JPH0888536A - Overtone rectangular crystal oscillator - Google Patents

Abstract

PURPOSE: To perform stable overtone oscillation without generating spurious frequencies and the fluctuation of a crystal impedance value and an oscillation frequency by making the width of a principal plane electrode specific times that a crystal piece and making the surface roughness of the plane X of the crystal piece rougher than that of another plane. CONSTITUTION: The crystal piece 1 consists of a rectangular crystal plate of AT cut causing thicknesswise slip vibration in which its Z axis is set in a longitudinal direction L, its X axis is set in a width direction W and its Y axis is set in a thickness direction T. The width W' of excitation electrodes 21 formed on the surface and back principal planes of the crystal piece 1 are set at 0.7-0.8 times the width W of the crystal piece 1. Moreover, the surface roughness of the plane X of the crystal piece 1 is made rougher than that of the planes Y, Z. In this way, the stable overtone oscillation can be performed without causing the spurious frequencies and the variation in the crystal impedance(CI) value and the oscillation frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overtone rectangular crystal oscillator capable of oscillating 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 FIG. FIG. 9 is a perspective view of a conventional crystal piece. The crystal piece 1 is made of an AT-cut rectangular crystal plate that performs thickness-shear vibration in which the Z ′ axis is the longitudinal direction, the X axis is the width direction, and the Y ′ axis is the thickness direction. If desired, L = 8 mm, W = 1.73 mm, T = 0.1
The dimension is set to 67 mm. Then, the surface roughness of each surface is finished to about 0.7 μm. Then, in order to improve the CI value (crystal impedance), the excitation electrodes 2 formed on the front and back main surfaces of the crystal piece 1 (only the surface is shown).
The width W'of the crystal was set to 85% or more of the width W of the crystal blank 1. For example, as a conventional example, the width dimension W'of the excitation electrode 2 formed on the front and back main surfaces of the crystal piece 1 is set to 1.64 mm, which is about 95% of the width dimension W of the crystal piece 1. These electrodes are formed by a vacuum vapor deposition method, a sputtering vapor deposition method, or the like.

[0003]

However, when the crystal element having the above-mentioned structure is caused to oscillate with a third-order overtone of 26 MHz, as shown in the graphs of FIGS. The secondary vibration (spurious) due to the contour vibration determined by the shape, the bending vibration, the thickness shear vibration, etc. is generated, and the CI and the oscillation frequency fluctuate discontinuously even if the temperature is continuously changed. When such various variations occur, the original cubic curve of AT cut is not exhibited and there is a problem that it cannot be put to practical use.

An object of the present invention is to prevent spurious generation and
(EN) Provided is a highly reliable overtone rectangular crystal oscillator capable of performing extremely stable overtone oscillation without fluctuations in I value and oscillation frequency.

[0005]

Therefore, according to the present invention, the longitudinal direction is the Z'-axis direction, the width direction is the X-axis direction, and the thickness direction is Y '.
In a rectangular crystal oscillator that is set in the axial direction and has thickness-shear vibration with AT cut in which main surface electrodes for excitation are formed on the front and back surfaces, the width dimension W'of the main surface electrode is set to 0 of the width dimension W of the crystal piece. 7 to 0.8 times, and the surface roughness of the X surface of the crystal piece was made rougher than at least the surface roughness of the Z ′ surface and the surface roughness of the Y ′ surface.

[0006]

FIG. 2 is a graph showing changes in the CI value with respect to changes in the dimensional ratio when the width dimension W'of the principal surface electrode is divided by the width dimension W of the crystal piece. As this graph shows, W '/
It can be seen that the CI value is minimum around W of 0.7 to 0.8.

3 to 8, the length in the longitudinal direction is 8 mm, the length in the width direction is 1.73 mm, and the thickness is 0.16.
In a rectangular crystal resonator having a frequency of 26 MHz with a 7 mm crystal piece and a third overtone oscillation, FIG. 3 shows W ′ / W of 0.95 and the same surface roughness (surface roughness 0. 7 μm) is a graph showing the CI value characteristic per frequency, and FIG. 4 is a graph showing the frequency characteristic per temperature in the case of FIG. 3. Figure 5 shows W '/
W is 0.8 and the surface roughness of each surface is the same (surface roughness 0.
7 μm) is a graph showing the CI value characteristic per frequency, and FIG. 6 is a graph showing the frequency characteristic per temperature in the case of FIG. In FIG. 7, W '/ W is 0.
8 and frequency per frequency when the surface roughness of the X surface (surface roughness 2 μm) is made rougher than at least the surface roughness of the other Z ′ surface and the surface roughness of the Y ′ surface (surface roughness 0.7 μm). C
9 is a graph showing I value characteristics, and FIG. 8 is a graph showing frequency characteristics per temperature in the case of FIG. 7. As can be seen from these graphs, the W ′ / W dimensional ratio is 0.7.
The characteristics are better in the range of 0.8 to 0.8, and the surface roughness of the X plane is at least that of other Z ′ planes and Y ′ planes as compared with the case where the surface roughness of each surface is the same. The characteristics are better when the surface is roughened than the surface roughness.

[0008]

EXAMPLE An example of the present invention will be described below with reference to FIG. FIG. 1 is a perspective view of a crystal piece showing an embodiment of the present invention. The same parts as those in the conventional example are designated by the same reference numerals. The crystal piece 1 has a Z ′ axis in the longitudinal direction (L), an X axis in the width direction (W), and a Y ′ axis in the thickness direction (T).
It consists of an AT-cut rectangular crystal plate that vibrates the thickness slip. This external dimension is selected as a dimension that suppresses the vibration of the contour system that becomes a spurious. For example, when 26 MHz is desired for the third overtone oscillation, L = 8 mm, W
The dimensions are set to 1.73 mm and T = 0.167 mm. Then, the Z'plane (Y'Z plane) and the Y'plane (Z'X
Surface) is finished to a surface roughness of about 0.7 μm, but X
The surface (Y'Z 'surface) is roughened to have a surface roughness of 2 μm. The roughness of these rough surfaces can be easily selected by appropriately selecting the mesh of the polishing material when polishing the crystal piece. Excitation electrodes 21 (only the surfaces are shown) are formed on the front and back main surfaces of the crystal piece 1, and the width dimension W ′ of the excitation electrodes 21 formed on the front and back main surfaces of the crystal piece 1 is formed.
Was set to 1.38 mm, which is about 80% of the width W of the crystal piece 1. These electrodes are formed by a vacuum vapor deposition method, a sputtering vapor deposition method, or the like. A necessary supporting structure is attached to the crystal piece configured as described above, and the crystal structure is completed by hermetically sealing with the package structure. In the examples of the present invention, the surface roughness of the X surface (Y'Z 'surface) is 2 μm.
However, the same effect can be obtained even if the surface is roughened to have a surface roughness of about 1 μm to 10 μm. The width W ′ of the excitation electrode 21 is 70% to 80% of the width W of the crystal blank 1.
Similar CI value characteristics are obtained in the category of%.

[0009]

According to the first aspect of the present invention, it is possible to obtain a highly reliable overtone rectangular crystal oscillator capable of suppressing frequency variation with respect to temperature, variation of CI value, spurious and the like as much as possible and performing extremely stable overtone oscillation. be able to.

[Brief description of drawings]

FIG. 1 is a perspective view of a crystal piece showing an embodiment of the present invention.

FIG. 2 is a graph showing a change in CI value with respect to a change in dimensional ratio when a width dimension W ′ of a principal surface electrode is divided by a width dimension W of a crystal piece.

FIG. 3 is a graph showing CI value characteristics per frequency when W ′ / W is 0.95 and the surface roughness of each surface is the same (surface roughness 0.7 μm).

FIG. 4 is a graph showing frequency characteristics per temperature in the case of FIG.

FIG. 5: C per frequency when W ′ / W is 0.8 and the surface roughness of each surface is the same (surface roughness 0.7 μm)
It is a graph which shows an I value characteristic.

FIG. 6 is a graph showing frequency characteristics per temperature in the case of FIG.

FIG. 7 shows that W ′ / W is 0.8 and the surface roughness of the X surface (surface roughness 2 μm) is at least the surface roughness of the other Z ′ surface,
It is a graph which shows the CI value characteristic per frequency when it is made rougher than the surface roughness (surface roughness 0.7 μm) of the Y ′ surface.

FIG. 8 is a graph showing frequency characteristics per temperature in the case of FIG.

FIG. 9 is a perspective view of a crystal piece showing a conventional example.

[Explanation of symbols]

 1 ... Quartz piece 2, 21 ... Excitation electrode

Claims (1)

[Claims] 1. A thickness shear vibration by AT cut in which the longitudinal direction is set to the Z ′ axis direction, the width direction is set to the X axis direction, and the thickness direction is set to the Y ′ axis direction, and main surface electrodes for excitation are formed on the front and back surfaces. In the rectangular crystal unit for performing the above, the width dimension W ′ of the principal surface electrode is set to 0.7 to 0.8 times the width dimension W of the crystal piece, and the surface roughness of the X surface of the crystal piece is set to at least another value. An overtone rectangular crystal oscillator characterized by being rougher than the surface roughness of the Z'plane or the Y'plane.