JPS5814617A - Tuning fork type quartz oscillator - Google Patents

Abstract

PURPOSE:To compensate the unbalance due to a residue of etching, by providing the level diffferences of different heights in the width direction at both sides of a tuning fork type quartz oscillator consisting of two oscillating arms and a basement. CONSTITUTION:A tuning fork type quartz oscillator 1 containing two oscillating arms 5, 5' and a basement 2 is formed out of a quartz thin plate by a lithography process. In this case, a so-called residue of etching is caused on the side face of the oscillator 1 to cause an unbalanced tuning fork. In this connection, the level differences 3 and 3' are provided in the width direction at both sides of the basement 2. The heights w1 and w2 of the levels 3 and 3' are set different from each other to compensate the unbalance of the tuning fork.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the shape of a tuning fork crystal oscillator composed of two vibrating arms and a base formed by a ring-tuffy process.

An object of the present invention is to reduce the vibration energy that leaks from the base of a tuning fork type crystal resonator to the outside through a customer device.

In recent years, there has been a demand for crystal oscillation type electronic watches to be smaller and thinner, and many of the tuning fork-shaped crystal units used in them are also formed using lithography processes. A tuning fork type crystal resonator using the flexural vibration mode is being used, but this resonator is similarly formed of four litho-datsu sweeps.

Now, one of the drawbacks of the tuning fork type crystal resonator is that a large amount of vibration energy leaks from the supporting portion to the outside. This is a major problem in a tuning fork type crystal resonator using a second-order bending vibration mode tube. For this reason, the first
As shown in the figure, it has been proposed to provide a step 3*3't- of a size equal to the base 20 of a tuning fork crystal resonator 10. In theory, by providing a step at the base of the tuning fork, the amount of vibration displacement near the base end 4 becomes extremely small, so the vibration energy leaking to the outside becomes small.However, in practice, lithography When we tried manufacturing a vibrator in the shape shown in Figure 1 (by process), we found that the effect was almost ineffective depending on the direction in which the vibrator was cut out. In fact, in some cases it got worse during the sentence. Here, the direction in which the vibrator is cut out is centered around the electric axis (X-axis) of the crystal as shown in Figure 3.
When g1 is rotated, it is determined.

As a result of intensive research into the phenomenon in which the base displacement of the conventional tuning fork crystal resonator with the shape shown in FIG. was born. The present invention will be explained below with reference to the drawings.

Since quartz crystal has anisotropy in etching rate, a resonator formed by a lithography process has the disadvantage that its shape is asymmetrical. i), 3rd
Due to the relationship between the crystal axis direction of the crystal and the etching speed shown in the figure, the tuning fork-shaped crystal resonator having the shape shown in FIG. As a result, the tuning fork becomes Dingumparang x2
- This unbalance is inconvenient because it increases the vibration displacement at the tuning fork base. Now, in Fig. 4, the etching remaining margin on the side is 3.
If you pay attention to 3', it becomes even bigger and the step is 3.31.
- is located at the boundary between the tuning fork vibrating arms 5, 51 and the base 2, so it can be clearly seen that the unbalance caused by the etching residue at the stepped portion significantly affects the vibration of mm1M5゜51. Therefore, although the shape shown in Figure 1 should theoretically reduce vibration leakage, the shape actually formed by the lithography process has almost no effect due to the influence of etching residue (K). In other words, there is a possibility that it may worsen significantly.

The present invention attempts to correct the unbalance caused by such etching residue by making the shape of the vibrator asymmetric. Now, FIG. 5 shows an embodiment of the tuning fork type crystal resonator of the present invention. Components common to those in FIGS. 1 and 4 are assigned the same numbers. Base 2 and vibrating arm 5.51
There is a step 3.31 near the border, and the size of each step 3.31 is different. Conventionally, it was required that the resonator shape be completely symmetrical, but when forming the resonator through a lithography process, the resonator shape is made asymmetric in advance in order to correct for imbalance caused by etching residue. Figure 6 shows a diagram of the vibrator shown in Figure 5 actually formed from a thin crystal plate using a lithography process.If you pay attention to the stepped portion 8.81 at the base, the stepped portion 8 on the left is due to the etching residue. It can be seen that the actual size of the step has become smaller by #. Therefore, an attempt is made to maintain balance by reducing the size of the lightning at the left step (8) (-8).

The difference in the size of the stepped portion is due to the size of the remaining elastin.
When −・, −−m bird≦ω.

Although we have experimentally confirmed that etching residues can vary in size depending on the cutting direction of the transducer and the plate thickness, especially when the cutting direction is -25 °~+25.

(The etching residue becomes very large when the etching is over such a wide range.) Therefore, the amount of unbalance that occurs in the vibrator also increases. For this reason, with the conventional shape of the vibrator shown in Figure 1, vibration leakage was extremely large, and phenomena such as increased loss and instability were major obstacles to practical application. Improvement was possible.

The present invention is particularly effective for vibrators using a second-order bending vibration mode. This is because providing a step at the base of the tuning fork is extremely effective against secondary bending vibration waves, and at the same time corrects the unbalance caused by etching residue. For the child, the level difference at the base does not make a large contribution, and only the unbalance correction by etching is effective.

According to the present invention), since the amount of displacement at the base of the tuning fork, that is, the vibration energy leaking to the outside, is extremely small, characteristics such as Ox (talistal impedance) value, Q value, and frequency change over time are significantly improved.

In addition, the design is easy because the amount of deviation in the size of the step at the base of the tuning fork (・i''-''m in Figure 5) can be set to an optimal value according to the cutting direction of the vibrator and the plate thickness. It is.

As described above, the effects of the present invention are tremendous, and its industrial value is great.

[Brief explanation of drawings]

FIG. 1 is a plan view showing the shape of a crystal resonator used in the present invention. FIG. 2 is a diagram for explaining the cutting direction of the crystal resonator. FIG. 3 is a graph showing the relationship between the crystal axis direction of quartz and the etching rate. FIG. 4 is a plan view showing a quartz crystal resonator formed by a conventional ring sweep. FIG. 5 is a plan view showing an embodiment of the crystal resonator of the present invention. FIG. 6 is a plan view showing a crystal resonator formed by the lithography process of the present invention. 1°, tuning fork crystal oscillator 2°. Tuning fork base 3.3+. , step 5 @ 5' provided at the base of the tuning fork
e * Tuning fork vibrating arm 6 @ II e @ * More than etching remains Fig. 1 Fig. 3 Fig. 2

Claims (1)

[Scope of Claims] ■ In a tuning fork-shaped crystal resonator composed of two vibrating arms and a base formed by the silisogelafie process using a thin crystal plate, each side of the base has two vibrating arms in the width direction. A tuning fork-shaped crystal resonator characterized in that a step is provided and the height of the step is different on each side. (2. In claim (1), the tuning fork type crystal resonator is characterized in that its main vibration is a high-order bending vibration field. In the range 0 term, the crystal thin plate has an orientation obtained by rotating two crystal plates (a crystal plate whose normal is parallel to the optical axis > t -25° to +25° around the electric axis (X axis) of the crystal. A tuning fork type crystal resonator characterized by: