Efficient Synthesis and Excellent Performance of Low-Temperature Sintering Cu@Ni Nanoparticle Materials for Power Electronic Packaging

Sintering interconnection technology based on Cu nanopaste material, due to its outstanding electrical, thermal properties, and electrical-migration resistance, it is gradually emerging as an appealing alternative for power electronic packaging in third-generation semiconductor devices (the service temperature of >350 °C). However, the characteristics of Cu nanoparticles (NPs), such as susceptibility to oxidation and the requirement for reduced-atmosphere sintering, constrain their application into AI chip and other fields of CSP and SiP. In this work, we successfully synthesized small-molecular-weight organics (~OAM) coated Cu@Ni NPs with small size (42 nm) and uniform distribution by one-step reduction after directly mixing conventional copper salts and nickel salts. Results demonstrated that the rapid coating of small-molecular-weight organics leads to the formation of a uniform and dense core-shell structure of Cu@Ni NPs, where the oxidation of Cu core is inhibited. Meanwhile, the sintering joints with a high shear strength of ~60.5 MPa were prepared through ultrasonic-assisted sintering (UAS) Cu@Ni nanopaste, significantly surpassing the shear strength of SnPb solder. The strengthening effect of joints may originate from the removal of residual organics by the unique friction effect of USW, and the ultrafast diffusion between Cu and Ni atoms with the increase of pressure and temperature. This offers broad commercial prospects for packaging in third-generation semiconductors and other power devices.