Creep properties assessment by shear punch creep test and IMC morphology of aged Pb-free solder joint/UBM

In this paper, we investigated the intermetallic compound (IMC) morphology of aged (0, 200, 600 h) conventional Sn-37Pb and Pb-free Sn-4Ag-0.5Cu solder joints/(Ni-P/Au) UBM; the creep properties of the solder joints were evaluated using a shear punch creep test (SPCT) method. The creep displacement-time curves of the solder joints exhibited different behaviors depending on stress application and aging treatment conditions. Empirical formulas such as the Power-law and Monkman-Grant relationship have been used to analyze the SPCT data. Furthermore, the IMC behavior of solder joints was investigated using energy-dispersive X-ray spectroscopy (EDS) and a scanning electron microscope (SEM). The result showed that with an increase of the aging time, the stress exponents (n) of solder joints were decreased, but the IMC thickness and size were increased. In most of the experimental conditions, the creep properties of Pb-free solder joints were superior to the conventional Sn-37Pb solder joints.