Fatigue-strength prediction of microelectronics solder joints under thermal cyclic loading

The stress-strain analyses for the solder joints in a thin single outline package (TSOP), a ball grid array (BGA) assembly, and a leadless ceramic 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 plastic behavior (yield stress) and creep behavior (creep properties) are taken into consideration in all numerical analyses. The results of finite element analysis (FEA) show that in an accelerated temperature cycling test, long high-temperature and low-temperature dwell times do not contribute to the increase of the cyclic inelastic equivalent strain range in solder joints (although the creep behavior occurring during the dwell times in an operating condition is important enough to be taken into consideration for estimating the fatigue life of solder joints). Based upon the results of the strain analyses, some efficient testing processes of temperature cycling and isothermal fatigue tests for the microelectronic solder joints are proposed, and the cycling tests are carried out. The experimental results show a good agreement with the analytic results.