1994 年 45 巻 2 号 p. 197-201
After nickel plating on copper substrates and tin plating on top of that, the effects of heat treatment on crystal structure, contact resistance and hardness of the double plating films were investigated. X-ray diffraction measurements showed that heating the tin/nickel double plating films at 180°C for one hour resulted in the formation of tin-nickel intermetallic compounds.
The contact resistance of the double plating films increased with increasing heat treatment time at 180°C, and showed higher contact resistance than bright nickel films. In a humidity cabinet test at 60°C and 90 percent relative humidity, double plating films after heat treatment at 180°C for four hours showed lower contact resistance than did bright nickel films.
The hardness of the double plating films was enhanced by heat treatment, and was greater than that of bright nickel films. The double plating films after heat treatment were similar in appearance to stainless steel, with a slightly pink color.