Effect of corrosion on the low cycle fatigue behavior of Sn–4.0Ag–0.5Cu lead-free solder joints

Isothermal low cycle fatigue tests using Sn–4.0Ag–0.5Cu solder joints were performed according to a full factorial design of experiments in different corrosive environments. Temperature, humidity and salt solution were varied according to literature. The application of salt solution resulted in extensive corrosion of the solder joints and a decrease in fatigue life. The factor with the highest effect on the fatigue life was salt solution followed by temperature. The factor humidity was not significant for the present fatigue tests performed. The experiments performed at room temperature at different strain ranges also revealed that the application of salt decreases the fatigue life (90% confidence). The fatigue exponent α increases and C decreases when salt solution (concentration of 1 M) is applied to the solder joints. The two Coffin–Manson plots diverged from each other when decreasing the plastic strain range.