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 Cu 11 In 9 , Cu 2 In, and Cu 7 In 3 , depending on the aging conditions. The activation energies for the growths of Cu 2 In and Cu 7 In 3 are estimated to be 17 kJ/mol and 40 kJ/mol, respectively. The compound Cu 2 In 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.