Effect of Ag and Ni on the melting point and solderability of SnSbCu solder alloys

To improve the properties of Sn10Sb8Cu solder alloy, two new solders (SnSbCuAg and SnSbCuNi) were formed by adding small amounts of Ag or Ni into the solder alloy. The results show that the melting point of the SnSbCuAg solder alloy decreases by 14.1°C and the spreading area increases by 16.5% compared to the matrix solder. The melting point of the SnSbCuNi solder alloy decreases by 5.4°C and the spreading area is slightly less than that of the matrix solder. Microstructure analysis shows that adding trace Ag makes the melting point decline due to the dispersed distribution of SnAg phase with low melting point. Adding trace Ni, Cu6Sn5 and (Cu, Ni)6Sn5 with polyhedron shape on the copper substrate can be easily seen in the SnSbCuNi solder alloy, which makes the viscosity of the melting solder increase and the spreading property of the solder decline.