Predictions of solder joint fatigue life

Procedures used to predict solder-joint life from calculations of the joint strains and low-cycle fatigue data are described. The fatigue lives of chip-carrier/printed-wiring-board joints are predicted and compared to measured values. This prediction utilizes a finite-element analysis of the string distributions in a typical joint acted upon by an imposed displacement. These strains are then used to determine the fatigue life through low-cycle fatigue data. The correlation with joint behavior requires a size-effect correction to the low-cycle fatigue lives. This correction is required because typical joint dimensions are smaller than the dimensions of the specimen utilized in the fatigue tests, and the fatigue life depends on the joint size.<
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