JP2009232376A - Method of manufacturing piezoelectric oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a piezoelectric oscillator capable of minimizing frequency variation. <P>SOLUTION: A piezoelectric oscillating piece 10, which includes an oscillating arm 16 and in which a metal film 34 and an exciting electrode film 24 are formed in the oscillating arm 16, is prepared. By forming ruggedness on the metal film 34 using a laser beam, a surface area of the metal film 34 is enlarged. The piezoelectric oscillating piece 10 is mounted in a package 40 thereafter. The metal film 34 is etched by an ion beam thereafter. An internal space of the package 40 is air-tightly sealed thereafter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

Conventionally, it is known that a weight made of a metal film is formed at the tip of a vibrating arm of a piezoelectric vibrating piece, and the frequency is adjusted by adjusting the weight of the vibrating arm by evaporating the metal film with a laser beam ( However, Patent Document 1) has a problem that the evaporated metal material is reattached, which may cause contamination of components and fluctuation of characteristics. Further, when the completed piezoelectric vibrator is exposed to a high temperature, the reattached metal material may evaporate and a frequency change may occur. Here, a manufacturing method is considered in which after the frequency coarse adjustment by the laser beam, the piezoelectric vibrating piece is attached to the package, and then the metal film is removed by ion beam etching to finely adjust the frequency. However, since the frequency adjustment rate by ion beam etching is low, the time required for ion beam etching becomes long. Alternatively, after the piezoelectric vibrating piece is attached to the package, it is necessary to further provide a frequency fine adjustment step using a laser beam before ion beam etching.
JP 2003-133879 A

  An object of the present invention is to provide a method of manufacturing a piezoelectric vibrator capable of minimizing frequency changes.

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 forms or application examples.
[Application Example 1] A method of manufacturing a piezoelectric vibrator according to this application example is as follows:
(A) preparing a piezoelectric vibrating piece having a vibrating arm and having a metal film and an excitation electrode film formed on the vibrating arm;
(B) expanding the surface area of the metal film by forming irregularities on the metal film with a laser beam;
(C) After the step (b), attaching the piezoelectric vibrating piece to a package;
(D) After the step (c), the step of etching the metal film with an ion beam;
(E) after the step (d), hermetically sealing the internal space of the package;
including. According to the present invention, since the metal film is etched by the ion beam after the piezoelectric vibrating piece is attached to the package, the metal material evaporated and reattached by the laser beam can be removed. Further, the frequency can be finely adjusted by the ion beam. Furthermore, since the unevenness is formed on the metal film with the laser beam, the area irradiated with the ion beam is increased, and the etching time by the ion beam can be shortened.
[Application Example 2] In the method of manufacturing a piezoelectric vibrator according to this application example,
In the step (a), a plurality of the piezoelectric vibrating pieces are prepared in a mutually connected state,
Performing the step (b) on a plurality of the piezoelectric vibrating pieces connected to each other;
After the step (b) and before the step (c), the method further includes a step of cutting the plurality of piezoelectric vibrating pieces into individual pieces,
In the step (c), the piece of the piezoelectric vibrating piece is attached to the package.
[Application Example 3] In the method of manufacturing a piezoelectric vibrator according to this application example,
In the step (b), the material of the metal film is evaporated by the laser beam to form a concave portion, and the evaporated material is reattached to the metal film to form a convex portion.
Application Example 4 In the method for manufacturing a piezoelectric vibrator according to the application example,
In the step (d), the metal film is irradiated with the ion beam through a mask.
Application Example 5 In the method for manufacturing a piezoelectric vibrator according to this application example,
The package has an opening and a through hole;
In the step (c), the piezoelectric vibrating piece is attached to the package from the opening, and a lid is attached to the opening.
In the step (d), the ion beam is irradiated to the metal film through the through hole,
In the step (e), the through hole is closed.
Application Example 6 In the method for manufacturing a piezoelectric vibrator according to the application example,
The package has an opening;
In the step (c), the piezoelectric vibrating piece is attached to the package from the opening, and a lid is attached to the opening.
The lid has a through hole;
In the step (d), the ion beam is irradiated to the metal film through the through hole,
In the step (e), the through hole is closed.

(First embodiment)
FIG. 1 is a plan view showing a part of an assembly of piezoelectric vibrating reeds prepared by the method for manufacturing a piezoelectric vibrator according to the first embodiment of the present invention. 2 is a cross-sectional view of the piezoelectric vibrating piece shown in FIG. 1 taken along the line II-II. FIG. 3 is a view showing a part of a cross section taken along line III-III of the piezoelectric vibrating piece shown in FIG. 4-7 is a figure explaining the manufacturing method of the piezoelectric vibrator which concerns on embodiment of this invention.

  Although one piezoelectric vibrating piece 10 is shown in FIG. 1, in this embodiment, an assembly of a plurality of piezoelectric vibrating pieces 10 is prepared. The aggregate is made of a piezoelectric material (crystal, lithium tantalate, lithium niobate, etc.). The assembly has a connecting portion 12 of a plurality of piezoelectric vibrating pieces 10.

  The piezoelectric vibrating piece 10 includes a base portion 14 and a vibrating arm 16 extending from the base portion 14. The piezoelectric vibrating piece 10 illustrated in FIG. 1 includes a pair of vibrating arms 16, but may include only one vibrating arm or may include three or more vibrating arms. The vibrating arm 16 may be formed with grooves 18 (see FIG. 8) extending in the longitudinal direction on the front and back surfaces. Since the vibrating arm 16 is easily moved by the groove 18 and vibrates efficiently, the CI value can be lowered.

  The piezoelectric vibrating piece 10 may have a pair of support arms 20. The pair of support arms 20 extend in directions opposite to the direction in which the vibrating arm 16 extends from the base portion 14 and extend in directions opposite to each other, and further bend and extend in the direction in which the vibrating arm 16 extends from the base portion 14. By bending, the support arm 20 is reduced in size. The support arm 20 is a part attached to a package 40 (described later), and the attachment of the support arm 20 causes the vibrating arm 16 and the base 14 to be in a floating state.

  A pair of cuts 22 are formed in the base 14 so as to face each other so that a shape confined to the surface on the same side as the front and back surfaces of the vibrating arm 16 appears. The pair of cuts 22 is formed in the base portion 14 adjacent to the pair of support arms 20 on the side where the pair of support arms 20 extends from the base portion 14 and bends. Since the transmission of the vibration of the vibrating arm 16 is blocked by the notch 22, it is possible to suppress the vibration from being transmitted to the outside (vibration leakage) via the base portion 14 and the support arm 20, and to prevent the CI value from increasing. . As the length (depth) of the notch 22 is longer (deeper) within a range in which the strength of the base portion 14 can be secured, the vibration leakage suppressing effect is larger.

  An excitation electrode film 24 is formed on the vibrating arm 16. The excitation electrode film 24 may have a multilayer structure including a base Cr film and an Au film formed thereon. The Cr film has high adhesion to the crystal, and the Au film has low electrical resistance and is difficult to oxidize. The excitation electrode film 24 constitutes first and second excitation electrodes 26 and 28.

  The first excitation electrode 26 is formed in the groove 18. The first excitation electrode 26 formed in the groove 18 on one side (for example, the front surface) of the front and back surfaces is electrically connected to the first excitation electrode 26 formed in the groove 18 on the other side (for example, the back surface) of the front and back surfaces. Has been. That is, the pair of first excitation electrodes 26 formed on the front and back surfaces are electrically connected. The pair of first excitation electrodes 26 formed on one vibrating arm 16 is connected to extraction electrodes 30 formed on the front and back surfaces on the base portion 14. These lead electrodes 30 are electrically connected by being connected to the second excitation electrode 28 of the other vibrating arm 16.

  The second excitation electrode 28 is formed on the side surface (surface connected to the front and back surfaces) of the vibrating arm 16. The second excitation electrodes 28 formed on both side surfaces of the vibrating arm 16 facing away from each other are electrically connected. The electrical connection is made by a connection electrode 32 formed on at least one (or both) of the front and back surfaces of the vibrating arm 16 where the groove 18 is not formed.

  The first excitation electrode 26 formed on one vibrating arm 16 and the second excitation electrode 28 formed on the other vibrating arm 16 are electrically connected by a lead electrode 30 on the base 14. . The extraction electrode 30 is formed up to the support arm 20 arranged next to the vibrating arm 16 where the second excitation electrode 28 is formed. The extraction electrode 30 is formed on the front and back surfaces (or further side surfaces) of the support arm 20. On the support arm 20, the extraction electrode 30 can be used as an electrical connection portion with the outside.

  On the vibrating arm 16, a metal film 34 is formed on at least one of the front and back surfaces (specifically, the tip portion). The metal film 34 is made of Au, Ag, Al or the like. The metal film 34 is directly formed on the surface of the material constituting the vibrating arm 16. The metal film 34 is formed avoiding the excitation electrode film 24 (in a non-contact manner). The metal film 34 plays the role of a weight of the vibrating arm 16, and the weight of the weight can be adjusted by removing a part thereof. The heavier the weight, the lower the vibration frequency of the vibrating arm 16, and the lighter the vibration frequency of the vibrating arm 16 becomes. This can be used to adjust the frequency.

  The method for manufacturing the piezoelectric vibrator may include the process of forming the piezoelectric vibrating piece 10 described above. The piezoelectric vibrating piece 10 is formed from a wafer of the constituent material. For example, when the piezoelectric vibrating piece 10 is made of quartz, the quartz wafer rotates in the range of 0 to 5 degrees clockwise around the Z axis in an orthogonal coordinate system composed of the X, Y, and Z axes. A crystal Z plate cut out by cutting and polishing to a predetermined thickness is used. A plurality of piezoelectric vibrating pieces 10 are cut out from one wafer in a connected state. Further, the excitation electrode film 24 and the metal film 34 are formed on the piezoelectric vibrating piece 10.

  As shown in FIGS. 2 and 3, in the present embodiment, the material of the metal film 34 is evaporated with a laser beam to form the recess 36. The recess 36 may be further advanced to form a through hole. By removing a part of the metal film 34 with the laser beam (forming the recess 36), the vibrating arm 16 can be lightened and easily vibrated, and the frequency can be adjusted. The frequency adjustment process performed on the metal film 34 is intended for rough adjustment, and can be called rough adjustment.

  Further, the material evaporated during the formation of the concave portion 36 is reattached to the metal film 34 to form the convex portion 38. By forming the concave portions 36 and the convex portions 38, the metal film 34 is formed with irregularities, and the surface area of the metal film 34 is increased. This step is performed simultaneously on the plurality of piezoelectric vibrating pieces 10 connected to each other. The convex portion 38 is formed around the concave portion 36. Therefore, the contour (dotted line) of the convex portion 38 in FIG. 2 is deviated in the ± Y-axis direction from the section taken along the line II-II. Similarly, the contour (dotted line) of the convex portion in FIG. 3 is deviated in the ± X axis direction from the section taken along the line III-III.

  As shown in FIG. 4, the plurality of piezoelectric vibrating pieces 10 are cut into individual pieces. For example, the connecting part 12 is cut. This step is performed after the laser beam processing described above is performed.

  As shown in FIG. 5, the individual piezoelectric vibrating piece 10 is attached to the package 40. The package 40 includes a bottom portion 42 to which the piezoelectric vibrating piece 10 is fixed and a frame wall portion 44 surrounding the bottom portion 42, and the inside of the frame wall portion 44 is an opening. The piezoelectric vibrating piece 10 is fixed to the bottom portion 42.

  As shown in FIG. 6, the metal film 34 is etched by an ion beam. Argon ions may be used as ions. The ion beam is applied to the metal film 34 through the mask 43. By using the mask 43, the excitation electrode film 24 is prevented from being irradiated with the ion beam.

  According to the present embodiment, since the metal film 34 is etched by the ion beam after the piezoelectric vibrating piece 10 is attached to the package 40, the metal material evaporated and reattached by the laser beam can be removed. Further, the frequency can be finely adjusted by the ion beam. Furthermore, since the metal film 34 is first formed with irregularities by the laser beam, the area of the metal film 34 irradiated with the ion beam is increased, and the etching time by the ion beam can be shortened.

  As shown in FIG. 7, the internal space of the package 40 is hermetically sealed. For example, the frame wall 44 and the lid 46 of the package 40 are joined by seam welding. Thus, the opening of the package 40 is closed by the lid 46. After the opening of the package 40 is closed by the lid 46, the inside of the package 40 closed by the lid 46 is evacuated through the through hole 48 formed in the package 40, and then the through hole 48 is closed by the brazing material 50. .

  FIG. 7 is also a diagram showing the piezoelectric vibrator manufactured by the method according to the embodiment of the present invention. In the piezoelectric vibrating piece 10 incorporated in the piezoelectric vibrator, a recess 36 is formed in the metal film 34. The recess 36 may be a through hole, and the front and back surfaces of the vibrating arm 16 may be exposed.

  The piezoelectric vibrator has a package 40. The package 40 includes a bottom portion 42 to which the piezoelectric vibrating piece 10 is fixed, and a frame wall portion 44 surrounding the bottom portion 42. A through hole 48 for evacuation is formed in the bottom portion 42, and the through hole 48 is closed with a brazing material 50 (AuGe or the like).

  The piezoelectric vibrating piece 10 is fixed to the bottom 42 of the package 40. The support arm 20 is fixed to the bottom portion 42, and the vibrating arm 16 is lifted from the package 40. The bottom 42 has a low area facing the tip of the vibrating arm 16 so that the bottom 42 is difficult to contact the bottom 42 even if the vibrating arm 16 is bent. Using the conductive adhesive 52, the lead electrode 30 (see FIG. 1) on the support arm 20 and the wiring 54 formed on the bottom 42 are electrically connected. The wiring 54 is electrically connected to the external electrode 56 on the bottom surface of the package 40. The piezoelectric vibrating piece 10 has two support arms 20, two external electrodes 56 are formed on the package 40, and the lead electrode 30 on one support arm 20 is electrically connected to one external electrode 56. The lead electrode 30 on the other support arm 20 is electrically connected to the other external electrode 56. The external electrode 56 is electrically connected by solder and mounted on a circuit board (not shown).

  The package 40 may be entirely formed of metal, but when it is mainly formed of nonmetal such as ceramics, the upper end surface of the frame wall portion 44 is metallized. For example, a Mo (or W) film, a Ni film, and an Au film are sequentially laminated on the non-metal part of the frame wall part 44, and the upper end surface is made of Au. The upper end surface has a shape surrounding the bottom 42.

  FIG. 8 is a diagram for explaining the operation of the piezoelectric vibrating piece according to the present embodiment. In the present embodiment, one side end of the vibrating arm 16 is extended and the other side end is contracted to bend and vibrate the vibrating arm 16. Specifically, a voltage is applied to the first and second excitation electrodes 26 and 28 of one vibrating arm 16, and a voltage is applied to the first and second excitation electrodes 26 and 28 of the other vibrating arm 16. Here, the first excitation electrode 26 of one (left side) vibrating arm 16 and the second excitation electrode 28 of the other (right side) vibrating arm 16 have the same potential (+ potential in the example of FIG. 8), and one ( The first excitation electrode 28 is set so that the second excitation electrode 28 of the left vibration arm 16 and the first excitation electrode 26 of the other (right) vibration arm 16 have the same potential (-potential in the example of FIG. 8). The electrode 26 and the second excitation electrode 28 are connected to an AC power supply by a cross wiring, and an alternating voltage as a drive voltage is applied. An electric field is generated by the applied voltage as shown by an arrow in FIG. 8, whereby the vibrating arms 16 are excited so as to be in reverse-phase vibration with each other (so that the distal ends of the vibrating arms 16 approach and separate from each other). Bends and vibrates. The alternating voltage is adjusted so as to vibrate in the basic mode.

  An oscillator or a sensor can be configured using the piezoelectric vibrator described above. When an oscillator is constituted by an oscillation circuit including a piezoelectric vibrator, an AC signal with high frequency accuracy can be obtained. A sensor using a piezoelectric vibrator is a sensor that detects a physical quantity by utilizing the fact that the frequency of the piezoelectric vibrating piece 10 varies according to the physical quantity. For example, a sensor that detects stress generated by temperature, acceleration, Coriolis force generated by angular velocity, and the like can be given as an example.

(Second Embodiment)
FIG. 9 is a diagram for explaining a method of manufacturing a piezoelectric vibrator according to the second embodiment of the invention. In the present embodiment, the package 40 described above is used, and the piezoelectric vibrating piece 10 is attached to the package 40 through the opening. A lid 146 is attached to the opening of the package 40. The lid 146 has a through hole 148. The through hole 148 is opposed to the metal film 34 (particularly, the concave portion 36 and the convex portion 38). Then, the metal film 34 is irradiated with an ion beam through the through hole 148. That is, the through hole 148 of the lid 146 is used as a mask. Thereafter, the through hole 148 is closed. Other details correspond to the contents described in the first embodiment.

(Third embodiment)
FIG. 10 is a diagram for explaining a method of manufacturing a piezoelectric vibrator according to the third embodiment of the invention. The package 240 used in this embodiment has a through hole 248 in addition to the opening. The piezoelectric vibrating piece 10 is attached to the package 240 from the opening. In this example, unlike the first and second embodiments, the piezoelectric vibrating piece 10 is attached so that the metal film 34 faces the package 240. Specifically, the metal film 34 (particularly, the concave portion 36 and the convex portion 38) is opposed to the through hole 248. Then, a lid 46 is attached to the opening. Then, the ion beam is irradiated to the metal film 34 through the through hole 248 of the package 240. That is, the through hole 248 of the package 240 is used as a mask. Thereafter, the through hole 248 is closed. Other details correspond to the contents described in the first embodiment.

  The present invention is not limited to the above-described embodiments, and various modifications can be made. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and results). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

FIG. 1 is a plan view showing a part of an assembly of piezoelectric vibrating reeds prepared by the method for manufacturing a piezoelectric vibrator according to the first embodiment of the present invention. 2 is a cross-sectional view of the piezoelectric vibrating piece shown in FIG. 1 taken along the line II-II. FIG. 3 is a diagram illustrating a part of a cross section taken along line III-III of the piezoelectric vibrating piece illustrated in FIG. 1. FIG. 4 is a diagram illustrating a method for manufacturing a piezoelectric vibrator according to an embodiment of the present invention. FIG. 5 is a diagram illustrating a method for manufacturing a piezoelectric vibrator according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a method for manufacturing a piezoelectric vibrator according to an embodiment of the present invention. FIG. 7 is a diagram for explaining a method of manufacturing a piezoelectric vibrator according to an embodiment of the present invention. FIG. 8 is a diagram for explaining the operation of the piezoelectric vibrating piece according to the present embodiment. FIG. 9 is a diagram for explaining a method of manufacturing a piezoelectric vibrator according to the second embodiment of the invention. FIG. 10 is a diagram for explaining a method of manufacturing a piezoelectric vibrator according to the third embodiment of the invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Piezoelectric vibration piece, 12 ... Connection part, 14 ... Base part, 16 ... Vibration arm, 18 ... Groove, 20 ... Support arm, 22 ... Notch, 24 ... Excitation electrode film, 26 ... First excitation electrode, 28 ... First 2 excitation electrode, 30 ... extraction electrode, 32 ... connection electrode, 34 ... metal film, 36 ... concave part, 38 ... convex part, 40 ... package, 42 ... bottom part, 43 ... mask, 44 ... frame wall part, 46 ... lid 48 ... Through hole, 50 ... Brazing material, 52 ... Conductive adhesive, 54 ... Wiring, 56 ... External electrode, 146 ... Cover, 148 ... Through hole, 240 ... Package, 248 ... Through hole

Claims (6)

(A) preparing a piezoelectric vibrating piece having a vibrating arm and having a metal film and an excitation electrode film formed on the vibrating arm;
(B) expanding the surface area of the metal film by forming irregularities on the metal film with a laser beam;
(C) After the step (b), attaching the piezoelectric vibrating piece to a package;
(D) After the step (c), the step of etching the metal film with an ion beam;
(E) after the step (d), hermetically sealing the internal space of the package;
The manufacturing method of the piezoelectric vibrator containing this. In the manufacturing method of the piezoelectric vibrator according to claim 1,
In the step (a), a plurality of the piezoelectric vibrating pieces are prepared in a mutually connected state,
Performing the step (b) on a plurality of the piezoelectric vibrating pieces connected to each other;
After the step (b) and before the step (c), the method further includes a step of cutting the plurality of piezoelectric vibrating pieces into individual pieces,
A method of manufacturing a piezoelectric vibrator in which the individual piezoelectric vibrating pieces are attached to the package in the step (c). In the manufacturing method of the piezoelectric vibrator according to claim 1 or 2,
In the step (b), a method of manufacturing a piezoelectric vibrator in which, in the step (b), the material of the metal film is evaporated with the laser beam to form a concave portion, and the evaporated material is reattached to the metal film to form a convex portion. In the manufacturing method of the piezoelectric vibrator according to any one of claims 1 to 3,
In the step (d), the piezoelectric vibrator is manufactured by irradiating the metal film with the ion beam through a mask. In the manufacturing method of the piezoelectric vibrator according to any one of claims 1 to 3,
The package has an opening and a through hole;
In the step (c), the piezoelectric vibrating piece is attached to the package from the opening, and a lid is attached to the opening.
In the step (d), the ion beam is irradiated to the metal film through the through hole,
A method of manufacturing a piezoelectric vibrator that closes the through hole in the step (e). In the manufacturing method of the piezoelectric vibrator according to any one of claims 1 to 3,
The package has an opening;
In the step (c), the piezoelectric vibrating piece is attached to the package from the opening, and a lid is attached to the opening.
The lid has a through hole;
In the step (d), the ion beam is irradiated to the metal film through the through hole,
A method of manufacturing a piezoelectric vibrator that closes the through hole in the step (e).