Mechanism of Whisker Initiation & Suppression for SnCu-Electrodeposited Leads

Abstract

Electrodeposited SnCu coating on two different Cu leadframes showed drastically different tendencies of whisker initiation for long term storage at RT. Whisker initiation & suppression mechanism, which can explain the interrelation among minor elements in leadframe, IMC formation morphologies, compressive stresses, and whisker initiation tendencies, was established. Compressive stress distribution, Sn diffusion along GB, whisker root position, and whisker grain orientation were investigated to clarify the mechanism quantitatively by FEA/ED calculations and EBSP measurement.