Microstructural stability and failure modes in eutectic Sn-Ag-Cu solder

Microstructural stability in eutectic Sn-3.8Ag-0.7Cu (SAC) solder has been investigated during isothermal annealing at 401 K or 454 K and cyclic annealing between 253 K to 401 K. Bulk Ag₃Sn and Cu₆Sn₅ intermetallics are found to be quite stable at these elevated temperatures. The distribution of local strain fields within SAC solder interconnections have been investigated under shear loading at ambient temperature by a digital image correlation (DIC) technique. DIC measurements show inhomogeneous distribution of strain fields in the solder interconnections, and localization of strains predominantly near the interface(s). Creep experiments have also been performed at 373 K and 423 K and are compared to the shear loading experiments. SAC solder interconnections show the largest plastic deformation and the highest creep-resistance and exhibit fracture in ductile mode.