Effect of content of Ag on physical properties and solderability of Sn0.7Cu solder

SnCu eutectic solder is considered as the most potential substitutes of SnPb solder,particularly in wave soldering.But compared to other lead-free solders,its poor physical properties and spreading peformance limits its wide application.A new solder is made by adding trace Ag into Sn0.7Cu alloy to improve its performance.The results show that content of Ag has little influence on the melting point of Sn0.7CuxAg solder.The melting point of Sn0.7Cu0.2Ag is higher only 0.3℃ than that of matrix solder.The resistivity increases with the increase of the content of Ag.At the same time,the spreading performance of the new solder is improved by adding trace Ag into Sn0.7Cu.The spreading area of Sn0.7Cu0.2Ag reaches the maximum value of 28.61 mm² and is increased 25.5% than that of the matrix solder,which is mainly related to the formation of the rich Ag phase and the thickness and shape of the metal intermetallic compound between the solder and the substrate.