid 35 to be welded. However, in the lid body 35, there is heat generated and accumulated in a portion where the laser beam L is already irradiated and heated before the irradiation is stopped. This heat is transmitted to the corner portion 78 of the lid body 35 to be welded, so that the corner portion of the lid body and the base substrate can be welded to such an extent that airtightness is ensured.

  That is, according to the method for manufacturing the crystal resonator 20 of the present embodiment, when the base substrate 31 and the lid 35 are welded, the irradiation of the laser beam L is stopped before the corner portion 78 of the lid 35. It is possible to reduce the intensity of welding of the corner portion 78 of the lid 35 due to the irradiation of the laser beam L, and to reduce the accumulated heat without being released. Therefore, the occurrence of distortion due to the accumulated heat can be reduced, and damage to the crystal unit 20 can be reduced.

  Moreover, it can be reduced that the lid 35 is melted too much and a leak path is formed between the lid 35 and the base substrate 31 so that the sealing is not completed without ensuring airtightness. Therefore, the package 30 can be reliably welded, variation in the welding strength of the crystal resonator 20 can be reduced, and a reduction in product yield can be reduced.

<Laser beam scanning>
As shown in FIG. 2, the scanning locus 70 of the laser beam L corresponds to the four straight portions 77 corresponding to the sides of the rectangle of the lid 35 along the outer periphery of the lid 35 and the corners therebetween. 4 shows a position on the lid 35 where the laser beam L is scanned and welded to the base substrate 31.

  In the present embodiment, scanning of the laser beam L is started from any start position 71 (corner portion 78) set on the lid 35, and slightly before the next corner portion 78 in the scanning locus 70 of the laser beam L. Scanning is performed on the straight line portion 77 up to the end position 72 located at, and the irradiation of the laser beam L is stopped.

  As a method of stopping the irradiation of the laser beam L, a program of a control device (not shown) is set in advance so that the power of the laser beam source 11 is turned off or a switch for operating the irradiation stopping function is turned on. Alternatively, a shutter that blocks the laser beam L may be installed on the optical path to the lid 35 through which the laser beam L passes.

  In this way, the method of scanning the respective linear portions 77 from the start position 71 to the end position 72 on the lid 35 is repeated, and the laser beam L is sequentially scanned so as to make one round of the scanning locus 70. In the present embodiment, since the upper surface of the lid 35 is rectangular, scanning is repeated four times.

  The scanning direction of the laser beam L is changed by changing the direction of the scanning direction of the laser beam L by 90 degrees in the plane of the lid 35 by a control device (not shown) of the laser welding apparatus 10 at each corner portion 78. By doing. Further, the scanning direction of the laser beam L may be changed in the rotating direction and order.

  The scanning speed of the laser beam L is set in advance, and the start position 71 of the scanning locus 70 is set in accordance with a scanning speed pattern stored in the control device described above or a memory device (not shown) connected to the control device. To the end position 72.

  Usually, the scanning speed is rapidly accelerated for a short time immediately after the start of irradiation, and is rapidly decelerated for a short time immediately before the end of irradiation. The scanning speed is not constant over the entire scanning locus 70 except for a short time immediately after the start of irradiation and immediately before the end of the irradiation, and is set to change continuously or intermittently. Is common.

  In the present embodiment, the scanning speed is set slightly slower for the short time immediately after the start of irradiation compared to the other times, and then the scanning speed is slightly increased to maintain the constant scanning speed up to the end position 72 as it is. Is set.

<Quartz crystal>
FIG. 3 is a cross-sectional view showing the structure of the crystal resonator according to the first embodiment of the invention. Hereinafter, the crystal resonator 20 as a piezoelectric device will be described with reference to FIG.

  As shown in FIG. 3, the crystal resonator 20 includes a base substrate 31, a package 30 including a lid 35, and a crystal resonator element 60 described later. Furthermore, the base substrate 31 has a rectangular bottom plate 32 having a concave recess 38 in which a quartz crystal vibrating piece 60 is mounted in the center, and an internal space 29 formed inside the base substrate 31 and open on the lid 35 side. And a side wall 33 which is laminated on the upper surface of the bottom plate 32 and is disposed so as to surround the crystal vibrating piece 60, and a seam ring 34 which is laminated on the upper surface of the side wall 33.

  The lid 35 is placed in a state in which the bonding surface 36 side of the lower surface of the lid 35 is in close contact with the seam ring 34 of the base substrate 31 in plan view of the base substrate 31. In other words, the lid 35 is placed on the upper surface of the seam ring 34 with the bonding surface 36 facing the seam ring 34 of the base substrate 31 so as to close the opening on the upper surface of the recess 38.

  At this time, the outer edge of the outer peripheral portion 37 of the lid 35 is set smaller than the outer edge of the seam ring 34 over the entire periphery. Therefore, in the plan view of the base substrate 31, the space W between the outer edge of the outer peripheral portion 37 and the outer edge of the seam ring 34 is placed so as to be substantially constant over the entire circumference.

  The joining surface 36 of the lid 35 is provided with a brazing material (not shown) made of, for example, silver (Ag) brazing. In the welding process, the joining surface 36 of the lid 35 and the seam of the base substrate 31 are provided. The ring 34 is welded by melting the brazing material.

  By using the brazing material, it is possible to lower the temperature required for welding compared to the case where welding is performed without using the brazing material. Therefore, welding can be facilitated, damage to the package 30 including the lid 35 and the seam ring 34 can be reduced, and a highly reliable piezoelectric device can be manufactured.

The base substrate 31 is formed of an aluminum oxide ceramic green sheet that is an insulating material, and is formed by a sintering process after the forming. The base substrate 31 includes a pad electrode portion 40 provided on the upper surface of the bottom plate 32 of the base substrate 31 and a mounting electrode portion 41 provided on the lower surface of the bottom plate 32 and electrically connected to the pad electrode portion 40. And have.
The internal space 29 accommodates a crystal vibrating piece 60 as a piezoelectric element, which will be described later, and is electrically connected and fixed to the pad electrode portion 40 by applying a conductive adhesive 61.

  The pad electrode unit 40 is a pad-like electrode used for connecting to an external mounting substrate via the mounting electrode unit 41 and supplying a driving voltage to the crystal vibrating piece 60. The pad electrode portion 40 and the mounting electrode portion 41 are formed on, for example, tungsten (W) by nickel (Ni) plating and gold (Au) plating.

  The conductive adhesive 61 is obtained by adding fine particles (conductive filler) such as silver (Ag) or copper (Cu) to an epoxy-based synthetic resin agent as an adhesive component that exhibits bonding strength. . The conductive adhesive 61 is not limited to the synthetic resin agent being epoxy-based, and silicone-based, bismaleimide-based, polyimide-based conductive adhesive, and the like can be used. The fine particles are silver (Ag). A metal other than copper (Cu) may be used.

  Furthermore, a metal protruding electrode such as a gold (Au) stud bump may be used, and other conductive materials such as copper (Cu), aluminum (Al), and solder balls may be used in addition to gold (Au).

  The lid 35 is preferably made of a material that has a thermal expansion coefficient close to that of the base substrate 31 and can be easily welded. For example, the same ceramic material as the base substrate 31 or iron (Fe) and cobalt (Co) is used. An alloy such as Kovar or stainless steel can be used. Here, Kovar is used, and nickel (Ni) plating (not shown) is applied to the surface of Kovar.

The seam ring 34 is joined in advance to the upper surface of the side wall 33 of the base substrate 31 so as to surround the crystal vibrating piece 60 in a plan view of the crystal vibrating piece 60, so that the lid 35 can be easily welded to the base substrate 31. For example, the bonding material is formed of a Kovar material.
Since the melting point of Kovar constituting the lid 35 and the seam ring 34 is a high temperature of about 1450 ° C., the portion where the lid 35 and the seam ring 34 overlap is locally and quickly welded. It is desirable.

<Crystal resonator element>
Next, the crystal vibrating piece 60 as a piezoelectric element housed in the internal space 29 of the crystal resonator 20 will be described.
The quartz crystal vibrating piece 60 that is an example of a piezoelectric element uses an AT-cut quartz crystal substrate (piezoelectric substrate) that is formed of quartz as an example of a piezoelectric material. Piezoelectric materials such as quartz belong to the trigonal system and have crystal axes X, Y, and Z that are orthogonal to each other. The X axis, the Y axis, and the Z axis are referred to as an electric axis, a mechanical axis, and an optical axis, respectively.

  Then, the quartz substrate is used as the quartz crystal vibrating piece 60 along a plane obtained by rotating the XZ plane about the X axis by a predetermined angle θ. For example, in the case of an AT cut quartz substrate, θ is approximately 35 ° 15 ′. Note that the Y-axis and the Z-axis are also rotated by θ around the X-axis to become the Y′-axis and the Z′-axis, respectively. Accordingly, the AT-cut quartz substrate has crystal axes X, Y ′, and Z ′ that are orthogonal to each other.

  The AT-cut quartz substrate has a thickness direction of the Y ′ axis and an XZ ′ plane (a plane including the X axis and the Z ′ axis) orthogonal to the Y ′ axis is the main surface, and thickness shear vibration is excited as the main vibration. Is done. By processing this AT-cut quartz substrate, a piezoelectric substrate as a piezoelectric element of the quartz crystal vibrating piece 60 can be obtained.

  That is, the piezoelectric substrate is tilted in the −Y direction of the Y axis around the X axis of the orthogonal coordinate system including the X axis (electrical axis), the Y axis (mechanical axis), and the Z axis (optical axis). The axis is the Z ′ axis, the Y axis is tilted in the + Z direction of the Z axis, the Y ′ axis is composed of planes parallel to the X axis and the Z ′ axis, and the direction parallel to the Y ′ axis is the thickness. It consists of an AT-cut quartz substrate.

  Note that the piezoelectric element according to the present embodiment is not limited to the AT-cut quartz substrate having the angle θ of approximately 35 ° 15 ′ as described above, and has various forms other than the AT-cut vibrating piece, such as a tuning fork. Other piezoelectric substrates such as a mold vibrating piece, a gyro sensor vibrating piece, and a BT cut vibrating piece can also be applied.

  Also, for example, the crystal electrical axis is the X axis, the mechanical axis is the Y axis, the optical axis is the Z axis, and the X axis is rotated by α = 3 ° to 30 ° clockwise around the Z axis. A so-called double having a side parallel to the set X ′ axis and a side parallel to the Z ′ axis obtained by rotating the Z axis clockwise around β ′ = 33 ° to 36 ° around the X ′ axis. A rotation-cut quartz substrate may be used. At this time, when α = about 22 ° and β = about 34 °, an SC-cut vibrating piece is obtained.

  The quartz crystal vibrating piece 60 of the present embodiment is a rectangular vibrating piece obtained by dividing the AT-cut quartz crystal substrate. Various types of electrodes (not shown) such as excitation electrodes provided on the front and back surfaces, connection electrodes for connecting to other electrodes, and extraction electrodes for connecting the excitation electrodes and the connection electrodes are formed on the resonator element.

Furthermore, the materials are lithium tantalate (LiTaO ₃ ), lithium tetraborate (Li ₂ B ₄ O ₇ ), lithium niobate (LiNbO ₃ ), lead zirconate titanate (PZT), and zinc oxide (ZnO). Other piezoelectric materials such as aluminum nitride (AlN), and non-piezoelectric materials such as silicon (Si) and germanium (Ge) having a configuration in which a piezoelectric material is wound may be used.

<Quartz crystal manufacturing process>
Next, a flowchart of the manufacturing process of the crystal unit 20 as the piezoelectric device according to the first embodiment of the present invention, focusing on the process of welding the base substrate 31 and the lid 35, that is, the sealing process of the package 30. A description will be given below with reference to FIGS. 1 and 4.
FIG. 4 is a flowchart showing manufacturing steps of the crystal unit according to the first embodiment of the present invention.

[Step ST1 for Preparing Cover and Base Substrate]
First, in plan view of the quartz crystal vibrating piece 60, the base substrate 31 on which the seam ring 34 is disposed so as to surround the quartz crystal vibrating piece 60, the lid body 35 having the corner portion 78, the laser beam source 11, and the transmitting portion 12. And a laser welding apparatus 10 including a chamber 13 having Here, the lid body 35 and the base substrate 31 are separately manufactured and prepared.

[Step of placing lid on base substrate ST2]
The lid 35 is placed so as to overlap the upper surface of the seam ring 34 so that the crystal vibrating piece 60 is accommodated between the seam ring 34 and the lid 35 of the base substrate 31.

[Process for welding the lid and seam ring ST3]
The laser beam L emitted from the laser beam source 11 provided outside the chamber 13 is transmitted through the transmission part 12 provided on the upper surface of the chamber 13, and the processing stage of the internal space 19 sealed in the chamber 13 14, the lid 35 of the crystal resonator 20 placed on the substrate 14 is irradiated, and the lid 35 and the seam ring 34 of the base substrate 31 are welded.

  At this time, the internal space 19 of the chamber 13 in which the base substrate 31 and the lid 35 are disposed is decompressed to an atmosphere in which the atmospheric pressure is lower than the atmospheric pressure using the vacuum pump 18. Alternatively, it may be filled with an inert gas using the compressor 17 so that the atmospheric pressure is slightly higher than the atmospheric pressure.

  As described above, the scanning of the laser beam L is performed before the corner portion 78 of the lid 35, for example, 1% or more and 30% with respect to the length of the seam ring 34 of the base substrate 31 in the scanning direction of the laser beam L. This is performed by a method in which the irradiation of the laser beam L is stopped before a portion corresponding to the following length.

In this manner, the lid 35 and the seam ring 34 are heated and melted by the irradiation of the laser beam L, whereby the internal space 29 of the crystal unit 20 is hermetically cut off from the outside, and the crystal vibration The package 30 of the child 20 is sealed.
Through the above steps, the manufacturing process of the crystal unit 20 is completed, and the crystal unit 20 is completed.

  The energy beam is not limited to the laser beam L, but also includes an electron beam or other lasers.

  From the above, according to the manufacturing method of the crystal unit 20 of the present embodiment, the strength of welding is reduced at the corner portion 78 of the lid 35 and the heat accumulated by the irradiation of the laser beam L is reduced. It is possible to reduce staying without being released. Therefore, it is possible to reduce the local rise in temperature, reduce the distortion caused by the accumulated heat, and reduce the damage to the crystal unit 20.

  In addition, it is possible to reduce the incomplete sealing of the package 30 because the lid 35 is excessively melted and a leak path is formed between the lid 35 and the base substrate 31 and airtightness is not ensured. As a result, it is possible to reduce the variation in the welding strength of the crystal resonator 20 and reduce the yield reduction of the product.

(Modification 1)
FIG. 5 is a cross-sectional view showing the structure of a crystal resonator as a piezoelectric device according to Modification 1 of the present invention. Below, the manufacturing method of the crystal resonator 20a which concerns on the modification 1 is demonstrated, referring FIG. Note that the crystal resonator 20a according to Modification 1 has a package structure different from that of the crystal resonator 20 of the first embodiment. The parts common to the first embodiment will be denoted by the same reference numerals, description thereof will be omitted, and parts different from the first embodiment will be mainly described.

<Quartz crystal>
As shown in FIG. 5, the crystal resonator 20 a includes a flat base substrate 31 a, a package 30 a including a cap-shaped lid 35 a, and a crystal vibrating piece 60.
Both the base substrate 31a and the lid 35a are substantially rectangular (rectangular) in plan view of the base substrate 31a. However, the planar view shapes of the base substrate 31a and the lid 35a are not limited to a rectangle, and may be a polygon such as a hexagon or an octagon.

  The lid 35a is made of a metal plate such as stainless steel (SUS) or Kovar, and has a cap shape (cap shape) including a flange portion (collar portion) 46 on the outer periphery of the concave portion 45 that covers the crystal vibrating piece 60 by pressing. Is formed. Further, a metal film such as nickel (Ni) or gold (Au) is formed on the surface of the lid 35a by plating or the like.

  A brazing material (not shown) made of, for example, silver (Ag) brazing is provided on the lower surface of the flange portion 46 of the lid 35a. When welding, a laser beam L is applied to the brazing material. As the material melts, the lower surface of the flange portion 46 and the seam ring 34a formed in a frame shape on the upper surface of the base substrate 31a are joined. The brazing material is not limited to silver (Ag) brazing, but may be copper (Cu) brazing or gold tin (Au-Sn).

  In addition, the joining method of the base substrate 31a and the cover body 35a is not limited to this, For example, you may join using low melting glass.

  As described above, the opening of the concave portion 45 of the lid 35a is closed by the base substrate 31a, and is concave downward (toward the base substrate 31a) to form the internal space 29a. The internal space 29a accommodates the crystal vibrating piece 60 or the like as the piezoelectric element described above, and the crystal vibrating piece 60 is conductively bonded to the pad electrode portion 40 disposed on the upper surface of the base substrate 31a. The agent 61 is applied and electrically connected and fixed.

The recess 45 includes a side wall 47 and a ceiling surface 48, the ceiling surface 48 and the flange portion 46 are formed in parallel, and the wall surface of the side wall 47 is orthogonal to the ceiling surface 48 and the flange portion 46. Is formed.
In other words, when the lid 35a is welded to the base substrate 31a and the base substrate 31a is disposed horizontally, the side wall 47 is perpendicular to the base substrate 31a, that is, the angle between the upper surface of the base substrate 31a and the side wall is It is formed to be 90 degrees.

  Similarly to the first embodiment, the base substrate 31a is formed of an aluminum oxide ceramic green sheet that is an insulating material, and is formed by a sintering process after the forming. The base substrate 31a includes a mounting electrode part 41 on the lower surface.

  Examples of the constituent material of the seam ring 34a include tungsten (W), molybdenum (Mo), manganese (Mn), copper (Cu), silver (Ag), palladium (Pd), gold (Au), and platinum (Pt). A metal material such as can be used.

  From the above, according to the crystal resonator 20a of the present modification, the flat plate-shaped base substrate 31a and the cap-shaped lid 35a are provided, and therefore the quartz crystal vibrating piece 60 vibrates due to the swelling of the lid. Possible internal space can be secured. In addition, the base substrate 31a can be formed in a flat plate shape, which makes it easier to manufacture the base substrate and reduce the cost as compared with the case where the concave portion is provided.

(Modification 2)
FIG. 6 is an explanatory diagram of a lid sheet and a base substrate sheet in the manufacturing process of the crystal resonator according to the second modification of the present invention. Hereinafter, a method for manufacturing the crystal resonator 20 as the piezoelectric device according to the second modification will be described with reference to FIG. The parts common to the first embodiment will be denoted by the same reference numerals, description thereof will be omitted, and parts different from the first embodiment will be mainly described.

<Quartz crystal manufacturing process>
As shown in FIG. 6, a sheet-like base substrate sheet 51 in which a plurality of base substrates 31 are arranged at a predetermined interval, and a sheet shape that is cut into a size corresponding to the base substrate 31 to become a lid 35. The lid sheet 55 is prepared.

  Similarly to the first embodiment, each base substrate 31 of the base substrate sheet 51 includes a quartz crystal vibrating piece 60 mounted by applying a conductive adhesive 61 to the concave portion 38 at the center on the upper surface side, and a quartz crystal vibration. And a seam ring 34 arranged in a frame shape on the upper surface side so as to surround the piece 60.

  The position is adjusted so that the individual base substrates 31 and the individual lid bodies 35 overlap, and the lid body sheet 55 is placed on the upper surface of the seam ring 34 of the base substrate sheet 51.

  Next, the laser beam L is irradiated toward the lid body sheet 55 corresponding to the portion overlapping the seam ring 34 of the base substrate sheet 51, and the base substrate sheet 51 and the lid body are scanned by the laser beam L scanning method described above. The sheet 55 is welded together.

  Next, the body sheet 55 and the base substrate sheet 51 which are integrated by welding are cut and divided into pieces by dicing or the like according to the outer shape of the crystal resonator 20. In this way, a plurality of crystal resonators 20 can be obtained at one time.

  From the above, according to the method for manufacturing the crystal unit 20 of the present invention, the surface area of the lid that is irradiated with the laser beam L is increased to have a sheet shape. The heat generated by the irradiation with the laser beam L is easily released to the peripheral lid sheet 55.

  Therefore, in the corner portion 78 of the lid 35, distortion due to thermal stress can be reduced, and damage to the package 30 can be reduced. As a result, it is possible to reduce the variation in the welding strength of the crystal unit 20 and to reduce the product yield.

Second Embodiment
As an example of a method for manufacturing a crystal resonator as a piezoelectric device according to the second embodiment of the present invention, a method for sealing the package 30 of the crystal resonator 20 along the method for manufacturing a crystal resonator will be described. In addition, about a common part with 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted and it demonstrates centering on a different part from 1st Embodiment.

  In the present embodiment, the welding process described in the first embodiment is divided into two stages, a first welding process (ST3) and a second welding process (ST5), so that the internal space of the crystal unit 20 is obtained. 29 can be sealed in an atmosphere (substantially vacuum) at atmospheric pressure lower than atmospheric pressure. This will be described below.

<Laser beam scanning>
FIG. 7 is a perspective view showing a scanning locus of a laser beam according to the second embodiment of the present invention.
First, as shown in FIG. 7, scanning of the laser beam L is started from the start position 71 set in any one of the linear portions 77, and is scanned to the end position 72 located slightly before the next corner portion 78, The irradiation of the laser beam L is stopped. In this way, the scanning method described above is repeated one after another in another linear portion 77, and the scanning locus 70 is scanned so as to make one round of the outer periphery of the lid 35.

  At this time, a certain one corner part 78 is left without welding, and another area is welded. That is, the scanning is performed toward the first linear portion 77 to the first end position 73 positioned before the start position 71 so as to make a round of the outer peripheral portion 37 of the lid 35. This process is called a first welding process.

  Next, the scanning is started from the second start position 75 located slightly before the first end position 73 so that the scanning locus 70 scanned with the laser beam L in the first welding process partially overlaps, and the lid body Scanning is performed along the outer periphery of 35 to the second end position 76 slightly past the start position 71 of the linear portion 77 where welding is first started. This process is called a second welding process. That is, sealing of the crystal unit 20 is completed through the first welding process and the second welding process.

<Quartz crystal manufacturing process>
FIG. 8 is a flowchart showing manufacturing steps of the crystal unit 20 according to the second embodiment of the present invention. About the manufacturing method of the crystal oscillator as the piezoelectric device according to the second embodiment of the present invention, the process of welding the base substrate 31 and the lid 35, that is, the sealing process, with reference to FIG. A manufacturing method that divides the process into two steps will be described below.

  Also in the second embodiment, since ST1 and ST2 described above in the first embodiment are the same, description thereof is omitted.

[Step of welding lid and seam ring (first welding step) ST3]
First, in an atmosphere filled with an inert gas and having an atmospheric pressure higher than atmospheric pressure, the laser beam L is irradiated along the scanning locus 70, leaving a partial region 80 of the lid 35, and the lid 35 and the base substrate. The 31 seam rings 34 are melted together, and the lid 35 and the seam ring 34 of the base substrate 31 are welded.

  In this state, the internal space 29 of the base substrate 31 communicates with the internal space 19 of the chamber 13 via a partial region 80 that remains without being welded, that is, between the lid 35 and the seam ring 34. It is in a state.

[Step of Depressurizing Internal Space of Base Substrate ST4]
Next, the pressure in the internal space 19 of the chamber 13 is reduced to a pressure lower than the atmospheric pressure by the vacuum pump 18 connected to the chamber 13. Here, in ST3, the lid 35 and the base substrate 31 that are welded while leaving the partial region 80 of the scanning locus 70 unwelded are placed in an atmosphere having a pressure lower than atmospheric pressure, for example, a reduced pressure atmosphere of about 10 Pa. Deploy.

  The air in the internal space 29 of the base substrate 31 has a pressure lower than the atmospheric pressure through a partial region 80 left without welding, that is, between the lid 35 and the seam ring 34 of the base substrate 31. It is discharged to the internal space 19 side of the chamber 13 that is in a reduced pressure atmosphere.

  Thereby, the internal space 29 of the base substrate 31 becomes the same atmosphere as the internal space 19 side of the chamber 13, that is, a reduced-pressure atmosphere having a lower atmospheric pressure than the atmospheric pressure. Note that the internal space 19 of the chamber 13 is not limited to a reduced-pressure atmosphere lower than the atmospheric pressure, and may be an inert gas atmosphere as in the first embodiment.

[Step of welding lid and seam ring (second welding step) ST5]
Next, the laser beam L is irradiated to a partial region 80 of the lid 35 that is left without being welded, and the lid 35 and the seam ring 34 of the base substrate 31 are melted together. The seam ring 34 of the base substrate 31 is welded while ensuring airtightness.

  In this step, scanning is started from the second start position 75 so that the scanning locus 70 scanned in ST3 partially overlaps, and the start position 71 of the first linear portion 77 is slightly set along the outer periphery of the lid 35. Scan to the second end position 76 that has passed.

  In this way, the seam ring 34 is irradiated with the laser beam L and the seam ring 34 is melted, whereby the base substrate 31 and the lid 35 are welded, and the internal space 19 is hermetically shut off from the outside. The package 30 of the crystal unit 20 is sealed. Thus, the manufacturing process of the crystal unit 20 is completed, and the crystal unit 20 in which the atmosphere in the internal space 29 is an atmosphere (substantially vacuum) lower than the atmospheric pressure is completed.

  In the present embodiment, as shown in FIG. 7, the remaining region is welded to the package 30 while leaving a partial region 80 of the lid 35. That is, in ST3, a partial region 80 that is not partially welded is formed. Such a partial region 80 may be one place as shown in FIG. 7, two places, or more, but if it is too many, subsequent operations become complicated. In ST3, it is preferable that the partial region 80 that is not partially welded is made small enough to allow ventilation between the internal space 29 of the package 30 and the outside.

  Further, the portion where the lid 35 and the base substrate 31 are welded by the laser beam L of ST5 is a partial region 80 of the lid 35 that is left without being welded in ST3, and therefore the welding distance is long. Short and heating time is short. Accordingly, since the distortion due to the thermal stress generated during welding is reduced as compared with the case where the outer periphery of the lid 35 is turned around in one step and welded, damage to the package 30 can be reduced. As a result, it is possible to reduce the variation in the welding strength of the crystal unit 20 and to reduce the product yield.

  In ST3, since there is a partial region 80 that is not welded, the time for heating the lid 35 is shortened in ST5 without stagnating the outgas generated in ST3 inside the crystal resonator 20, Compared with the case where the outer periphery of the lid 35 is welded in one step, the generation of outgas is reduced, and the crystal resonator 20 having a high degree of vacuum can be sealed. As a result, the crystal resonator 20 having a low CI (crystal impedance) value can be obtained.

  DESCRIPTION OF SYMBOLS 10 ... Laser welding apparatus, 11 ... Laser beam source, 12 ... Transmission part, 13 ... Chamber, 14 ... Processing stage, 16a ... Vent pipe, 16b ... Vent pipe, 17 ... Compressor, 18 ... Vacuum pump, 19 ... Internal space, DESCRIPTION OF SYMBOLS 20 ... Crystal oscillator, 29 ... Internal space, 30 ... Package, 31 ... Base substrate, 32 ... Bottom plate, 33 ... Side wall, 34 ... Seam ring, 35 ... Lid, 36 ... Joining surface, 37 ... Outer peripheral part, 38 ... Recessed part 40 ... Pad electrode part 41 ... Mounted electrode part 45 ... Recessed part 46 ... Flange part (collar part) 47 ... Side wall 48 ... Ceiling surface 51 ... Base substrate sheet 55 ... Cover sheet 60 ... Crystal vibrating piece 61 ... Conductive adhesive, 70 ... Scanning locus, 71 ... Start position, 72 ... End position, 73 ... First end position, 75 ... Second start position, 76 ... Second end position, 77 ... Linear part, 8 ... corner section, 80 ... partial region, L ... laser beam, W ... interval.

Claims (8)

A step of preparing a base substrate on which a piezoelectric element is mounted and a joint portion is disposed so as to surround the piezoelectric element in a plan view of the piezoelectric element, and a rectangular lid in a plan view ;
Placing the lid over the joint so as to accommodate the piezoelectric element between the base substrate and the lid; and
Irradiating a portion of the lid that overlaps the joint with an energy beam while scanning, and welding the base substrate and the lid,
The joint portion includes a straight line portion along each side of the rectangle in a plan view, and a corner portion where the straight line portions intersect each other,
In the welding step, the energy beam is scanned along the straight line portion, irradiation of the energy beam is stopped before the corner portion , and the energy beam is irradiated between the front side and the corner portion. A method for manufacturing a piezoelectric device , wherein the base substrate and the lid are welded without irradiation . The straight portion includes a first straight portion and a second straight portion along a first direction, and a third straight portion and a fourth straight portion along a second direction intersecting the first direction, Including,
The corner portion includes a first corner portion where the first straight portion and the third straight portion intersect, and a second corner portion where the first straight portion and the fourth straight portion intersect. Including
In the welding step, the energy beam is scanned from the first corner portion along the first straight portion, and irradiation of the energy beam is stopped before the second corner portion. Item 2. A method for manufacturing a piezoelectric device according to Item 1. In the step of preparing, the lid body has a brazing material on one side;
3. The method of manufacturing a piezoelectric device according to claim 1, wherein, in the step of arranging, the one surface is arranged toward the joint portion side. In the step of the preparing, the base substrate has a concave cavity, method for manufacturing a piezoelectric device according to any one of claims 1 to 3, wherein the lid is a flat plate shape. In the step of the preparing, the base substrate is a flat plate, the lid manufacturing method of the piezoelectric device according to any one of claims 1 to 3, characterized in that a cap-shaped. In the welding step, the energy beam is scanned along the straight portion, and a portion corresponding to a length of 1% to 30% with respect to the length of each straight portion before the corner portion. leaving, the energy beam method for manufacturing a piezoelectric device according to any one of claims 1 to 5, characterized in that stops the irradiation of. Wherein in the step of welding, method for manufacturing a piezoelectric device according to any one of claims 1 to 6, characterized in that said energy beam is a laser beam. In the welding step, at least one of the corner portions is not welded but left as an unwelded portion, and the first welding step of welding the remaining corner portions;
Method for manufacturing a piezoelectric device according to any one of claims 1 to 7, characterized in that it comprises a second welding step of welding at a reduced pressure atmosphere the unwelded portion.

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