Anisotropic mechanical properties of Cu6Sn5 and (Cu,Ni)6Sn5

The mechanical reliability of solder joints is influenced by a layer of Cu Sn intermetallics (IMC) present at the interface of tin-based solders/Cu substrates. We have discovered that the mechanical properties of hexagonal Cu Sn are strongly related to the crystal orientation, using Electron Back Scattered Diffraction (EBSD) and nanoindentation on unidirectionally solidified Sn4 wt% Cu with/without 0.05 wt% Ni. This fundamental discovery on the anisotropic mechanical properties of Cu Sn may find practical applications in designing soldering processes to obtain preferred IMC orientations