Effect of joining conditions on the joint strength of Ag nanoporous bonding

Nowadays, silver nanoparticle paste has a great attention as a substitution for lead-based high temperature die-attach material due to its superior thermal conductivity, mechanical properties and high melting point. There are many reports on the Ag nanoparticle sintering using unique properties of nanoparticles related with high surface energy. But there are still some concerns about unexpected voids and gaps caused by solvent trap and coffee ring effect. In this study, we suggested solid-state bonding method using Ag nanoporous sheet without solvent and flux. The effects of joining temperature and atmosphere on the joint strength of Ag nanoporous bonding (NPB) for the high temperature die attachment were investigated. Ag nanoporous sheet was fabricated using dealloying method in the hydrochloric acid from Al-Ag precursor alloy. The NPB of electroless nickel immersion gold coat ed Cu samples were conducted at the bonding temperature of 200 to 400 °C for 30 min with pressure of 20 MPa. Joining process was conducted in nitrogen and air atmosphere for comparison. Shear strength of NPB joints shows from 14 to 27 MPa according to the joining temperature and atmosphere. These results show similar values with conventional Pb-5Sn solder and NPB can be satisfied demand of mechanical property of the die attach joint.