Understanding the corrosion protection effect by surface oxide film to underlying Sn solder substrate under thermal exposure condition

Oxide film formed on Sn-based lead-free solder surface plays an important role in protecting the solder joints in electronic devices. However, corrosion resistance of oxide film varied significantly under the effect of waste heat generated by electronic devices. In this work, the physicochemical properties of oxide film on pure Sn and SnAg solders were disclosed through analysing the corresponding electrochemical impedance spectroscopy (EIS) data using measurement and power-law models. The resolved data from EIS were fully corresponded to X-ray photoelectron spectroscopy and transmission electron microscope observations, which highlight the EIS approaches in illustrating the oxide film properties on Sn-based solder.