SURFACE TREATMENT OF SILVER PLATING FILM

PROBLEM TO BE SOLVED: To provide a surface treatment method for Ag plating films capable of effectively executing the dissolution for the purpose of the thickness adjustment of the Ag plating films formed on the very small area parts of the surface while effectively suppressing the dissolution of copper alloy parts which are the greater parts of the non-Ag plating parts, capable of completely dissolving and removing the unnecessary Ag plating films formed by the leakage of an Ag plating liquid in the non-Ag plating parts, capable of completely suppressing the discoloration which occurs in the dissolved parts after the dissolution work thereof and capable of eventually forming the Ag plating films free from discoloration. SOLUTION: In the surface treatment method for the Ag plating films applied on the very small area parts of the surface of a copper alloy-base lead frame, the greater parts of the non-plating parts are masked by solid mask materials 3, 4 so as to expose only the Ag plating film parts 1-(2) of the copper alloy-base lead frame 1. A fluid chemical liquid for washing is then passed to the exposed Ag plating film parts to wash these parts and thereafter, the washed silver plating film parts are subjected to a rinsing treatment.