JPH0119459Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a tuning fork type crystal resonator (hereinafter referred to as a tuning fork for short) that is manufactured from a thin crystal plate by wet etching both the front and back surfaces simultaneously. It is related to the shape of

FIGS. 2A and 2B are perspective views showing a conventional tuning fork formed from a Z'-cut quartz thin plate by wet etching. Here, the Z'-cut crystal thin plate is a Z-cut crystal thin plate that is placed around the X-axis (electrical axis) from the Y-axis (mechanical axis) at an angle θ (hereinafter θ is called the cut angle, and the positive direction of θ is This refers to a thin crystal plate cut from a position rotated by an angle (counterclockwise). The value of the cut angle θ is selected in the range of −5° to 5°. Forming a tuning fork by etching this crystal thin plate is described in, for example, Japanese Patent Application Laid-Open No. 48-3575 and Japanese Patent Application Laid-Open No. 49-48288.

FIG. 2A shows the tuning fork viewed from the top (positive direction of the Z' axis), and FIG. 2B shows the tuning fork viewed from the bottom (negative direction of the Z' axis).

The legs 31 and 32 of the tuning fork 30 vibrate in a bending fundamental vibration mode in the XY' plane, and the directions of vibration displacement of the legs 31 and 32 are in the X-axis direction, and the directions are opposite to each other. At this time, the vibration node positions of the legs 31 and 32 are considered to be on the extension line of the slit bottom. For example, the tips of the legs 31 and 32 are made of gold (Au).
Frequency adjustment weights 35 and 36 consisting of are fixedly attached. The weights 35 and 36 have the same mass.

The bottom protrusion 33 of the tuning fork 30 protrudes from the bottom of the slit in a pyramid shape along the longitudinal direction of the inner surfaces of the two legs 31 and 32. Further, on the inner surface of the leg 31 except for the vicinity of the bottom of the slit, an inner surface protrusion 31a is uniformly formed along the longitudinal direction of the leg 31, and on the outer surface of the leg 32, an outer surface protrusion 32a is formed on the inner surface of the leg 31. It occurs in the same way. The reason why these protrusions occur is that the quartz thin plate is simultaneously etched from both the upper and lower surfaces by wet etching, and the etching rate of the quartz crystal varies greatly depending on the direction and direction of the crystal axis of the quartz crystal. This is caused by anisotropy and is an unavoidable phenomenon in etching processing. Regarding the etching anisotropy of crystal thin plates, for example,
It is described in Publication No. 46090. Inner surface protrusion 31
The formation of the outer surface protrusions 32a and 32a is due to the fact that the etching speed differs depending on the positive and negative directions of the X-axis of the crystal thin plate.
An inner surface protrusion 31a and an outer surface protrusion 3 are located on the positive side of the
2a is formed.

In the conventional tuning fork 30, the width dimensions of the upper and lower surfaces of both legs are equal at _h0 , and the length dimensions are also equal at both legs at _l0 . When the legs 31 and 32 are regarded as cantilever beams with a length dimension l ₀ , the natural frequency of each of the legs is the The natural frequency is slightly larger than that of the leg 31. That is, the natural frequencies of both legs are not equal. Assuming that the vibration amplitudes at the tips of both legs are equal, the inertial forces in the X-axis direction acting on the weights 35 and 36 at the tips of both legs do not completely cancel each other out. Also, the moment of inertia about the node (the length of the arm of the moment is l ₀ ) does not completely cancel out between the legs.

Therefore, conventional tuning forks formed by etching have the following problems.

That is, when the tuning fork 30 is vibrated in the fundamental vibration mode of bending in the XY' plane, the support part 34 of the tuning fork 30
The inertial force and the moment of inertial force that remain uncancelled act on . Therefore, if this support part 34 is supported from the outside, this support part 3
Vibration leakage occurs from the tuning fork 30, and as a result, the resonant frequency of the tuning fork 30 varies significantly depending on how the holder (not shown) of the tuning fork 30 is attached to the circuit board.

An object of the present invention is to provide a tuning fork shape that can prevent vibration leakage.

In order to achieve the above object, the tuning fork of the present invention has the following configuration.

That is, from a Z'-cut crystal thin plate cut out at a position where the cut angle θ is rotated by θ=-5° to 5° around the X-axis, one leg is etched by simultaneously etching both the front and back sides. An inner surface protrusion is formed on the inner surface, an outer surface protrusion is formed on the outer surface of the other leg, and a bottom surface protrusion is formed on the bottom of the slit. The amount of protrusion on the leg side where the part is formed is large,
In a tuning fork equipped with a weight for frequency adjustment at the tip of each leg, the mass of the weight at the tip of each leg is the same for both legs, the length of the legs is the same for both legs, and the top and bottom surfaces of the legs are the same. The width dimension is set such that the width of the leg on the side where the amount of protrusion of the bottom protrusion is small is set to be large, and the width of the leg on the side where the amount of protrusion of the bottom protrusion is large is set to be small.

When the tuning fork of the present invention vibrates in the fundamental vibration mode of bending in the It's summery. Therefore, if the vibration amplitudes at the tips of both legs are made equal, the inertial force in the X-axis direction acting on the weight at the tip of the legs will be completely canceled out by both legs. The moments related to the nodes of the above-mentioned inertial forces are also completely canceled out by both legs. Therefore, in the tuning fork of the present invention, even if the support part is supported from the outside, vibrations do not leak from the support part.

Embodiments of the present invention will be described below based on the drawings. FIG. 1 is a perspective view showing the tuning fork of the present invention.

The tuning fork 10 has a cut angle θ around the X axis of θ=-
It is formed by wet-etching both the front and back sides simultaneously from a Z'-cut crystal thin plate cut at a value between 5° and 5°. By this etching process, protrusions 11a and 12 of the same shape as the conventional tuning fork shown in FIG. 2 are formed on the inner and outer surfaces of the legs and the bottom of the slit.
a, 13 occurs. In order to equalize the natural frequencies of both legs, the width dimension of the upper and lower surfaces of the leg 11 on the side where the protrusion amount of the bottom protrusion 13 is smaller is h ₀ +Δh, and the width dimension of the upper and lower surfaces of the leg 11 on the side where the protrusion amount of the bottom protrusion 13 is larger. The width dimension of the upper and lower surfaces of 12 is h ₀ . The length dimensions of the legs 11 and 12 are both equal to l ₀ , and the thickness dimension of the tuning fork 10 is uniform everywhere and is t. Furthermore, the mass of the frequency adjustment weights 15 and 16 at the ends of both legs is equal. The value of Δh is determined by the support part 14 of the tuning fork 10.
determined experimentally to minimize vibration leakage from the For tuning fork 10, l ₀ = 2500 μm, h ₀ = 250 μm,
When t=100 μm, the protrusion amount of the bottom protrusion 13 is approximately 60 μm along the inner surface of the leg 12 and approximately 15 μm along the inner surface of the leg 11. Also leg 11
The maximum protrusion dimension in the X-axis direction of the inner surface protrusion 11a of the leg 12 is approximately 15 μm, and the
The maximum axial protrusion dimension is also approximately 15 μm. According to experiments, when the tuning fork 10 has the above dimensions, the optimum value of Δh is 1.5 μm. In other words, the width of the upper and lower surfaces of leg 11 is 251.5 μm, and that of leg 12 is
If it is 250.0μm, the natural frequencies of both legs will be equal.

At this time, vibration leakage from the support portion 14 of the tuning fork 10 is minimized.

As is clear from the above description, according to the present invention, there is no vibration leakage from the support portion, so the resonant frequency of the tuning fork does not change depending on the state of attachment of the tuning fork to the circuit board. Therefore, the present invention has a great effect in improving the quality of tuning forks.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a tuning fork type crystal resonator of the present invention formed by etching process, and FIGS. 2A and B are perspective views showing a conventional tuning fork type crystal resonator formed by etching process. It is a diagram. 10,30... Tuning fork type crystal resonator, 11,1
2, 31, 32...Legs, 11a, 31a...Inner surface protrusion, 12a, 32a...Outer surface protrusion, 13,
33... Bottom protrusion, 14, 34... Support part, 1
5, 16, 35, 36... weights.

Claims (1)

[Scope of utility model registration request] The cut angle θ of the Z-cut crystal thin plate around the X axis (the positive direction of θ is counterclockwise) is θ=
By simultaneously etching both the front and back sides of a Z' cut crystal thin plate cut out at a position rotated by -5° to 5°,
An inner protrusion is formed on the inner surface of one leg, an outer protrusion is formed on the outer surface of the other leg, and a bottom protrusion is formed on the bottom of the slit, and the bottom protrusion is a protrusion on the leg side on which the inner protrusion is formed. In a tuning fork type crystal resonator in which the amount of protrusion is small, and the amount of protrusion on the leg side where the outer surface protrusion is formed is large, and a weight for frequency adjustment is provided at the tip of each leg, the mass of the weight at the tip of the leg is The length of the two legs is the same, and the width of the upper and lower surfaces of the legs is the width of the leg on the side where the amount of protrusion of the bottom protrusion is smaller than the protrusion of the bottom protrusion. A tuning fork type crystal resonator characterized in that the width of the leg is set larger than the width of the leg on the side where the protruding amount of the part is large.