As a typical soldering material, the Sn-Pb alloys are widely used in the electronic and plumbing industries due to their excellent properties. However, in recent years, many countries have introduced relevant regulations and ban on toxic and hazardous substances. As a result, lead-free has become an inevitable trend on developing solder products. Therefore，Sn-Ag, Sn-Ag-Cu, and Sn-Cu alloys are the most commonly used lead-free solders, currently.