Fracture of sustained tensile-loaded Sn-3.0Ag-0.5Cu solder alloy in NaCl solution

The fracture of Sn-3.0Ag-0.5Cu solder alloy has been investigated by a constant sustained tensile-loading test in 0.9. wt.% NaCl aqueous solution at room temperature. Under applied stress in the solution, many cracks nucleate and propagate on the side surface of the specimen. The fracture is not an ordinary creep rupture mode and is probably caused by the decrease in cross section of the specimen due to crack propagation. The preferential dissolution of Ag and Cu ions is clearly observed under applied stress in the solution. The time to fracture and the critical stress for fracture in the solution are lower than those in the atmosphere. The present results indicate that the reliability of lead-free solder alloys must be evaluated considering the effects of the combination of environment and applied stress.