JP3709113B2 - Piezoelectric vibrator and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a piezoelectric vibrator in which a piezoelectric vibrating piece is hermetically sealed with a lid, and more particularly, to a method for manufacturing a piezoelectric vibrator using anodic bonding.
[0002]
[Prior art]
As shown in FIG. 7, the conventional surface mount type piezoelectric vibrator 50 includes a piezoelectric vibrating piece 51, a container 52 that fixes one end of the piezoelectric vibrating piece 51, and a lid body 56 that seals the container 52. .
The container 52 to which the piezoelectric vibrating piece 51 is fixed has a concave portion 53 that defines a space that does not hinder the vibration of the piezoelectric vibrating piece 51, and the concave portion 53 has a step that is shallower than the other portions. A portion 54 is provided. The piezoelectric vibrating piece 51 is fixed to the upper surface of the stepped portion 54 of the container 52 by an adhesive layer 55 such as a solder material or a conductive adhesive. Then, a lid 56 is bonded to the upper portion of the container 52 by an adhesive layer 57 similar to the fixing of the piezoelectric vibrating piece 51, and the piezoelectric vibrating piece 51 is hermetically sealed in the recess 53 of the container 52.
[0003]
As another conventional technique, there is a piezoelectric vibrator using anodic bonding, but no example has been commercialized. This is because in the case of using anodic bonding, it is required that the difference in coefficient of thermal expansion between the members to be bonded is small. For example, Pyrex glass has a thermal expansion coefficient of 3.25 ppm / ° C., and quartz has a thermal expansion coefficient of 11 to 14 ppm / ° C. When these are joined at a high temperature of 300 ° C. or higher and cooled to room temperature, cracks and cracks are generated and practical application is difficult.
[0004]
[Problems to be solved by the invention]
In the conventional surface-mount type piezoelectric vibrator as shown in FIG. 7, there is a difference in thermal expansion coefficients between the container 52, the adhesive layer 55, and the piezoelectric vibrating piece 51, and the stress applied to the piezoelectric vibrating piece 51 changes depending on the temperature. As a result, there is a problem that the resonance or oscillation frequency of the piezoelectric vibrating piece changes.
[0005]
In view of such circumstances, an object of the present invention is to provide a piezoelectric vibrator that does not deteriorate the characteristics of the piezoelectric vibrator and a method for manufacturing the piezoelectric vibrator.
It is another object of the present invention to provide a piezoelectric vibrator using anodic bonding that does not generate cracks or cracks by improving the selection and structure of members.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention for solving the above-described problem, a piezoelectric vibrating plate having a piezoelectric vibrating piece, a frame-like portion integrally connected to a base end portion thereof and surrounding the piezoelectric vibrating piece, and a piezoelectric The excitation electrode films formed on the upper and lower surfaces of the vibrating piece, the bonding films formed on the upper and lower surfaces of the frame-like portion, and the piezoelectric vibration on both surfaces of the piezoelectric vibrating plate without interfering with the vibration of the piezoelectric vibrating piece In the piezoelectric vibrator for joining a pair of lids that hermetically seal the pieces, the piezoelectric diaphragm and the pair of lids have the same thermal expansion coefficient, and the pair of lids are joined to the joining electrode film and the joining layer. It is a piezoelectric vibrator characterized by having.
[0007]
According to a second aspect of the present invention, in the first aspect, the bonding electrode film is selected from the group consisting of chromium, aluminum, and alloys thereof, and the bonding layer is made of hard glass or soda lime glass. It is a vibrator.
In both of the above embodiments of the present invention, the step of forming a metal film over substantially the entire surface of both sides of the piezoelectric diaphragm, the patterning of the metal film to form the excitation electrode film on the piezoelectric vibrating piece, and the frame-shaped portion are supported. Forming a bonding film to be bonded to the pair of lids in a region to be bonded, forming a bonding electrode film on one surface of the lid, and a bonding layer over the entire surface of the lid on which the bonding electrode film is formed When the bonding layer is hard glass, the temperature is 250 to 400 ° C., and the bonding layer is soda lime glass. And a step of applying a voltage of 0.5 to 5.0 kV to the bonding electrode film and the bonding film with the piezoelectric vibration plate side as a positive electrode. It is in the manufacturing method of a child.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is an exploded perspective view showing an example of a piezoelectric vibrator, and FIG. 2 is a cross-sectional view thereof.
The piezoelectric vibrator of the present embodiment is a quartz vibrator having a tuning fork type quartz vibrating piece made of, for example, quartz (SiO ₂ ). As shown in FIG. 1, the quartz vibrator 12 having the quartz vibrating piece 11 and A pair of lids 14a and 14b that are bonded to both surfaces of the quartz-crystal vibrating plate 12 and hermetically seal the quartz-crystal vibrating piece 11 in a state capable of vibrating.
[0009]
The quartz vibrating plate 12 includes a tuning fork type quartz vibrating piece 11 and a frame-like portion 15 that is integrally connected to the base end portion 50 and surrounds the periphery of the quartz vibrating piece 11.
Further, as shown in FIG. 2, in order to vibrate the crystal vibrating piece 11, the crystal vibrating piece 11 is thinner than the frame-like portion 15. The processing method of the crystal vibrating piece 11 can be arbitrarily selected from etching, injection processing, and the like. In the present embodiment, the tuning-fork type crystal vibrating piece 11 is formed by etching both front and back surfaces.
[0010]
Furthermore, the excitation electrode film 16a and the excitation electrode film 16b are provided on the front, back, and side surfaces of the crystal resonator element 11. The bonding film 17 made of the same material as the excitation electrode film 16a and the excitation electrode film 16b on the front and back surfaces of the region corresponding to the frame-like portion 15 is used for bonding the crystal diaphragm 12, the lid body 14a, and the lid body 14b. Is provided. The excitation electrode film 16a and the excitation electrode film 16b are extended to the end of the crystal diaphragm 12, and are a part of the bonding film 17 on the upper surface of the frame-like part 15 on the same side as the excitation electrode film 16a. 17a and the terminal connecting bonding film 17b. In the present invention, the bonding film 17 serves as both a bonding to the lid and a lead electrode for extracting the excitation electrode.
[0011]
The pair of lids 14a and 14b are, for example, quartz plates cut out at the same cut angle as the quartz diaphragm 12. The thermal expansion coefficient of the surface of the quartz plate changes depending on the cut angle. For example, as shown in FIG. 6, the thermal expansion coefficient in the short direction of the arrow 31 and the long direction of the arrow 32 of the quartz plate 33 cut at a certain cut angle is the heat of the diaphragm cut at another cut angle. It is not necessarily the same as the expansion rate. By matching the cut angle, the residual stress at the joint surface can be minimized, and problems such as cracks and cracks can be solved.
[0012]
As shown in FIG. 2, the lid body 14 a and the lid body 14 b have a bonding electrode film 21 on the surface facing the crystal vibrating plate 12 and a bonding layer 22 on the upper surface of the bonding electrode film 21. In the lid 14b, a through hole 60 and a through hole 61 penetrate through the bonding electrode film 21 and the bonding layer 22 on the lid 14b in order to draw the excitation electrode film 16a and the excitation electrode film 16b to the outside of the crystal resonator. Provided. In the through holes 60 and 61, the lead electrode 18a and the lead electrode 18b having different polarities are formed in the bonding electrode film 21, but the lead electrodes are formed by the bonding electrode film 21 so as not to be electrically short-circuited. In this embodiment, the lead electrodes are insulated from each other by patterning so that the bonding electrode film 21 is not formed around the through hole 60 and the through hole 61.
[0013]
The lid 14a, the bonding layer 22 on the lid 14b, and the bonding film 17 on the frame-like portion 15 are bonded together by so-called anodic bonding, as will be described in detail later, and the crystal diaphragm 12, the lid 14a, and the lid The body 14b is joined. In this embodiment, the excitation electrode film 16a, which is one of the poles, is connected to the lead electrode 18a formed on the through hole 60 of the lid 14b via the terminal connection bonding film 17a corresponding to a part of the bonding film 17. Connected to. The excitation electrode film 16b serving as the other pole is extended to the terminal connection bonding film 17b corresponding to a part of the bonding film 17 through an electrode provided on the side surface of the crystal vibrating piece 11, although not shown. The lead electrode 18b formed on the through hole 61 of the body 14b is connected. The terminal connection bonding film 17a and the terminal connection bonding film 17b are provided on a part of the bonding film 17 so as not to short-circuit each other.
[0014]
Although not shown, at least a part of the bonding film 17 on both surfaces of the frame-shaped portion 15 of the crystal plate 12 is formed on the frame-shaped portion 15 so as to surround the crystal vibrating piece 11 on both surfaces. . After bonding, the crystal vibrating piece 11 is thinner than the frame-like portion 15, so that the space formed between the crystal vibrating plate 12 and the upper and lower bonding layers 22 is hermetically sealed.
[0015]
Hereinafter, a manufacturing process of such a crystal unit will be described. FIG. 3 is a cross-sectional view showing the manufacturing process of the piezoelectric vibrator according to this embodiment.
First, as shown in FIG. 3A, etching is performed except for the frame-like portion 15 of the quartz plate that becomes the quartz-crystal vibrating plate 12, and the space and the frame-like portion 15 in which the quartz-crystal vibrating piece 11 that is an actual drive unit can vibrate are formed. Form.
[0016]
Next, as shown in FIG. 3B, the portion etched in FIG. 3A is further etched to form the crystal vibrating piece 11.
Next, as shown in FIG. 3C, a metal film 20 is formed on both sides of the quartz crystal plate 12 over the entire surface by sputtering or the like. The metal film 20 includes an excitation electrode film 16a and an excitation electrode film 16b for vibrating the crystal resonator element 11, a terminal connection bonding film 17a connected to the excitation electrode film 16a and the excitation electrode film 16b, and a terminal connection bonding film. 17b and a film constituting the bonding film 17 used for actual bonding between the lid body 14a and the lid body 14b, and the material thereof is not particularly limited. For example, chromium, aluminum, and respective alloys are preferable, but chromium is used. It is particularly preferable to use it.
[0017]
Next, as shown in FIG. 3 (d), the metal film 20 is patterned to form a bonding film over the entire circumference in portions corresponding to the excitation electrode film 16a, the excitation electrode film 16b, and the surrounding frame-like portion 15. 17 and although not shown, a terminal connection bonding film 17a and a terminal connection bonding film 17b are formed on part of the bonding film 17 on the upper surface of the frame upper part 15 on the side where the excitation electrode film 16a is formed.
[0018]
As shown in FIG. 2, a bonding electrode film 21 is formed on the surfaces of the lid body 14a and the lid body 14b facing the crystal diaphragm 12 by sputtering or vapor deposition. The bonding electrode film 21 is preferably chromium, aluminum, and alloys thereof, but it is particularly preferable to use chromium from the viewpoint of adhesion to the lid body 14a and the lid body 14b.
Further, the bonding electrode film 21 functions as an electrode when the bonding film 17 and the bonding layer 22 are anodically bonded, and does not need to be formed on the upper and lower portions of the crystal vibrating piece 11.
[0019]
Next, the bonding layer 22 is formed on the bonding electrode film 21 by sputtering or vapor deposition. The bonding layer 22 is made of hard glass, soda lime glass, or the like, and has a film thickness that does not cause dielectric breakdown due to anodic bonding conditions.
A through hole 60 and a through hole 61 are provided in the lid 14b so as to penetrate the bonding electrode film 21 and the bonding layer 22 on the lid 14b at positions facing the terminal connecting bonding film 17a and the terminal connecting bonding film 17b. However, when the lead electrodes 18a and 18b having different polarities are formed in the through holes 60 and 61, it is necessary to prevent the lead electrodes from being electrically short-circuited by the bonding electrode film 21. For example, in this embodiment, the lead electrodes are insulated from each other by patterning so as not to form the bonding electrode film 21 around the through hole 60 and the through hole 61. It is sufficient that at least one of the through hole 60 and the through hole 61 is insulated.
[0020]
Next, the pair of lids 14a and 14b and the quartz plate 12 formed as described above are stacked in a vacuum so that the quartz plate 12 is sandwiched between the pair of lids 14a and 14b as shown in FIG. Joining by anodic bonding. At this time, each member is heated to 100 ° C. to 400 ° C., and the DC power supply 40 is used to connect the bonding film 17 and the bonding electrode film 21 on each surface of the quartz crystal vibration plate 12 to the anode on the bonding film 17 side. It is preferable to apply a DC voltage of 0.5 to 5.0 kV. For example, in this embodiment, each member was heated to about 300 ° C. and a DC voltage of about 1.0 kV was applied.
[0021]
Then, by anodic bonding of the bonding film 17 and the bonding layer 22, the crystal diaphragm 12 and the lid body 14 are bonded well. Since the quartz plate 12 and the pair of lids 14 are made of the same material and have the same cut angle, the thermal expansion coefficient of the quartz plate is the same, and the residual stress after joining can be minimized. That is, cracks and cracks due to the difference in thermal expansion coefficient do not occur.
[0022]
In practice, a quartz substrate on which a plurality of quartz vibrating plates 12 on which the quartz vibrating piece 11, the excitation electrode films 16 a and 16 b, the bonding film 17, etc. are formed is bonded to a position corresponding to the plurality of quartz vibrating plates 12. Individual crystal vibrations are obtained by superposing and anodic bonding so that a plurality of lids 14a and 14b formed with a film 21 and a bonding layer 22 are sandwiched by a plurality of lid-forming substrates, and then cutting at predetermined positions. Become a child.
[0023]
As described above, in this embodiment, the quartz crystal vibrating plate 12, the lids 14a, and the lid 14b are joined by anodic bonding, and the quartz vibrating piece 11 is hermetically sealed. There is no risk that the degree of vacuum will decrease. In addition, since the excitation electrode films 16a and 16b, the terminal connection bonding films 17a and 17b, and the bonding film 17 are formed of the same material, they can be formed at a time, and the manufacturing process can be simplified. it can.
[0024]
Further, in the above-described embodiment, the crystal vibrating plate 12 is provided with a step in the crystal vibrating piece 11 and the frame-like portion 15 by etching twice so as to form a space that does not inhibit the vibration of the crystal vibrating piece 11. However, the present invention is not limited to this. For example, as shown in FIG. 5, recesses 70 and 71 are provided in the lid body 14a and the lid body 14b, respectively, so as to form a space that does not hinder the vibration of the crystal vibrating piece 11. May be.
[0025]
Furthermore, in the above-described embodiment, the piezoelectric diaphragm is formed of quartz, but is not limited thereto, and may be formed of ceramic or the like, for example.
Further, in the above-described embodiment, the pair of lid bodies 14a, lid bodies 14b, and crystal diaphragm 12 formed so as to be capable of anodic bonding, respectively, are joined at the same time. The lid 14b may be joined individually instead of simultaneously.
[0026]
In any of these structures, as described above, the piezoelectric vibrator and the lid can be reliably and easily joined.
[0027]
【The invention's effect】
As described above, in the present invention, a bonding film made of the same material as the excitation electrode film is formed on the surface of the piezoelectric diaphragm, and the bonding electrode film and the bonding layer are formed on the lid, and the bonding film and the bonding film are formed. The piezoelectric diaphragm and the lid were joined by anodic bonding. Thereby, taking advantage of the anodic bonding such as being suitable for downsizing and reducing outgas, the piezoelectric diaphragm and the lid can be made of members having the same thermal expansion coefficient. A member that cannot be bonded by conventional anodic bonding is realized by interposing a film or a layer that can be bonded by anodic bonding.
[0028]
In addition, the bonding film can be formed in the same process as the excitation electrode film, and the manufacturing process can be simplified.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of a piezoelectric vibrator according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a piezoelectric vibrator according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a manufacturing process of the piezoelectric vibrator of the present invention.
FIG. 4 is a schematic view showing wiring at the time of anodic bonding of the piezoelectric element of the present invention.
FIG. 5 is a cross-sectional view showing another example of a piezoelectric vibrator according to the present invention.
FIG. 6 is an explanatory diagram for explaining the thermal expansion coefficient of the piezoelectric vibrator according to the present invention.
FIG. 7 is a cross-sectional view of a piezoelectric element according to a conventional technique.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Crystal oscillator 11 Crystal vibrating piece 12 Crystal diaphragm 14a, 14b Cover 15 Frame-shaped part 16a, 16b Excitation electrode film 17 Bonding film 17a, 17b Terminal connection bonding film 18a, 18b Lead electrode 40 DC power supply 50 Base end 60, 61 Through hole 70, 71 Recess

Claims (8)

A piezoelectric vibrating plate having a piezoelectric vibrating piece on which an excitation electrode film is formed, and a frame-like portion integrally connected to a base end portion of the piezoelectric vibrating piece and surrounding the piezoelectric vibrating piece;
In order to hermetically seal without disturbing the vibration of the piezoelectric vibrating piece, a pair of lids provided on both sides of the piezoelectric vibrating plate;
A bonding film formed on the upper and lower surfaces of the frame-shaped portion;
A bonding electrode film formed on the pair of lids;
A bonding layer provided between the bonding film and the bonding electrode film,
The piezoelectric vibrator, wherein the piezoelectric diaphragm and the pair of lids are bonded by anodic bonding using the bonding layer. The piezoelectric vibrator according to claim 1, wherein the piezoelectric diaphragm and the pair of lid bodies have the same thermal expansion coefficient. The piezoelectric vibrator according to claim 1 or 2, wherein the bonding electrode film is a metal film. The piezoelectric vibrator according to any one of claims 1 to 3, characterized in that said bonding layer is made of hard glass or soda lime glass. The piezoelectric vibrator according to any one of claims 1 to 4, characterized in that said bonding layer and the bonding electrode film is made of the same material. Forming a metal film on a piezoelectric vibrating plate in which a piezoelectric vibrating piece and a frame-like portion surrounding the piezoelectric vibrating piece are integrally formed; and
Patterning the metal film to form a bonding film on the frame-shaped portion;
Forming a bonding electrode film on the lid;
Forming a bonding layer on the bonding electrode film;
The bonding film and the bonding electrode film are opposed to each other through the bonding layer so that the pair of lids and the piezoelectric vibration plate are stacked, and the piezoelectric vibration plate and the piezoelectric film are bonded to each other by anodic bonding using the bonding film. A method of manufacturing a piezoelectric vibrator, comprising: joining a pair of lids. The bonding layer is made of hard glass, the temperature during the anodic bonding is set to 250 to 400 ° C., and a voltage of 0.5 to 5.0 kV is applied to the bonding electrode film and the bonding film. The method for manufacturing a piezoelectric vibrator according to claim 6. The bonding layer is made of soda lime glass, the temperature at the time of the anodic bonding is set to 100 to 300 ° C., and a voltage of 0.5 to 5.0 kV is applied to the bonding electrode film and the bonding film. A method for manufacturing a piezoelectric vibrator according to claim 6.

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