Spectacular epitaxial growth of (Cu, Ni)6Sn5 formed on Ni substrate

The texture as well as epitaxial growth of intermetallic compounds (IMCs) are becoming important issues, due to increases in IMCs-solder ratios in the development of micro-bumping. (Cu, Ni)₆Sn₅ formed on Ni substrate didn´t simply grow in an unexpected manner, but did so, producing a spectacular morphology. Even in the presence of very few Ni atoms dissolved in (Cu, Ni)₆Sn₅, a strongly preferential orientation growth was still observed. The crystal orientation relationships between (Cu, Ni)₆Sn₅ and Ni was recognized as: (12̅0)_{(Cu, Ni)6Sn5}||(11̅1)_Ni; [001]_{(Cu, Ni)6Sn5}||[110]_Ni, according to EBSD and TEM analysis. The outcome of this study explicitly demonstrates that the morphology of (Cu, Ni)₆Sn₅ is determined by the preferred orientation relationship with Ni, and therefore one could predict the morphological texture of (Cu, Ni)₆Sn₅, once the crystal orientations of Ni were known. Moreover, because a coherent interface between (Cu, Ni)₆Sn₅ and Ni was observed, this study also verified that no (Ni, Cu)₃Sn₄ IMCs had formed at the interface of (Cu, Ni)₆Sn₅/Ni.