FATIGUE-STRENGTH PREDICTION OF MICROELECTRONICS SOLDER JOINTS UNDER THERMAL CYCLIC LOADING

The stress-strain analyses for the solder joints in a thin single outl ine package (TSOP), a ball grid array (EGA) assembly, and a leadless c eramic chip carrier (LCCC) are carried out to investigate the plastic- creep behavior, and stress relaxation behavior due to the temperature cycling or isothermal cyclic loading, The temperature dependence of pl astic behavior (yield stress) and creep behavior (creep properties) ar e taken into consideration in all numerical analyses, The results of f inite element analysis (FEA) show that in an accelerated temperature c ycling test, long high-temperature and low-temperature dwell. times do not contribute to the increase of the cyclic inelastic equivalent str ain range in solder joints (although the creep behavior occurring duri ng the dwell times in an operating condition Is important enough to be taken into consideration for estimating the fatigue life of solder jo ints), Based upon the results of the strain analyses, some efficient t esting processes of temperature cycling and isothermal fatigue tests f or the microelectronic solder joints are proposed, and the cycling tes ts are carried out, The experimental results show a good agreement wit h the analytic results.