Phase formation and microstructure evolution in Cu/In/Cu joints
Abstract In this study, Cu/In/Cu sandwich structures were fabricated at 180 °C, which was followed by aging at 245 °C, 273 °C, and 290 °C for different time periods. The microstructural evolutions were investigated using scanning electron microscopy (SEM), electron backscattering diffraction (EBSD), and energy dispersive X-ray spectroscopy (EDS). The results show that the intermetallic compounds formed included Cu11In9, Cu2In, and Cu7In3, depending on the aging conditions. The activation energies for the growths of Cu2In and Cu7In3 are estimated to be 17 kJ/mol and 40 kJ/mol, respectively. The compound Cu2In tended to encircle voids, and wavy edges formed presumably due to the grain orientations of the Cu substrates. The mechanical properties of the compounds were measured by the nanoindentation test. The results show that Cu In compounds have better mechanical properties than Cu Sn compounds.