Effect of Fe and Bi Additives on Electrochemical Migration Behavior of SAC105

This study investigates the electrochemical migration (ECM) behavior of novel SAC105-based solder alloys with varying Fe and Bi contents (0.05 Fe 2 Bi, 0.1 Fe 2 Bi, 0.1 Fe 1 Bi) in comparison to SAC105 without additives. The evaluation was conducted using a water drop test with a 1 mM NaCl electrolyte under an applied voltage of 3 V to determine the time to failure (TTF). Electrode surface, dendrite formations, and precipitates were characterized through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The ECM behaviors were then compared to the corrosion properties determined using a polarization test. The results indicate that the SAC105 alloy without additives exhibited the shortest TTF, and the incorporation of Fe and Bi additives enhanced ECM resistance, with the 0.1 Fe 1 Bi alloy demonstrating the highest TTF. However, EDX analysis reveals that there is no iron or bismuth in the dendrites; only tin was observed to deposit at the cathode. The polarization test revealed an opposite outcome, as the 0.1 Fe 1 Bi alloy showed the lowest corrosion resistance. The findings underscore the necessity to contemplate both mechanisms in order to ensure the reliability of solder alloys.