Feasibility of Copper-Base Leadframe Preplated with a Cu-Sn Alloy instead of Ni
A preplated frame (PPF) consisting of Au/Pd/Cu-Sn/Cu substrate, i.e., preplated with a Cu-Sn alloy instead of Ni commercially used, was fabricated by electroplating and then the feasibility of the frame as an alternative PPF was investigated. The wettability of the Cu-Sn alloy was better than that of Ni, resulting in excellent contact with the substrate and smoother surface on the upper Au/Pd protective layer. By XPS analyses, it was confirmed that Cu atoms in the Cu-Sn alloy layer did not diffuse through the thin protective layer to the surface at temperatures used in IC assembly. The wire pull-strength and solderability of the Cu-Sn alloy PPF were almost equivalent to those of the Ni PPF. However, the former showed much better corrosion resistance than the latter.
Byung Tae Ahn, Hyeongtag Jeon, Bo Young Hur, Kibae Kim and Jong Wan Park
D. H. Lee et al., "Feasibility of Copper-Base Leadframe Preplated with a Cu-Sn Alloy instead of Ni", Solid State Phenomena, Vols. 124-126, pp. 227-230, 2007