Electrochemical migration of micro-alloyed low Ag solders in NaCl solution

Abstract

The reliability investigation of lead-free solders is still a current issue. In this paper, Electrochemical Migration (ECM) behaviour of novel lead-free micro-alloyed low Ag content solders was investigated by water drop test in NaCl solution. The results were compared to commonly used lead-free and lead bearing solder alloys. It was found that some micro-alloyed solders can have as low ECM susceptibility as lead bearing ones. Xray photoelectron spectroscopy was also carried out to find the root cause of different ECM behaviour of micro-alloyed solders. The results of water drop test and X-ray photoelectron spectroscopy were in good agreement in terms of electrochemical migration susceptibility, since SAC0807 solder alloy has shown higher corrosion rate than SAC0307 and has a higher ability for ECM as well. It is concluded that some lead-free micro-alloyed low Ag content solder alloys (e.g.: SAC0807) may pose a high reliability risk in electronic devices during operation.