JPH0856134A - Piezoelectric vibrator for oscillating overtone - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric vibrator for oscillating overtone with high reliability in which more stable third-degree overtone oscillation is attained and high frequency processing is conducted. CONSTITUTION:Two main electrodes 21a, 22a confining major vibration of overtone vibration and a peripheral electrode 41a forming a vibration energy absorbing section via an electrode absence part 31 constituting a vibration energy propagation section around the two electrodes 21a, 22a are provided on one side of a piezoelectric disk 11, and at least the major electrode, the electrode absence part, a full side electrode with respect to a face opposite to the surrounding electrode are formed on the other side of the piezoelectric disk 11. Moreover, the thickness of the electrode adjacent between the major electrodes at least among the peripheral electrodes is selected to be thicker than the thickness of the main electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator for overtone oscillation which enables oscillation at a desired overtone frequency without requiring an overtone resonance circuit.

[0002]

2. Description of the Related Art A conventional technique will be described with reference to FIGS. FIG. 9 is a plan view of a conventional piezoelectric substrate, and FIG. 10 is a bottom view of FIG. The piezoelectric substrate 1 is made of an AT-cut quartz plate that causes thickness shear vibration, and the main electrode 2 is provided at the center of the front surface of the piezoelectric substrate 1 and the electrode 5 is provided at the center of the back surface of the piezoelectric substrate 1.
By providing the main vibration energy confinement section,
A vibration energy propagating portion (electrode absent portion) 3 having a cutoff frequency Fc higher than the cutoff frequency fc of the main vibration energy confining portion is provided around it, and vibration having a cutoff frequency lower than the cutoff frequency Fc is further provided outside thereof. An energy absorbing portion (peripheral electrode) 4 is provided, and the cutoff frequency Fc is set to be lower than the desired sub-vibration frequency of the overtone vibration and higher than the main vibration frequency f0 of this overtone vibration. The vibration energy absorbing portion is configured to absorb energy in a vibration mode (including a fundamental vibration mode) of a lower order than a desired overtone order and to leak a sub-vibration higher than the main vibration to the outside.

[0003]

SUMMARY OF THE INVENTION For example, in a piezoelectric vibrator in which a third overtone is oscillated, the diameter of a main electrode is reduced or the diameter of a piezoelectric substrate is reduced in order to increase the frequency. Although there is a design method, if the size of the main electrode is too small, the CI value of the third overtone tends to deteriorate. When the size of the main electrode is increased, the CI value of the third-order overtone becomes better, but the CI ratio of the fundamental wave and the third-order overtone becomes 2 to 4 times, which is a CI ratio for suppressing the fundamental wave that is generally required. The yield is about 50%, which is poor compared to 3 times. In addition, the method of reducing the diameter of the piezoelectric substrate alone without decreasing the diameter of the main portion electrode to increase the frequency is limited by the size and shape of the peripheral electrode, which is the energy absorbing portion, There was a problem that the physical characteristics could not be obtained. Therefore, more stable overtone oscillation is difficult.

An object of the present invention is to provide a C of the third order overtone.
Provided is a highly reliable piezoelectric resonator for overtone oscillation, which can obtain more stable third-order overtone oscillation without deteriorating the I value and can achieve high frequency.

[0005]

Therefore, the present invention provides a piezoelectric vibrator that oscillates overtone in a desired order,
On one surface of the piezoelectric plate, the main electrode constituting the main vibration energy confining portion for confining the main vibration of the overtone vibration of the desired order, and the vibration through the electrode absent portion constituting the vibration energy propagating portion around the main electrode. An overtone oscillation in which a peripheral electrode that constitutes an energy absorbing portion is provided, at least the main electrode and the electrode absent portion are formed on the other surface of the piezoelectric plate, and a full surface electrode is formed on the opposing surface of the peripheral electrode. In the piezoelectric vibrator for use, the main electrode is divided into two.

Further, the electrode thickness of the peripheral electrodes adjacent to at least the respective main electrodes is made thicker than the thickness of the main electrodes.

[0007]

According to the first aspect, even if the diameter of the main electrode is reduced, the area of the excitation counter electrode is doubled, so that the parallel capacitance C ₀ of the equivalent circuit in the piezoelectric vibrator is increased. And
Increase the CI value of the fundamental wave to increase the CI of the third overtone.
Since only the value can be reduced, the CI ratio between the fundamental wave and the third-order overtone is earned, and the effect of suppressing the fundamental wave is improved.
Further, since the amount of change in the oscillation frequency at the time of Overton oscillation is increased, it becomes possible to increase the frequency.

According to claim 2, the thickened peripheral electrode further absorbs the vibration energy of the fundamental wave, and the fundamental wave suppressing effect is further improved.

The experimental data which is the basis of the above-mentioned action is shown below. FIG. 8 shows a piezoelectric vibrator having a structure (shape A and shape B) according to the present invention as shown in FIG. 1, and a piezoelectric vibrator having a conventional structure (shape C) shown in FIG. 6 is a graph showing comparative statistical data of CI values of a fundamental wave and a third-order overtone. The details will be described below. As a common matter in the experimental examples, in a crystal oscillator having a frequency of 64 MHz with a third overtone oscillation, the crystal plate had a diameter of 4 mm, the back electrode had a diameter of 3.6 mm, and each electrode had a thickness of 0.1 μm. For shape A and shape B, the dimension (G) of the electrode absent portion is 0.
2 mm, each main electrode (one of the two main electrodes)
Has a diameter of 1.2 mm, and for shape C, the dimension (G) of the electrode absent portion is 0.4 mm and the diameter of the main electrode is 1.75.
mm. Regarding the shape A, only the thickness of the peripheral electrode was set to 0.2 μm. From this graph, compared to the shape C (conventional), the shape B (the structure corresponding to claim 1) has a better fundamental wave suppression effect, and the shape B is further improved.
It can be seen that the shape A (configuration corresponding to claim 2) and the fundamental wave suppression effect are further improved.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a piezoelectric substrate showing a first embodiment of the present invention, and FIG. 2 is a bottom view of FIG. The piezoelectric substrate 11 is composed of a disk-shaped AT-cut quartz plate that vibrates in thickness shear. The piezoelectric substrate 11
On the surface of, the direction perpendicular to the holding direction (vertical direction in the figure)
The main electrodes 21a and 22a are provided in parallel with each other, and a peripheral electrode 41a is further provided on the outer side of the main electrode 21a and 22a via an electrode absent portion 31 having a width G. In addition, the piezoelectric substrate 11
An electrode 51a is provided on substantially the entire surface of the piezoelectric substrate 11 on the back surface of the piezoelectric substrate 11 so as to correspond to the surface electrode group. In such a structure, the main part electrodes 21a and 22a and a part of the back surface electrode 51a corresponding thereto constitute a main vibration energy confining part, and the electrode absent part 31 and the back surface electrode 51 corresponding thereto.
A part of a constitutes a vibration energy propagation part, and the peripheral electrode 4
1a and a part of the back surface electrode 51a corresponding thereto constitute a vibration energy absorbing portion. In addition, the main electrode 21a,
22a is commonly connected via the lead electrode 21b and is drawn out to one end of the piezoelectric substrate 11.
The peripheral electrode 41a and the back surface electrode 51a are commonly connected to each other by forming lead electrodes 41b and 51b up to the opposite end of the piezoelectric substrate 11. Then, these electrodes are formed by a vacuum deposition method, a sputtering method, or the like. Incidentally, in the first embodiment, the main electrodes 21a, 22a
Although the parallel direction is not specified in the axial direction, the main electrodes 21a and 22a are provided in parallel in the X-axis direction of the piezoelectric substrate, so that the fundamental wave having a larger vibration displacement is influenced by the end portion of the piezoelectric substrate. In response to this, the CI value becomes high, and acts to earn a CI ratio between the fundamental wave and the third-order overtone.
As a result, the fundamental wave suppression effect is further improved.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a plan view of a piezoelectric substrate showing a second embodiment of the present invention. FIG. 4 is a bottom view of FIG. The same parts as those in the first embodiment are designated by the same reference numerals. The piezoelectric substrate 11 is composed of a disk-shaped AT-cut quartz plate that vibrates in thickness shear. On the surface of the piezoelectric substrate 11, main electrodes 23a and 24a are provided in parallel in the holding direction (left-right direction in the drawing), and further, the electrode absent portion 32 having a width G is provided on the outer side and further around the periphery. An electrode 42a is provided. Further, on the back surface of the piezoelectric substrate 11, an electrode 52a is provided on almost the entire surface of the piezoelectric substrate 11 corresponding to the above-mentioned surface electrode group. In such a structure, the main-part electrodes 23a, 24a and a part of the back-surface electrode 52a corresponding to the main-part electrodes 23a, 24a constitute a main-vibration energy confining part
The electrode absent portion 32 and a part of the back surface electrode 52a corresponding to it constitute a vibration energy propagation portion, and the peripheral electrode 42a and a part of the back surface electrode 52a corresponding to it constitute a vibration energy absorption portion. In addition, the main electrodes 21a and 22a
Are commonly connected by the common electrode 23b and are led out to one end of the piezoelectric substrate 11 by the lead electrode 24b. The peripheral electrodes 42a and the back surface electrode 52a are connected to the lead electrodes 42b and 52b up to the opposite ends of the piezoelectric substrate 11.
To form a common connection. Then, these electrodes are formed by a vacuum deposition method, a sputtering method, or the like. In the second embodiment, the main electrode 23
The parallel directions of a and 24a are provided without specifying the axial direction, but the main electrodes 23a and 24a are arranged toward the X-axis direction of the piezoelectric substrate.
By providing a in parallel, the fundamental wave having a larger vibration displacement is affected by the end portion of the piezoelectric substrate, and the CI value becomes higher, so that the CI ratio between the fundamental wave and the third-order overtone acts. As a result, the fundamental wave suppression effect is further improved.

Next, a third embodiment of the present invention will be described with reference to FIGS. 5, 6 and 7. 5 is a plan view of a piezoelectric substrate showing a third embodiment of the present invention, FIG. 6 is a cross-sectional view taken along the line AA of FIG. 5, and FIG. 7 is a line BB of FIG.
It is sectional drawing which follows the line. The piezoelectric substrate 12 is made of a rectangular AT-cut crystal plate that vibrates in thickness shear. On the surface of the piezoelectric substrate 12, main electrodes 25a and 26a are provided in parallel with the direction orthogonal to the holding direction (the left-right direction in the drawing), and further outside via an electrode absent portion 33 having a width G, and further. A peripheral electrode 43a is provided around the periphery. Further, on the back surface of the piezoelectric substrate 12, a back surface electrode 53a (only a cross-sectional view is shown) is formed on almost the entire surface of the piezoelectric substrate 12 in correspondence with the front surface electrode group.
Is provided. In such a structure, the main part electrodes 25a and 26a and a part of the back surface electrode 53a corresponding to the main part electrodes 25a and 26a constitute a main vibration energy confining part, and the electrode absent part 3 is formed.
3 and a part of the back surface electrode 53a corresponding thereto constitute a vibration energy propagating portion, and the peripheral electrode 43a and a part of the back surface electrode 53a corresponding thereto constitute a vibration energy absorbing portion. The main electrodes 25a and 26a are commonly connected via the lead electrode 25b, and the piezoelectric substrate 12
Has been pulled out to one end. The peripheral electrode 43a and the back surface electrode 53a are commonly connected by being provided up to the opposite end of the piezoelectric substrate 12. Then, these electrodes are formed with a thickness of 0.1 μm by, for example, vacuum vapor deposition. Then, with respect to the convex portion 43d of the peripheral electrode provided between the part 43c of the peripheral electrode 43a and the main electrode, vacuum vapor deposition is performed again with the vapor deposition mask exposing the electrode group. As a result, the thickness of the upper surface electrodes 43c and 43d is 0.
It becomes 2 μm. Therefore, the effect of absorbing vibration energy is improved. Incidentally, in the third embodiment, the convex portion 43d of the peripheral electrode provided between the part 43c of the peripheral electrode 43a and the main electrode.
Regarding the above, the thickness of the electrode was increased, but the peripheral electrode 43a
There is no particular problem even if the thickness of the electrodes in all the parts is increased. Further, in the third embodiment, the parallel direction of the main electrodes 25a, 26a is provided without specifying the axial direction, but by providing the main electrodes 25a, 26a in parallel toward the X-axis direction of the piezoelectric substrate, The fundamental wave having a larger vibration displacement is affected by the end portion of the piezoelectric substrate to increase the CI value, and acts to earn a CI ratio between the fundamental wave and the third overtone. As a result, the fundamental wave suppression effect is further improved.

[0013]

According to claim 1, the effect of suppressing the fundamental wave is improved without deteriorating the CI value of the third-order overtone, and more stable overtone oscillation is obtained.
Further, it is possible to provide a highly reliable piezoelectric resonator for overtone oscillation capable of increasing the frequency.

According to the second aspect of the present invention, there is provided a highly reliable piezoelectric resonator for overtone oscillation, which absorbs the vibration energy of the fundamental wave, improves the fundamental wave suppression effect, and can perform more stable overtone oscillation. You can

[Brief description of drawings]

FIG. 1 is a plan view of a piezoelectric substrate showing a first embodiment of the present invention.

FIG. 2 is a bottom view of FIG.

FIG. 3 is a plan view of a piezoelectric substrate showing a second embodiment of the present invention.

FIG. 4 is a bottom view of FIG.

FIG. 5 is a plan view of a piezoelectric substrate showing a third embodiment of the present invention.

6 is a cross-sectional view taken along the line AA of FIG.

7 is a cross-sectional view taken along the line BB of FIG.

FIG. 8 is a graph showing comparative statistical data of CI values of a fundamental wave and a third-order overtone.

FIG. 9 is a plan view of a piezoelectric substrate showing a conventional example.

FIG. 10 is a bottom view of FIG.

[Explanation of symbols]

1, 11, 12 ... Piezoelectric substrate 2, 21a, 22a, 23a, 24a, 25a, 26a
... Main electrode 3,31,32,33 ... Electrode absent part 4,41a, 42a, 43a ... Peripheral electrode 5,51a, 52a, 53a ... Back surface electrode

Claims (2)

[Claims] 1. A piezoelectric vibrator for overtone oscillation in a desired order, wherein a main electrode constituting a main vibration energy confinement portion for confining a main vibration of the overtone vibration of the desired order is provided on one surface of a piezoelectric plate. A peripheral electrode that constitutes the vibration energy absorbing portion is provided around the electrode through an electrode absent portion that constitutes the vibration energy propagating portion, and at least the main electrode and the electrode are provided on the other surface of the piezoelectric plate. In the piezoelectric resonator for overtone oscillation, in which the entire surface electrode is formed on the absent portion and the opposing surface of the peripheral electrode,
A piezoelectric vibrator for overtone oscillation, wherein the main electrode is divided into two. 2. The piezoelectric vibrator for overtone oscillation according to claim 1, wherein an electrode thickness of at least a portion of the peripheral electrode adjacent to each main electrode is larger than a thickness of the main electrode.