Development of Sn-1.0Ag-0.7Cu composite solder with improved resistivity and strength-ductility synergy through additions of Ni, Te and MWCNT

Multi-walled carbon nanotubes (MWCNTs) reinforced Sn-1.0Ag-0.7Cu (SAC107) composite solders have fabricated by mechanical mixing method. The effects of small amount of Te, Ni and MWCNTs additions on the microstructure evolution, electrical resistivity and mechanical properties have investigated. The elemental mapping analysis of SAC107-0.1Ni-0.1Te-0.1MWCNT composite solder shows that the MWCNTs promote the formation of core-shell polygonal particles, where polygonal core of Te is located at the center of the particles and surrounded by a shell of Cu with the presence of MWCNT at the inner Te core and outer copper shell. The microstructure also shows a large volume fraction of 30% for the Cu6Sn5, Ag3Sn, beta-Sn, SnTe, (Cu, Ni)(6)Sn-5,Sn- and core-shell polygonal particles. The modified structure reduces the electrical resistivity by similar to 16.3% and induces high work-hardening ability, in which the strength and ductility are simultaneously increased by 71.5% and 55.9%, respectively. Such enhancement in strength and ductility is activated by different strengthening mechanisms; involving the creation of polygonal particles, Rayleigh-Plateau instability model, formation of multiscale nature of heterogeneous domain structure, and reduction of Ag3Sn, Cu6Sn5, and SnTe particles size, which effectively act as dislocation sources and barriers.

Automated summary

The addition of MWCNTs improved the microstructure of the Sn-1.0Ag-0.7Cu composite solder, reduced the electrical resistivity, and increased both strength and ductility.