Numerical prediction of mechanical properties of Pb-Sn solder alloys containing antimony, bismuth and/or silver ternary trace elements

Solder joint interconnects are mechanical means of structural support for b ridging the various electronic components and providing electrical contacts and a thermal path for heat dissipation. The functionality of the electron ic device often relies on the structural integrity of the solder. The dimen sional stability of solder joints is numerically predicted based on their m echanical properties. Algorithms to model the kinetics of dissolution and s ubsequent growth of intermetallic from the complete knowledge of a single h istory of time-temperature-reflow profile, by considering equivalent isothe rmal time intervals, have been developed. The information for dissolution i s derived during the heating cycle of reflow and for the growth process fro m cooling curve of renew profile. A simple and quick analysis tool to deriv e tensile stress-strain maps as a function of the reflow temperature of sol der and strain rate has been developed by numerical program. The tensile pr operties are used in modeling thermal strain, thermal fatigue and to predic t the overall fatigue life of solder joints. The numerical analysis of the tensile properties as affected by their composition and rate of testing, ha s been compiled in this paper. A numerical model using constitutive equatio n has been developed to evaluate the interfacial fatigue crack growth rate. The model can assess the effect of cooling rate, which depends on the leve l of strain energy release rate. Increasing cooling rate from normalizing t o water-quenching, enhanced the fatigue resistance to interfacial crack gro wth by up to 50% at low strain energy release rate. The increased cooling r ates enhanced the fatigue crack growth resistance by surface roughening at the interface of solder joint. This paper highlights salient features of pr ocess modeling. Interfacial intermetallic microstructure is affected by coo ling rate and thereby affects the mechanical properties.