Effect of germanium on shearing strength and fracture surface of SnAgCu/Cu soldering joint

In Periodic Table of the Elements, germanium (Ge)is adjacent to tin.They are both the elements in the main group Ⅳ and resemble each other in physical and chemical property.A little element Ge was added into lead-free solder Sn2.5Ag0.7Cu (0.25, 0.5, 0.75, 1.0 wt%), and the shear test specimens were designed and welded.The joint shearing strengths were measured and fracture surfaces were analyzed by scanning electron microscope and energy dispersive X-ray analysis method.The result indicates that the shearing strength of the joint increases obviously. The joint fracture forms of the Sn-Ag-Cu-Ge lead-free solder are mainly ductile fracture, and most of them have secondary cracks. Lots of dimples formed on the fracture surface when adding element Ge, and IMC Cu6Sn5 play a part on the dimple forming.