Effect of polyvinyl chloride fire smoke on the long-term corrosion kinetics and surface microstructure of tin–lead and lead-free solders

With the rapid increase of electric power use, wire and cable fire occurs more and more frequently. While the fire smoke could corrode the solders on the printed circuit boards, which seriously affects the function of electronic equipment. In this research, the long-term corrosion behavior of Sn–37Pb, Sn–0.7Cu, and Sn–3.0Ag solders under 140 g m⁻³ polyvinyl chloride fire smoke atmosphere were investigated. The mass loss of all solders increased sharply on the first day and then varied exponentially in the subsequent time period. Particularly, the mass loss of Sn–37Pb solder gradually stabilized after 10 days, while that of lead-free solders was after 12 days. Meanwhile, the corrosion morphology indicated that the corrosion products of both Sn–37Pb and Sn–0.7Cu solders grew to be larger and denser. While those of Sn–3.0Ag solder grew larger firstly and then became smaller and denser because the grain growth dominated firstly and then the nucleation dominated with corrosion time. The corrosion mechanism was analyzed by using EDS, XRD, and XPS. The result showed that the carbon particulates from the fire smoke was detected which might promote the corrosion process and all solders had a common corrosion product, Sn₂₁Cl₁₆(OH)₁₄O₆. Besides, Sn–37Pb solder also contained other corrosion product, PbCl₂. The present work could provide guidance to the risk assessment for electronic equipment rescue after a fire.