Low-Temperature Copper Sintering Bonding Technology Based on Non-Spherical Bimodal Design and Solvent Optimization

Wide bandgap semiconductors, silicon carbide (SiC) and gallium nitride (GaN), hold significant importance in applications such as new energy vehicles, aerospace, and 5G technology due to their high breakdown voltage, excellent thermal conductivity, and outstanding radiation resistance. However, traditional lead-free solder has limitations in electrical and thermal performance, making it difficult to meet the demands of electronic packaging. Although silver (Ag) sinter-joining technology has high performance, its cost is relatively high and its resistance to electrochemical migration is weak, making high-cost-performance copper (Cu) sinter-joining technology a promising alternative. To overcome the oxidation risk and agglomeration tendency of nanoparticles in Cu pastes, this study introduces micron-Cu flakes, aiming to strike a balance between stability and sintering ability. We optimize the ratio of bimodal particles using a combination of computer simulations and experimental methods. The study shows that the optimal packing density and sintering performance are achieved when the ratio of submicron-Cu spheres to micron-Cu flakes is 7:3. On this basis, the solvent system of Cu paste is improved, enhancing its low-temperature sintering performance. At an ultra-low temperature of 160 °C, the shear strength is up to 46 MPa, providing significant application potential and commercial value in the field of high-power electronic device packaging.