The decrease in fatigue life of solder joints under the high temperature environment is a major problem in semiconductor packages for automotive applications. To clarify the mechanism of the fatigue-life decrease, we carried out the mechanical cyclic fatigue test of the Sn-3mass%Ag-0.5mass%Cu solder joint after high-temperature heat treatment. We studied a correlation between the heat treatment condition and the fatigue-life decrease. The method for estimating the fatigue life decrease from the heating history of heat cycle tests was also studied. The fatigue-life decrease of the solder joints after heat treatment was explained as the temporal change in the fatigue ductility coefficient of the Coffin-Manson's low, and the decreasing rate of fatigue life was converged within the range from 60 to 70%. We found that the fatigue-life decrease can be quantitatively estimated by using Arrhenius's low with the consideration of the heating temperature, hold time and the number of reliability target cycle of the heat cycle test.
