Application of copper nanoparticles as die attachment for high power LED

Although lead-free tin-based solders is the dominant material currently used in electronics packaging, gold-based solders or silver nanoparticles pastes are also used in applications where high thermal conductivity between joints are required. In this study, we evaluate the application of copper nanoparticles as a die attach material. The copper nanoparticles have a size less than 20 nm which allows low temperature fusion, an organic passivation layer which prevents spontaneous particle fusion and growth at ambient temperatures, as well as avoiding oxidation before its usage. We studied the mechanical strength of Si chips bonded with the copper nanoparticles paste, and they demonstrate good reliability after thermal aging tests. We then applied the paste to bond commercial LED chips to ceramic substrate, which gives better electrical and optical properties than Au-Sn solders while maintaining the mechanical strength of the joint.