Study on the influence of environmental humidity on lead-free solders in fire smoke atmosphere

The damage caused by fire smoke corrosion to electronic devices accounts for the majority of the economic losses after a fire. Lead-free solder is a crucial aspect for ensuring the reliability of electronic devices. This work explores the influence of relative humidity on the corrosion of lead-free solder in PVC fire smoke environment. The results show that relative humidity of 90% RH is the turning point for the corrosion behavior of Sn-3.0Ag lead-free solder. As the relative humidity increases, the multi-layered stack structure of the corrosion products significantly thickens. When the relative humidity increases to 98% RH, the corrosion products decrease. The corrosion degree of Sn-3.0Ag lead-free solder and the relative humidity present a non-monotonic relationship that first shows a positive correlation and then decreases. This phenomenon is due to the limited cathode depolarization caused by the reduced oxygen diffusion coefficient in the 98% RH environment. The Sn-3.0Ag lead-free solder substrate in the fire smoke environment undergoes a typical two-stage oxidation process to form the SnO phase and the SnO 2 phase, and a complex Sn 21 Cl 16 (OH) 14 O 6 deposition process occurs. This result is helpful for assessing the damage degree of electronic devices after a fire, to take timely and effective fire rescue measures.