Synthesis of Air-Sinterable Copper Nanoparticles for Die-Attachment

Paste based on Cu nanoparticles (NPs) is a promising die-attachment material for high-power electronic devices due to their high conductivity and inexpensive-cost. However, the rapid oxidation of Cu NPs during sintering in air hinders their application. In this work, we synthesized stable Cu NPs with a diameter of 50~110 nm for die-attachment in air. Unlike most of the previous reports about copper pastes, nano-Cu paste prepared from the synthesized Cu NPs can be sintered at low temperatures without a protective atmosphere. By investigating the effect of different solvents on the conductivity of the sintered copper film, a mixture of glycerin and ɑ terpineol was selected as a carrier solvent to prepare nano-Cu paste. After sintering, the formed Cu-Cu joints exhibited the high shear strength, which reaches a maximum of 44.5 MPa at 275°C with a pressure of 10 MPa in air. Thus, this work shows a feasibility of the sintering of nano-Cu paste in air and the great potential of nano-Cu paste in the packing of the next-generation power devices.