JP3500286B2 - Frequency adjustment method of piezoelectric element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is directed to a piezoelectric element such as a crystal oscillator by colliding it with argon ions, or
The present invention relates to a frequency adjustment method of performing frequency adjustment by removing a part of an electrode film of a piezoelectric element by sputter etching or by irradiating an ion beam.

[0002]

2. Description of the Related Art A conventional frequency adjusting method for a piezoelectric element typified by a crystal oscillator is a vapor-deposition frequency adjusting method for adding a mass to obtain a desired frequency. There has been developed a method for adjusting the frequency of sputter etching or an ion beam to reduce the frequency and obtain a desired frequency.

The latter frequency adjustment technique will be described below.

Since a piezoelectric element finished by cutting and polishing to a predetermined cutting angle and shape forms a base electrode, a mask simulating the shape of the electrode is adhered to the front and back of the piezoelectric element, and a metal such as silver is usually used in vacuum. Deposit the film. At this time, the frequency is controlled by the film thickness monitor, and the resonance frequency is set to be 500 to 2000 ppm lower than the desired value.

Next, the piezoelectric element is mounted on the holder by using solder, a conductive adhesive, or the like in order to make mechanical connection and electrical conduction.

Then, in the frequency adjustment processing apparatus, the resonance frequency of the piezoelectric element is measured before performing the frequency adjustment processing to obtain the frequency difference from the matching frequency, and the sputter etching or ion beam is calculated from the processing rate of the frequency adjustment processing. When the irradiation time is calculated and frequency adjustment processing is performed, the measurement system is electrically disconnected, frequency adjustment processing is performed, and these operations are repeated several times to adjust the frequency difference to zero. To do.

Incidentally, the processing rate generally becomes slower as the area of the base electrode becomes larger, and becomes faster as the processing energy applied to the piezoelectric element becomes larger. Therefore, an appropriate value is previously obtained for each frequency and processing condition. deep.

[0008]

Even if the processing rate of frequency adjustment processing is the same frequency band, the piezoelectric elements are different from each other, or the processing rate is unsatisfactory due to the frequency adjustment source of the sputter gun or ion beam gun. Since it is stable and has variations, the machining rate obtained in advance differs from the actual machining rate, and the resonance frequency after frequency adjustment has deviated from the matching frequency.

Further, the processing rate of the frequency adjustment processing is controlled by changing the applied current of the frequency adjustment source, but in order to maintain the frequency adjustment source in a steady state, a certain amount of electric power or more is supplied. It was necessary, and it was difficult to secure a minute processing rate.

Further, as described above, the frequency before frequency adjustment varies widely among the respective piezoelectric elements. Therefore, if the processing rate is fixed, the piezoelectric element having a large difference from the fitting frequency will have a longer processing time. It was a cause of lowering the mechanical capacity.

On the other hand, in the conventional method, when sputter etching or ion beam irradiation is performed, positively charged argon ions collide with the electrode film of the piezoelectric element, so that the electrode film is positively charged. The charged positive charge tends to flow to the ground, but if a measurement system for measuring the frequency is connected, an oscillation circuit and a transmission wave measuring instrument (this measuring instrument is hereinafter referred to as a network analyzer) will be passed through the measurement system.
Flows to. Since the oscillating circuit and the network analyzer operate with an AC signal, there is a risk of destroying the function when a DC current flows, and it was necessary to electrically disconnect the measurement system during frequency adjustment processing.

Further, if a minute processing rate cannot be obtained or if the processing rate is increased so as not to reduce the mechanical ability, a time difference will occur when the frequency adjustment source is shut off by a shutter or a power source, and the adjustment will be performed. The amount of adjustment is too large for the frequency, and the desired frequency cannot be adjusted.

Therefore, an object of the present invention is to remove a part of the electrode film of the piezoelectric element by colliding argon ions, by sputter etching, or by irradiating with an ion beam.
An object of the present invention is to provide a frequency adjustment method capable of performing frequency adjustment processing while measuring the resonance frequency of the piezoelectric element by removing the positive charge that is charged on the piezoelectric element.

[0014]

According to a first aspect of the present invention, the mass of the electrode film is reduced by causing argon ions to collide with the electrode film formed on the surface of the piezoelectric device to reduce the resonance of the piezoelectric device. In the method of adjusting the frequency,
An impedance matching circuit configured by a parallel circuit of a coil and a resistor connected so as to short-circuit the piezoelectric element and the ground, drops the positive charge charged on the electrode film of the piezoelectric element to the ground, and While removing and measuring the resonance frequency of the piezoelectric element,
The resonance frequency of the piezoelectric element is adjusted from a low frequency to a high frequency to obtain a target frequency.

According to a second aspect of the present invention, there is provided a method for adjusting the resonance frequency of the piezoelectric element by reducing the mass of the electrode film by sputter etching the electrode film formed on the surface of the piezoelectric element. An impedance matching circuit configured by a parallel circuit of a coil and a resistor connected so as to short-circuit the piezoelectric element and the ground, removes the positive charge charged on the electrode film of the piezoelectric element from the electrode film to the ground. Further, while measuring the resonance frequency of the piezoelectric element, the resonance frequency of the piezoelectric element is adjusted from a low frequency to a high frequency to obtain a target frequency.

According to a third aspect of the present invention, there is provided a method for adjusting the resonance frequency of the piezoelectric element by irradiating the electrode film formed on the surface of the piezoelectric element with an ion beam to reduce the mass of the electrode film. The electrode film is configured to drop a positive charge charged on the electrode film of the piezoelectric element to the ground by an impedance matching circuit configured by a parallel circuit of a coil and a resistor connected to short-circuit the piezoelectric element and the ground. And measuring the resonance frequency of the piezoelectric element, the resonance frequency of the piezoelectric element is adjusted from a low frequency to a high frequency to obtain a target frequency.

[0017]

[0018]

[0019]

[Function] The impedance matching circuit of the measuring system (hereinafter referred to as a fixture) usually consists of only a resistor, but by using an impedance matching circuit in which a coil is connected between the piezoelectric element and the ground as the charge removing means. , The DC component that flows into the measurement system can be blocked and only the AC component can be bypassed. As a result, the frequency of the piezoelectric element can be measured without destroying the measurement system.

[0020]

[0021]

Embodiments of the present invention will be described below with reference to FIGS. 1, 2, 3 and 4.

(Embodiment 1) FIG. 1 is a schematic diagram of a frequency adjustment processing apparatus of the present invention.

Inside the frequency adjusting means, that is, the frequency adjusting source 9, there is an electrode rod 6 made of stainless steel and having a diameter of 10 mm, to which a DC power source 13 is connected. The outer peripheral portion 7 of the frequency adjustment source 9 is covered with cylindrical stainless steel having a diameter of 100 mm. The electrode rod 6 and the outer peripheral portion 7 are insulated,
The outer peripheral portion 7 is grounded. Frequency adjustment source 9
The piezoelectric element 3 is housed inside a vacuum container 10, and the vacuum container 10 is evacuated by a rotary pump 12 via a mechanical booster pump 11.

After evacuating the vacuum container 10 to a level of 10 ^-3 Torr, the gas cylinder 8 is placed inside the frequency adjusting source 9.
Argon gas is introduced so as to have a vacuum degree of about 10 ^-1 to 10 ^-2 Torr, and a direct current voltage is applied to the electrode rod 6, so that the electrode rod 6 and the outer peripheral portion 7 are grounded.
An argon plasma is generated between them. The generated plasma turns the argon gas into radicals and ions, and the ionized argon gas jumps out from the ejection port 5 of 3 mm in diameter provided in the tip direction of the electrode rod 6, and the piezoelectric element 3 such as a quartz oscillator located in the opposite direction. Hit the surface of.
When the argon ions collide with the piezoelectric element 3, the electrode film 4
Since the silver of the above is flipped off, the mass of the electrode is reduced, and as a result, the frequency of the piezoelectric element 3 changes from the low frequency to the high frequency.

The frequency of the piezoelectric element 3 which is changed by the collision of the argon ions is changed by the fixture 2.
It can be measured by resonating with the frequency measuring means, that is, the network analyzer 1. For connection between the network analyzer 1 and the fixture 2, a 50Ω system coaxial cable is used.

FIG. 3 is a circuit diagram of the fixture of the present invention.

The resistors 19, 20, 21 are arranged in a π type,
The coil 22 is connected in parallel with the resistor 21. Since the coil 22 is connected so as to short-circuit the piezoelectric element 3 and the ground, even if the piezoelectric element 3 is charged with positive charges and a direct current component flows through the signal line, the coil 22 drops to the ground. Therefore, only the AC component flows into the network analyzer 1, and the frequency of the piezoelectric element 3 can be measured.

The same effect can be obtained with a simple circuit in which the resistors 19 and 20 are omitted.

The measured frequency of the piezoelectric element 3 is sent to the external arithmetic processing unit 15, and the optimum processing rate is calculated from the measurement difference from the fitting frequency. The distance between the piezoelectric element 3 and the ejection port 5 for obtaining the calculated processing rate is calculated, and a signal is sent to the driving device 14 of the frequency adjustment source 9,
The frequency adjustment source 9 is moved back and forth.

The distance between the piezoelectric element 3 and the ejection port 5 is 5 to 2
It has a mechanism that can be changed up to 0 mm, and is kept at a distance of 5 mm before starting frequency adjustment processing. When the machining is started, the frequency adjusting source 9 gradually moves backward while slowing the machining rate while adjusting the frequency according to the programmed frequency difference from the frequency difference and the set value of the machining rate, and slowing the machining rate. When the resonance frequency of 1 matches the matching frequency, the generation of plasma is shut off.

To irradiate and block the argon ions to the piezoelectric element 3, the DC power supply 13 may be directly opened or closed, or the shutter 16 is controlled by the shutter drive mechanism 17 to open or close while plasma is continuously generated. Good. FIG. 4 is a diagram showing a process of changing the frequency of the piezoelectric element whose frequency is adjusted by the frequency adjustment processing device provided with one frequency adjustment source of the present invention.

When the DC power source is turned on, the frequency of the piezoelectric element gradually approaches the tuning frequency, and when the frequency is near the tuning frequency, the frequency adjusting source 9 is moved away from the piezoelectric element 3 to obtain an optimum processing rate. Is possible.

(Embodiment 2) Further, a description will be given with reference to the schematic diagram of FIG. 2 so as to provide a more efficient frequency adjustment control device.

This apparatus has three frequency adjustment sources 9a-9
A piezoelectric element for adjustment, which has c and is composed of a coarse adjustment (H) for roughly adjusting the frequency from the left, a coarse adjustment (M) for performing an intermediate adjustment, and a fine adjustment (L) for performing the final adjustment. 3 is transported by the transport mechanism 18 in steps of coarse adjustment, coarse fine adjustment, and fine adjustment, and the frequency is adjusted.

Rough adjustment is 2000 pp above the base electrode.
The distance from the piezoelectric element 3 to the frequency adjusting source 9a is about 5 mm, which is close to that of other frequency adjusting sources, and is set to a distance of about 5 mm. As a result, a high processing rate of about 800 ppm / sec can be obtained.

For the coarse and fine adjustment, the piezoelectric element 3 for which the coarse adjustment has been raised is used.
The distance between the piezoelectric element 3 and the frequency adjusting source 9b is set to about 10 mm, and the processing rate is about 100 ppm / sec.

For fine adjustment, the piezoelectric element 3 for coarse and fine adjustment is adjusted to 0p.
Taking the adjustment up to pm, the distance between the piezoelectric element 3 and the frequency adjusting source 9c is set to about 20 mm, and a slow processing rate of about 20 ppm / sec can be obtained.

The frequency adjusting sources 9a to 9c individually measure the resonance frequency of the piezoelectric element 3 with the network analyzer 1 via the fixture 2 and manage the frequency difference from the matching frequency with the external arithmetic unit 15 to optimize the resonance frequency. A control signal is sent to the driving device 14 so that the processing rate is obtained, and the distance between the piezoelectric element 3 and the frequency adjusting sources 9a to 9c is changed.

Regarding the operation of each frequency adjusting means,
Since it is the same as the description in FIG. 1, it is omitted.

The present invention is not limited to the above embodiment, and it goes without saying that many modifications can be made.

[0041]

According to the present invention, the frequency adjustment is performed by removing a part of the electrode film of the piezoelectric element by colliding with argon ions, by sputter etching, or by irradiating with an ion beam. In the method for adjusting the frequency of a piezoelectric element, the frequency adjustment processing is performed while measuring the frequency of the piezoelectric element, and the method is configured by a parallel circuit of a coil and a resistor connected so as to short-circuit the piezoelectric element and ground. Since the impedance matching circuit is used to drop the positive charges charged in the piezoelectric element to the ground, the effect of shortening the processing time can be obtained with a simple configuration.

[0042]

[0043]

[Brief description of drawings]

FIG. 1 is a schematic diagram of a frequency adjustment control device of the present invention.

FIG. 2 is a schematic diagram of another frequency adjustment control device of the present invention.

FIG. 3 is a circuit diagram of a fixture of the present invention.

FIG. 4 is a graph showing a frequency adjustment process of the piezoelectric element.

[Explanation of symbols]

1 Network analyzer 2 fixture 3 Piezoelectric element 4 electrode film 5 spout 6 electrode rod 7 Outer periphery 8 gas cylinders 9 Frequency adjustment source 10 vacuum container 11 Mechanical booster pump 12 Rotary pump 13 DC power supply 14 Drive 15 External computing device 16 shutters 17 Shutter drive mechanism 20 Piezoelectric element transport mechanism 19 resistance 20 resistance 21 Resistance 22 coils

   ─────────────────────────────────────────────────── ─── Continued front page       (56) Reference JP-A-5-48363 (JP, A)                 Japanese Patent Laid-Open No. 4-196708 (JP, A)                 Japanese Patent Laid-Open No. 4-196707 (JP, A)                 JP-A-4-196610 (JP, A)                 JP-A-3-209906 (JP, A)                 JP-A-2-122624 (JP, A)                 JP 63-9935 (JP, A)                 3 ЛЕКТРОННАЯ ТЕХНИ               КА, СЕР. РАДИОДЕ ТАЛ               И И РАД И ОКО МПО НЕНТ               Ы 2 [47] (1982) (Russia) P. 51-55

Claims (3)

(57) [Claims] 1. A frequency adjusting method for a piezoelectric element, comprising adjusting the resonance frequency of the piezoelectric element by reducing the mass of the electrode film by bombarding the electrode film formed on the surface of the piezoelectric element with argon ions. An impedance matching circuit configured by a parallel circuit of a coil and a resistor connected so as to short-circuit the piezoelectric element and the ground removes the positive charge charged on the electrode film of the piezoelectric element to the ground and removes it from the electrode film. And while measuring the resonance frequency of the piezoelectric element,
A method for adjusting a frequency of a piezoelectric element, wherein a resonance frequency of the piezoelectric element is adjusted from a low frequency to a high frequency to obtain a target frequency. 2. A frequency adjusting method for a piezoelectric element, wherein the resonance frequency of the piezoelectric element is adjusted by reducing the mass of the electrode film by sputter etching the electrode film formed on the surface of the piezoelectric element. And a grounded positive charge that is charged on the electrode film of the piezoelectric element by an impedance matching circuit configured by a parallel circuit of a coil and a resistor connected so as to short-circuit and ground, and is removed from the electrode film, And while measuring the resonance frequency of the piezoelectric element,
A method for adjusting a frequency of a piezoelectric element, wherein a resonance frequency of the piezoelectric element is adjusted from a low frequency to a high frequency to obtain a target frequency. 3. A frequency adjusting method for a piezoelectric element, wherein the mass of the electrode film is reduced by irradiating an electrode film formed on the surface of the piezoelectric element with an ion beam to adjust the resonance frequency of the piezoelectric element. An impedance matching circuit configured by a parallel circuit of a coil and a resistor connected so as to short-circuit the piezoelectric element and the ground removes the positive charge charged on the electrode film of the piezoelectric element to the ground and removes it from the electrode film. And while measuring the resonance frequency of the piezoelectric element,
A method for adjusting a frequency of a piezoelectric element, wherein a resonance frequency of the piezoelectric element is adjusted from a low frequency to a high frequency to obtain a target frequency.