A methodology to establish baseline metrics for assessing the isothermally aging of Sn-Pb solder interconnects

摘要

A methodology was developed to establish baseline metrics for assessing the isothermal aging of 63Sn-37Pb (Or 60Sn-4OPb) solder joints in circuit board assemblies. Those metrics were the intermetallic compound layer thickness at the Sn-Pb solder/Cu interface and the Pb-rich phase particle size distribution in the solder. The baseline, or as-fabricated, values for these metrics were 0.71 ± 0.27 μm and 3.2 ± 6.5 × 10{sup}(-6) mm{sup}2 respectively. The rate kinetics were determined for growth of the intermetallic compound layer and coarsening of the Pb-rich phase particles by isothermal aging experiments. The/were: (1) intermetallic compound layer thickness (μm) = 0.714 + 3.265 × 10{sup}3 t{sup}0.58 exp(- 52200/RT); and (2) P-rich phase particle size (mm{sup}2) = 3.2 × 10{sup}(-6) +1.47 × 10{sup}(-3) t{sup}0.32 exp(-31000/RT).