JP2005286890A - Piezoelectric vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric vibrator on which the thin film of a photocatalytic material is formed so as to cover electrodes on front and rear surfaces of a piezoelectric blank plate. <P>SOLUTION: In order to achieve the above object, in the piezoelectric vibrator formed by housing the piezoelectric blank plate and hermetically sealing it, the thin film of photocatalytic material is formed on the front and rear surfaces of the piezoelectric blank plate so as to cover the electrodes formed on the front and rear surfaces and so as not to cover support plates each communicating to the electrodes, and the piezoelectric blank plate of the piezoelectric vibrator forms a plane, biconvex or plano-convex shape. Thus, the above problem can be solved. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

     The present invention relates to a piezoelectric vibrator in which a thin film of a photocatalytic material is formed so as to cover electrodes on the front and back surfaces of a piezoelectric element plate.

     The piezoelectric vibrator has a temperature characteristic in which the frequency changes depending on the environmental temperature. Among oscillators equipped with crystal resonators with these characteristics, for example, oscillators used in mobile phone terminals, which are one of mobile communication devices, have very high fluctuations in oscillation frequency due to ambient temperature changes. Because it is required to be small and have high accuracy, a high-accuracy temperature-compensated crystal oscillator (Temperature Compensated Crystal Oscillator) with a circuit that compensates the frequency change due to the temperature of the crystal unit in the oscillator, There are many oscillators called Oven Temperature Compensated Crystal Oscillators, which are used in equipment and require a high-accuracy and very stable frequency output. Exists.

     In the above-described constant-temperature chamber type crystal oscillator, for example, a support plate having a support structure of a piezoelectric element plate as shown in FIG. 4, that is, the piezoelectric element plate is fixed to two metal terminals hermetically penetrating the metal base. In many cases, a piezoelectric vibrator having a support structure of a piezoelectric vibrator supported by the above-described structure is used. The piezoelectric element plate of such a piezoelectric vibrator is made of a crystal plate, and the shape seen from the side direction is a flat plate, biconvex (double-sided convex), or plano-convex (single-sided convex) shape due to required characteristics. In general, electrodes made of gold (Au) or silver (Ag) are formed on the front and back surfaces of the main surface of the piezoelectric element plate.

When contamination such as extremely fine organic matter or inorganic particles such as metal particles of the electrode material adheres to the electrode surface of the piezoelectric element plate of the above-described piezoelectric vibrator, the oscillation of the piezoelectric vibrator becomes unstable, There is a risk of problems such as non-oscillation. Therefore, in the manufacturing process of the piezoelectric vibrator, the above-described dirt is not generated in all processes, and even if the dirt is generated and adheres to the electrode surface, the piezoelectric vibrator In practice, various cleaning processes such as UV ozone cleaning and plasma cleaning are incorporated in order to remove the dirt before the vibrator is hermetically sealed.
JP 2002-320015 A JP 2003-243761 A

     The applicant has not found any prior art documents related to the present invention other than the prior art documents specified by the prior art document information described above by the time of filing of the present application.

     However, gold (Au), which is generally used as the electrode material described above, tends to attract organic substances, and therefore UV ozone cleaning and plasma cleaning are performed. In UV ozone cleaning, the piezoelectric vibrator that performs this ozone cleaning is used. When a conductive adhesive is used, there is a problem that the characteristics of the conductive adhesive may be impaired.

     In addition, the energy of the ultraviolet rays irradiated by the UV ozone cleaning described above is relatively high, handling is necessary, and the UV lamp light source is also expensive.

     Also, plasma cleaning has a high cleaning ability that can remove substances other than organic substances, and if the cleaning time of this plasma cleaning is increased, the electrode material of the electrode of the piezoelectric vibrator is reduced by removal by plasma cleaning, and as a result, There has been a problem that the desired frequency of the piezoelectric vibrator may be changed.

     The present invention has been made under the technical background as described above. Therefore, the object is to form a thin film of a photocatalytic substance so as to cover the electrodes on the front and back surfaces of the piezoelectric element plate. It is to provide a piezoelectric vibrator.

     In order to achieve the above object, the present invention provides a piezoelectric vibrator comprising a piezoelectric element plate that is hermetically sealed and covers electrodes formed on the front and back surfaces of the main surface of the piezoelectric element plate, In addition, a thin film of a photocatalytic substance is formed so as not to cover the support plates that communicate with the electrodes, or both.

     Further, the piezoelectric element plate of the piezoelectric vibrator has a flat plate shape, a biconvex shape, or a plano convex shape.

     With the piezoelectric vibrator of the present invention, UV ozone cleaning that may impair the properties of the conductive adhesive and plasma cleaning that may change the desired frequency of the piezoelectric vibrator are included in the manufacturing process of the piezoelectric vibrator. It is possible to remove the dirt adhering to the electrode surface of the piezoelectric element plate of the piezoelectric vibrator without using it, and to greatly increase its reliability.

     In addition, the piezoelectric vibrator of the present invention eliminates the possibility that the oscillation of the piezoelectric vibrator becomes unstable or does not oscillate due to the adhesion of dirt to the electrode surface of the piezoelectric element plate. The production yield can be significantly increased.

     In addition, the titanium dioxide thin film used in one embodiment of the present invention has a photocatalytic action and can decompose organic substances even when using an ultraviolet irradiation device such as black light which has relatively low ultraviolet energy and is easy to irradiate. Thus, it is possible to efficiently and safely remove dirt adhering to the electrode surface of the piezoelectric element main surface.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In addition, the same code | symbol in each figure shall show the same object.

     FIG. 1 shows a piezoelectric vibrator 2 in which a titanium dioxide (titanium oxide) thin film 7, which is a thin film of a photocatalyst material, is formed so as to cover an electrode 5 on the main surface 3 of the piezoelectric element plate of the present invention. It is a schematic front view seen from the main surface direction. As shown in FIG. 1, a titanium dioxide thin film 7 is formed by vapor deposition so as not to cover the two support plates 6 connected to the electrodes 5 at the same time so as to cover the electrodes 5 of the piezoelectric element main surface 3. . The titanium dioxide thin film 7 has a photocatalytic action by irradiating ultraviolet rays. In the manufacturing process of the piezoelectric vibrator 2, after forming the electrode 5 and forming the titanium dioxide thin film 7 thereon, a relatively ultraviolet irradiation such as black light is performed. Even when ultraviolet rays are irradiated using a weak energy ultraviolet irradiation device, it has a photocatalytic action, and thus organic matter can be efficiently and safely removed. Further, as shown in FIG. 1, the titanium dioxide thin film 7 is formed so as to cover the electrode 5 surface of the piezoelectric element main surface 3 and not to cover the two support plates 6 individually connected to each electrode 5. After forming the titanium dioxide thin film 7 on the electrode 5 surface of the piezoelectric element main surface 3, the electrode 5 of the piezoelectric element main surface 3 is transferred to the support plate 6 via the conductive adhesive 9. The piezoelectric vibrator 2 can be assembled without hindering any electrical connection. The thin film formed so as to cover the electrode 5 of the piezoelectric element main surface 3 is not limited to a titanium dioxide (titanium oxide) thin film, and may be a thin film of another photocatalytic substance, and this case also falls within the technical scope of the present invention. Needless to say, it is included. Further, in FIG. 1, the thin film of the photocatalytic material formed on the front and back surfaces of the piezoelectric element plate covers the electrode and has the same concentric shape as the electrode shape. A thin film of a photocatalytic substance may be formed on the entire surface of the piezoelectric element plate excluding only the portion to which the agent is applied.

     FIG. 2 is a schematic view of the piezoelectric vibrator 2 of FIG. 1 in which a titanium dioxide (titanium oxide) thin film 7 is formed so as to cover the electrodes 5 on the front and back surfaces 4 of the piezoelectric element plate of the present invention as viewed from the upper surface side of the piezoelectric element plate 1. FIG. A titanium dioxide thin film 7 is formed so as to completely cover the electrodes 5 on the front and back surfaces of the vibrating portion of the piezoelectric element plate 1 of the piezoelectric vibrator 2. The electrodes 5 on the front and back surfaces 4 of the piezoelectric element plate and the respective electrodes 5 and the support plate 6 are connected via the conductive adhesive 9 but do not cover the two support plates 6 that are individually connected to the respective electrodes 5. Thus, since the titanium dioxide thin film 7 is formed, there is no possibility of impairing the conductive performance of the conductive adhesive 9, and the piezoelectric element plate 1 can be assembled to the support plate 6 via the conductive adhesive 9. As shown in the figure, the titanium dioxide thin film 7 is formed so as to cover the surface of the electrode 5, so that a titanium dioxide (titanium oxide) is used by using an ultraviolet irradiation device such as a black light which has a relatively low ultraviolet energy and can be easily irradiated. ) By the photocatalytic action of the thin film 7, the organic matter on the surface of the piezoelectric element plate 1 can be decomposed and removed, and dirt remains attached to the electrode 5 surface of the piezoelectric element main surface 3 efficiently and safely. The fear of doing it can be eliminated. At the same time, the titanium dioxide thin film 7 acts as a protective film, and when the organic substance becomes a binder for decomposing the organic substance, contamination of the electrode 5 material such as inorganic particles such as metal particles such as gold and silver (Contamination) ) Also has the effect of making it difficult to adhere.

     3 shows a piezoelectric vibrator 2 in which a titanium dioxide thin film 7 is formed on the front and back surfaces 4 of a piezoelectric base plate 1 in which the piezoelectric base plate 1 has a biconvex shape. 1 is a schematic top view seen from the top surface direction of FIG. The titanium dioxide thin film 7 is formed by vapor deposition. Although not shown in the drawing, the support structure by the support plate 6 may not be formed, and the piezoelectric vibrator 2 having a configuration in which the connection electrode of the piezoelectric element plate 1 is supported on the conductive pad may be used. Needless to say, such a case is included in the technical scope of the present invention.

     FIG. 4 is a schematic view of a piezoelectric vibrator 2 supported by a support plate 6 fixed to two metal terminals hermetically penetrating the metal base 1 from the principal surface direction of the piezoelectric base plate 1. It is a front schematic diagram.

It is the schematic front schematic diagram which looked at the piezoelectric vibrator in which the titanium dioxide thin film was formed so that the electrode of the piezoelectric element main surface of this invention might be covered from the principal surface direction. It is the schematic upper surface schematic diagram which looked at the piezoelectric vibrator in which the titanium dioxide thin film was formed so that the electrode of the front and back of the piezoelectric element plate of this invention might be covered from the upper surface direction of the piezoelectric element plate. FIG. 3 is a schematic top view of a piezoelectric vibrator in which a titanium dioxide thin film is formed so as to cover the electrodes on the front and back surfaces of a biconvex-shaped piezoelectric base plate when viewed from the top direction of the piezoelectric base plate. . FIG. 5 is a schematic front view of a conventional piezoelectric vibrator supported by a support plate fixed to two metal terminals hermetically penetrating a metal base when viewed from the principal surface direction of the piezoelectric element plate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric base plate 2 Piezoelectric vibrator 3 Piezoelectric base plate main surface 4 Front and back surfaces of piezoelectric base plate 5 Electrode 6 Support plate 7 Titanium dioxide thin film 9 Conductive adhesive

Claims (2)

     In a piezoelectric vibrator comprising a piezoelectric element plate and hermetically sealed, both front and back electrodes of the piezoelectric element plate cover electrodes formed on the front and back surfaces, and support plates that respectively communicate with the electrodes. A piezoelectric vibrator characterized in that a thin film of a photocatalytic substance is formed so as not to be exposed.      2. The piezoelectric vibrator according to claim 1, wherein the piezoelectric element plate of the piezoelectric vibrator according to claim 1 has a flat plate shape, a biconvex shape, or a plano-convex shape.

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