It is well known that thermal fatigue easily occurs in the solder joints of electronic devices. In this study, we tried to evaluate thermal fatigue life of solder joints with the stress singularity parameters near the solder joint edges. Firstly, we made constitutive equations of the solder materials and confirmed its precision. Next, using finite element method (FEM) analyses, we calculated stress singularity parameters near the solder joint edges for power modules under the conditions of thermal cycle experiments and power cycle experiments. Finally, we made evaluation equations of thermal fatigue life for solder joints by connecting stress singularity parameters and experiment results with fatigue laws. It is clarified that the fatigue laws based on the stress singularity parameters is valid and useful for predicting the thermal fatigue life of solider joints in electronic devices.
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