Silver paste pressureless sintering on bare copper substrates for large area chip bonding in high power electronic packaging

We developed a novel copper-bondable silver paste for the pressureless bonding of large-area chip on bare copper substrate. This paste includes silver nanoparticles, silver sub-micron-sized flakes, and organics. The finally densification, which is controlled by grain boundary and lattice diffusions, was developed by the formation of robust solid necks among the nanoparticles and flakes. The sintered silver joint showed high shear strength, low porosity, low thermal impedance, and barely any void. This silver paste is very promising for the attachment of power device on bare copper substrate.