JPH0349307A - Rectangular crystal resonator for overtone - Google Patents

Abstract

PURPOSE:To obtain a stable overtone rectangular crystal resonator whose frequency fluctuation and CI value fluctuation with respect to temperature by applying roughing whose surface roughness is 1mum-10mum to the side face in the lengthwise direction. CONSTITUTION:A rectangular crystal raw plate 1 is cut out from an AT-cut crystal plate in the size of length l in the lengthwise direction with respect to the Z' axis, width W with respect to the X axis and thickness (t) with respect to the Y' axis. The outer side is selected to be a size to suppress the vibration of a contour system or the like being a spurious vibration. The entire lengthwise side face (Y', Z' face) is subject to roughing whose surface roughness is nearly 2mum. The surface roughness is decided properly depending on the range of suppressing spurious radiation or the allowable CI value or the like, and in general, it is required to increase the surface roughness as the frequency increases. Moreover, the range of the roughing on the Y' Z' face is not limited to the entire face in the lengthwise direction and at least larger than the length l' in the lengthwise direction of the exciting electrode 2.

Description

[Detailed Description of the Invention] (Industrial Application Field) A crystal blank cut out by AT cutting has a frequency-temperature characteristic expressed by a cubic curve. It is widely used as an extremely stable cut that can reduce change to zero.

The present invention relates to a rectangular crystal resonator that uses this AT-cut crystal blank plate and is used at an overtone vibration frequency.

(Prior art) Conventionally, rectangular crystal resonators have used AT-cut blank plates with the Z-axis in the longitudinal direction, the X-axis in the width direction, and the Y-axis in the thickness direction, and the CI (crystal impedance) In order to improve the roughness, the surface of the base plate was polished to a surface roughness of 1 μm or less. Here, when each of the Z- and Y-axes is cut out by AT cut, that is, the Z-axis (optical axis) and Y-axis (mechanical axis) are 35 degrees to the left about the X-axis (electrical axis).
15 means the axis obtained by one rotation.

(Problem to be Solved by the Invention) However, when a rectangular crystal crystal as described above is vibrated at a third-order overtone (for example, '32 MHz), in addition to the main vibration, discontinuous vibrations occur in the vicinity of the main vibration. Secondary vibrations caused by contour vibrations or bending vibrations determined by the external shape (
(spurious) occurs, and discontinuous fluctuations in CI and oscillation frequency occur even when the temperature is continuously changed. When such various fluctuations occur, the AT force/soto no longer exhibits the original cubic curve, resulting in a problem that cannot be put to practical use.

The present invention has been made to solve the above problems,
It is an object of the present invention to provide an extremely stable rectangular crystal resonator for overtones that does not generate spurious waves even when used in overtone oscillations and does not cause fluctuations in the CIF direct 9 oscillation frequency.

(Means for Solving the Problems) The rectangular crystal resonator for overtone according to the present invention is cut out by AT cutting, and the longitudinal direction is the Z-axis direction and the width direction is the X-axis direction.
Special effects include a rectangular crystal resonator whose axial and thickness directions are set in the Y-axis direction, and whose longitudinal side surface (Z'Y' surface) is roughened to a surface roughness of 10 μm from IJim. It is.

FIG. 7 is a graph showing how the CI value changes with respect to surface roughness, and FIG. 8 is a graph showing the upper limit of DL (drive level) that can suppress spurious with respect to surface roughness.

If the surface roughness of the longitudinal side surface is 1011 m or more, the seventh
As shown in the figure, when C11m became too high and the surface roughness was set to 1 μm or less, DL, which could suppress spurious noise, was too low, and conversely, the crystal resonator sometimes did not resonate. When the surface illumination is in the range of 1 to 10L1m, the above-mentioned disadvantages do not occur, and the electrical characteristics of the vibrator are stable and in good condition.

(Example) Embodiments according to the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing each crystal axis direction of a rectangular crystal vibrating plate;
FIG. 2 is a schematic diagram showing a state in which the longitudinal side surface (Z'Y' surface) is roughened and electrodes are formed.

As shown in FIG. 1, the rectangular crystal blank plate 1 is made of AT cut crystal temporary, with the Z-axis in the longitudinal direction (Q), the X-axis in the width direction (W),
It is cut out so that the thickness direction (1) is along the Y-axis. This external dimension is selected to suppress contour system vibrations that cause spurious, for example, 3rd order overtone oscillation.
If 2MHz is desired, Q=8.0mm, w=1.8
The dimensions are chosen to be 8 mm, t=0.156 mm.

The main surface (Z-X plane) and the radial side surface (Y-X plane) are finished with a surface roughness of about 0.7 μm, but the entire longitudinal side surface (Yl-plane) has a surface roughness of 2 μm. The surface is roughened to a certain degree.

Determination of this surface roughness determines the range in which spurious can be suppressed,
Alternatively, it may be determined appropriately based on the CI tolerance value, etc.
-As for boat fishing trends, the higher the frequency, the greater the surface roughness needs to be.

Further, the roughness of the rough surface can be easily selected by appropriately selecting the mesh of the abrasive material when polishing the crystal blank. (For example, as is well known, 1000 #
The surface roughness of the lapped surface using this method is 1.9 μm. ) The range of surface roughening on this Yl-plane is not limited to the entire surface in the longitudinal direction, and as shown in FIG. If so, the effects of the present invention can be obtained.

(Comparative example 1) External dimensions Q = 8 mm, w = 2.18 mm, t = 0°15
6mm rectangular crystal plate, 3rd order overtone oscillation
When oscillating at 2MHz, t-DLl uw, the surface roughness of the Y-Z plane is 0.76μm (conventional example) and the same <2Jim (invention) against temperature change. A graph showing frequency changes is shown in FIG. 3, and a graph showing changes in the same <CI is shown in FIG. 4. This graph shows that in the conventional example, both the frequency and the C11 frequency fluctuate around 10℃ or 40℃, whereas the product of the present invention has stable frequency and CI characteristics over the entire temperature range. I know that there is.

(Comparative Example 2) External dimensions Q = 8 mm, w = 1.96 mm, t = 0°1
25mm rectangular crystal plate, 3rd overtone oscillation 4
When oscillating 0MH2 with DLIμW, Y-
Z-plane surface roughness is 0.76 μm (conventional example)
Figure 5 shows a graph showing the frequency change with respect to temperature change for the same <4.7 nm (invention).
A graph showing the change in I is shown in FIG. It can be seen that in this comparative example as well, as in comparative example 1, the product of the present invention is stable in both frequency and CI.

(Effects of the Invention) As is clear from the above Examples and Comparative Examples, according to the present invention, frequency fluctuations and CI value fluctuations with respect to temperature can be suppressed as much as possible, and a stable rectangular crystal resonator for overtones can be obtained. I can do it.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the axial direction of a rectangular crystal resonator, FIG. 2 is a diagram showing a roughened rectangular crystal resonator, and FIGS. 3 to 6 are graphs of comparative examples. Figure 7 shows CI for surface roughness.
A graph showing the values, FIG. 8, is a graph showing the upper limit of DL that can suppress spurious due to surface roughness. 1... Rectangular crystal base plate 2... Excitation electrode

Claims (1)

[Claims] In a rectangular crystal resonator that is cut out by AT cutting and whose longitudinal direction is set to the Z' axis direction, width direction to the X axis direction, and thickness direction to the Y' axis direction, the longitudinal side surface (Z'Y' plane)
A rectangular crystal resonator for overtone use, characterized in that the surface is roughened to a surface roughness of 1 μm to 10 μm.