Corrosion behavior of lead-free SAC-type solder alloys in liquid media

• The ternary Sn–Ag–Cu (SAC) alloys are currently the most popular lead-free solders.
• The corrosion potential and current were measured using a potentiodynamic technique.
• The SAC solders were relatively resistant to corrosion in the tested aqueous media.
• The spontaneous corrosion rate was lower than that derived from the potentiodynamic experiments.
• Blocking the reaction surface by corrosion products was significant in NaCl solutions.

New lead-free solders are developed for electronic assemblies as a replacement for traditional Pb-containing alloys. The main goal of this study was to investigate the corrosion resistance of ternary Sn–Ag–Cu (SAC) alloys in the air-saturated aqueous solutions of NaCl (including sea water) and containing NO3−, SO42−, Cl− ions of concentration equivalent to those in acid rains. The Atomic Absorption Spectrometry (AAS) was used to determine Ag, Cu and Sn concentrations in the corrosive media. The corrosion potential and current were obtained using the potentiodynamic polarization technique. Corrosion resistance experiments of Sn–Ag–Cu alloys with the potentiodynamic method revealed that the solders were considerably resistant to corrosion in the liquid media used. The eutectic composition alloy was characterized by a higher resistance than the near eutectic one despite very small differences in the chemical composition. Corrosion rate during spontaneous dissolution was considerably lower than that derived from the potentiodynamic experiments because of blocking the reaction surface with corrosion products.