Revealing effects of common nonmetallic impurities on the stability and strength of Cu–Sn solder joints: A first-principles investigation

Nonmetallic elements can affect the stability and usability of Cu–Sn solder joints intensively. The electronic structure, adhesion work, and tensile strength of Cu(111)/Cu3Sn(001) interface doping with H, C, O and S have been systematically investigated herein using the first-principles calculations. Cu(Cu)-terminated interface is the most stable among the clean Cu(111)/Cu3Sn(001) interfaces. In the non-metallic atoms doping Cu(111) surface system, H atom tends to occupy tetrahedral interstitial sites, while C, O and S atoms prefer to octahedral interstitial sites. The calculated segregation heat (ΔGseg) indicates that H and O atoms tend to stay in the interior, while C and S atoms tend to segregate to the Cu(111)/Cu3Sn(001) interface. From adhesion works, the order of binding strength is SOct > clean interface > OOct > COct > HTet. Finally, electronic structures of doping systems are analyzed to reveal the effects of nonmetallic impurities on the stability and strength of Cu–Sn solder joints. These results will provide guidance for the design of modified Cu–Sn solder joints.