| 摘要 |
PURPOSE:To develop a surface-treated steel sheet for lead frames having superior characteristics, by providing, as a semiconductor lead frame material, a Cu coating layer containing a Cu-diffused layer to the surface of a carbon steel sheet or a steel sheet containing specific small amounts of Cu or Cu and Ni. CONSTITUTION:A steel stock having a composition containing, by weight, <0.30% C or further 0.05-1.0% Cu or further 0.05-3.0% Ni is subjected to hot rolling, cold rolling, and annealing treatment to be formed into a steel sheet as the semiconductor lead frame material. The surface of this steel sheet as a material is electroplated with Cu, which is subjected to heat treatment in a nonoxidizing or reducing atmosphere on the continuous annealing system at 600-850 deg.C for 30-180sec or on the box annealing system at 450-650 deg.C for several - 30hr. The Cu plating layer is partially diffused into the steel sheet to form a Cu-diffused layer of 0.1-3mu and a Cu coating layer of 0.5-15mu, so that surface-treated steel sheet for lead frames excellent in corrosion resistance, solderability, and adhesive strength of Cu coating layer can be obtained.
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