Electrodeposition of Sn-Cu solder alloy for electronics interconnection

Eutectic Sn-Cu alloy is one of the lead-free solder candidates for electronics interconnection. The methanesulphonic acid based baths were investigated for the electrodeposition of Sn-Cu alloys. The effect of iso-octyl phenoxy polyethoxy ethanol (Triton X-100) as a surfactant was studied, its addition proved to facilitate achieving the near eutectic composition of Sn-Cu alloy with improved microstructure. Different morphologies of deposited films were analysed using scanning electron microscopy (SEM). X-ray diffraction (XRD) results indicated that a biphasic structure of beta-Sn and Cu₆Sn₅ was present in the as-electroplated film. Fine pitch near eutectic Sn-Cu solder bumps were also produced on a test wafer.