Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-11-10
2001-07-17
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S614000, C338S021000, C338S308000
Reexamination Certificate
active
06260258
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method for manufacturing a varistor.
BACKGROUND ART
Conventionally, after forming electrodes on the surface of a varistor element mainly composed of ZnO, a high resistance layer made of glass was formed on the surface of the varistor element, and the surface of the electrodes was plated to obtain a varistor.
However, the high resistance layer made of glass could not be formed selectively on the surface of the varistor element alone, and it was hard to form in a uniform thickness. Accordingly, when plating, plating flow occurred to cause shorting, or moisture invaded into the varistor element to deteriorate the electric characteristic of the varistor.
DISCLOSURE OF THE INVENTION
It is hence an object of the invention to present a method for manufacturing a varistor having a high plating resistance and a high moisture resistance by selectively forming a compact high-resistance layer with a uniform thickness on the surface of a varistor element.
To achieve the object, a method for manufacturing a varistor of the invention comprises a first step of obtaining a varistor element by forming a material mainly composed of ZnO, a second step of forming at least two first electrodes at a specific spacing on the surface of the varistor element, a third step of applying a first heat treatment to the varistor element, and a fourth step of applying a second heat treatment after disposing Si powder on the surface of the varistor element.
According to this method, since a dense high-resistance layer having a uniform thickness is formed, a varistor excellent in a moisture resistance and a plating resistance can be obtained.
REFERENCES:
patent: 4290041 (1981-09-01), Utsumi
patent: 4700169 (1987-10-01), Tanno
patent: 5070326 (1991-12-01), Yoshimoto et al.
patent: 62-122103 (1987-06-01), None
patent: 3-173402 (1991-07-01), None
patent: 5-36501 (1993-02-01), None
Higashitani Miho
Tokunaga Hideaki
Wakahata Yasuo
Matsushita Electric - Industrial Co., Ltd.
Parkhurst & Wendel L.L.P.
Smith Sean
Young Lee
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