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 µm and 5 µm 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 × 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 µm × 200 µm 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 × 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.

Enhanced Capillary‐Fed Boiling in Copper Inverse Opals via Template Sintering

“…Microporous metals feature high specific surface area, high thermal and electrical conductivities, and high density of interconnected fluid‐permeable pores. They are common as wick structures in two‐phase thermal management systems such as heat pipes and vapor chambers due to their potential to reduce the transport resistance associated with the heat supply, liquid replenishing, and vapor removal . Passive microporous structures depend on capillary pressure to supply liquid to the phase‐change surface where the working fluid evaporates.…”

Enhanced Heat Transfer Using Microporous Copper Inverse Opals

“…An enhanced cooling of high heat flux applications performance of high heat flux electronic devices [1][2][3][4]. The increase in total power dissipation requirements over small area has initiated significant interest in phase change cooling schemes, and the recent advancements in material development and nano/micro fabrication technologies have created tremendous possibilities for enhanced phase change heat transfer such as via structured surface, porous media, and three-dimensional manifold cooling configurations [5][6][7][8][9][10][11][12][13][14][15][16][17].…”

“…Micro/nanoscale surface modifications have been investigated by many researchers especially for thermal management solutions in high power density devices, since they allow remarkable increases in both heat transfer coefficient (HTC) and critical heat flux (CHF) [5][6][7][11][12][13][14][15][16][17]. Dhillon et al [5] integrated nanotextured surfaces on Si micropillars and dissipated heat fluxes up to 211 W/cm 2 .…”

“…Metal inverse opal structure can be a promising material for microfluidic heat exchangers due to the high thermal conductivity with the relatively high permeability compared to other porous metals such as sintered cooper, woodpile scaffolds, or nanowire networks [18]. However, there has been relatively little research aimed at investigating thermal performance and heat transfer characteristics of inverse opal structures [16][17][18].…”

Experimental Investigation of Embedded Micropin-Fins for Single-Phase Heat Transfer and Pressure Drop

“…As the number of chips in the 3D-chip stack is increased, the heat dissipation and thermal conduction resistance to the heat sink (usually at the top) also increase resulting in significant temperature rise and degradation in performance and reliability. The intrachip microfluidic single-or two-phase cooling emerged as a viable solution for 3Dchips architecture and high heat flux applications [5][6][7][8][9][10][11][12][13].…”