Fatigue Life Prediction Methods And Experimental Based On Crack Propagation Theory

The wide application of BGA gives strong demand on the reliability and servicelife. The research on the reliability and life prediction is of great importance. The creepfailure theory of the solder joints has been widely adopted in the recent studies. Thefailure theories based on solder crack propagation are rare. In this paper the crackpropagation theory is used to study the reliability of BGA package.Based on the theory of fatigue crack propagation and the research of NationalAeronautics and Space Administration (NASA), the paper uses the circular crackpropagation model and the stress intensity factor to analyze BGA solder crack growthmodel. The prediction method of BGA solder is given according to the Pairs subcriticalcrack growth law. The fatigue life prediction is presented and the“load-life”curve isobtained under the given solder model. The solder joint fatigue testing machine isdeveloped to study the change and the expansion of the crack, and the two constants Cand n which are used in Pairs subcritical crack growth law can be obtained through theexperiment. The experimental results confirm that the prediction method based onfatigue crack propagation is feasible.