Intermetallic Growth of Cu6Sn5 as a function of Cu crystallographic orientation

The morphologies and growth behavior of Cu₆Sn₅ intermetallic compound (IMC) formed between Sn-based solder and large-grain polycrystalline Cu substrate were systematically investigated. Hexagonal Cu₆Sn₅ grains were observed to form at certain reflow condition, which matches well with the literature results for IMC growing on single crystal substrate. The kinetics of IMC growth was also investigated and different mechanisms were proposed for different evolution stages. It was observed that facet formation should be a growth shape rather than an equilibrium shape, and the orientation relationship between Cu and Cu₆Sn₅ was studied using scanning electron microscope (SEM) and Electron backscatter diffraction (EBSD), and were visualized on inverse pole figure.