JPH05175775A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To adjust easily and accurately the resonance frequency of the piezoelectric resonator employing a crystal vibrator with an electrode through chemical etching. CONSTITUTION:In the piezoelectric resonator employing a non-contact electrode type crystal vibrator, the crystal vibrator is chemically etched by using a hydrofluoric acid or the like to adjust a resonance frequency (f) to a prescribed value. For example, when the resonance frequency (f) is 10MHz, the thickness (t) is selected to be 160mum, and when the accuracy of the resonance frequency requires 10Hz, the accuracy DELTAt of the thickness is selected to be ¦DELTAt¦=1.6nm. In the case of the chemical etching, the concentration of etchant is diluted to decrease a rate of the etching. That is, the processing accuracy of the thickness is improved. As the etchant condition, in the case of 50%HF (23 deg.C+ or -0.5 deg.C), the etching rate is 105-110Hz/sec, the thickness results in 0.88nm/sec by taking the etching from both sides into account and the high processing accuracy is obtained. The accuracy of 110Hz is obtained by controlling the etching time with the accuracy of nearly 1sec.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator using an AT-cut crystal resonator, and more particularly to a method of adjusting resonance frequency.

[0002]

2. Description of the Related Art Conventionally, there are a crystal resonator with an electrode and a crystal resonator of a non-contact electrode type as a piezoelectric resonator using the thickness shear vibration of an AT-cut crystal resonator. Most crystal oscillators with electrodes have a structure in which electrodes are formed on the center of both sides of the oscillator by vapor deposition to support the outer periphery of the oscillator, and the vibration energy of the oscillator does not escape to the outside. As described above, the shape of the vibrator is formed into a convex type (lens type) or a single step type as shown in FIG. Further, as the non-contact electrode type crystal unit, as shown in FIG.
Disk-shaped upper outer plate 21, lower outer plate 2
2. A vibrator 23 having a convex cross section which is sandwiched between both plates.
The vibrator 23 is connected to the two external plates 21 and 22 so that the electrode portions 21a and 22a formed on the electrodes 1 and 22 face each other.
It is composed by sandwiching from both sides. To adjust the resonance frequency of a crystal unit with electrodes, gradually increase the film thickness of electrodes deposited on both sides of the unit by vapor deposition and increase the mass added to the unit to increase the resonance frequency. Has been used. To adjust the resonance frequency of the non-contact electrode type crystal unit,
A method has been used in which the resonance frequency is raised to a predetermined value by gradually reducing the thickness of the vibrator.

[0003]

However, in the resonance frequency adjusting method shown in the above-mentioned prior art, a large-scale device is required, and in the non-contact electrode type crystal resonator, in order to obtain the absolute frequency accuracy, There were problems such as high precision required for polishing.

The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a piezoelectric resonator in which the resonance frequency can be easily and accurately adjusted.

[0005]

The structure of the present invention for solving the above-mentioned problems is, in a piezoelectric resonator using a crystal resonator with electrodes, the resonance frequency of the piezoelectric resonator is adjusted by chemical etching. It is characterized by doing so. In addition, a non-contact electrode type crystal unit is used, in which the crystal unit is sandwiched by two outer plates from both sides so that the vibrating unit of the crystal unit and the electrode section formed on the outer plate face each other. In the piezoelectric resonator described above, the resonance frequency of the piezoelectric resonator is adjusted by chemical etching.

[0006]

According to the present invention, the resonance frequency of the piezoelectric resonator is adjusted by chemical etching, and the resonance frequency can be easily adjusted with high accuracy.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. The resonance frequency f of the piezoelectric resonator is determined only by the thickness t of the AT-cut crystal resonator and is given by the following equation. f = a / t However, a is a constant, and in the case of fundamental vibration, a = 1.6 × 10 ³ MHz · μm.

In the piezoelectric resonator using the non-contact electrode type crystal resonator shown in FIG. 2, the crystal resonator is chemically etched using hydrofluoric acid or the like to generate a resonance frequency f.
Can be adjusted to a predetermined value. Here, from the above equation, Δf = (− a / t ² ) · Δt is obtained. For example, if the resonance frequency f is 10 MHz, the thickness t is 160 μm according to the equation, and if the resonance frequency accuracy is 100 Hz, the thickness accuracy Δt is | Δt from the expression. High processing accuracy of │ = 1.6 nm is required, and it is difficult to perform mechanical processing such as polishing. However, in the case of chemical etching, the etching rate can be lowered, that is, the processing accuracy of the thickness can be increased by reducing the concentration of the etchant. For example, as shown in FIG. 3, when 50% HF (23 ° C. ± 0.5 ° C.) is used as the etchant condition,
The etching rate is 105 to 110 Hz / sec, which is 0.88 nm / se in consideration of etching from both sides when converted into the processing accuracy of the thickness t.
Therefore, it can be seen that high processing accuracy can be obtained. That is, if the etching time is controlled with an accuracy of about 1 sec, an accuracy of 110 Hz can be obtained. Further, the etching rate can be lowered by lowering the concentration of the etchant, and in this case, higher processing accuracy can be obtained.

Further, even in the case where the frequency is determined by the thickness like the SC cut crystal oscillator, the adjustment of the resonance frequency by chemical etching can be applied.

As described above, in the present invention, the resonance frequency of the piezoelectric resonator is adjusted by chemical etching,
The resonance frequency can be easily adjusted with high accuracy.

[0011]

As described above in detail with reference to the embodiments, according to the present invention, chemical etching is used to adjust the resonance frequency of the piezoelectric resonator, and the resonance frequency is easily and accurately adjusted. be able to.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram showing an example of a crystal resonator with electrodes.

FIG. 2 is a cross-sectional configuration diagram showing an example of a piezoelectric resonator using a non-contact electrode type crystal resonator.

FIG. 3 is a diagram showing a relationship between resonance frequency and etching time.

Claims (2)

[Claims] 1. A piezoelectric resonator using a crystal resonator with an electrode, wherein the resonance frequency of the piezoelectric resonator is adjusted by chemical etching. 2. The crystal unit is arranged so that the vibrating part of the crystal unit and the electrode part formed on the outer plate face each other.
A piezoelectric resonator using a non-contact electrode type crystal resonator sandwiched between two external plates, wherein the resonance frequency of the piezoelectric resonator is adjusted by chemical etching. Resonator.