Corrosion and electrochemical migration evolution of oxidized Ag3Sn and β-Sn in halogen environment

摘要

Flux residues and marine service conditions expose lead -free solder join ts to environments containing halide ions, which can induce corrosion and electrochemical migration[1,2]. The role of silver (Ag) in electrochemical migration within Ag-containing lead-free solders remains under investigation[3]. In this study, we synthesized an Ag- 60Sn alloy with approximately 20% Ag 3Sn content and examined the effects of high - temperature and high-humidity oxidation, as well as various halides, on the corrosion and electrochemical migration behaviors of Ag 3Sn and β -Sn. Following high - temperature and humidity exposure, selective oxidation of Ag3Sn led to the formation of pure Ag. Both before and after oxidation, β-Sn showed preferential corrosion in NaCl, NaBr, and Na 2SO4 solutions, with minimal corrosion of Ag 3Sn. Conversely, Ag 3Sn corroded in NaI solution prior to oxidation, whereas a fter oxidation, Ag corroded and β-Sn remained unaffected. In terms of electrochemical migration, Sn dendrites consistently formed in NaCl and NaBr solutions, irrespective of oxidation state, while Ag dendrites appeared in NaI environments after oxidation. No dendritic growth was observed in Na 2SO4 solutions. This study identified critical corrosion conditions for Ag3Sn and used X -ray Photoelectron Spectroscopy (XPS) to analyze dendrite composition. Based on these results, we developed an electrochemical mig ration model for Ag3Sn and β-Sn in halide media.