Development of Low-Temperature Air-Sinterable Copper Paste for Die Attach and Substrate-to-Heatsink Bonding

In this study, a low-temperature, air-sinterable Cu paste was successfully developed for both die-attach and large-area substrate-to-heatsink bonding. The results demonstrated that strong Cu–Cu joints can be achieved by sintering in air, with an average shear strength of 36.1 MPa for chip-scale joints and 43.3 MPa for large-area (30mmx30mm) joints. SEM and TEM analyses revealed that the use of polyethylene glycol 300 (PEG300) and ascorbic acid (AA) effectively reduced Cu oxide and generated fine Cu nanoparticles (<10 nm), which enhanced neck growth and densification during sintering. These findings indicate that the developed Cu paste enables rapid, robust, and oxidation-tolerant bonding in air, offering a promising low-cost alternative to Ag-based sintering materials for power device packaging applications.