A Novel Electronic Packaging Method to Replace High-Temperature Sn-Pb Solders

The In/Ni/Cu/Ni/In multilayer was prepared by an electroplating method to replace high-temperature Sn-Pb solders that are conventionally used but are very harmful to the environment. This study shows all the sandwich couples that formed the (Cu,Ni)(6)(Sn,In)(5) and Cu2In3Sn phases at the interface. When the solder joint was reflowed at 200A degrees C, a planar layer (Ni,Cu)(3)(Sn,In)(4) formed near the Ni layer. When the reflowing temperature was increased to 300A degrees C, another planar layer Cu-3(Sn,In) formed near the Cu substrate. The greater part of the intermetallic compounds in this case were the (Cu,Ni)(6)(Sn,In)(5) and Cu-3(Sn,In) phases. The Cu-3(Sn,In) phase thickness was increased with increasing aging time. The thicker formation of Cu-3(Sn,In) phase improved the solder-joint strength. The samples reflowed at 300A degrees C exhibited the best mechanical strength, which was 57.6 kg/cm(2) as reflowed. This In/Ni/Cu/Ni/In multilayer structure is a suitable candidate for high-temperature Pb-free solders.