Prediction of the Fatigue Crack Growth Life in Microelectronics Solder Joints

In order to predict the crack growth life in microelectronics solder joints, an FE A (finite element analysis) program employing a new scheme for crack growth analysis is developed. Also some experimental data necessary for the practical application of this program are obtained. Above all, the data related to the crack growth rate play a key role and are obtained in terms of the maximum opening stress range Δσθ _max as $$ {{da} \mathord{\left/ {\vphantom {{da} {dN = }}} \right. \kern-\nulldelimiterspace} {dN = }}\beta \left[ {\Delta \sigma _{\theta max} - \gamma } \right]^\alpha , $$ where α = 2.0 and β = 2.5 x 10-9mm5/N2 are independent of the test conditions, and γ is dependent on the solder material. The calculated values of the crack growth life by the FEA are in good agreement with the experimental ones. This indicates at the same time that the crack growth rate and path are certainly controlled, through the above equation, by Δσθ _max measured at a certain radial distance from the crack tip.