JPS5832524B2 - Electrode structure of tuning fork crystal resonator - Google Patents

Abstract

The vibrating element (6) consists of an X-cut crystal plate with a rotation of 0 DEG to 10 DEG about the X axis and a rotation of 70 DEG to 90 DEG about the Y' axis. The electrodes are produced by means of photochemical etching techniques. The peripheral outer electrodes (3 and 4) are galvanically connected to side electrodes (7 and 8) over the greatest proportion of their longitudinal dimension. The peripheral electrodes (3, 4) are arranged in parallel with the plane of vibration of the crystal plate and have a width dimension which is equal to or less than the width dimension of the fork tine carrying them; the side electrodes (7, 8) are arranged perpendicular to the plane of vibration of the crystal plate and partially overlap the peripheral electrodes at their common joint. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tuning fork type crystal resonator manufactured by a photoetching method.

More specifically, the present invention relates to the shape and dimensions of the electrodes arranged on the plane and side surfaces of the vibrator.

The present invention aims to reduce the crystal impedance (CI) of such a vibrator.

FIG. 1 is a conceptual diagram of a conventional embodiment, and a tuning fork type crystal resonator 1 made by photoetching is a
It is made from °-X type board.

That is, in the figure, α is from 00 to 100, and β is from 700 to
It is 900.

The center electrode 2 is connected to the peripheral electrode 3 of the other fork, and the peripheral electrode 4 is connected to the center electrode 5 of the other fork.

FIG. 2 is a cross-sectional view of this vibrator taken along the X-2 plane, and the arrows indicate the direction of the electric field.

In this cross-sectional view, β-900 is used for simplicity.

With this vibrator, a CI several steps lower than the conventional NT cut vibrator can be obtained, but when considered as a watch vibrator,
Further impedance reduction was expected.

The present invention aims to achieve the above object and will be described below with reference to the drawings.

FIG. 3 is a general view of a tuning fork type vibrator 6 according to the present invention, and the cut angle is the same I:, 5°-X system as the above-mentioned vibrator 1, but electrodes 1 are also provided on the side of the vibrator. They are different in that they are

FIG. 4 is a sectional view for explaining the present invention in detail,
It is β-900.

The thickness of the electrode film is exaggerated.

The peripheral electrodes 3, 4 and the side electrodes 7.8 are connected without being separated at the edge.

As is clear from the comparison with Figure 2, in this example, due to the effect of the side electrodes, the X-direction component of the electric field increases, and C
I decreases significantly.

In our experiments, we obtained a value of 1/2 as shown in FIG.

Hereinafter, the effects of the present invention will be explained in detail using figures.

FIG. 5 is an enlarged half of FIG. 4, and the width of the prongs is W.

(Note that the electrode thickness is exaggerated).

As is well known, the amount of strain caused by bending motion is proportional to the distance between the center line A and the center line A-.

Therefore, from the viewpoint of impedance reduction, it is desirable to apply the electric field as far away from the center line as possible, that is, to a portion close to the side surfaces.

FIG. 6 depicts the relationship between the width d of the outer peripheral electrode 30 and CI in FIG. 5.

Note that this graph is the result obtained for a vibrator with a thickness of 100 μm and a width W of 380 μm.

It can be seen from the figure that a minimum value of CI exists between d/W of 176 and 0.

Next, a specific example of forming such an electrode on the side surface will be described in the seventh section.
This will be explained with reference to the drawings and FIG.

A large number of oscillators 6 whose external shapes and electrodes have been formed by a crystal etching process are tightly sandwiched between two vapor deposition masks 10 and 11 while being connected to a frame 9.

In this state, the crystal plate is placed in a vapor deposition apparatus and an electrode film is deposited only on the side surface corresponding to the hole 12 provided in the mask.

Considering the error in mask alignment, hole 1 of the above mask
2 must be recessed into the vibrator side by at least 10μ.

In other words, the side electrodes are deposited by vapor deposition not only on the sides of the vibrator but also on the outer periphery of the tuning fork plane with a width of about 10 μm, overlapping the outer periphery electrodes.
Conductivity is ensured between the outer circumferential electrode and the side electrode.

From the above-mentioned viewpoints of electric field application efficiency and manufacturing technology, it is convenient for the width of the outer peripheral electrode to be more than 10 μm and smaller than 1/6 W for practical use.

According to the present invention, a vibrator with a CI value that is approximately half that of the conventional example can be obtained with a slight increase in the number of steps, so that a particularly excellent small vibrator for a wristwatch can be obtained.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of a conventional embodiment. FIG. 2 is a sectional view of a conventional embodiment. FIG. 3 is a conceptual diagram of the vibrator 6 according to the present invention. FIG. 4 is a sectional view of the vibrator 6 according to the present invention. FIG. 5 is an enlarged view of the side surface of the vibrator. FIG. 6 shows the relationship between electrode width and CI. FIG. 7 is a diagram showing a method for manufacturing a vibrator according to the present invention. FIG. 8 is a sectional view for explaining the process shown in FIG. 7. 3.4...peripheral electrode, 2,5...center electrode, γ. 8... Side electrode, 6... Vibrator, 10
, 11... Vapor deposition mask, 12... Vapor deposition hole.

Claims (1)

[Claims] 1. In a tuning fork type crystal oscillator, the oscillator rotates the X plate by 700 to 90 degrees around the
It is formed using a photoetching method from a thin crystal plate rotated by 0 to 0 degrees, and a center electrode and peripheral electrodes sandwiching it are provided on a plane parallel to the vibration plane of the vibrator. and the peripheral electrode of the other fork are electrically connected, and the peripheral electrode is narrower than 1/6 of the width of the fork of the tuning fork, and wider than 10 μ, at a portion involved in generating vibration, and An electrode structure for a tuning fork type crystal resonator, characterized in that the electrodes are connected to side electrodes provided on a plane perpendicular to the vibration surface of the tuning fork.