Abstract: A lead-free bonding technique using Sn/Bi alloy as joint was studied.Cr/Ni/Cu/Sn multilayer was electroplated on substrate and Cr/Ni/Cu/Bi was electroplated on chip,then these two were bonded at 240℃in vacuum.This fluxless bonding process can prevent micro device being polluted.The thickness of the joint is uniform along the entire cross section.The strength of the joint is high.This process can make a very hermetic bonding,so it is suitable for hermetic packaging of electronic device and MEMS movable parts at low temperature.