Electrochemical Migration Investigation on Lead-Free Sn-based Solder Alloys in 3.5 wt.% NaCl Solution

Abstract

Electrochemical migration (ECM) behavior of three lead-free Sn-based solder alloys (SAC305, Sn-3.7Ag, and Sn-0.7Cu) was investigated in 3.5 wt.% NaCl solution at 10 VDC bias voltage to determine the resistance to ECM. The findings of the water drop (WD) test revealed that Sn-0.7Cu had the lowest ECM resistance by showing the lowest Mean-Time-To-Failure (MTTF) value compared to the other two solder alloys. However, significant differences between the MTTF values were not observed. After the WD test, the microstructure and chemical composition of the dendrites were studied by scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) methods, which showed a tree-like structure for Sn-3.7Ag and SAC305 and fishbone-like structure for Sn-0.7Cu, Sn was the main component of the formed dendrites.