Optimization of hybrid wick structures for extreme spreading in high performance vapor chambers

Abstract

The demand for increasingly aggressive heat spreading in high power electronics has pushed the limits of existing vapor chamber wick technology. For optimal thermal performance, a vapor chamber wick must be able to provide enough capillary pressure to sustain fluid delivery while still maintaining a low thermal resistance. To minimize thermal resistance and increase capillary forces, small feature sizes are typically desired near the hotspot. The low porosity and permeability of these small feature size regions, however, often provide too much fluid resistance to sustain capillary driven flow through the entire wick. Hybrid and biporous wicks have therefore emerged as promising solutions where high permeability, high thermal resistance structures are used to feed fluid to low permeability, low thermal resistance structures located above the hotspot. In this study, a novel hybrid wick structure is investigated that increases the total heat transfer rate by repurposing typically low thermal performance fluidic routing structures as additional extended areas for heat transfer. A coupled semiemprical heat transfer and numerical fluid flow model is developed to optimize the total heat transfer and pressure drop for a variety of wick geometries and material properties.