Interfacial reactions on Pb-free solders with Au/Pd/Ni/Cu multilayer substrates

In this study, the interfacial reactions on Sn, Sn-3.0Ag-0.5Cu, Sn-0.7Cu, Sn-58Bi and Sn-9Zn lead-free solders with the Au/Pd/Ni/Cu multilayer substrate at 240-270 degrees C for 20 min to 20 h were investigated. The experimental results showed that the (Ni, Cu)(3)Sn-4 phase is converted to the (Cu, Ni)(6)Sn-5 and Cu3Sn phases in the Sn/Au/Pd/Ni/Cu system when the reaction time is longer than 4 h. In Sn-3.0Ag-0.5Cu/Au/Pd/Ni/Cu and Sn-0.7Cu/Au/Pd/Ni/Cu systems, the (Cu, Ni)(6)Sn-5 and Cu3Sn phase were observed, and only the Ni3Sn4 phase was formed at the Sn-58Bi/Au/Pd/Ni/Cu interface. Furthermore, the Pd2Zn9 and NiZn phases were formed in the Sn-9Zn/Au/Pd/Ni/Cu system. When the reaction time was longer than 4 h, the Pd2Zn9, NiZn, and Ni5Zn21 phases were formed at the interface. The reaction mechanism for all the reaction systems was diffusion-controlled. The Sn-58Bi/Au/Pd/Ni/Cu system was found to have the lowest activation energy when compared with other systems, and its value was 17.43 kJ/mol. (C) 2010 Elsevier B.V. All rights reserved.