To provide a film thickness control method for gold plating which makes it possible to judge existence of an extremely thin gold-flash-plated film of 0.01 μm or less easily and in a short time, and to make sure of the realization of a mass production line.
Existence of an extremely thin gold-flash-plated film is judged using a color difference meter or spectrophotometer. In a plating apparatus for plating the surface of a lead frame, as a concrete favorable method, the part of the lead frame is masked with a tape before performing gold plating, the lead frame gold-flash-plated is washed after that by water and dried. After that, the masking tape is stripped. The gold-flash-plated part and the masking tape stripped part are measured using the spectrophotometer or color difference meter, and existence of a gold-flash-plated film is judged. It is desirable that the wavelength of the light source of the sperophotometer should be 200-400 nm. It is preferable that the wavelength of the light source of the color difference meter should be 400-700 nm.
CHINDA SATOSHI
TOMOBE MASAKATSU
