Preparation of nanoparticle and nanowire mixed pastes and their low temperature sintering

A new mixed nano paste consisting of silver nanoparticles, silver nanowires and copper nanoparticles has been proposed as the active material in an alternative joining approach for interconnection in electronic packaging. The mixed nano paste was optimized by adding different contents of copper nanoparticles into silver nanoparticle and nanowire pastes. Compared with the common silver nanoparticle paste, the electrochemical migration time of this mixed nano paste increased with greater addition of copper nanoparticles. Silver nanowires were also found to decrease the resistance of this mixed nano paste effectively due to their continuity. Although higher additions of copper nanoparticles into the mixed nano paste could facilitate the desired result of anti-electrochemical migration, they also decrease the shear strength of the sintered joints using the mixed pastes. In order to balance anti-electrochemical migration and sintering properties of the mixed nano pastes, when 10% copper nanoparticles were added to the mixed silver nanoparticle and nanowire pastes, the average shear strength of sintered joints at 250-350 °C was above 25 MPa. Based on the comprehensive properties, the mixed silver nanoparticle nanowire with 10% copper nanoparticle pastes were determined to be a better paste for sintered connections in electrical packaging.