To plate only the end terminal of a varistor with an electrically conductive metal by forming an electrically insulating phosphate coating film on the main body of the varistor by causing a reaction between an oxide semiconductor exposed on the surface of the main body and a phosphate and, thereafter, saturating the main body in a plating solution.
Each electrode 26 of a varistor has a contacting section 28 and the end terminal 30 of the varistor covers the terminal area 32 of the main body 22 of the varistor and comes into contact with the electrodes 26. The part of the main body 22 which is not covered with the terminal 30 is coated with an electrically insulating zinc phosphate layer 35. The layer 34 is formed in a passivation process in which a reaction is caused between a metal oxide semiconductor layer 24 exposed on the external surface of the main body 22 and a phosphate solution. Then the main body 22 is plated with an electrically conductive metal, such as nickel, thin-lead, etc. Therefore, an electrically conductive metallic layer 36 can be formed only on the end terminal 30.
SPALDING TREVOR
CONNELL ANDREW MARK
BARRETT JOHN
ROHAN JAMES
