JPH0463009A - Thickness-shear crystal resonator - Google Patents

Abstract

PURPOSE:To generate oscillation with frequency of over tone by using a non- adjust oscillation circuit by forming an excitation electrode by forming a fundamental wave electrode with small area in the center part of one side plane of a crystal piece which excites thickness-shear oscillation and providing a fine gap at the fundamental wave electrode with area larger than that of the fundamental wave electrode. CONSTITUTION:The fundamental wave electrode 12 with small area is formed in the center part of one side plane of the crystal piece 11. The excitation electrode 13 with area larger than that of the fundamental wave electrode 12 is formed at the same plane where the fundamental wave electrode 12 is located by providing the fine gap (t). By providing the fundamental wave electrode 12 and the excitation electrode 13 by forming the fine gap (t), the energy of the fundamental wave electrode 13 generated in the excitation electrode 13 can be attenuated by transmitting to the fundamental wave electrode 12. A frequency adjusting electrode 14 with large area is formed on another side plane of the crystal piece 11 at least confronting with the fundamental wave electrode 12 and the excitation electrode 13.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a thickness-shear crystal resonator that can easily perform overtone oscillation.

(Technical background of the invention and its problems) Recently, many electronic devices use inexpensive and high-performance crystal resonators as standards for frequency, time, etc., so crystal resonators are manufactured and used in large quantities. ing.

The vibration modes of such a crystal resonator include various vibration modes such as bending vibration, deflection vibration, and thickness vibration. In a crystal resonator whose resonance frequency is on the order of MHz, a thickness shear vibration moat is mainly used. As described above, the resonant frequency of a crystal resonator excited in the thickness-shear vibration mode is inversely proportional to the thickness of the crystal piece. Therefore, the thickness of a vibrator with a resonant frequency of IOMHz is approximately 0.167 mrn, and the thickness of a vibrator with a resonant frequency of 30 MHz is approximately 0.056 mm.
become. In other words, the thickness of the crystal piece becomes thinner in inverse proportion to the resonant frequency, and as the frequency increases, the strength of the crystal piece increases.
Manufacturing is extremely difficult due to processing and other issues.

For this reason, when a crystal resonator with a high resonance frequency is required, an overtone mode is used. Overtone motes resonate at frequencies that are odd multiples of the resonant frequency of the fundamental wave, and are generally 3rd, 5th, and 7th order.
Modes such as:

However, in such an overtone oscillation circuit, a tuning circuit is provided to suppress the resonance of the fundamental wave. Therefore, it is difficult to downsize the tuning circuit, especially the inductance, and furthermore, there is a problem in that adjustment is required.

In recent years, in order to downsize oscillation circuits and eliminate the need for adjustment, micro-sized oscillators, for example, in which a crystal resonator and an integrated circuit are integrated to form a non-adjustment oscillation circuit, have been manufactured and used in large quantities. However, since the oscillation circuit having such a configuration does not have a tuning circuit, it is not possible to utilize the overtone mode. For this reason, the maximum frequency of the oscillation output is limited to about 30 MHz for boat fishing due to limitations in the processing of crystal pieces.

Several crystal resonators have been proposed that are capable of oscillating at an overtone frequency using an unadjusted oscillation circuit by suppressing the fundamental vibration moat.

For example, there is a method that suppresses the fundamental wave vibration mode by transmitting the vibration energy of the fundamental wave to the supporting part of the crystal piece and attenuating it. However, this type of device has a problem in that it is extremely difficult to adjust the frequency due to irregularities in the distance between the supporting portion of the crystal piece and the electrode.

There are also methods that suppress the fundamental wave vibration mode by unevenly distributing the electrodes around the periphery of the crystal blank, or by making the electrode dimensions match the dimensions of the crystal blank.

However, in such a device, the crystal piece needs to have a special structure, and since the positions of the electrode and the supporter are close to each other, there is a problem that a special holding structure is required.

(Object of the Invention) The present invention has been made in view of the above circumstances, and it is possible to easily perform frequency adjustment work, have a simple structure, and standardize the overtone frequency using an unadjusted oscillation circuit. The object of the present invention is to provide a thickness-shear crystal resonator that can oscillate at .

(Summary of the Invention) The present invention forms a fundamental wave electrode with a small area in the center of one side plate surface of a crystal piece that is excited with thickness shear vibration, and has a small area on the fundamental wave electrode with a larger area than the fundamental wave electrode. A frequency adjustment electrode is formed on the other side plate surface of the crystal piece, facing at least the fundamental wave electrode and the excitation electrode, and this electrode is electrically connected to the fundamental wave electrode. The main surface of the crystal piece is not chamfered.

(Example) Hereinafter, a crystal resonator according to an example of the present invention will be described in detail with reference to a side view shown in FIG. 1 and a plan view of an example board shown in FIG.

In the figure, numeral 11 is an AT-cut thickness sliding crystal piece, which is formed by cutting a quartz crystal at a predetermined angle with respect to its crystal axis and forming it into a round plate shape. Incidentally, this crystal blank 11 is not chamfered at the peripheral edge in order to suppress the vibration of the fundamental wave and encourage the vibration of the overtone.

A fundamental wave electrode 12 having a small area is formed in the center of one side plate surface of this crystal piece 11. That is, since the vibration of the fundamental wave is unevenly distributed in the central part of the plate surface, the fundamental wave electrode 12 having a small area is provided in this central part.

The fundamental wave electrode 1 is placed on the same plate surface as this fundamental wave electrode 12.
The excitation electrode 13 having an area larger than 2 is formed with a minute gap t. That is, since overtone vibrations are generated over a wide range without being concentrated in the center of the plate surface, overtone vibrations can be excited even if the excitation electrode 13 is unevenly distributed from the periphery of the plate surface. be able to.

Then, the fundamental wave electrode 12 and the excitation electrode 13 are connected with a minute gap t.
By providing such a structure, the energy of the fundamental wave vibration generated in the excitation electrode 13 is transmitted to the fundamental wave electrode 12 and attenuated.

A large-area frequency adjustment electrode 14 is formed on the other side plate surface of the crystal blank 11, facing at least the fundamental wave electrode 12 and the excitation electrode 13.

Then, by connecting the fundamental wave electrode 12 to this frequency adjustment electrode 14 with a lead wire or the like to electrically short-circuit the vibration energy of the fundamental wave, the fundamental wave vibration is suppressed and the overtone vibration is relatively promoted. I try to do that.

By forming electrodes on the front and back surfaces of the crystal blank 11 polished to a thickness corresponding to the desired resonance frequency, and then depositing a minute mass on the frequency adjustment electrode 14, the resonance frequency can be adjusted by the mass addition effect. Adjust accurately.

Note that the gap t between the fundamental wave electrode 12 and the excitation electrode 13 is 0.2
Crystal impedance of the fundamental wave (hereinafter referred to as CI) when changed in the range of ml11 to 0.0711Im
CI at the frequency of R1 and the third overtone, R
The relationship between the impedance ratio R1/R3 and the resonant frequency of 3 was as shown in the graph shown in FIG.

That is, as the gap t is made narrower, the impedance ratio becomes larger and better characteristics are exhibited.If the gap t is constant, the impedance ratio R1/R3 becomes smaller and the characteristics deteriorate as the frequency becomes higher.

Note that making this interval t too narrow is not recommended for electrodes 12.13.
It is easy to cause problems such as blurring of edges during vapor deposition, making it impossible to maintain electrical insulation, and at least 0.05
It is preferable to set it as more than mm.

On the other hand, in order to suppress the fundamental wave vibration and reliably oscillate at the overtone frequency, the impedance ratio R1/
The value of R3 needs to be at least 3 or more. Therefore, if the desired resonance frequency is 80 MH2 or less, the upper limit of the gap t is preferably 0.2 mm, and if the desired resonance frequency is 100 MH2 or less, the upper limit of the gap is preferably 0.1 mm.

Therefore, when constructing a conventionally known unadjusted oscillation circuit using the crystal resonator of the above embodiment, the excitation electrode 13 is used as one terminal, and the commonly connected fundamental wave electrode 12 and frequency adjustment electrode 14 are used as the other terminal. shall be. In this way, the CI value of the overtone frequency is smaller than the CI value of the fundamental frequency.
Since the value is small, the fundamental vibration can be suppressed and oscillated at the overtone frequency.

Since an unadjusted oscillation circuit can be used as the oscillation circuit, no inductance is required and it is possible to integrate the circuit, making it possible to significantly reduce the size and construct an unadjusted oscillator that can obtain high-frequency oscillation output. .

It should be noted that the present invention is not limited to the above-mentioned embodiments, and in the above-mentioned embodiments, a round plate-shaped crystal piece is used, but for example, a strip-shaped crystal piece can be used as shown in FIG. Good too.

Further, in the above embodiment, the fundamental wave electrode 12 and the frequency adjustment electrode 14 are connected by a lead wire or the like, but for example, the fundamental wave electrode 12 and the frequency adjustment electrode 14 are connected by going around the periphery of the crystal blank. A connecting electrode may also be formed.

(Effects of the Invention) As detailed above, by using the crystal resonator of the present invention, overtone oscillation can be performed using an unadjusted oscillation circuit, making it possible to use an integrated oscillation circuit. I can,
It is possible to provide a crystal resonator that can constitute a small-sized oscillator.

[Brief explanation of the drawing]

FIG. 1 is a side view illustrating a crystal resonator according to an embodiment of the present invention, FIG. 2 is a plan view of an example of the crystal piece of the above embodiment, and FIG. A graph showing the relationship between the CI ratio of the tone, the frequency, and the gap between the fundamental wave electrode and the excitation electrode. FIG. 4 is a plan view of an example of a crystal piece according to another embodiment of the present invention. 11...Crystal blank 12...Fundamental wave electrode 13...Excitation electrode 14...Frequency adjustment electrode Figure 1 Atsushi Figure 2 and 14 Figure 3 A', Tun; Q next side - 9; t-;

Claims (1)

[Scope of Claims] A crystal piece to which thickness shear vibration is excited; a fundamental wave electrode with a small area formed at the center of one side plate surface of the crystal piece; and a fundamental wave electrode formed on one side plate surface of the crystal piece. an excitation electrode formed with a large area and a small gap between the fundamental wave electrode; and an excitation electrode formed on the other side plate surface of this crystal piece facing at least the fundamental wave electrode and the excitation electrode; A thickness-slide crystal resonator comprising a large-area frequency adjustment electrode electrically connected to an electrode, and characterized in that the main surface of a crystal piece is not chamfered.