Rapid and low temperature sintering bonding using Cu nanoparticle film for power electronic packaging

It is of great interest but very difficult to achieve both rapid (few minutes) and low temperature (<200 °C) sintering bonding using Cu nanoparticles, which is mainly due to the diffusion dominated process and complex organics in the nanoparticle paste. In present work, a copper nanoparticle film (CNF) fabricated by pulsed laser deposition (PLD) has been developed. Under the reduction of ethylene glycol (EG) and protection of inert atmosphere, it can be sintering bonded at even 140 °C, having adequate shear strength higher than that of Pb-5Sn. A remarkable high strength of 65 MPa for Cu-DBC joints and 50 MPa for Si-DBC joints were achieved when sintered at 250 °C for only 1 min. The rapid and low temperature sintering of CNF is mainly attributed to the efficient oxide film removal by EG at low-temperature, since it is an organic free dry film without the complex organics which decompose or evaporate at high temperature. The relationships among joint strength, porosity of microstructure and interfacial connection ratio have also been discussed.