Liquid Metal Based Soft-Connected Packaging of Press-Pack SiC Power Module for Pressureless Interconnection and Double-Sided Cooling

Owing to the advantages in high breakdown voltage and low switching loss, the silicon carbide (SiC) device is promising to integrate with the press-pack (PP) packaging for high-voltage and high-power applications. However, the higher Young's modulus and heat flux of SiC dies, compared to silicon counterparts, pose significant challenges for conventional PP packaging. Rigid PP packaging suffers from uneven contact pressure, while the flexible PP packaging offers only single-sided cooling. To tackle these issues, a soft-connected PP packaging enabled by liquid metal, and a matched structure is proposed to replace the spring structure, thus realizing pressureless interconnection and efficient double-sided cooling. Finite element analysis and experimental assessment for the soft-connected packaging of the PP SiC module and its two counterparts with conventional interconnections are conducted. Experimental results indicate that the contact pressure on the SiC die with the soft interconnection is decoupled from the external clamping force and reduced by 99% compared to both conventional packaging baselines, thus making the module highly suitable for easy series connection. Compared to the conventional rigid and flexible PP SiC modules, the optimal junction-to-fluid thermal resistance of the soft-connected PP SiC module is reduced by 83% and 55%, respectively. The reliability of the power module and the stability of the liquid metal have been preliminarily verified through thermal shock testing. The proposed soft-connected packaging thus facilitates the deployment of SiC technology in advanced PP power modules.