JP2007081749A - Tuning-fork crystal vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tuning-fork crystal vibrator capable of raising strength against a mechanical shock by filling the through-hole or groove of each tuning fork arm with a filler for reinforcement, obtaining excellent crystal impedance by raising electric field efficiency, and promoting miniaturization. <P>SOLUTION: The pair of tuning fork arms having grooves in their principal surfaces are extended from a base, and driving electrodes are arranged on the inner peripheral surfaces of the grooves concerning the tuning-fork vibrator. The grooves are filled with the filler for reinforcement, and penetrate the tuning fork arms from both the principal surfaces. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tuning fork type crystal resonator having grooves on both main surfaces of a tuning fork arm (hereinafter referred to as a tuning fork type resonator), and more particularly to a tuning fork type resonator having improved mechanical strength.

(Background of the Invention)
The tuning fork vibrator is built in an electronic circuit including a clock as a clock source together with an oscillation circuit. In recent years, with the miniaturization of various electronic devices, tuning fork vibrators are required to be ultra-small, for example, 3.2 × 1.5 mm or less. One of such devices is one in which grooves are provided on both main surfaces of a pair of tuning fork arms to improve driving efficiency.

(Example of conventional technology)
FIG. 3 is an external view of a tuning fork vibrator for explaining one conventional example. The tuning fork vibrator is composed of a Z-cut crystal piece whose main surface is orthogonal to the Z axis of the crystal axis (XYZ), and a pair of tuning fork arms 1 (ab) extending from the base 2. However, the X axis of the crystal axis (XYZ) is the width, the Y axis is the length, and the Z axis is the thickness direction. And it has the groove | channel 3 in both the main surfaces of a pair of tuning fork arms 1 (ab).

  Each main surface (groove 3) and both side surfaces of each tuning fork arm 1 (ab) have drive electrodes 4 (abcd) as shown in FIG. 4 (cross-sectional view). The drive electrodes 4 (ab) in the grooves 3 on both main surfaces are formed on the inner peripheral surface and the bottom surface. Each drive electrode 4 (abcd) is connected by a lead electrode (not shown). In addition, both main surfaces and both side surfaces of the drive electrode 4 (abcd) in each tuning fork arm 1 (ab) have the same potential, and both main surfaces and both side surfaces have different signs.

  Further, between the tuning fork arms 1 (ab), the driving electrode 4 (ab) on both main surfaces and the driving electrode 4 (cd) on both side surfaces have the same potential, and different between both main surfaces and between both side surfaces. It is a sign. Thereby, in each tuning fork arm 1 (ab), bending vibration is generated by the electric fields “arrows in FIG. 4 (a)” that are opposite to each other generated between both main surfaces and both side surfaces. Arise.

  For example, in one tuning fork arm 1a, an electric field in the X axis direction from both main surfaces to the inner surface causes an Y region in the outer region of the tuning fork arm 1b, as indicated by an upward arrow in FIG. 4 (b). Stretch. Further, due to the electric field in the X-axis direction from both main surfaces toward both the inner sides, the inner region of the tuning fork arm 1a is reduced in the Y-axis direction as indicated by a downward arrow. Therefore, one tuning fork arm 1a bends inward as indicated by a horizontal arrow.

  Then, when an electric field is generated in one tuning fork arm 1a from both side surfaces to both main surfaces, as shown in FIG. 4 (c), the outer region is reduced in the Y-axis direction as shown in FIG. Then, it expands in the Y-axis direction. Therefore, one tuning fork arm 1a bends outward. These bendings are alternately generated by an alternating voltage from the oscillation circuit, and bending vibration is generated.

  In the other tuning fork arm 1b, since the electric field generated between both main surfaces and both side surfaces is opposite to that of one tuning fork arm 1a, the same applies when one tuning fork arm 1a bends inward. When it bends inward and one tuning fork arm 1a bends outward, it similarly bends outward. Therefore, the pair of tuning fork arms 1 (ab) vibrate in the horizontal directions opposite to each other, so-called tuning fork vibration is generated.

In such a case, the groove 3 is provided on the main surface of the pair of tuning fork arms 1 (ab), and the drive electrode 4 (ab) is formed particularly on the inner peripheral surface. Therefore, the electric field efficiency increases because the electric field in the X-axis direction is linear between the drive electrodes 4 (cd) on both side surfaces. As a result, even when the length of the tuning fork vibrator is shortened, the driving efficiency (electric field efficiency) is increased, so that the size reduction can be promoted.
JP 2002-261575 A (Seiko Epson)

(Problems of conventional technology)
However, in the tuning fork vibrator having the above-described configuration, although the driving efficiency is increased by the groove 3 provided on the main surface of the tuning fork arm 1 (ab), there is a problem that it is weak against mechanical shock and may be damaged. . Further, the groove 3 on the main surface of the tuning fork penetrates into the through groove 3A (FIG. 5), and the electric field efficiency is enhanced by providing the drive electrode 4 on the entire inner surface of the through groove 3A. However, in this case, there is a problem that sufficient bending vibration cannot be obtained by the through groove 3A, and unnecessary vibration is generated to adversely deteriorate the crystal impedance (CI).

  That is, by the through groove 3A, in each tuning fork arm 1 (ab), for example, one tuning fork arm 1a, the inner region and the outer region are expanded and contracted by the electric field in the X-axis direction. However, since there is no mechanical coupling in the central region, which is the through groove 3A, the tuning fork arm 1 (ab) is not bent outward and inward, and eventually tuning fork vibration is inhibited. For this reason, there is a problem in that unnecessary vibration is caused and CI is deteriorated.

(Object of invention)
It is an object of the present invention to provide a tuning fork vibrator having an increased strength against mechanical impact and an improved CI.

  According to the present invention, as shown in the claims (Claim 1), a pair of tuning fork arms having grooves on both main surfaces extend from the base, and a tuning fork type having a drive electrode on the inner peripheral surface of the groove. In the vibrator, a reinforcing filler is embedded in the groove. According to a second aspect of the present invention, the groove penetrates from both main surfaces of the tuning fork arm.

  With the above configuration (claim 1), since the reinforcing filler is embedded in the groove of the tuning fork main surface, the electric field strength can be increased and the mechanical strength can be maintained.

  According to the second aspect of the present invention, since the groove is a through groove, the electric field strength at the center portion of the tuning fork arm is increased. In this case, since the reinforcing filler is embedded in the through groove, each tuning fork arm maintains bending vibration and does not hinder tuning fork vibration. Accordingly, the CI can be improved by increasing the mechanical strength.

  FIG. 1 is a view for explaining an embodiment of the present invention. FIG. 1 (a) is an external view of a tuning fork type vibrator, and FIG. In addition, description of the same part as a prior art example is simplified or abbreviate | omitted.

  As described above, the tuning fork type vibrator is composed of a Z-cut crystal piece in which a pair of tuning fork arms 1 (ab) extends from the base 2, and each tuning fork arm 1 (ab) is penetrated through both main surfaces here. Has a groove 3A. The drive electrodes 4 are provided on both main surfaces and both side surfaces including the inner surface of each through groove 3A. Further, a filler 5 made of glass, for example, is embedded in each through groove 3A.

  Similarly to the above, the drive electrodes 4 are connected by routing electrodes (not shown), and the drive electrodes 4 (ab) on the inner peripheral surface of the through groove 3A of each tuning fork arm 1 (ab), and the drive electrodes on the outer side surface and the inner side surface. 4 (cd) are set to the same potential. Also, the drive electrode 4 (ab) on the inner peripheral surface and the drive electrode 4 (cd) on both side surfaces have different signs. In addition, between the pair of tuning fork arms 1 (ab), the drive electrodes 4 (ab) on the inner peripheral surface of the through groove 3A and the drive electrodes 4 (cd) on both side surfaces have different signs.

  In these, a drive electrode and a lead-out electrode are integrally formed in a state of a crystal wafer (not shown), and then molten glass as a filler is embedded in the through groove 3A and cured. Then, it is divided into individual tuning fork vibrators.

  With such a configuration, the drive electrode 4 (ab) is formed on the entire inner peripheral surface of the through groove 3A of each tuning fork arm 1 (ab). Accordingly, the electric field between the drive electrode 4 (ab) on the inner peripheral surface of the through groove 3A and the drive electrode 4 (cd) on the outer and inner surfaces of each tuning fork arm 1 (ab) includes the central portion. Everything becomes linear.

  Thereby, since electric field efficiency increases, for example, CI can be improved and miniaturization can be promoted. And since the filler 5 is embed | buried in 3 A of through-grooves, mechanical strength can be raised.

(Other matters)
In the above embodiment, the groove 3 of each tuning fork arm 1 (ab) is the through groove 3A. However, it may be a non-penetrating groove having a groove depth increased from both main surfaces. For example, as shown in FIG. 2 (cross-sectional view), 90% or more of the thickness (for example, 45% or more from one side) may be provided from both main surfaces to embed the filler. Even in this case, since the filler is embedded, the mechanical strength can be maintained, and the area of the drive electrode 4 (ab) on the inner peripheral surface can be increased to increase the CI. And since the contact area of an inner peripheral surface including the bottom face of the groove | channel 3 and the filler 5 increases, the joint strength between both is further raised.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining an embodiment of the present invention, where FIG. 1A is an external view of a tuning fork vibrator, and FIG. It is sectional drawing of the tuning fork type | mold vibrator explaining other embodiment of this invention. It is an external view of a tuning fork type vibrator for explaining a conventional example. It is a figure explaining a prior art example, the figure (a) is a sectional view of a tuning fork type vibrator, and the figure (bc) is a front view. It is sectional drawing of the tuning fork type | mold vibrator explaining a prior art example.

Explanation of symbols

  1 tuning fork arm, 2 base, 3 groove, 4 drive electrode, 5 filler.

Claims (2)

  A tuning fork type crystal resonator having a pair of tuning fork arms having grooves on both main surfaces extending from the base, and a driving electrode on the inner peripheral surface of the groove, wherein a reinforcing filler is embedded in the groove. Tuning fork type crystal resonator.   2. The tuning fork type crystal resonator according to claim 1, wherein the groove is passed from both main surfaces of the tuning fork arm.

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