Design Optimization of Graded Three-Dimensional Micropillar Wicks for Vapor Chamber Evaporators

With the increasing power density of electronic devices combined with the development of advanced package technologies, thermal management has become an increasingly critical challenge. Passive heat spreaders such as vapor chambers provide a promising solution for mitigating hotspots. Vapor chambers operate with microporous wicks that move the working fluid via capillary action, while fluid vaporization from the wick menisci facilitates efficient heat dissipation. While many prior studies have focused on optimizing evaporator wick to increase the maximum capillary-limited heat flux, an equally important design goal is to minimize the thermal resistance of heat areas. In this study, we introduce a systematic modeling framework to optimize the design of segmented micropillar wicks consisting of diverse geometric zones and height variations corresponding to a specific heating configuration. Using the NSGA-II algorithm, we generate Pareto fronts of the optimal distributions of segmented micropillars with pitch ranging from 20-50 μm and height ranging from 25-100 μm. Our model captures the effect of varying interfacial meniscus shapes across the micropillar wick to determine the spatial distribution of temperature and heat flux. We find that optimized segmented wicks, featuring graded height and density, are capable of increasing the dry-out heat flux by 333% while reducing thermal resistance by 71% compared to homogeneous wicks. The specific fractions of each segment within the wick can vary depending on the targeted heat flux and thermal resistance operating criteria. This research provides useful design guidelines for graded, three-dimensional micropillar wicks and the same methodology can be extended to other types of wick structures as well.