JP3736224B2 - Piezoelectric vibrating piece processing method and processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to, for example, an improvement in a processing method and a processing apparatus for a piezoelectric vibrating piece used in a frequency adjusting method or the like in a manufacturing process of a piezoelectric vibrator having a piezoelectric vibrating piece incorporated in a package.
[0002]
[Prior art]
In recent years, miniaturization and thinning of devices have been remarkable in small information devices such as HDDs (hard disk drives), mobile computers, and IC cards, and mobile communication devices such as mobile phones, car phones, and paging systems. Piezoelectric devices such as piezoelectric vibrators used in the industry are also required to be small and thin.
At the same time, there is a need for a surface mount type piezoelectric vibrator that can be mounted on both sides of the circuit board of the apparatus.
[0003]
Therefore, an example of a conventional piezoelectric vibrator will be described using a low-medium-frequency crystal vibrator shown in the structural diagram of FIGS. 8A and 8B in which a tuning-fork type crystal vibrating piece is used as the piezoelectric vibrating piece. . The low-medium frequency crystal resonator is a crystal resonator having a frequency of 32.768 KHz for a typical timepiece and a frequency of several KHz to several hundred KHz used for an IC card or a pager.
[0004]
8A and 8B, the piezoelectric vibrating piece 2 is formed as a tuning fork type from a quartz substrate, and is formed as a quartz vibrating piece provided with a driving metal electrode on the surface thereof.
[0005]
The quartz crystal resonator element 2 is mounted and joined to a pedestal portion 4 of a base 3 formed of a ceramic laminated substrate with a conductive adhesive 5 or the like. And it is sealed in a vacuum atmosphere by a lid 6 formed of a transparent glass material so as to close the internal space of the base 3 from above.
[0006]
[Problems to be solved by the invention]
By the way, in the above-described piezoelectric vibrator 1, as described above, after vacuum sealing with the lid 6, trimming is further performed through the glass lid 6 with a laser or the like to adjust the frequency. Here, as shown in FIG. 9, the laser beam is transmitted through the lid 6 to the frequency adjusting portion 2a that is provided on the electrode at the tip of the piezoelectric vibrating piece 2 and is previously provided with a metal coating. By irradiating with L, this metal coating portion is heated to a high temperature at a location corresponding to the focused spot of the laser beam and evaporated.
[0007]
Thereby, the piezoelectric vibrating piece 2 is lightened by that amount, and is adjusted from about 700 ppm to about 50 ppm in terms of frequency performance.
[0008]
However, in the conventional frequency adjustment by the laser beam, as shown in FIG. 9, the light beam L by the laser beam transmits not only the frequency adjustment unit 2a but also the transparent quartz material to the metal coating unit 2b on the back side. There was a case where it was heated.
[0009]
As a result, the metal of the metal cover portion 2b on the back surface is scattered and adheres to the inner surface of the base 3, or it adheres between the insulated electrode portions by peeling off due to impact or the like. There was an inconvenience.
[0010]
Furthermore, since the frequency fluctuates by about 5 ppm to 10 ppm in one step (one shot) during processing with laser light, the overall variation after sealing becomes as large as 50 ppm to 100 ppm, resulting in a defective product. There was a problem that the yield decreased.
[0011]
The object of the present invention has been made to solve the above-mentioned problems. The object of the present invention is to reduce the amount of frequency deviation in one step when adjusting the frequency by laser light, and to precisely adjust the frequency. It is to provide a processing method and a processing apparatus for obtaining a highly accurate piezoelectric vibrator and the like that can be adjusted.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, the piezoelectric vibrating piece is housed in a package, and trimming is performed by irradiating a metal film on a predetermined metal coating portion of the piezoelectric vibrating piece with a laser beam. A processing method for adjusting the frequency by adjusting the laser power to a wavelength of 700 nm or less from the laser light generating means, and condensing the laser light on the metal film by a short-focus light focusing means. This is achieved by a method for processing a piezoelectric vibrating piece.
[0013]
According to the configuration of the first aspect, the laser beam adjusted to reduce the power can be focused on the metal film on the surface side of the piezoelectric vibrating piece with an appropriate spot diameter by the short-focus light focusing means. . Thereby, trimming can be performed only on the surface side of the piezoelectric vibrating piece.
[0014]
That is, if the focal length of the light focusing means is long, the spot diameter on the surface side of the piezoelectric vibrating piece to be processed, and this back side when the light beam penetrates the material of the piezoelectric vibrating piece in the thickness direction and passes to the back side. Since the spot diameter is not changed much from the spot diameter on the front side and is condensed with the same spot diameter, the front side and the back side are processed at the same time. Therefore, in the first aspect of the invention, an appropriate small beam spot is formed on the surface side of the piezoelectric vibrating piece to be processed by setting the light focusing means to a short focal point and setting the wavelength of the laser light to 700 nm or less. can do.
[0015]
Here, the reflectance of the irradiated metal surface differs depending on the wavelength of the laser beam. When the laser beam is 700 nm or less, the reflectance is lowered and is easily absorbed. For this reason, even if a small beam spot is formed on the surface side of the piezoelectric vibrating piece to be processed, more energy is absorbed by the metal surface to be processed, so that it can be processed effectively.
[0016]
Moreover, by adjusting so as to reduce the power of the laser beam, the power necessary for processing is condensed only on the front side to be processed, and this laser beam has a large spot diameter on the back side of the piezoelectric vibrating piece, and Because the power is small, it is not processed.
[0017]
For this reason, the amount of adjustment of the frequency by one process can be made small, and precise adjustment becomes possible. In addition, the metal film on the back side of the piezoelectric vibrating piece exhibits the effect that it is not evaporated.
[0018]
According to a second aspect of the invention in the configuration of claim 1, wherein the laser beam is a YAG laser, is generated by a YVO ₄ laser or a YLF laser, a wavelength of the laser beam, the YAG laser, harmonic of a YVO ₄ laser or a YLF laser Waves are used.
[0019]
According to the second aspect of the present invention, if the harmonics of the YAG laser, the YVO ₄ laser, or the YLF laser are used, it is possible to easily obtain laser light that is focused at a short focal point.
[0020]
According to a third aspect of the present invention, in the configuration of the first or second aspect, the spot diameter of the laser beam is approximately 5 μm at the irradiation position with respect to the piezoelectric vibrating piece.
[0021]
According to the configuration of the third aspect, the irradiation position on the piezoelectric vibrating piece, that is, the back side that further transmits the quartz material by irradiating the metal film on the surface side of the piezoelectric vibrating piece with a spot diameter of about 5 μm. Then, the spot diameter becomes large, and the metal film on the back side of the piezoelectric vibrating piece is not evaporated.
[0022]
According to a fourth aspect of the present invention, in the structure of any one of the first to third aspects, at least the periphery of the processing portion is cooled during the processing by the laser beam.
[0023]
According to the configuration of the fourth aspect, it is possible to prevent the high temperature of the processing spot where the laser beam is focused from being transmitted to the periphery, and it is possible to prevent the piezoelectric vibrating piece from changing in frequency due to heat during processing.
[0024]
According to a fifth aspect of the present invention, in the configuration according to any one of the first to fourth aspects, a laser beam having a wavelength of 700 nm or less focused on a predetermined metal film of the piezoelectric vibrating piece by a short-focusing light focusing means. Irradiation with a power of 1 causes the metal film on the surface of the piezoelectric vibrating piece to evaporate, and allows the laser beam to pass through the piezoelectric vibrating piece to evaporate the metal film on the back surface. The fine adjustment is performed by irradiating the surface of the piezoelectric vibrating piece with a smaller second power and further evaporating only the metal film on the surface.
[0025]
First, the front and back surfaces of the piezoelectric vibrating piece are processed with laser light to roughly adjust the frequency, and then only the metal film on the surface side of the piezoelectric vibrating piece is evaporated to adjust the frequency precisely.
[0026]
Further, in the invention according to claim 6, the object is to generate laser light having a wavelength of 700 nm or less, means for adjusting to reduce the power of the laser light, and the adjusted This is achieved by a piezoelectric vibrating piece processing apparatus comprising a short-focus light focusing means for focusing laser light on a predetermined irradiation position of the piezoelectric vibrating piece.
[0027]
According to the configuration of the sixth aspect, the power of the light beam from the laser light generating means is reduced, and the spot diameter appropriate for the metal film on the surface side of the piezoelectric vibrating piece is reduced by the short-focusing light focusing means. The laser beam can be focused, so that trimming can be performed only on the surface side of the piezoelectric vibrating piece. For this reason, the amount of frequency adjustment by one processing can be reduced, and precise adjustment can be performed.
[0028]
A seventh aspect of the invention is characterized in that, in the configuration of the fifth or sixth aspect, a plurality of light beams are generated by disposing a light splitting means in front of the light focusing means.
[0029]
According to the configuration of claim 7, by dividing the laser light of the wavelength from the light source into a plurality of light beams by the light dividing means, a plurality of light beams with appropriate power can be obtained, By using the divided light beam, a plurality of portions of one piezoelectric vibrating piece can be trimmed simultaneously.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of a piezoelectric vibrator of the present invention will be described with reference to the drawings.
[0031]
1 and 2 are examples of a 32.768 KHz quartz crystal resonator for a watch using a tuning fork type quartz crystal vibrating piece as a piezoelectric vibrating piece, for example, FIG. 1 is a longitudinal sectional view thereof, and FIG. It is a top view.
[0032]
As shown in these drawings, in the piezoelectric vibrator 10, a base 11 is provided so as to form an internal space S with three layers of ceramic substrates 11a, 11b, and 11c. Of these, electrode portions 12a and 12b, which are metallized with metal and plated with Ni and Au, are formed at one end on a base 11 on which two layers of ceramic substrates 11a and 11b are laminated. An electrode portion (not shown) of a tuning-fork type crystal vibrating piece 13 as a piezoelectric vibrating piece having a driving metal electrode formed on the surface thereof is aligned and mounted on the electrode portions 12a and 12b of the base 11. The conductive adhesives 15 and 15 are electrically connected and fixed. Here, the crystal vibrating piece 13 includes two vibrating arms 13a and 13a that are divided into two on the tip side. A metal coating 13b such as Au or Ag is formed in advance on the tip of the vibrating arm 13a by a technique such as sputtering.
[0033]
Further, a lid (lid) 16 formed of a light transmitting material, for example, glass is aligned with the base 11 and the sealing material 17 is used. For example, the sealing material 17 is melted by a heating furnace or the like and the first sealing is performed. It is sealed and fixed.
[0034]
In this manner, the piezoelectric vibrating piece 13 is sealed in the package 18 including the base 11 and the lid 16.
[0035]
As shown in FIG. 1, an opening 19 is formed on the bottom surface of the base 11 to communicate the inside of the package 18 with the outside. Then, after the frequency adjustment described later, the second sealing is performed using the opening 19.
[0036]
FIG. 3 shows a frequency adjustment step which is a processing step subsequent to the first sealing. The piezoelectric vibrator 10 subjected to the first sealing is arranged as shown in the figure, and a processing device 20 described later is arranged thereon. Then, the laser beam L for processing is irradiated to the metal coating portion 13b, which is a frequency adjustment portion (coarse / fine adjustment portion) of the piezoelectric vibrating piece 13 sealed in the piezoelectric vibrator 10, as shown in the figure. Then, the metal film of the metal film part 13b is evaporated by trimming at a high temperature, the weight of the vibrating arm 13a is reduced, and the frequency is adjusted in the direction of increasing the frequency.
[0037]
FIG. 4 is an optical block diagram showing a schematic configuration of such a processing apparatus 20.
[0038]
In the drawing, a processing apparatus 20 includes a laser beam generating unit 21, a power reducing unit 22 on which a light beam L 1 emitted from the laser beam generating unit 21 is incident, and an optical path of the light beam L 2 emitted from the power reducing unit 22. And a light focusing means 24 on which a light beam from the light path changing means 23 is incident. The laser light generating means 21 has a laser light source. In this case, as a laser light source, for example, a YAG (yttrium aluminum garnet) laser, a YVO ₄ laser, a YLF laser, or the like is used.
[0039]
Here, the YAG laser is widely used as a solid-state laser using a YAG laser rod doped with neodymium ions or holonium ions in a Y ₃ Al ₅ O ₁₂ base crystal, and the oscillation wavelength is usually 1064 nm. is there. In the present embodiment, the second harmonic of this YAG laser is preferably used without using this wavelength as it is.
[0040]
That is, for example, the laser beam generating means 21 incorporates means for generating the second harmonic of the YAG laser. Here, a laser beam having a predetermined power density generates several harmonics when passing through a transparent medium. Utilizing this property, the laser light generating means 21 includes a second-order nonlinear generator capable of phase matching, for example, a known second harmonic generating means SHG (second homogenator) using a wavelength conversion element such as KDP or LiNbO3. ) Is provided.
[0041]
Thereby, for example, the light beam L1 emitted from the laser light generating means 21 is wavelength-converted to a wavelength of 532 nm as the second harmonic of the YAG laser. Here, the laser beam used for processing is not limited to the second harmonic of the YAG laser but can be used in the method of the present embodiment as long as the wavelength is 700 nm or less. By utilizing the second harmonic, a light beam having a wavelength suitable for processing can be obtained relatively easily.
[0042]
For example, an attenuator is used as the power reducing means 22 and the power is adjusted to emit a light beam L2 of 10 to 20 mW (milliwatt).
[0043]
For the optical path conversion means 23, for example, an optical path bending mirror using a reflecting mirror is used. By bending the optical path of the light beam L2 by 90 degrees, the overall configuration of the apparatus can be reduced.
[0044]
The light focusing means 24 on which the light beam L2 is incident is configured as shown in FIG. 5, for example.
[0045]
As the light focusing means 24, a short focal point is used, and the focal length is preferably 50 mm or less. When the focal length f of the light focusing means 24 is long, the spot diameter focused on the metal film 13b on the surface side of the vibrating arm 13a of the piezoelectric vibrating piece 13 to be processed, and the light beam L3 changes the material of the piezoelectric vibrating piece 13. When passing through the thickness direction and passing through to the back side, the spot diameter on the metal film 13c on the back side does not change much from the spot diameter on the front side, and is similarly condensed, so the front side and the back side are processed simultaneously. Because it will end up. In this respect, since the thickness of the material of the piezoelectric vibrating piece 13 is about 100 μm, it is particularly important to set this focal length short. In this embodiment, for example, a short focus convex lens is used as the light focusing means 24. If the light converging means 24 has a function of converging the light beam L2 onto the metal film 13b formed on the vibrating arm 13a of the piezoelectric vibrating piece 13, other optical elements such as a hologram element can be used as appropriate.
[0046]
In this case, the convex lens 24 can have a spot diameter d = 5 μm when the lens shape D = 16 mm, the focal length = 100 mm, and the wavelength λ = 532 nm of the incident light beam L2, and the light beam L2 A suitable processing spot could be obtained. At this time, the laser power by the laser light generating means 21 was about 10 mW to 15 mW when the number of repetitions of pulse oscillation was 3 kHz, and a time of about 60 ns was set for one shot.
[0047]
Here, the wavelength of the light beam L3 emitted from the light focusing unit 24 is set to λ = 532 nm and 700 nm or less as described above. The reason why the laser beam is set in this way is that the reflectivity of the irradiated metal surface differs depending on the wavelength of the laser beam. When the laser beam is 700 nm or less, the reflectivity is reduced and is easily absorbed, and a small beam spot is formed. Because it can. For this reason, even if a small beam spot is formed on the metal film 13b on the surface side of the piezoelectric vibrating piece 13 to be processed, it can be processed effectively.
[0048]
Thus, by using the processing apparatus 20 as described above and adjusting the frequency by the laser beam as shown in FIG. 3, only the metal coating 13b on the surface side of the piezoelectric vibrating piece 13 can be evaporated, and the back side The metal coating 13c is not processed.
[0049]
As a result, it is possible to adjust the frequency to about 0.1 ppm by one-shot processing, and in the performance after the second sealing in which the opening 19 in FIG. It can be set to about minus 2 ppm, and precise frequency adjustment can be realized.
[0050]
Here, it is more preferable to perform the laser processing while blowing nitrogen or the like at least near the tip of the piezoelectric vibrating piece 13 using the opening 19. As a result, it is possible to prevent the high temperature of the processing spot where the laser beam is focused from being transmitted to the periphery, and it is possible to prevent the piezoelectric vibrating piece from changing in frequency due to heat during processing.
[0051]
FIG. 6 is a diagram illustrating a main part of a modification of the processing apparatus 20. In this case, the light beam L4 from the light source is, for example, a harmonic of a YAG laser, a YVO ₄ laser, or a YLF laser, as in FIG. Waves etc. can be used.
[0052]
The light beam L4 is incident on a half-wave plate 25 disposed on the optical path, and the light emitted from the half-wave plate 25 is a polarized light beam as a subsequent light separation unit, for example, a polarization separation unit. A light beam L6 incident on the splitter 26 and emitted from the polarization beam splitter 26 is incident on the light focusing means 24 of FIG.
[0053]
The half-wave plate 25 converts the ratio of the P-polarized component and the S-polarized component with respect to the linearly polarized light of the laser light L4.
[0054]
The polarization beam splitter 26 is, for example, a cubic beam splitter having a polarization separation film 26a made of a dielectric multilayer film between the oblique sides where two triangular prisms are abutted. As a result, the linearly polarized light beam L5 is incident on the polarization separation film 26a at a predetermined angle, so that the optical action causes the P-polarized component and the S-polarized component of the linearly polarized components to be at a predetermined ratio. Polarized light is separated. That is, with respect to the polarization separation film 26a, a polarized light component having an appropriate power wavelength of 700 nm or less is transmitted through (or reflected from) the polarization separation film 26a based on transmission and reflection characteristics designed in advance. The light beam L6 composed of this polarization component is polarized and separated by the function of the polarization separation film 26a, so that the power is reduced.
[0055]
Thus, in this modification, the half-wave plate 25 and the polarizing beam splitter 26 constitute a means for reducing the power of the laser light from the light source.
[0056]
Therefore, by irradiating the light beam L6 onto the metal coating 13b of the piezoelectric vibrator 10 as described with reference to FIG. 3, the frequency adjusting device of FIG.
[0057]
Instead of the polarization beam splitter 26, a polarization separation means such as a polarization hologram element having an equivalent function may be used. Further, instead of the half-wave plate 25 and the polarizing beam splitter 26, for example, a Wollaston prism or the like is used to separate the light beam L4 from the light source into ordinary light and extraordinary light, thereby exhibiting an equivalent function. You may comprise.
[0058]
FIG. 7 shows still another modification of the processing apparatus 20 of FIG.
[0059]
In the figure, a configuration in which the light splitting means 27 is arranged in the preceding stage of the light focusing means 24 is shown.
[0060]
That is, as shown in FIG. 7, a light beam L1 having a wavelength of 700 nm or less is incident from the laser light generating means 21 to the light splitting means 27 arranged in the preceding stage of the light focusing means 24. The light splitting means 27 is, for example, a phase grating (diffraction grating-grating), splits the laser light L1 into zero-order light that is not diffracted and diffracted light whose phase is shifted by the diffraction action, and is focused by the light focusing means 24. A plurality of light beams, in the figure, at least three light beams can be provided.
[0061]
As a result, the power of the three light beams L8, L8, and L8 is smaller than that of the laser beam L1. Moreover, the three light beams L8, L8, and L8 can simultaneously process the three locations of the piezoelectric vibrating piece at the irradiation positions of the three locations S1, S2, and S3, and the processing efficiency is improved accordingly. .
[0062]
In this case, as the light splitting means 27, not only a diffraction grating but also a hologram element or the like that can split a light beam by a predetermined diffraction action may be used.
[0063]
Further, in the above-described processing method, first, the piezoelectric vibrating piece 13 is defocused or laser irradiation time is extended to perform the same laser processing as before, and then the laser beam is applied to the piezoelectric vibrating piece. Fine adjustment may be performed by irradiating only the surface of the metal coating and further evaporating only the metal coating on the surface.
[0064]
As a result, both the front and back surfaces of the piezoelectric vibrating piece 13 are processed with laser light to roughly adjust the frequency, and then only the metal coating 13b on the surface side of the piezoelectric vibrating piece 13 is evaporated to precisely adjust the frequency. it can.
[0065]
The present invention is not limited to the individual embodiments of the above-described embodiments and modifications, and the configurations can be arbitrarily combined.
[0066]
Further, the above processing method can be applied not only to the piezoelectric vibrator but also to a crystal oscillator, a real-time clock oscillator, an acceleration sensor, and the like in which an IC chip having an oscillation circuit or the like in a package and a crystal vibrator are incorporated.
[0067]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the amount of frequency adjustment in one step at the time of frequency adjustment using laser light, and to provide a highly accurate piezoelectric vibrator and the like that can precisely adjust the frequency. it can.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a piezoelectric vibrator to which a processing method according to an embodiment of the present invention is applied.
FIG. 2 is a plan view of a piezoelectric vibrator to which a processing method according to an embodiment of the present invention is applied.
3 is a schematic view showing a laser processing step of the piezoelectric vibrator of FIGS. 1 and 2. FIG.
FIG. 4 is a block diagram showing a schematic configuration of an optical system of a processing apparatus used in a processing method according to an embodiment of the present invention.
FIG. 5 is an explanatory view showing an example of light focusing means used in the processing apparatus of FIG. 4;
6 is an explanatory view showing a main part of a modification of the processing apparatus of FIG.
7 is an explanatory view showing a main part of another modification of the processing apparatus of FIG. 4;
8A and 8B are structural views showing an example of a piezoelectric vibrator, in which FIG. 8A is a plan view and FIG. 8B is a schematic side sectional view thereof.
9 is an enlarged view of a main part showing a state of processing a piezoelectric vibrating piece of the piezoelectric vibrator of FIG. 8;
[Explanation of symbols]
10 Piezoelectric vibrator 11 Base 13 Piezoelectric vibrating piece 13b Metal coating (coarse / fine adjustment)
13c Metal coating (back / rough adjustment)
16 Lid
21 Laser light generating means 22 Power reducing means 23 Optical path changing means 24 Light focusing means 25 1/2 wavelength plate 26 Polarization separating means 27 Phase grating

Claims (7)

A method of adjusting a frequency by housing a piezoelectric vibrating piece in a package and performing trimming by irradiating a laser beam to a metal film of a predetermined metal coating portion of the piezoelectric vibrating piece,
A method for processing a piezoelectric vibrating piece, wherein adjustment is made to reduce laser power having a wavelength of 700 nm or less from the laser light generating means, and the laser light is condensed on the metal film by short-focus light focusing means. The laser beam is a YAG laser, it is generated by a YVO ₄ laser or a YLF laser, a wavelength of the laser beam, the piezoelectric vibration according to claim 1, wherein the YAG laser, harmonic YVO ₄ laser or a YLF laser is used Processing method of the piece.   3. The method for processing a piezoelectric vibrating piece according to claim 1, wherein a spot diameter of the laser beam is approximately 5 μm at an irradiation position on the piezoelectric vibrating piece.   The method for processing a piezoelectric vibrating piece according to claim 1, wherein at least the periphery of the processing portion is cooled during processing by the laser beam. Irradiating a predetermined metal film of the piezoelectric vibrating piece with a first power with a laser beam having a wavelength of 700 nm or less, which is focused by a short focus light focusing means,
The transpiration of the metal film on the surface of the piezoelectric vibrating piece, the transpiration of the metal film on the back surface through the piezoelectric vibrating piece,
Next, fine adjustment is performed by irradiating the surface of the piezoelectric vibrating piece with the laser beam at a second power smaller than the first power and further evaporating only the metal film on the surface. 5. A method for processing a piezoelectric vibrating piece according to any one of 1 to 4. Laser light generating means for generating laser light having a wavelength of 700 nm or less;
Means for adjusting to reduce the power of the laser beam;
An apparatus for processing a piezoelectric vibrating piece, comprising: a short-focusing light focusing means for focusing the adjusted laser beam on a predetermined irradiation position of the piezoelectric vibrating piece.   The apparatus for processing a piezoelectric vibrating piece according to claim 6, wherein a plurality of light beams are generated by disposing a light splitting unit in front of the light focusing unit.

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