PROCESS FOR PREPARING TIN - SILVER ALLOY-PLATED FILM, TIN - SILVER ALLOY-PLATED FILM PREPARED THROUGH THIS PROCESS AND LEAD FRAME FOR ELECTRONIC MEMBER HAVING THIS FILM

摘要

PROBLEM TO BE SOLVED: To prepare a tin - silver alloy-plated film which does not contain lead as one of environmentally harmful substances, allows little discoloration after heating and exerts an excellent solder wettability and bending crack property.;SOLUTION: For example, the tin - silver alloy-plated film is formed on an outer lead part 3 of a lead frame through electroplating using a pulse pattern wherein the duration of the charging period is from 3 to 500 ms, the duration of the rest period is from 1 to 500 ms and the rest period is shorter than the charging period. The plated film has a reflection density of ≥1.0 and contains silver and tin. Here, tin has crystal orientation indices at planes (220), (211), (200) and (101) of from 0.7 to 5.4, from 0.8 to 3.0, ≤0.2 and ≤1.4, respectively.;COPYRIGHT: (C)2003,JPO