JPH029484B2 - - Google Patents

Description

[Detailed description of the invention] (a) Technical field of the invention The present invention is installed in satellite communications, submarine repeaters, etc.
This invention relates to highly stable crystal resonators that require high precision.

(b) Background of the technology The crystal blank used in highly stable crystal resonators is usually a round or rectangular plate with one side spherically processed to use a thickness-shear vibration mode.

Even under harsh environmental conditions in satellite communications, submarine repeaters, etc., not only semi-permanent long-term frequency stability but also short-term frequency stability is required, and a crystal oscillator with fast rise characteristics is required.

As such a high-stability crystal resonator, a two-rotation Y plate type crystal piece such as an AT cut or an IT cut, which is formed by rotating the cutting direction from the crystal crystal axis around the optical axis, is used. Furthermore, it is used housed in a thermostatic chamber that can cope with temperature changes in the outside world, and requires stability and high performance as a vibration source.

(c) Prior art and problems In order to obtain a resonator with excellent electrical characteristics, a large crystal piece is required.On the other hand, as equipment becomes more multiplexed and smaller, crystal resonators are also required to be smaller. For this reason, in thickness-shear resonators, which are advantageous for miniaturization, in order to suppress spurious resonance, a crystal piece is polished and formed into a spherical shape on one or both sides, which is effective for confining vibration energy in the center of the crystal plate. .

Electrode films are deposited on both sides of the formed crystal piece.
Usually, gold or silver is used for the electrode film. The final step of adjusting the frequency of the vibrator is performed by changing the thickness of the electrode film while measuring the frequency.

Figures A and B in Fig. 1 show a thickness-shear resonator with one side spherical; Figure A is a top view, and Figure B is a side view.

FIG. 2 is a diagram showing the configuration of a conventional crystal resonator. In the figure, 1 is a crystal piece, 2 is an electrode film, 3 is a metal cap, 4 is a base, 5 is a support plate, 6 is a lead, 7
1 and 2 respectively indicate glass fused parts.

Electrode films are formed on both sides of the crystal blank 1 by vapor deposition, and when a predetermined frequency adjustment is completed, the crystal blank 1 is housed in a container as a crystal resonator. The container consists of a metal cap 3 and a base 4 and has a hermetically sealed structure. A crystal resonator (crystal piece 1) is bonded and supported by a flexible support plate 5 made of nickel silver, phosphor bronze, etc. using bonding or adhesive, connected to an external lead 6, and fused and sealed with low melting point glass. Stop. When the inside is to be evacuated, an exhaust pipe is provided on the base 4, and after the exhaust is evacuated, it is sealed off by pressure melting.

However, with this structure, it is impossible to adjust the characteristics after assembly. In addition, since the resonator is used in an oscillation circuit system housed in a thermostatic chamber, frequency characteristic tests and frequency adjustments are performed at room temperature in the atmosphere using a quantitative conversion table corresponding to the operating temperature. ,
There were concerns that the product lacked stability and long-term reliability. Furthermore, it cannot cope with changes in frequency characteristic values over time caused by residual stress in the electrode film, which is seen in aging characteristics.

(d) Purpose of the Invention In view of the above points, the present invention aims to provide a sputtering mechanism for forming an electrode film that can be finely adjusted in a container housing a crystal resonator, and to obtain a highly stable crystal resonator. shall be.

(e) Structure of the Invention According to the present invention, the above-mentioned object is to house a coarsely adjusted crystal resonator in a sealed container, and to precisely adjust it in a constant temperature bath set to the same conditions as the usage conditions. This can be achieved by providing a vacuum exhaust system that shares an argon gas filling port, and applying a voltage between the anode that holds the crystal resonator and the target cathode that forms the electrode film, thereby depositing the sputtering electrode film.

(f) Embodiment of the Invention FIG. 3 is a diagram showing the configuration of a crystal resonator which is an embodiment of the invention. Electrode films 12 made of gold (Au) are formed on both sides of a thick shear vibrator 11 whose one side is processed into a spherical surface, and is supported and fixed by a support plate 15 made of highly flexible phosphor bronze or the like and external leads 16. Store in a container.

The container consists of a metal cap 13 and a base 14 made of an insulating material, and the periphery is sealed with a clasp or the like to form a hermetically sealed structure. Further, the lead terminal 16 is sealed and fixed with a low melting point glass 17 as shown in the figure.

On the other hand, a target electrode 18 targeting gold (Au) is provided, and a valve control system 21 is provided to perform gas inflow control for filling argon gas into an exhaust port 20 for reducing the pressure inside the container to vacuum, and for controlling exhaust pressure reduction.

The thus assembled crystal resonator is precisely adjusted in a constant temperature bath set at the same temperature as the operating temperature condition. Precise adjustment is performed by sputtering, in which a gold (Au) film is further laminated on one side of the electrode film so as to obtain a predetermined frequency characteristic.

Lead terminal 16 and support plate 15 for crystal resonator 11
A target electrode 1 which serves as an anode and a cathode through
DC high voltage is applied between the two poles of 8. The pressure inside the container is reduced to vacuum and replaced with argon gas, and a negative DC bias voltage is generated on the target 19 placed on the tip of the target electrode 18 inside the container facing the electrode film 12 of the crystal resonator 11. Accelerated argon ions (Ar ⁺ ) from the anode collide with the cathode to eject target atoms, and the frequency is measured by the frequency counter 30 while the oscillator 11
Precise adjustment is performed by laminating a sputtered film (Au) on the electrode film 12.

In this case, since the target 19 is small and placed relatively close to the electrode film 12, the sputtered film that is laminated and added is different from the original electrode film 1.
It does not protrude beyond 2, and there is no need to provide a mask.

By repeating sputtering in an airtight chamber and allowing fine adjustment without being affected by external conditions, a highly stable crystal resonator with highly accurate frequency characteristics can be obtained.

FIG. 4 is a block diagram showing a valve control system according to an embodiment of the present invention.

Close the valve V ₆ provided in the argon gas (Ar) filled pipe 22, and close the chamber 2 for mounting the crystal resonator.
Evacuate 3. That is, after opening the valve V ₁ and rough evacuation with the rotary pump 25, the valves V ₂ and V ₃ are opened, the valve V ₁ is closed, and the diffusion pump 24 is operated to evacuate to a high vacuum. At this time, valve 4 is open. After evacuation to a constant pressure, valve _V3 is appropriately throttled, and argon gas flow rate adjustment valve _V6 is opened to introduce argon gas.

Using the valve control system configured as described above, a spatter film is generated, and after the adjustment is completed, the argon gas is exhausted, the pressure is reduced to a constant pressure, and the exhaust port (see Fig. 3, 20) is sealed by pressure melt to create an airtight seal. Obtain a quartz crystal.

The applied voltage is 500 VDC, 5 mA, and sputtering is repeated for several seconds to adjust to the desired frequency. Adjustment range is omitted.
Since the container is evacuated to a high vacuum and baked without being exposed to the atmosphere, it is possible to adjust the set oscillation frequency with high accuracy, for example, to within 1 ppm (see Figure 3, 18).
Although it was sealed with the internal components inside, it had no effect on the characteristics and a stability of 5×10 ^-9 ppm/decade was obtained.

(g) Effects of the Invention As explained in detail above, the crystal resonator of the present invention provides highly stable characteristics compared to conventional ones, and furthermore, fine adjustment is performed in a constant temperature bath set to substantially the same conditions as the operating conditions. This has the effect of further improving reliability.

[Brief explanation of drawings]

Figures A and B in Figure 1 are diagrams showing a thickness-shear resonator with one side spherical, Figure A is a top view, Figure B is a side view, and Figure 2 is a diagram showing a conventional crystal oscillator configuration. FIG. 3 is a diagram showing the configuration of a crystal oscillator as an embodiment of the present invention, and FIG. 4 is a block diagram showing a valve control system as an embodiment of the present invention. In the figure, 11 is a crystal resonator, 12 is an electrode film, 13 is a metal cap, 14 is a base, 15 is a support plate, 16 is a lead terminal, 17 is a low melting point glass, 18 is a target electrode, 19 is a target, and 20 is an exhaust gas. mouth, 2
1 is a valve control system, 22 is an argon gas filled pipe, 23 is a chamber, 24 is a diffusion pump, 25 is a rotary pump, 30 is a frequency counter, V ₁ ~
V ₃ valve shown.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an AT-cut thickness-slide crystal resonator having one or both surfaces spherical and having electrode films formed on both sides, wherein the crystal resonator with frequency grain adjustment is sealed. The crystal oscillator is supported and fixed in a container, and in a constant temperature bath set at the same temperature as the operating temperature, an electrode forming metal is laminated and added to the electrode film of the crystal resonator supported and fixed in the container, and the frequency is adjusted. A method of manufacturing a crystal resonator characterized by precision adjustment. 2. An exhaust port that also serves as a gas filling inlet is provided in a part of the container with the above-mentioned sealed structure, and the external lead connected to the support plate holding the crystal resonator is used as an anode, and is insulated and hermetically planted independently of the external lead. A voltage is applied using the target electrode as a cathode, and the metal forming the target electrode placed on the tip of the target electrode in the container facing the electrode film of the crystal resonator is sputtered while measuring the frequency. Manufacture of a crystal resonator according to claim 1, characterized in that the crystal resonator is laminated and added to the electrode film of the crystal resonator, and after reaching a required frequency, the air is evacuated under reduced pressure and the exhaust port is sealed and cut. Method.