JPH0750544A - Crystal vibrator - Google Patents

Abstract

PURPOSE:To obtain an excellent and stable vibration characteristic and to make the size small by adhering a crystal chip stimulating piezo-electric vibration and a crystal made thin plate with an exciting electrode formed thereto in an atomic level. CONSTITUTION:This vibrator is provided with a crystal chip 11 stimulating piezoelectric vibration, a recessed part 12 with a very small depth formed to both side faces of the crystal chip 11, thin plates 13 consisting of crystal stuck onto both side faces of the crystal chip 11 in an atomic level, and electrodes 14 formed on the sticking faces of the thin plates 13 and used to simulate the crystal chip 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator, and more particularly to improvement of an electrode structure.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a crystal resonator, a crystal of an artificial crystal is cut at a predetermined angle with respect to a crystal axis to cut out, for example, a plate-shaped crystal piece. Then, in order to make the crystal piece have a predetermined resonance frequency, for example, the outer shape is polished and formed. For example, in an AT-cut crystal resonator that excites thickness shear vibration, a crystal piece is polished in the thickness direction and processed to have a desired resonance frequency. Then, a metal such as silver or aluminum is vapor-deposited on both side surfaces of the crystal piece to form an excitation electrode, and the thickness shear vibration is excited by the excitation electrode.

However, in such a structure, since the excitation electrode is formed directly on the plate surface of the crystal piece, when a chemical change such as oxidation of the electrode metal occurs, the vibration characteristics are greatly affected. I have a problem to give. Therefore, the crystal element on which the excitation electrode is formed is housed in an airtight container and the inside of the container is evacuated or an inert gas is sealed. However, even if the quartz piece is hermetically sealed in the container, the gas such as oxygen remaining in the container immediately after sealing reacts with the metal forming the electrode, so that the resonance frequency of the so-called aging characteristic Exhibit change. Then, such a change in the frequency continues until the concentration of the active gas in the container decreases to such an extent that a reaction does not occur, and thereafter, changes to a relatively stable state. In addition, when the excitation electrode is formed by vapor deposition, the vapor deposition metal may adhere to the plate surface of the crystal piece as a grain, and in such a state the vibration characteristics may be significantly impaired. There was a problem that management was difficult and required skill.

For this reason, conventionally, there has been a structure in which the crystal piece and the electrode are formed of separate members, and the electrodes are opposed to the plate surface of the crystal piece with a minute gap to excite the piezoelectric vibration. there were. FIG. 2 is a side sectional view showing an example of such a crystal resonator, which is a crystal resonator having a so-called pressure mount structure. In this crystal oscillator, an electrode plate 2, a crystal piece 3, and an electrode plate 2 are stacked and stored in this order inside a container 1 having an opening on one side. Then, the spring 4 is placed on the electrode plate 2 and the lid 5 is screwed. The crystal piece 3 has a thickness polished to have a desired resonance frequency. Further, the electrode plate 2 is formed with minute protrusions 5 at four corners, for example, so as to face each other with minute gaps on both sides of the crystal blank 1.

However, in such a structure, it is necessary to press the electrode plate 2 against the crystal piece 3 by using a strong spring 4 so that the relative position between the crystal piece 3 and the electrode plate 2 can be stably maintained. There is. For this reason, the container 1 needs to have a structure capable of mechanically obtaining sufficient strength, and the shape of the container 1 becomes large, so that there is a problem in that the overall shape cannot be reduced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is preferable to bond a crystal element that excites a piezoelectric vibration and a thin plate made of crystal having an excitation electrode to each other at an atomic level. Further, it is an object of the present invention to provide a crystal resonator that can obtain stable vibration characteristics and can be downsized in shape.

[0007]

DISCLOSURE OF THE INVENTION The present invention is directed to a crystal piece for exciting piezoelectric vibration, a concave portion having a minute depth formed on both side plate surfaces of the crystal piece, and both side plate surfaces of the crystal piece. It is characterized by comprising a thin plate made of crystal bonded at the atomic level and an electrode formed on the bonding surface of the thin plate for exciting the crystal piece.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the side sectional view shown in FIG. Reference numeral 11 in the drawing is a crystal piece formed into a substantially plate shape. This crystal piece 11 is, for example, an AT
The thickness of the cut piece is a crystal piece of artificial quartz, which is cut at a predetermined angle with respect to the crystal axis to form a plate having a size of about 5 mm square. Since the resonance frequency of the thickness-slip crystal oscillator is inversely proportional to the thickness, the crystal piece 11 is polished in the thickness direction so as to have a desired resonance frequency.

Then, in the central portion of both side plate surfaces of the crystal blank 11,
Small depth of about 3 mm square, for example 20 to 4
The concave portion 12 having a depth of 0 nm is formed. The bottom surface of the recess 12 is preferably formed as a smooth flat surface, and can be formed by a treatment such as ion beam or etching. Then, the thin plates 13 made of crystal having a thickness of about 50 to 100 μm are airtightly bonded to both side plate surfaces of the crystal piece 11. Crystal piece 1
When the thin plate 13 is attached to the substrate 1, if a glue or the like is used, the hardened adhesive is interposed between the crystal blank 11 and the thin plate 13 to increase the gap therebetween. Therefore, it is desirable that the crystal piece 11 and the thin plate 13 be adhered to each other directly or by a known method through a silicon oxide film so that they can be adhered to each other.

Prior to the bonding of the crystal piece 11 and the thin plate 13, the electrode 14 is formed on the bonding surface of the thin plate 13 by vacuum deposition or the like. This electrode 14 is led out to the outside and used, for example, for connecting to an electric circuit to excite the piezoelectric vibration of the crystal piece 11. Further, when the thin plate 13 is attached to the crystal piece 11, the recess 12 may be hermetically sealed. If you do this,
Generally, the thin plate 13 and the crystal piece 11 that are bonded together are housed in an airtight container, so that the recess 12 can be doubly sealed against the outside air and can be maintained in a stable state. However, when the recessed portion 12 is hermetically sealed, the thin plate 13 is damaged when a pressure difference occurs between the atmospheric pressure of the recessed portion 12 and the external atmospheric pressure, for example, when the sealed gas expands due to a temperature change. Therefore, it is necessary to consider to reduce the pressure difference as much as possible. For example,
If the volume of the recessed portion is extremely small, the amount of gas to be sealed can also be made extremely small and almost no pressure difference due to temperature change can occur. Furthermore, when positively equalizing the concave portion 12 of the crystal piece 11 and the outside, for example, the crystal piece 1
A groove may be preliminarily formed on the surface to which the thin plate 13 of No. 1 is attached. In this way, the recess 12 and the outside are communicated with each other through the groove, so that the pressure can be equalized and the thin plate 13 can be reliably prevented from being damaged due to the difference in atmospheric pressure.

With such a configuration, the plate surface of the crystal piece 11 and the electrode 14 are separate bodies, so that the plate surface of the crystal piece 11 can be maintained in a clean state and an extremely good resonance characteristic can be obtained. Obtainable. Further, the crystal piece 1 of the electrode 14
Since the surface facing No. 1 that greatly affects the vibration characteristics is in close contact with the thin plate 13, it does not touch the outside air. Therefore, the surface of the electrode 13 facing the crystal blank 11 is maintained chemically and physically stable, and the resonance characteristics such as aging characteristics do not change. In particular, when the concave portion 12 is hermetically sealed by the thin plate 13, the plate surface of the crystal blank 11 is isolated from the outside and is not affected thereby. Furthermore, if the crystal blank 11 is sealed in an airtight container, it will not be affected by the environment inside the container and will be doubly isolated from the outside, so that an extremely stable environment can be maintained.

[0009]

As described above in detail, according to the present invention, it is possible to provide a crystal resonator which has good and stable vibration characteristics and can be downsized.

[0010]

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is a side sectional view showing an example of a conventional crystal resonator.

[Explanation of symbols]

 11 Crystal Piece 12 Recess 13 Thin Plate 14 Electrode

Claims (4)

[Claims] 1. A crystal plate for exciting piezoelectric vibration, a recessed portion having a minute depth formed on each side plate surface of the crystal plate, and a thin plate made of crystal bonded to each side plate surface of the crystal plate. And a electrode that is formed on the bonding surface of the thin plate and excites the crystal piece. 2. The crystal oscillator according to claim 1, wherein the crystal piece is an AT-cut thickness-sliding crystal piece. 3. The crystal unit according to claim 1, wherein the crystal piece is an SC-cut crystal piece. 4. The crystal unit according to claim 1, wherein the thin plate hermetically seals the recessed portion.