Prediction of thermal fatigue life of lead-free BGA solder joints by finite element analysis

초록

This study was focused on the numerical prediction of the thermal fatigue life of a mu BGA (Micro Ball Grid Array) solder joint. Numerical method was performed to predict three-dimensional finite element analysis with various solder alloys such as Sn-37 mass%Pb, Sn-3.5 mass%Ag. Sn-3.5 mass%Ag-0.7 mass%Cu and Sn-3.5 mass%Ag-3 mass%In-0.5 mass%Bi during a given thermal cycling. Strain values, which were obtained by the result of mechanical fatigue tests for solder alloys, were used to predict the solder joint fatigue life using the Coffin-Manson equation. The numerical results showed that Sn-3.5 mass%Ag with the 50 degree ball shape geometry had the longest thermal fatigue life in low cycle fatigue. Also a practical correlation for the prediction of the thermal fatigue life was suggested by using the dimensionless variable gamma.

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