Corrosion properties of Sn–9Zn/Cu solder joint reflowed by microwave hybrid heating

This study focuses on the properties of Sn–9Zn/Cu solder joints produced using microwave hybrid heating (MHH) and subsequently subjected to simulated marine corrosion environments. The solder joints were reflowed under high-power MHH for varying durations and immersed in a 3.5 wt% NaCl solution. The analysis included assessments of joint integrity, corrosion behavior, surface morphology evolution, phase transitions, and elemental distribution. The MHH process demonstrated comparable intermetallic compound formation to conventional oven reflow techniques. Initial immersion induced the formation of ZnO and ZnCl 2 layers, offering temporary passivation. However, prolonged exposure led to surface cracking, corrosion pit development, and a measurable reduction in mechanical integrity, evidenced by a 16.2 % decrease in hardness after 28 days. The early-stage dissolution of Zn facilitated ZnO formation, which initially suppressed corrosion progression but eventually contributed to elemental instability. The use of a silicon wafer as a substrate enabled process optimization, with shorter reflow durations enhancing joint quality and corrosion resistance. These findings support the application of MHH as a promising method for fabricating corrosion-tolerant solder joints in marine electronic systems.