Effect of Ni, Ge and P addition in Sn-Ag-Cu lead-free solder on solder joint properties with electroless Ni/Au electrodes

The effect of addition of small amount of Ni, Ge and P into Sn-3Ag-0.5Cu lead-free solder was investigated on microstructures and ball shear force of solder ball joints with electroless Ni/Au electrodes. At low shear speed, fracture mainly occurred in solder and ball shear force increased with increasing shear speed regardless of the solder type. At high shear speed, the fracture mode changed from solder fracture to IMC fracture and thus ball shear force decreased. The effect of single Ge addition was negligible on microstructures and ball shear force of the solder ball joints. On the contrary, the single P addition degraded ball shear force. The complex addition of Ni and P was effective to inhibit the degradation of ball shear force by the single P addition.