Effect of different sizes of Cu nanoparticles on the shear strength of Cu-Cu joints

In order to enhance the bonding strength of joints by using Cu nanoparticles paste at a relative low bonding temperature and a suitable pressure, a novel mixed Cu nanoparticles of 20 nm and 100 nm (in diameter) paste for Cu-Cu joints was investigated in this study based on the density increment of packing two different sizes of spheres. The optimized mass ratio of 20-100 nm nanoparticles for maximum sintering density was proposed (9/1) by simulation and experiments. The bonding strength of joints over 15 MPa was achieved even at a lower bonding temperature of 250 °C and pressure of 4 MPa.