STRENGTH EVALUATION OF THERMAL CYCLING FATIGUE FOR SURFACE-MOUNDED SOLDER JOINTS

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In this research project the following results have been gotten :(1) A three-dimensional finite element method program has been developed to carry out the heat conduction and the thermal stress analysis for surface-mound assembly.(2) The heat-cycle fatigue tests were carried out for the solder joints, and the results show good agreement with the analytical results.(3) An experimental method of mechanical fatigue has been proposed as the accelerated test for the heat-cycle fatigue test, and a testing equipment for the mechanical fatigue experiment has been developed.(4) The mechanical fatigue tests were carried out with several kinds of leaded solder joints, and the results show good agreement with the analytical results.(5) The elastic-plastic and creep analytical method has been proposed to investigate the thermal stress-strain behaviors of the solder joint. It is found that by using this method the complicated mechanical behaviors of solder joint can be evaluated accurately.(6) By collecting the analytical and experimental results, it is supposed that the thermal fatigue strength of the solder joints can be predicted by the Coffin-Manson relationship with the modification due the creep behavior.