A direct brazing approach to low-warpage, high-thermal-efficiency Cu/Si₃N₄/Cu substrates for power electronics

Direct brazing was employed to fabricate a “Cu circuit layer–Si₃N₄ ceramic–Cu heat sink” structure for power electronic devices, enabling a shortened heat dissipation path and enhanced thermal management. Structural components (60 mm × 60 mm and 30 mm × 30 mm) were brazed at 780 °C for 20 min to simulate finless and finned heat sinks. The effects of composite brazing filler metal and copper underlayer stiffness on warpage and thermal resistance were systematically evaluated. Results show that composite fillers effectively suppressed warpage, reducing deformation in a 60 × 60 mm²-finned component from 0.95% to 0.73%, with a measured thermal resistance of 0.1936 K/W. After surface soldering of the IGBT, the total thermal resistance from junction to ambient decreased by 10.2% compared with conventional structures. This study demonstrates a practical route to improve heat dissipation and optimize the thermal design of high-power modules, providing an industry-ready thermal management solution for high-power-density SiC/GaN devices.