Conventional and topologically optimized polymer manifolds for direct cooling of power electronics

Abstract

Single-phase liquid-cooled heat sinks are a preferred mode of thermal management for many power dense electronic applications. This paper studies the design, optimization, and thermal-hydraulic performance of polymer manifolds directing coolant to the base plate of multi-chip power modules. Direct cooling eliminates the need for thermal interface materials which form a major bottleneck to junction-to-coolant thermal resistance reduction in state-of-the-art metallic cold plates. We use 2D topology optimization (TO) to develop designs using side view (SVTO) and top view (TVTO) sections of the flow domain in contact with the power module base plate. We also use 3D TO design (CTO) which combines SCTO and TVTO. The TO designs are compared against conventional mini-channel designs including rectangular, zig-zag and serpentine channels. Cooling performance of the different designs is computed using computational fluid dynamic (CFD) simulations. Experimental quantification is achieved through measurements of the silicon carbide device junction temperature and inter-device temperature difference along with the pressure drop influencing the pumping power requirement. The CFD simulations were used to identify optimized manifold designs which were fabricated using selective laser sintering of PA12 and validated experimentally using surrogate heaters. Zig-zag designs showed the best performance among the conventional designs (0.93 (cm2·K)/W), at the cost of high pressure drop (> 2.4 kPa). Serpentine channel designs were effective in limiting inter-device temperature difference (< 0.26⁰C) through multiple changes of flow direction. The TO designs improved the performance (1.1 (cm2·K)/W) when compared against conventional channels showing lower maximum temperatures with lower pressure drops (0.8 kPa). Fluid manifolds are shown to greatly influence the coolant flow field, leading to flow maldistribution with low velocity pockets, emphasizing the need for optimizing the complete manifold design.