Reliability improvement of SnAgCu interconnections under extreme temperature condition by TiO₂ nanoparticles doping: Experiments and first principles calculations

Electronic components of the spacecraft during their service may endure intricate and extreme temperature environments. In this study, the interfacial microstructure evolution and reliability of Cu/Sn-3.0Ag-0.5Cu (SAC305)/Ni and Cu/Sn-3.0Ag-0.5Cu-0.05TiO₂ (SAC305–0.05TiO₂)/Ni interconnections under thermal shock from −196 °C to 150 °C are investigated. Short-column-type (Cu,Ni)₆Sn₅ intermetallic compounds (IMCs) are developed at the solder/Ni interface for both interconnections after the reflow process, and their morphology changes to long-rod type after 200 cycles. Extremely thin and discontinuous (Ni,Cu)₃Sn₄ phases are generated between (Cu,Ni)₆Sn₅ and Ni only in SAC305 interconnections after 200 cycles. The rate of interfacial IMCs growth in SAC305–0.05TiO₂ interconnections is slower than that in the SAC305 interconnections. Cracks are formed in the IMC layer of the SAC305 interconnection after 200 cycles, which propagate through the whole IMC layer after 250 cycles. While for the SAC305–0.05TiO₂ interconnection, no crack is observed until after 250 cycles. TiO₂ nanoparticles doping could suppress the interfacial IMC growth, leading to an enhancement in the interconnection reliability under thermal shock. First-principles calculations are performed to further understand the mechanism for phase transformation of Ni-Cu-Sn IMCs and the reliability improvement of interconnections.