In order to investigate the use of Sn-8Zn-3Bi solder as a potential substitute for Sn-Pb solder, which has a lower melting point than Sn-Ag family solders, we studied interfacial reaction between Sn-8Zn-3Bi solder and Ni/Au plating on Cu pad. The joint strength was also evaluated. In particular, the effect of reflow peak temperature on the joint strength and interfacial microstructure were investigated. From microstructural observations, the reaction process between Ni/Au plating and Sn-8Zn-3Bi solder is assumed as follows: When peak temperature is low, Zn in molten solder, which is known as reactive element, rapidly reacted with Au plating to form the continuous layer of AuZn3. As a reflow peak temperature become higher, once formed AuZn3 layer dissolved into the molten solder to become thin, and simultaneously thin Ni3Sn4 type interfacial reaction layer including Cu and Zn formed between the solder and the Ni plating by interdiffusion of Ni and Sn in the solder. In bump pull test, the joint strength was improved with increasing the reflow peak temperature up to 498K. In conclusion, the interfacial structure consisting of thin Ni3Sn4 type intermetallic compound improved the joint strength, and the combination of 50nm Au plating thickness and reflow peak temperature of 498K resulted in the best joint reliability in the as soldered condition and also after aging treatment.