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 (Delta G(seg)) 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 S-Oct > clean interface > O-Oct > C-Oct > H-T(et). 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.