JPH03209907A - Piezoelectric vibrator and its frequency adjusting method - Google Patents

Abstract

PURPOSE:To reduce the secular change and to adjust the frequency continuously by supporting a vibrator where an electrode is arranged, storing it hermetically in a container in an energized state, and vaporizing a coat film in the container and sticking it on the electrode of the vibrator piece. CONSTITUTION:The crystal resonator piece 6 which has nickel-made electrodes 7 arranged on its top and reverse surfaces is supported at the holding part 4 of a lead terminal 3 with a conductive adhesive 5 and energized. The coat film 9 is vapor-deposited at the center part of a glass cover 1. The vibrating piece 6 is sealed airtightly by the case 2 and cover 1 with the sealing agent 8. Then the coat film 9 is irradiated with YAG laser light obtained by making continuous oscillation light passed through the cover 1 to pulsate through a Q switch. Consequently, metal 10 which vaporizes sticks on one surface of the electrode 7 instantaneously and the oscillation frequency of the resonator 6 varies.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a piezoelectric vibrator used as a reference clock of various electronic devices, and a method for adjusting its frequency.

2. Conventional technology A piezoelectric vibrator using a single crystal such as quartz has an extremely large Q value and can provide highly stable performance. Furthermore, adjustment of this oscillation frequency requires advanced technology. Piezoelectric vibrators have various vibration modes, but currently it is common to use the thickness shear mode, and in the thickness shear mode, the oscillation frequency of the piezoelectric vibrator is inversely proportional to the thickness of the vibrating piece. It is also known that the oscillation frequency decreases due to the effect of adding mass to the electrodes, and in the past, the oscillation frequency was adjusted using this effect of adding mass.

A conventional piezoelectric vibrator and its frequency adjustment method will be described below with reference to the drawings.

FIG. 3 is a structural diagram showing, in particular, a crystal resonator among conventional piezoelectric resonators, and FIG. 4 is a conceptual diagram showing a method for adjusting the frequency of the crystal resonator. In FIG. 3, an electrode 15 is disposed on the crystal vibrating piece 12 and is supported by a holding portion 17 of a lead terminal 13 by a conductive adhesive 18 and is electrically connected to the lead terminal 13 through a hermetic glass 14. Teke3 It is led out to the outside of page 19. Further, a secondary electrode 16 after frequency adjustment is added to the center of the electrode 16.

In FIG. 4, an oscillation circuit 26 is connected to the crystal vibrating piece 12 before being hermetically sealed, but the oscillation frequency still varies. The crystal vibrating piece 12 is placed in a vacuum container 21, and silver 22 for frequency adjustment is passed through a mask 2o to an evaporation source 23.
The oscillation frequency can be read by a counter 26 while the film is being deposited. Then, when the oscillation frequency drops to a certain set value due to the mass addition effect, the oscillation frequency is adjusted by closing the shutter 24 using the comparator 27 and stopping the vapor deposition. Although the general method for adjusting the frequency of a crystal resonator has been described above, studies have recently been conducted to increase the oscillation frequency by removing the electrode 15 using a laser (for example, see Japanese Patent Laid-Open No. 5913412).

Problems to be Solved by the Invention As mentioned above, frequency adjustment in the conventional general vapor deposition method requires a high vacuum of about 10-5 Torr, which incurs a lot of cost for vacuum equipment and requires batch work. Therefore, the efficiency of frequency adjustment was low.

In addition, conventionally, frequency adjustment had to be performed in the pre-hermetic sealing process, but since the oscillation frequency of the piezoelectric vibrator changes even during the hermetic sealing process, the oscillation frequency of the finished product can be adjusted with high precision. It was very difficult to do. Furthermore, silver particles that had adhered to the frequency adjustment equipment could adhere to vibrating pieces and be carried into the finished product, affecting the reliability of the piezoelectric vibrator.

In some frequency adjustment methods in which the electrodes are removed using a laser, the electrodes that apply the electric field to the vibrating element are partially removed.The more the frequency is adjusted, the larger the area to be removed and, as a result, the electric field applied to the vibrating element becomes weaker. This leads to an increase in equivalent resistance. In addition, frequency adjustment is virtually impossible if the amount of frequency adjustment is within a range that does not affect the equivalent resistance because the adjustment range is narrow and frequency variations cannot be absorbed. Therefore, the crystal vibrating piece is stored in an airtight container, and the silver or gold provided on the inner surface of the transparent part of this airtight container is evaporated (or scattered) by irradiating a laser beam from outside the airtight container.
There is also a device that finely adjusts the frequency by attaching it to an electrode.

However, silver and gold are not only expensive, but also have low stability after being attached to an electrode, and have the problem that the oscillation frequency shifts due to changes over time.

Therefore, an object of the present invention is to obtain a piezoelectric vibrator which is inexpensive and shows little change over time.

Means for Solving the Problems In order to achieve this object, the present invention focuses on the above-mentioned problems, and supports a vibrating piece having nickel electrodes on the front and back sides on the holding part of the lead terminal with a conductive adhesive. In an electrically conductive state, the device is hermetically housed in a container that is at least partially transparent, and a nickel coating film is arranged on the inside of the container. Then, the frequency is adjusted by evaporating the coating film using a laser beam from the outside through the transparent part of the container and attaching it to the electrode of the vibrating element.

Effect 67: With the above configuration, the present invention allows frequency adjustment in the atmosphere and does not require a vacuum device. 9. Frequency adjustment can be performed continuously with a simple configuration. Furthermore, since the frequency is adjusted after hermetically sealing, there is no need to consider frequency variations in post-processing, and frequency deviations in the finished product can be reduced. Further, although a laser beam is used for frequency adjustment, there is no need to remove the electrodes as in the conventional method, and there is less degradation in the equivalent resistance, and the adjustment range can be adjusted to the same level as the conventional vapor deposition method. In addition, nickel is cheaper than silver or gold, and is highly stable after electrode attachment, eliminating deviations in oscillation frequency due to changes over time.

Example Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a partially cutaway perspective view showing an embodiment of the present invention. A crystal vibrating piece e having nickel electrodes 7 arranged on the front and back sides is supported by the holding part 4 of the lead terminal 3 by a conductive adhesive 5 and is electrically connected to the holding part 4 of the lead terminal 3. A coating film 9 made of Nipponbai Co., Ltd. is applied to the center of the transparent glass cover 1 by vapor deposition.

In this embodiment, the material of the coat film 9 is nickel, which is the same as the electrode 7. The crystal vibrating piece 6 is hermetically sealed between the case 2 and the glass cover 1 using a glass sealant 8. Here, the electrode 7 will be explained. First, a crystal vibrating piece 6 processed to have constant external dimensions and thickness.
To remove the damaged layer, chemical etching is performed using an aqueous ammonium hydrogen fluoride solution, followed by precision cleaning. Next, parts other than the electrode forming part are masked, and the film is set in a vapor deposition container. The melting point of nickel, the electrode material, is 1453
°C, which is very high compared to 960°C for silver and 63°C for gold 1Q, making vapor deposition by resistance heating difficult. For this reason, in this example, the nickel material was evaporated by heating with an electron beam. That is, a nickel material is placed as an evaporation source in a vapor deposition container together with the crystal vibrating piece 6, and is irradiated with an electron beam to heat it, thereby causing the vapor of the nickel material generated to adhere to the electrode forming portion of the crystal vibrating piece 6. It's like that.

Furthermore, compared to gold and silver, nickel material has a stronger adhesion strength to the surface of the crystal resonator 6, so there is no need to form the first layer of electrodes such as chromium, unlike when electrodes are formed with gold or silver. , electrode formation became easy. Since the first layer electrode is not used yet, there is no negative effect on the aging of the first layer electrode, and since nickel material has a higher melting point than gold or silver and is stable over time, it is possible to maintain the frequency for a long period of time. Improves stability.

FIG. 2 is a sectional view showing an embodiment of the frequency adjustment method of the present invention, and also shows the concept of frequency adjustment using laser light. Frequency adjustment is performed after hermetically sealing. The lead terminal 3 is connected to an oscillator, and the oscillation frequency can be checked with a frequency counter. Galanu cover 1 from the outside here.
The continuous oscillation light is converted into high/l/s with a Q switch.
The AG laser beam is focused and irradiated near the nickel coat film 9. The YAG laser beam can pass through the glass cover 1 and selectively evaporate only the coating film 9. The evaporated metal 1o adheres to one side of the electrode 7 disposed on the crystal vibrating piece 6, so that the oscillation frequency of the crystal vibrating piece 6 is lowered due to the added mass effect. Furthermore, the YAG laser is swept and the oscillation frequency of the crystal vibrating piece 6 is repeated until it reaches a certain set value. In this embodiment, a YAG laser was used as the laser beam, but any laser beam that can be transmitted through the glass cover 1 may be used.

According to the above configuration and frequency adjustment method, the piezoelectric vibrator itself can be placed in the atmosphere, so the conventional high vacuum equipment is not required, and frequency adjustment can be performed using equipment with a simple configuration. The speed can also be increased compared to conventional evaporation methods, making it possible to continuously and efficiently adjust the frequency. In the conventional process, hermetic sealing is performed after frequency adjustment, but there was a problem that the oscillation frequency changed due to distortion of the lead terminal 3 in this hermetic sealing process, but the frequency adjustment according to this embodiment is airtight sealing. Since this can be done after stopping, the frequency deviation can be reduced as a result. Furthermore, unlike the conventional example using a laser, the electrode 7 is not directly connected to the agent 9, so that the equivalent resistance of the piezoelectric vibrator is hardly degraded. Further, although the present invention uses laser light, from the perspective of the crystal vibrating piece 6, there is basically no difference compared to frequency adjustment using the conventional vapor deposition method, and the frequency adjustment range can be the same as before.

Effects of the Invention As is clear from the above description, the piezoelectric vibrator and its frequency adjustment method according to the present invention have the effect of being able to continuously and efficiently adjust the frequency in the atmosphere. Still, it is possible to adjust the frequency after hermetic sealing, and the effect is that the frequency deviation of the finished product can be reduced. Furthermore, similar to the frequency adjustment using the conventional vapor deposition method, the adjustment range can be widened and there is no deterioration in equivalent resistance, so an excellent effect can be obtained in that a production process with extremely high mass productivity can be realized.

In addition, in the present invention, both the electrode and the coating film are made of nickel, making them inexpensive, and since nickel does not change over time compared to gold or silver, there is no deviation in the oscillation frequency, making it extremely stable. Become.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view showing an embodiment of the piezoelectric vibrator of the present invention, FIG. 2 is a sectional view showing an embodiment of the frequency adjustment method for a piezoelectric vibrator of the present invention, and FIG. 4 is a half-sectional front view showing a conventional piezoelectric vibrator, and FIG. 4 is a conceptual diagram showing a frequency adjustment method using a conventional vapor deposition method. 1...Glass cover, 2...Case,
3... Lead terminal, 4... Holding part, 6...
... Conductive adhesive, 6... Crystal vibrating piece,
7...Electrode, 8...Sealing agent, 9...
... Court lament, 1Q ... Evaporated metal.

Claims (2)

[Claims] (1) A vibrating piece with nickel electrodes arranged on the front and back sides is supported by a conductive adhesive on the holding part of the lead terminal, and is airtightly placed in an at least partially transparent container with electrical continuity. A piezoelectric vibrator that is housed and has a nickel coated film on the inside of the container. (2) In the piezoelectric vibrator according to claim 1, after the vibrating piece is hermetically sealed, the coating film is evaporated with a laser beam from the outside through the transparent part of the container and attached to the electrode of the vibrating piece to adjust the frequency. How to adjust the frequency of a vibrator.