Fatigue of 60/40 Solder

Plastic strain versus fatigue life data are presented for tests run at -- 50, 35, 125, and 150°C. It was found that these data could be correlated by the Coffin-Manson fatigue law, with an exponent of approximately 0.5 for the tests run at -35°C to 125°C. At 150°C the exponent was reduced to 0.37. These results were obtained for plastic strain limited tests. Different results are obtained when total strain limits are employed. This difference is discussed. The influence of cycling frequency and temperature changes are also discussed. A model is presented which describes the influence of plastic strain and cycling frequency. Corrections to the model predicted fatigue life, which account for temperature changes, cycling waveshape, and joint geometries, are also discussed.