Wetting behaviour and interfacial microstructure of Sn-Ag-Zn solder alloys on nickel coated aluminium substrates

Abstract

Wetting behaviours of two lead free solders (Sn-2�625Ag- 2�25Zn and Sn-1�75Ag-4�5Zn) on nickel coated aluminium substrates were investigated. Sn-2�625Ag-2�25Zn exhibited better wettability compared to Sn-1�75Ag-4�5Zn solder. Contact angles of the solders increased with increasing roughness of the substrate. The Young-Dupre equation was used to evaluate the work of adhesion of solder on the substrate. Sn-2�625Ag-2�25Zn solder exhibited higher work of adhesion than Sn-1�75Ag-4�5Zn. A thin continuous layer of Ni 3Sn was detected at the interface between Sn-2�625Ag- 2�25Zn solder and nickel coated Al substrate. Sn-1�75Ag- 4�5Zn solder exhibited scallop intermetallic compounds (IMCs) growing into the solder field as well as a thin continuous IMC in some cases. Ni 3Sn and Ni3Sn4 IMCs were observed at the interface of Sn-1�75Ag-4�5Zn solder and nickel coated Al. � 2011 Institute of Materials, Minerals and Mining.