Review of Copper-Silver Core-Shell Sintering Pastes: Technology and Future Trends

For power electronics packaging, die attach materials are developing towards higher working temperature and higher current density. Traditional packaging materials such as solder paste and conductive adhesives no longer meet the requirements of advanced packaging, especially for wideband gap chip packages. Copper-silver core-shell (Cu@Ag) particle is an emerging material that can be used for advanced packaging. It combines the excellent electrical and thermal conductivity of copper and silver particles, while avoiding the shortcomes such as the electromigration of silver and the oxidation of copper. The sintered paste prepared by Cu@Ag has excellent electrical and thermal conductivity and is low in cost compared with commercial silver sintered paste, which has attracted the interest of researchers and companies all over the world. In this work, Cu@Ag particles preparation methods, paste preparation, and sintering process were listed and compared. Furthermore, molecular simulations regarding such core-shell particles were also concluded. The main preparation methods of Cu@Ag particles include physical vapor deposition, spray pyrolysis, direct displacement, liquid-phase chemical reduction, etc. Commonly used sintering methods for Cu@Ag sintering paste include hot pressing sintering, ultrasonic assisted sintering, and pulse current sintering. Copper-silver core-shell nanoparticles have a larger radius of curvature between the grain boundaries than bulk materials due to their smaller size, and the sintering temperature is greatly reduced, so the sintering kinetics is also different from that of bulk materials. The molecular dynamics simulation (MD) software LAMMPS can simulate the particle sintering process and explore the sintering mechanism.