Thermocompression bonding of Ag-MWCNTs nanocomposite films as an alternative die-attach solution for high temperature packaging of SiC devices

Power electronics faces increasing demands for greater power density and high temperature handling capability. Wide band gap materials were shown to enable improved performance at the chip level, however, new packaging solutions that replace Pb solders at high temperatures have yet to be found. This work investigates the use of a Ag-MWCNTs composite as a novel die-attach material to bond SiC Schottky diodes to DBC substrates. Ag and MWCNTs are co-deposited to form a thin film on the backside of a chip. The joint is then produced by thermocompression flip-chip bonding at 350°C for 10 min with a 40 N applied force, in air. Die shear tests demonstrate that a joint strength of 2 MPa on average can be achieved, over twice the MIL standard. Thermal cycling and thermal aging tests in high temperature environments also demonstrated the good resistance of the bonded assembly to thermomechanical fatigue. It was thus found that strong and reliable joints, that are able to operate at high temperatures, can be created using the developed bonding technology.