The impact properties of solder ball joints with Sn-Ag-Cu-Ni-Ge lead-free solders and Cu electrodes were investigated in the aged conditions at 393 K. The impact properties evaluated was compared with Sn-Ag and Sn-Ag-Cu solder joints. The impact properties of Sn-AgCu-Ni-Ge joints were superior to those of Sn-Ag and Sn-Ag-Cu joints. In the cases of Sn-Ag and Sn-Ag-Cu joints, fracture mainly occurred in the intermetallic compounds (IMC) layer formed in the joint interface regardless of aging treatment. On the contrary, main fracture mode was solder fracture in as-reflow Sn-Ag-Cu-Ni-Ge joints. Although the main fracture mode gradually changed from solder fracture to IMC fracture upon aging, Sn-Ag-Cu-Ni-Ge joints had excellent impact reliability compared with Sn-Ag and Sn-Ag-Cu joints even after aging at 393 K for 1000 h.

Impact properties of a solder ball joint with a Sn-0.75mass%Cu lead-free solder were investigated under aging conditions at 393 K. Moreover, obtained impact properties were compared with those of the joints with Sn-3.5mass%Ag and Sn-3.5mass%Ag-0.5mass%Cu solders. Ball impact force of a Sn-0.75Cu joint was stable at 4.5~5 N, which is similar to that of a Sn-3.5Ag-0.5Cu joint without aging, upon aging at 393 K for 1000 h. In the Sn-0.75Cu joint without aging, main fracture mode was complex fracture of the solder and an intermetallic compound (IMC) formed in a joint interface. Main fracture mode changed from the complex mode to solder fracture upon aging, and thus the impact toughness improved.