A Sn-Ag-Cu-In quaternary Pb-free solder composition is provided to suppress an increase in the cost of the Pb-free solder composition and sufficiently secure processability and mechanical properties of the Pb-free solder composition as a solder material by adding a proper amount of indium(In) and optimizing the content of silver(Ag). A Sn-Ag-Cu-In quaternary Pb-free solder composition comprises not less than 0.3% to less than 2.5% by weight of silver(Ag), not less than 0.2% to less than 2% by weight of copper(Cu), not less than 0.2% to less than 0.8% by weight of indium(In), and the balance of tin(Sn). The Sn-Ag-Cu-In quaternary Pb-free solder composition further comprises not less than 0.0001% to less than 1% by weight of one element or a mixture of at least two elements selected from phosphorous(P), germanium(Ge), gallium(Ga), aluminum(Al), and silicon(Si). to improve oxidation resistance of the Pb-free solder composition. The Sn-Ag-Cu-In quaternary Pb-free solder composition further comprises not less than 0.0001% to less than 2% by weight of one element or a mixture of at least two elements selected from zinc(Zn) and arsenic(As) to improve interfacial reaction characteristics of the Pb-free solder composition.
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