Electrochemical Corrosion Assessment of Low-Ag SAC Lead-Free Solder Alloys

The current work assesses the short-term and long-term electrochemical corrosion (ECC) behavior of SAC305 and SAC0307-Bi-xMn in 3.5 wt.% NaCl solution. The short-term assessment was implemented by linear sweep voltammetry (LSV) which showed no significant difference in corrosion current density values among the investigated alloys. However, the long-term assessment represented by cyclic series of open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) illustrated that SAC0307-Bi-xMn exhibited superior long-term ECC performance, notably delaying the onset of localized corrosion initiation. It is believed that the combination effect of reducing Ag content in SAC alloys and doping with Bi and Mn enhance the corrosion resistance of the native oxide film on the SAC solder surface. Such findings illustrate the importance of the surface native (pre-existed) oxide film in postponing the commencement of local corrosion of SAC alloys in NaCl solution.