Extreme Two-Phase Cooling from Laser-Etched Diamond and Conformal, Template-Fabricated Microporous Copper

Abstract

This paper reports the first integration of laser-etched polycrystalline diamond microchannels with template-fabricated microporous copper for extreme convective boiling in a composite heat sink for power electronics and energy conversion. Diamond offers the highest thermal conductivity near room temperature, and enables aggressive heat spreading along triangular channel walls with 1:1 aspect ratio. Conformally coated porous copper with thickness 25 mu m and 5 mu m pore size optimizes fluid and heat transport for convective boiling within the diamond channels. Data reported here include 1280 W cm(-2) of heat removal from 0.7 cm(2) surface area with temperature rise beyond fluid saturation less than 21 K, corresponding to 6.3 x 10(5) W m(-2) K-1. This heat sink has the potential to dissipate much larger localized heat loads with small temperature nonuniformity (5 kW cm(-2) over 200 mu m x 200 mu m with <3 K temperature difference). A microfluidic manifold assures uniform distribution of liquid over the heat sink surface with negligible pumping power requirements (e.g., <1.4 x 10(-4) of the thermal power dissipated). This breakthrough integration of functional materials and the resulting experimental data set a very high bar for microfluidic heat removal.