Whisker growth on surface treatment in the pure tin plating

Whisker behavior at various surface treatment conditions of pure Sn plating are presented. The temperature cycling test for 600 cycles and the ambient storage for 1 year was performed, respectively. From the temperature cycling test, bent-shaped whiskers were observed on matte and semibright Sn plating, and flower-shaped whisker on bright Sn plating. The bright Sn plating has smaller whiskers than the other types of Sn plating, and the whisker growth density per unit area is also lower than the others. After 1 year under ambient storage, nodule growth of FeNi42 lead frame (LF) was observed in some parts. The Cu LF showed about a 9.0 μm hillock-shaped whisker. This result demonstrated that the main determinant of whisker growth was the number of temperature cycling (TC) in the FeNi42 LF, whereas it was the time and temperature in the Cu LF. Also, whisker growth and shape varied with the type of surface treatment and grain size of plating.