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Impact Properties of Sn-0.75Cu Lead-Free Solder Ball Joint

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.