JPH06237026A - Forming method of thick-film electrode - Google Patents

Abstract

PURPOSE:To improve the stability of electrode characteristics by previously forming the thin-films of glass for joining on approximately the whole surfaces of the surface and rear of a ceramic board and forming a conductive film. CONSTITUTION:A ceramic board is prepared by molding and baking a piezoelectric ceramic material using a PZT as a base, and the ceramic board in specified thickness is acquired by lapping. Borosilicate glass is used as glass for jointing, the raw material powder of the borosilicate glass is laminated on the ceramic board 1 in thickness of 800Angstrom through sputtering to form the thin-films 3 of glass for jointing, and the surfaces of the ceramic board 1 are improved. The thin-films of glass are homogenized through annealing at 700 deg.C. The surfaces of the thin-films 3 of glass for jointing are coated with silver paste, dried and baked to shape conductive films 4, thus forming a thick-film electrode. Accordingly, the stability of electrode characteristics can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a thick film electrode on a piezoelectric ceramic substrate. For example, a silver paste is used as an electrode for forming a piezoelectric substrate utilizing an energy trapping spread vibration mode. The present invention relates to a method for forming a thick film electrode formed by the above method.

[0002]

2. Description of the Related Art Conventionally, a piezoelectric ceramic substrate is formed by molding and firing a piezoelectric ceramic material. When this ceramic substrate is used in the energy confinement type spreading vibration mode, after smoothing the required surface of the ceramic substrate and forming a thick film electrode across the ceramic substrate,
A high voltage, for example, 2 to 5 KV / mm, is applied in a thick film electrode in insulating oil across a ceramic substrate to polarize it and form a piezoelectric substrate. By the way, the method of forming a thick film electrode on the conventional ceramic substrate described above includes a step of smoothing the surface of the ceramic substrate 1 on which the electrode is formed by lapping as shown in FIG. 3 (FIG. 3A). This is a step (FIG. 3B) of applying an electrode material in which a glass frit component is mixed to silver paste and baking it to form the thick film electrode 2.

[0003]

As described above, in the conventional method for forming a thick film electrode on a ceramic substrate, the surface of the ceramic substrate on which the electrode is formed is smoothed by lapping the thick film electrode. Is forming. However, since the ceramic substrate is obtained by molding and firing a piezoelectric ceramic material, the surface is inevitably porous, and if a thick film electrode is formed on this porous surface, the adhesion of the thick film electrode will be improved. Poor, the electrical characteristics of the electrode are poor. Therefore, in order to improve the adhesion of the thick film electrode, an electrode material in which a glass frit component is mixed with silver paste is applied and baked to form the thick film electrode. However, even when the electrode material in which the glass frit component is mixed with the silver paste is used, the amount of diffusion of the glass frit into the ceramic substrate is unstable because the glass particle size and concentration distribution in the glass frit vary. There is a problem in that the adhesion of the membrane electrode is poor, the characteristics of the piezoelectric ceramics are affected, and the quality of the electrical characteristics of the electrode deteriorates.

The present invention has been made to solve the above-mentioned problems of the prior art. A thick film electrode capable of forming a stable thick film electrode on a piezoelectric ceramic substrate and improving the quality of the thick film electrode is provided. It is intended to provide a forming method.

[0005]

A method of forming a thick film electrode according to the present invention for solving the above problems is to form glass thin films for bonding on both main surfaces of the front and back of a piezoelectric ceramic substrate. After modifying the surface of the substrate, a silver paste is applied to form a thick film electrode. As a glass raw material for forming a thin film of glass for bonding, various materials such as silica glass, lead glass, barium glass, and other oxide glass can be used regardless of halide glass. Alternatively, a mixture of such glass with material components of piezoelectric ceramics such as lead zirconate titanate may be used. The glass forming the glass thin film may be one that has good adhesion to the ceramic substrate and does not significantly affect the characteristics of the substrate.

[0006]

According to the method of forming a thick film electrode according to the present invention, a piezoelectric ceramic material is molded and fired, and a lapping process is performed to smooth a required surface to obtain a ceramic substrate having a predetermined thickness. The thickness of this ceramic substrate is determined by the specifications required for the piezoelectric substrate, but a thickness of about 200 to 1200 μm is used. A thin film of glass for bonding to the required surface of the ceramic substrate, sputtering, vaporization of the raw material powder as in vapor deposition to freeze the surface of the ceramic substrate, or to create a liquid raw material, formed by the sol-gel method, Modify the surface of the ceramic substrate. The thickness of this glass thin film depends on the state of the surface of the ceramic substrate, but is 100-
Set to about 9000Å. If it is too thin, the effect of forming a glass film is small, and if it is too thick, the characteristics of the piezoelectric substrate change. Next, annealing is performed at 600 to 800 ° C. to homogenize the glass thin film. Then, a silver paste is applied to the surfaces of the thin glass films facing each other with the ceramic substrate sandwiched therebetween, and the silver paste is baked to form a thick film electrode. Then, a high voltage is applied to form the piezoelectric substrate.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for forming a thick film electrode of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a film formation state for explaining a method of forming a thick film electrode according to an embodiment of the present invention. A ceramic substrate 1 is formed by molding and firing using a piezoelectric ceramic material. A glass layer is formed on substantially the entire front and back main surfaces of the ceramic substrate 1, modified, and then annealed to homogenize the glass layer to form a glass thin film 3 for bonding (FIG. 1). (A)). Next, the silver paste 4 is applied, dried, and then baked to form a thick film electrode (FIG. 1B). The composition and thickness of the glass thin film for bonding described above vary depending on the annealing conditions, the composition and thickness of the piezoelectric ceramic material, and the required characteristics of the ceramic substrate.

In this example, a piezoelectric ceramic material based on PZT was molded and fired to form a ceramic substrate, and a ceramic substrate 1 having a predetermined thickness was obtained by lapping. Borosilicate glass is used as the bonding glass, and the raw material powder of the borosilicate glass is sputtered to form a thin glass film 3 for bonding on the ceramic substrate 1 with a thickness of about 800 Å. Modified. Then, annealing was performed at 700 ° C. to homogenize the glass thin film. Next, as shown in FIG. 1B, a silver paste was applied to the surface of the thin glass film 3 for bonding, dried, and then baked to form a conductive film 4, thereby forming a thick film electrode. As shown in FIG. 2, a high voltage power source 5 is connected to the thick film electrodes 4 facing each other on the front and back of the ceramic substrate 1 on which the thick film electrodes 4 are thus formed,
The ceramic substrate 1 was polarized by applying 5 KV / mm to the thick film electrode 4. Then, the piezoelectric substrate for an element was cut out by cutting it into a predetermined size. According to this embodiment, the amount of the bonding glass formed on the surface of the ceramic substrate 1 can be controlled, and the influence of the glass diffusion of the glass thin film 3 on the ceramic substrate 1 can be controlled. As a result, the adhesion between the thick film electrode and the ceramic substrate 1 can be formed favorably and uniformly,
The quality of the electrode could be improved and the stability of the electrode characteristics could be improved.

According to the present invention, since a glass film for bonding is thinly formed on substantially the entire front and back main surfaces of the ceramic substrate, a silver paste is applied to form a thick film electrode. It is possible to control the amount of glass for bonding formed on the surface of the substrate and to control the influence of the glass diffusion of the glass thin film on the ceramic substrate. As a result, the adhesion between the thick film electrode and the ceramic substrate can be formed favorably and uniformly, the quality of the electrode can be improved, and the stability of the electrode characteristics can be improved. Although the ceramic substrate for the spreading vibration mode has been described in the above embodiment, the invention can be similarly applied to the ceramic substrate for other thickness longitudinal or spreading vibration mode or the thick film electrode of another electronic component.

[0010]

As described above, according to the method for forming a thick film electrode of the present invention, a thin film of glass for bonding is formed in advance on substantially the entire both main surfaces of the front and back surfaces of the ceramic substrate, and then the conductive film is formed. Since it is formed, the adhesion between the thick film electrode and the ceramic substrate can be favorably and uniformly made, the quality of the electrode can be improved, and the stability of the electrode characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a film formation state for explaining a method of forming a thick film electrode according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a polarization method of a ceramic substrate on which a thick film electrode of the above-mentioned embodiment is formed.

FIG. 3 is a perspective view for explaining a conventional method of forming a thick film electrode.

[Explanation of symbols]

 1 Ceramic substrate 3 Glass thin film 4 Thick film electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H03H 3/02 B 7719-5J

Claims (1)

[Claims] 1. A thick film electrode is formed by forming thin films of glass for bonding on both front and back main surfaces of a piezoelectric ceramic substrate, modifying the surface of the ceramic substrate, and then applying a silver paste. A method of forming a thick film electrode, comprising: