Effect of Pd content on microstructure and properties of Ag-Cu-Pd solder

The effects of Pd content on the melting properties, spreading properties on oxygen-free copper and nickel, as-cast organization of Ag-Cu-Pd solder, and brazing interface were studied. The results show that the solidus temperature and the liquidus temperature of Ag-Cu-Pd solder are obviously improved with the increase of Pd content. Accordingly, the temperature interval of solid-liquid phase line also increases. When Pd is 10 % and 20 %, the solder spreadability is optimal. In addition, the spreadability of solder alloy is reduced with the rising Pd content. When Pd is increased to 30 %, solder spreadability begins to deteriorate and there are signs of slight erosion. The Pd in Ag-Cu-Pd alloy is mainly present in the Cu-rich phase. The brazing interface forms a continuous intermetallic compound (IMC) layer when Ag-28Cu-20Pd solder is welded to the oxygen-free copper plate, with most of Pd distributing in IMC layer.