JPH0257009A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To form the piezoelectric resonator of a high Q-value and a small secular change by forming a step part, whose cross-section is projected, in central parts on the both surfaces of a disk, forming an oscillating body, for which a linking beam is formed in the position of zero power sensitivity coefficient, and an electrode plate with using the crystal of same quality as this oscillating body and forming a metallic layer, which goes to be a spacer, with metal. CONSTITUTION:An oscillating body 20 is a disk to be produced from an AT cut crystal substrate and the center (a B-part) of the both surfaces is made slightly thick and formed in the projecting shape in the cross section. Near the surrounding edge of this disk, a circle-shaped through hole 28 is formed with remaining a linking beam 27 in four spots in the position, where the power sensitivity coefficient goes to be zero. In the central parts of electrode boards 21 and 22 which are formed from an AT cut crystal substrate of the same quality as the oscillating body, thin film electrodes 23 and 24 of Au are formed and in the surrounding edge, metallic layers 25 and 26 of the Au are formed to be operated as the spacer. Since a projecting part is provided in the oscillating body, oscillation energy can be shut in the projecting part. Accordingly, since the deplacement of a part excepting for the projecting part of the oscillating body can be decreased, the Q-value can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a piezoelectric resonator, and relates to facilitating the processing of a vibrator and an electrode plate.

<Prior Art> FIG. 9 is a sectional view showing a conventional example of this type of piezoelectric resonator. In FIG. 9, reference numeral 1 denotes a disc-shaped vibrating body, one surface of which is flat and the other surface spherical. Reference numerals 2 and 3 refer to electrode plates having an electrode 4.degree.5 formed in the center and a ring-shaped spacer 6.7 formed on the periphery. 8.9 is electrode 4
, 5 is the power supply connection terminal. Note that Figure 1 shows the state before the vibrating body and the electrode plate are combined.
7, the electric fii 4 and the spherical surface of the vibrating body, and the electrode 5 and the flat surface are fixed facing each other with a small distance between them.

FIG. 10 is a plan view of the vibrating body. In the figure, reference numeral 10 denotes a ring-shaped through hole, which is formed near the periphery of the vibrating body, leaving four connecting beams 11 connecting the central opening and the peripheral edge A. Note that these are stored in a container (not shown).

In the above configuration, when an AC power source is connected to the connection terminal 8.9, the vibrating portion supported by the connecting beam 11 vibrates due to natural vibration.

<Problems to be Solved by the Invention> By the way, in the above-mentioned conventional example, one side of the vibrating body is processed into a spherical shape in order to confine the vibration generated in the vibrating body inside and prevent vibration attenuation.

However, if one surface of the vibrating body is machined into a spherical shape as in this conventional example, not only the spherical surface must be processed, but also the surface of the electrode plate must be processed into a spherical shape, which increases manufacturing costs. There's a problem. Furthermore, conventionally, the through holes are pressurized by ultrasonic machining.

This processing method is not suitable for mass production, and since distortion remains after processing, there is a problem that deterioration occurs over time and the natural frequency changes.

The present invention has been made in view of the above-mentioned problems of the prior art, and by making the vibrating body into a shape that is easy to process and using a method that does not cause processing distortion, piezoelectric resonance with a high Q value and high stability over the long term can be achieved. The aim is to realize the vessel.

The structure of the present invention for solving the problem described in item 1 is that a stepped portion having a convex cross section is formed at the center of both sides of the disc, and a step portion having a convex cross section is formed at the center of both sides of the disc, and the peripheral edge of the disc is a crystal vibrating body having a through hole formed in a link shape with four connecting beams connecting the center portion and the peripheral portion remaining in the vicinity at a position where the force sensitivity coefficient becomes 0; and a crystal vibrating body having a diameter approximately the same as that of the vibrating body. An electrode is formed at the center of one surface, and a pair of electrode plates formed of metal thicker than the convex portion is formed on the periphery of the electrode, and the stepped portion of the vibrating body and The vibrating body is fixed to the electrode plate in a sandwich shape with the electrodes of the electrode plate facing each other.

Practical Can Example> Two aspects of the present invention will be explained below based on the drawings. FIG. 1 is a cross-sectional configuration diagram showing an embodiment of a piezoelectric resonator according to the present invention, FIG. 2 is a plan view of a vibrating body, and FIG. 3 is a plan view of an electrode plate.

In these figures, the vibrating body 2o is a disk made from an AT-cut crystal substrate, and has a convex cross-section with a slightly thick center (mouth) on one side. Near the periphery of this disk, the force sensitivity coefficient becomes 0, fi (-1-
Circular through-holes 28 are formed with connecting beams 27 remaining at four locations (a position rotated about 60° left and right about the X-axis, and a position further rotated about 60' from there).

23. Reference numeral 22 denotes an electrode plate formed from a crystal substrate to an AT cup 1 made of the same material as the vibrating body, with thin film electrodes 23 and 24 made of Au formed in the center thereof, and metal made of Au which functions as a spacer around the 4th periphery. Layer 2526 is formed. Note that the central thin film electrode 2324 is taken out to the outside by removing a part of the link-shaped metal layer, as shown in FIG.

In the above configuration, electrodes 23 and 24 are connected to the power source (not shown).
When an AC voltage is applied to the vibrating body 2o, the vibrating body 2o vibrates at its natural frequency, or because the vibrating body has a convex part, the vibration is reflected at the step at the boundary with the convex part, which is transmitted to the position of the through hole. . As a result, vibration energy can be confined in the convex portion. Therefore, the displacement of the parts other than the convex portions of the vibrating body can be reduced, and the Q value can be increased.

Figure 4 is a diagram showing the relationship between the position of the connecting beam of the vibrating body and the force sensitivity coefficient.The sensitivity coefficient was obtained while applying force F at a position at an angle ψ centered on the -+-X axis. be. According to the figure, it can be seen that the force sensitivity coefficient becomes 0 at a position of about 60 degrees and a position of about 120 degrees left and right about the +X axis.

Therefore, in the present invention, by forming a connecting beam at this position, the support part is 1.5 mm, and the diameter a of the convex part is 8 mm and 10 mm.
The relationship between the amount of one step difference and the amount of attenuation of vibration amplitude is shown in mm.

According to the figure, by setting the step amount to about 1 to 3 μm, the amount of attenuation of the vibration amplitude can be reduced to 99% or less.

FIG. 6 is an explanatory view schematically showing the processed culm of the vibrating body of the present invention. I will briefly explain it according to the two culms.

Process 1) Clean the crystal wafer.

Process 2) Cr and Au are sputtered on both sides of the wafer.

Process 3) Apply resist and perform resist patterning.

Step 4) Perform patterning to etch the exposed Au and Cr, and perform resist patterning on the portion that is to be the first step (within thickness).

Step 5) Perform anisotropic etching of the crystal to form a disc-shaped vibrating body.

Process 6) Etch the peripheral edge to form a step.

Process 7) Perform etching of Au and Cr.

Next, a schematic processing process of the electrode plate will be shown using FIG. A simple explanation will be given step by step.

Process 1) Clean the crystal wafer.

Step 2) Cr and Au are sputtered on both sides of the wafer, resist is applied, and patterned into the shape in which the metal layer is to be formed.

Step 3) Perform Au plating on the Cr and Au layers to form a metal layer with a thickness of about 10 μm.

Process 4) Apply resist to the entire wafer including the metal layer.

Patterning is performed in the shape of the electrode plate.

Step 5) Etch the Au and Or that are not exposed by patterning to expose the crystal.

Step 6) Perform anisotropic etching of the crystal to form two disc-shaped electrode plates.

Process 7) Perform etching of Au and Cr.

The vibrating body and electrode plate of the present invention are manufactured by the above-mentioned process, but since etching is used in all crystal processing, no stress is generated due to processing.

FIG. 8 shows another embodiment of the vibrating body, in which the convex portions are formed in multiple stages. By processing it into such a shape,
It is possible to more completely confine vibration energy in the convex portion.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, a stepped portion having a convex cross section is formed at the center of both sides of one circular plate, and a stepped portion is formed at a position where the force sensitivity coefficient is O. We created a piezoelectric resonator with a high Q value and little deterioration over time because we created an electrode plate using a vibrating body that formed a connecting beam and a crystal made of the same material as the vibrating body, and a metal layer that served as a spacer was made of gold. can be realized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional configuration diagram showing an embodiment of the resonator of the present invention,
Fig. 2 is a plan view of the vibrating body, Fig. 3 is a plan view of the electrode plate, Fig. 4 is a diagram showing the relationship between the position of the connecting beam and the force sensitivity coefficient, and Fig. 5 is a plan view of the vibrating body.
The figure shows the attenuation state of the vibration amplitude at the step part of the vibrating beam, Figure 6 shows the outline of the machining process of the vibrating body, Figure 7 shows the outline of the machining process of the electrode plate, and Figure 8 shows the vibration Figures 9 and 10 showing other embodiments of the body are diagrams showing conventional examples. 20... Vibrating body, 21.22... Electrode plate, 23.2
4... Electrode, 25.26... Metal layer, 27... Connecting beam. 28...Through hole. Se〈゛? A waste of time to see the mushrooms 1 clam E 2nd drawing ice crystal c====================F e-C
Hi, AαS〕 に〕 Rolog = i Mikoguchi Ω (KζC 口OC] Teguchi Diagram 1θ Figure

Claims (1)

[Scope of Claims] 1) A stepped portion with a convex cross section is formed at the center of both sides of the disk, and the center and the periphery are formed near the periphery of the disk at a position where the force sensitivity coefficient is 0. A crystal vibrating body having a through hole formed in a ring shape, leaving four connecting beams connecting the parts, having approximately the same diameter as the vibrating body, and having an electrode formed in the center of one surface. It has a pair of electrode plates each having a metal layer thicker than the convex portion formed on its periphery, and the vibrating body is held between the electrode plates with the stepped portion of the vibrating body facing the electrode of the electrode plate. A piezoelectric resonator characterized by being fixed in a sandwich shape. 2) Claims characterized in that the crystal vibrating body and the electrode plate are formed using an AT plate using photolithography and anisotropic etching techniques, and gold is used as the material of the electrode and the metal layer. The piezoelectric resonator according to item 1.