Effect of nano Ni additions on the structure and properties of Sn-9Zn and Sn-8Sn-3Bi solder in ball grid array packages

The effect of nano Ni additions in Sn-9Zn and Sn-8Zn-3Bi solders on their interfacial microstructures and shear strengths with Au/Ni/Cu pad metallization in ball grid array (BGA) applications were investigated. After addition of nano Ni powder in Sn-based lead-free solders, there was no significant changes in the interfacial microstructure. But, in the solder region a very fine Zn phase was observed. Also, on the fracture surfaces fine Zn-Ni compound was found. After addition of nano Ni powder in Sn-based solders, the shear loads were increased and in addition, ductile fracture surfaces were clearly observed. The shear loads of Sn-9Zn and Sn-8Zn-3Bi solder were about 1798 gm and 2059 gm, respectively. After addition of nano Ni powder, their strengths were about 2172 gm and 2212 gm, respectively.