Synthesis of Ag-Cu-Sn Nanocrystalline Alloys as Intermediate Temperature Solder by High Energy Ball Milling

To obtain intermediate temperature alloy solders with melting temperature of 400~600°C, (Ag-Cu28)-25Sn and (Ag-Cu28)-30Sn alloys were prepared by high energy ball milling. Ag-Cu-Sn nanocrystalline alloys have been obtained after milling for 40h. XRD results show that the (Ag-Cu28)-25Sn alloy consists of Ag4Sn and Cu3Sn, and the (Ag-Cu28)-30Sn alloy contains Ag4Sn, Cu3Sn and Cu6Sn5. The small polydispersed particles with size ranging from 1μm to about 25μm are observed from the (Ag-Cu28)-30Sn alloys milled for 40h by SEM. A large amount of small particles comprised of two or three grains are commonly observed by HRTEM, and average grain size is about 17.50nm. DSC results indicate that the melting points of the (Ag-Cu28)-25Sn and (Ag-Cu28)-30Sn alloys milled for 40h are 548.5°C and 539.3°C, respectively.