Effect of indium on the microstructure of the interface between Sn3.13Ag0.74CuIn solder and Cu substrate

Influence of indium in Sn3.13Ag0.74Cu solder containing 4, 15, 30, 50 and 75 at.% In on the microstructure at the solder/Cu interface after wetting at 523 K for 1800 s was studied. The scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), standard and spatially resolved X-ray diffraction (XRD) techniques were used to determine the phases present at the solder/Cu interface. It was found that for In concentration up to 30 at.% the interface is formed by Cu6Sn5 phase. For higher In content (50 and 75 at.% In) interface consists of copper rich Cu41Sn11 phase.