Synergic effect of Te, Ni and MWCNT on creep behavior and microstructural evolution of Sn-1.0Ag-0.7Cu low-Ag solder

Abstract

Avoiding the weak interface bonding of multi-walled carbon nanotubes MWCNT with Sn-Ag-Cu solder matrix is vital to produce high performance large scale Sn-Ag-Cu solder alloys. In this work, Sn-1.0Ag-0.7Cu (SAC107) composite solders were developed by incorporating MWCNT in SAC107 alloy with Ni and Te. The results indicate that the MWCNTs and Cu can be instantaneously adsorbed at the surface-active of Te atoms to in situ compose the core multi-shell (Te/C/Cu/C) polygonal particles, linking MWCNT with SAC solder matrix. The polygonal particles are well dispersed through the Cu6Sn5, Ag3Sn, β-Sn, SnTe and (Cu,Ni)6Sn5 IMC precipitates. These structural variations produce a combination of increased creep resistance 15 times and enlarged creep life time (14 times) than that of plain SAC107 alloy. Although Ni and Te additions decreased the creep resistance of SAC, the SAC-Ni-Te-MWCNT composite alloy exhibits significant change in dislocation creep resistance with creep stress exponent of ~ 6.6 at 25 °C: the creep threshold stress is decreased by 58.8% (5 MPa) in SAC-Ni-Te alloy, while increased by 17.6% (1.5 MPa) in SAC-Ni-Te-MWCNT composite alloy owing to the presence of polygonal particles.