Optimization and thermal characterization of uniform micropillar based silicon evaporator in advanced vapor chambers

Micropillar based wicks were widely studied in recent years. They were proven to be promising candidates for evaporators inside vapor chambers as they possess advantages of high capillary pressure, permeability, large areas for thin film evaporation and easy-controlled fabrication processes. In this work, optimization of uniform evaporator with cylindrical silicon micropillars are conducted with Brinkman's equation derived model. Sample with optimized geometries is designed, fabricated and thermally tested inside a vacuum chamber. Theoretically, the best combination of micropillar geometries are d= 20.7 μm, h=l=36.3 μm. The calculated heat flux for optimized evaporator is q"=93.5 W/cm2 at superheat of 15 °C. Measured maximum heat flux of the actual sample is q"= 80.6 W/cm2 at 13.2 °C superheat due to deviation in pillar height. The model is proven to have good correlation with preliminary experimental results.