JP2002204140A - Piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric vibrator in which etching liquid dripped into a recess for the purpose of fine frequency regulation of a quartz element piece does not leak through action of surface tension at the narrow width part of a groove and the frequency can be regulated correctly and precisely and high accuracy stabilized vibration characteristics can be attained through enhancement of mount accuracy. SOLUTION: An opposite mesa type AT cut crystal unit 1 comprises a crystal oscillation piece 2 provided, on the surface and rear of a crystal element piece 5, with thin exciting parts 6 having recesses 6a and 6b and a pair of exciting electrodes 8a and 8b and a thick reinforcing part 7 on the periphery thereof. At the base end part of the crystal vibration piece, grooves 10a and 10b extending from the recesses, with the same depth, to the edge of the crystal vibration piece and provided with narrow width parts by protrusions 11a and 11b at the end part on the recess side are made in the thick reinforcing part and electrodes 12a and 12b are led out from the exciting electrodes on the bottom face thereof. The crystal vibration piece is bonded to the lead-out electrodes in the groove through a conductive adhesive 16 with inner leads 15a and 15b being positioned by protrusions and sealed hermetically in a case 4 while being cantilevered by a plug 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrator mainly used in a thickness-shear mode for use in various electronic devices, and more particularly to an excitation electrode provided on a thin vibrating portion recessed on a main surface of a piezoelectric element piece. The present invention relates to a so-called inverted mesa type piezoelectric vibrator in which is formed.

[0002]

2. Description of the Related Art Piezoelectric vibrators have been widely used as clock sources for electronic circuits in various electronic devices including OA devices such as information communication devices and computers and consumer devices such as electronic watches. In particular, in the information communication field represented by mobile phones, in response to the increase in the communication frequency and the speed of the system due to the increase in the capacity and speed of information transmission, the frequency has been further increased from the conventional frequency up to about several tens of MHz. High, 90-
There is a demand for a piezoelectric vibrator that operates in a high frequency range of about 200 MHz. At the same time, with the miniaturization of various electronic devices, there is a demand for a correspondingly smaller piezoelectric vibrator.

For example, in a piezoelectric vibrator whose main vibration is a thickness shear mode using an AT-cut quartz vibrating piece or the like,
In order to increase the frequency, it is necessary to reduce the thickness of the resonator element made of quartz or other piezoelectric material, particularly, the thickness of the excitation section. However, as the thickness of the piezoelectric vibrating piece becomes thinner, mechanical processing such as polishing becomes more difficult, and its mechanical strength is reduced, and the piezoelectric vibrating piece is more likely to be damaged by impact or the like during processing or during use. Therefore, recently, for example, JP-A-11-355094, JP-A-11-205062, and WO 98/038
As described in Japanese Patent Publication No. 736, a thick support portion is integrally formed around a thin excitation portion, thereby eliminating chipping and cracking of the resonator element, improving mechanical strength, and improving handling and handling. A so-called inverted mesa type piezoelectric vibrator has been proposed which can be easily mounted and can realize a high frequency.

In such an inverted-mesa type piezoelectric vibrator, the extraction electrode extending from the excitation electrode of the thin portion to the thick portion passes through the sharp edge portion of the quartz plate due to the step between the concave portion and the thick portion.
In some cases, some or all of the electrodes may be cut, resulting in poor conduction. For this reason, the high-frequency piezoelectric vibration device described in Japanese Patent Application Laid-Open No. 7-254837 discloses a high-frequency piezoelectric vibrating device in which a thick reinforcing portion provided around the piezoelectric vibrating region where the excitation electrode is formed has a thickness substantially equal to that of the piezoelectric vibration region. By providing an electrode extraction region in a groove shape and forming an extraction electrode in the groove, a highly reliable configuration that eliminates the possibility that the extraction electrode is cut at the edge portion is adopted.

[0005]

In the above-described manufacturing process of the inverted-mesa type piezoelectric vibrator, the frequency of the piezoelectric element piece is measured before forming the excitation electrode in the thin excitation section, and based on the measurement result. Fine adjustment is performed by dropping a predetermined amount of an etching solution on the thin-walled excitation unit and etching a part of the thin-film excitation unit. However, when a part of the etching solution leaks from the groove-shaped electrode lead-out region provided in the thick reinforcing portion, the etching amount of the thin exciting portion becomes smaller than a desired amount, and the frequency may not be adjusted accurately. there were.

Further, in a piezoelectric vibrator having a structure in which a piezoelectric vibrating piece is mounted on a plug called a hermetic terminal having leads for electrically connecting to the outside, and the piezoelectric vibrating piece is hermetically sealed in a case, the groove-shaped portion is provided. The piezoelectric vibrating reed is mounted on the plug by fixing the lead to the extraction electrode with a conductive adhesive in the electrode extraction region. However, as the size of the piezoelectric vibrator is reduced and the frequency is increased, there is a problem that the mounting accuracy of the piezoelectric vibrating piece greatly influences its vibration characteristics, and it becomes difficult to mount the piezoelectric vibrating piece with high accuracy.

Accordingly, the present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an inverted-mesa type piezoelectric vibrator in which a break or a break of an extraction electrode from a thin excitation portion is completely prevented. It is an object of the present invention to provide a configuration capable of finely adjusting the frequency of a piezoelectric vibrating reed with high precision while preventing and securing high reliability. It is a further object of the present invention to provide an inverted-mesa type piezoelectric vibrator which has a high mounting accuracy of a piezoelectric vibrating reed and can improve the stability and reliability of vibration characteristics.

[0008]

According to the present invention, in order to achieve the above object, a piezoelectric element piece having a thin excitation portion and a thick reinforcement portion around the thin excitation portion, and both front and back main surfaces of the thin excitation portion are provided. And a pair of extraction electrodes extending from each of the excitation electrodes to one edge of the piezoelectric element piece, and the thick reinforcement portion includes a pair of excitation electrodes from the thin excitation portion. A groove extending to the one edge at the same depth as the thin excitation portion is formed, the groove has a narrow portion at an end on the thin excitation portion side, and an inner surface of the groove. A piezoelectric vibrating reed on which the extraction electrode is formed, and a piezoelectric vibrating reed 1
A plug having a pair of leads, and a plug for mounting the piezoelectric vibrating reed by conductively connecting the respective leads to the corresponding lead electrodes, and a case for hermetically sealing the piezoelectric vibrating reed mounted on the plug And a piezoelectric vibrator characterized by comprising:

By obtaining a flat surface with no steps from the thin excitation section to one edge of the piezoelectric element piece, the extraction electrode can be formed to have a uniform film thickness along the concave groove without causing breakage or disconnection on the way. In addition to being able to form, the narrow portion of the groove is etched by the action of surface tension at the entrance of the groove when a predetermined amount of etching solution is dropped on the thin excitation portion to finely adjust the frequency of the piezoelectric element piece. Since the liquid is prevented from leaking into the groove, proper and precise frequency adjustment is possible.
Moreover, when mounting the piezoelectric vibrating reed on the plug, the lead can be positioned according to the narrow portion of the concave groove,
Mounting accuracy is increased.

In one embodiment, the thin excitation portion is formed by a concave portion formed on each of the front and back main surfaces of the piezoelectric element piece,
In addition, a concave groove is formed on each of the front and back main surfaces of the piezoelectric element piece at the same depth as each concave part.

In this case, if the concave grooves are arranged point-symmetrically with respect to the center of the cross section of the piezoelectric element piece so as not to overlap with each other in the plane position, the thick reinforcing portion is particularly mounted. Since a thin portion having the same thickness as the thin excitation portion is not formed at the base end, the piezoelectric vibrating reed can be maintained at a sufficient mechanical strength. Further, since the connection between the extraction electrode and the lead is sufficiently separated on both sides of the piezoelectric element piece, it is possible to prevent an unnecessary conductive adhesive from causing an electrical short between them. Also,
Since the piezoelectric vibrating reed can be arranged so that its cross section passes through the center of the plug, the plug and the case can be reduced in size while securing a sufficient gap between the piezoelectric vibrating reed and the inner surface of the case.

[0012]

1A and 1B schematically show the configuration of an embodiment of an inverted-mesa type AT-cut crystal resonator to which the present invention is applied. The crystal resonator 1 includes a crystal resonator element 2, a plug 3 for mounting the crystal resonator element 2 in a cantilever manner at a base end thereof, and a metal case 4 having a bottomed cylindrical shape. As shown in FIG. 2 (B), the crystal vibrating piece 2
On both front and back main surfaces of the rectangular thin plate-shaped crystal element piece 5, a thin excitation section 6 composed of rectangular recesses 6a and 6b having the same dimensions and a thick reinforcement section 7 are provided around the excitation section. At a substantially center of the thin excitation section 6, a pair of excitation electrodes 8a and 8b having the same rectangular pattern are formed. The plug 3 is shown in FIG.
A so-called hermetic terminal as shown in (A), which has two leads 9a and 9b penetrating an insulator made of glass with a metal ring fitted on the outer periphery thereof.

At the base end of the crystal vibrating reed 2, concave grooves 10a and 10b are formed on both the front and back surfaces to extend from the concave portions 6a and 6b to the edge of the crystal element piece 5 at the same depth as the concave portions. I have. As shown in FIG. 1B, the concave grooves 10a and 10b are arranged point-symmetrically with respect to the center O in the cross section, and are not overlapped with each other in the plane position. For this reason, the reinforcing portion 7 is thicker at any portion of the base end than the thin-walled exciting portion 6, so that its mechanical strength can be sufficiently maintained. Each of the grooves has a recess 6
Projections 11a, 11 formed at the ends on the sides a, 6b, respectively
A narrow portion by b is provided.

As best shown in FIGS. 2A and 2B,
The flat surfaces without steps extend from the rectangular recesses 6a, 6b to the edge of the crystal element piece 5 on the bottom surfaces of the concave grooves 10a, 10b.
Further, extraction electrodes 12a and 12b from the respective excitation electrodes
Are respectively formed. Therefore, the extraction electrodes 12a,
12b can be formed with a uniform film thickness without the risk of tearing or disconnection in the middle as in the prior art.

Next, the steps of manufacturing the AT-cut quartz resonator of the present embodiment will be described. The quartz-crystal vibrating piece 2 of this embodiment is manufactured by the same process as that of the conventional inverted-mesa-type quartz-crystal vibrating piece.
Processing can be performed without increasing man-hours.

First, a quartz thin plate having a predetermined thickness is subjected to wet etching or dry etching using a photolithography technique to process a quartz element piece having a desired outer shape of a quartz vibrating piece. FIG. 3 shows a rectangular crystal wafer 13 in which a large number of crystal element pieces 5 having the outer shape of the crystal resonator element 2 are processed in this manner. Can be manufactured.

Next, a concave portion 14 having the shape of the concave portion and the concave groove is formed on both surfaces of each crystal element piece 5 by performing wet etching or dry etching using a photolithography technique. At this time, the etching is controlled such that the size and depth of each recess 14 are within a predetermined value or range corresponding to a desired frequency. For example, in the case of wet etching, the crystal wafer 1
A corrosion-resistant film composed of a Cr film and an Au film is formed on both surfaces of the film 3 by vapor deposition or sputtering, and a resist film is applied thereon and patterned, and then the exposed corrosion-resistant film is removed with an etchant. The quartz wafer 13 is further immersed in an etching solution mainly composed of hydrofluoric acid to be etched to a predetermined depth, and thereafter, the remaining resist film and corrosion resistant film are completely removed.

Next, each of the crystal element pieces 5 is kept in a wafer state.
Using a conventionally known method, for example, the quartz wafer 13 is placed on an electrode plate having a counter electrode at a position corresponding to each of the thin-walled excitation units 6, and the measuring terminals are arranged closely above each of the thin-walled excitation units 6. Then, it is measured with a measuring device such as a frequency meter. Based on the measurement result, the frequency is finely adjusted by further etching the rectangular concave portion 6a or 6b of each crystal element piece 5, and more specifically, by dripping a predetermined amount of an etching solution into the concave portion. . At that time, the etching solution of the rectangular recess 6a or 6b is applied to the recess 10a or 1b.
Since the opening to Ob is narrowed by the protrusions 11a or 11b, surface tension acts to prevent leakage into the groove. For this reason, the concave portion can be etched by a desired amount, that is, the thin excitation portion 6 can be etched to a desired thickness.

The quartz wafer 13 thus etched is
An electrode material such as Au, Ag or the like is deposited or sputtered on the Cr underlayer on the bottom surface of each recessed portion 14 to form the electrode films of the excitation electrode and the connection electrode to a predetermined thickness. When each of the crystal element pieces 5 is cut from the crystal wafer 13, the crystal vibrating piece of the present invention is obtained.

As shown in FIG. 1A, the leads 9a, 9
b has inner leads 15a and 15b protruding from the plug 3 into the case 4, and the inner leads 15a and 15b
b is fixed by the conductive adhesive 16, respectively.
The crystal vibrating piece 2 is supported by the plug 3 in a cantilever manner, and allows the excitation electrodes 8a and 8b to be electrically connected to the outside via leads 9a and 9b. Each inner lead 15a, 15
b is positioned in such a manner that its tip comes into contact with the protrusions 11a and 11b, respectively, and is arranged in the concave grooves 10a and 10b. As a result, the mounting accuracy is improved, and the crystal resonator element 2 can always be accurately mounted on the plug 3, so that the vibration characteristics of the crystal resonator 1 are stabilized, and high reliability and improved yield can be realized. Finally, the metal ring of the plug 3 whose outer surface has been subjected to solder plating is press-fitted into the opening of the case 4 so that the quartz vibrating piece 2 is hermetically sealed in the case 4 which is usually maintained in a vacuum or nitrogen atmosphere. Sealed.

In this embodiment, as shown in FIG. 1B, the extraction electrodes 12a and 12b of the crystal vibrating reed 2 are separately connected to the corresponding inner leads 15a and 15b on both front and back sides. . For this reason, both extraction electrodes 12a,
It is possible to prevent excess conductive adhesive from causing an electrical short between 12b. At the same time, the crystal vibrating piece 2
Is arranged so that its cross section passes through the center O of the plug 3, so that the diameters of the plug 3 and the case 4 can be reduced while securing a sufficient gap between the inner surface of the case 4 and the crystal resonator element. The size can be reduced.

Next, a modified example of the present invention will be described.
The narrow portions of the concave grooves 10a and 10b provided in the crystal element piece 5 can be formed in various shapes. FIGS. 4A and 4B show the narrow portions having different shapes. In the modification shown in FIG. 4A, a narrow portion 18 is formed by two grooves 18a and 18b defined between two protrusions 17a and 17b projecting from both sides of the concave groove 10a (10b). Have been. Thereby, while finely adjusting the frequency by etching the crystal element piece 5 while ensuring a sufficient line width of the extraction electrode 12a (12b) passing through the narrow portion of the concave groove 10a (10b), the etching solution is removed by the concave portion 6a ( 6b) can be more effectively prevented from leaking into the concave groove 10a (10b). When mounting the crystal resonator element 2,
The tip of the inner lead 15a (15b) can be positioned by abutting the protrusion 17a.

In the modification shown in FIG. 4B, the concave grooves 10a (1
A narrow portion 20 is formed between two projections 19a and 19b projecting from both sides of 0b) in a crank shape bent at right angles at two places. Thereby, similarly, the crystal element piece 5
When the frequency is finely adjusted by etching, the etching liquid can be effectively prevented from leaking from the rectangular recess 6a (6b) to the concave groove 10a (10b), and the inner leads 15a (15b ) Can be positioned by abutting the tip of the projection 19a on the projection 19a.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and may be implemented with various modifications and alterations within the technical scope thereof. be able to. For example, although the inverted mesa type crystal resonator of the above embodiment has the concave portion and the concave groove formed on both surfaces of the crystal element piece, even when the concave portion and the concave groove are formed only on one main surface of the crystal element piece, The same applies and similar effects can be obtained. Further, the present invention can be similarly applied to an inverted mesa type piezoelectric vibrator made of a piezoelectric material other than quartz.

[0025]

The piezoelectric vibrator of the present invention is an inverted-mesa type piezoelectric vibrating reed having a thin-walled excitation part on which an excitation electrode is formed and a thick reinforcing part around the thin-walled excitation part. To the edge of the thin excitation portion at the same depth as the thin excitation portion and by providing a concave groove having a narrow portion at the end on the thin excitation portion side, on a flat surface with no steps along the concave groove Since the extraction electrode can be formed without causing breakage or disconnection in the middle, high reliability is ensured, and at the same time, when the etching solution is dropped on the thin-walled excitation unit to finely adjust the frequency of the piezoelectric element piece, Since the narrow portion of the groove prevents the etchant from leaking into the groove due to the effect of surface tension at the entrance, proper and highly accurate frequency adjustment becomes possible. In addition, by positioning the lead in accordance with the narrow portion of the groove, the piezoelectric vibrating reed can be mounted on the plug with high accuracy, so that the stability and reliability of the vibration characteristics can be improved.

[Brief description of the drawings]

FIG. 1A is a front view showing an embodiment of a crystal resonator according to the present invention, and FIG. 1B is a cross-sectional view taken along line BB of FIG. 1A.

FIG. 2A is a plan view of the crystal resonator element shown in FIG. 1,
(B) is a longitudinal sectional view of the crystal resonator element taken along line BB in FIG. (A), (C) is a cross-sectional view of the crystal resonator element taken along line CC in FIG. (A), and (D) is a view. FIG. 3A is a cross-sectional view of the crystal resonator element taken along line DD in FIG.

FIG. 3 shows a process of manufacturing a crystal resonator element according to the present invention.
FIG. 3 is a plan view showing a crystal wafer obtained by processing a large number of crystal element pieces having the outer shape of the crystal vibrating piece of FIG. 2.

FIGS. 4A and 4B are partially enlarged views of a concave groove showing a modification of the present invention, respectively.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz crystal oscillator 2 Quartz crystal vibrating piece 3 Plug 4 Case 5 Crystal element piece 6 Thin excitation part 6a, 6b Concave part 7 Reinforcement part 8a, 8b Excitation electrode 9a, 9b Lead 10a, 10b Concave groove 11a, 11b Projection part 12a, 12b Pull out Electrode 13 Quartz wafer 14 Depressed portion 15a, 15b Inner lead 16 Conductive adhesive 17a, 17b, 19a, 19b Projection 18, 20 Narrow portion 18a, 18b Groove

Claims (3)

[Claims] 1. A piezoelectric element piece having a thin excitation portion and a thick reinforcement portion around the thin excitation portion, a pair of excitation electrodes formed on both front and back main surfaces of the thin excitation portion, and a piezoelectric element from each of the excitation electrodes. A pair of extraction electrodes extending to one edge of the piece; and a recess extending from the thin excitation portion to the one edge at the same depth as the thin excitation portion, the pair of extraction electrodes extending to one edge of the piece. A piezoelectric vibrating reed in which a groove is formed, the groove has a narrow portion at the end on the thin-wall excitation portion side, and the extraction electrode is formed on the inner surface of the groove, and is electrically connected to the outside. A plug for mounting the piezoelectric vibrating reed by electrically connecting each of the leads to the corresponding lead electrode; and hermetically sealing the piezoelectric vibrating reed mounted on the plug. A piezoelectric vibrator comprising: a sealing case. 2. The piezoelectric device according to claim 1, wherein the thin excitation portion is formed by a concave portion formed on each of the front and back main surfaces of the piezoelectric element piece, and the concave groove has the same depth as each of the concave portions on the front and back main surface of the piezoelectric element piece. The piezoelectric vibrator according to claim 1, wherein the piezoelectric vibrator is formed of: 3. The piezoelectric element according to claim 1, wherein the concave grooves are arranged point-symmetrically with respect to the center of the cross section of the piezoelectric element piece so as not to overlap with each other at a plane position thereof. Vibrator.