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Research Papers: Electronic Cooling

# Experimental Investigation of an Ultrathin Manifold Microchannel Heat Sink for Liquid-Cooled Chips

[+] Author and Article Information
W. Escher

Zurich Research Laboratory, IBM Research GmbH, Rüschlikon 8803, Switzerland; Department of Mechanical and Process Engineering, Laboratory of Thermodynamics in Emerging Technologies, ETH Zurich, Zurich 8092, Switzerland

T. Brunschwiler, B. Michel

Zurich Research Laboratory, IBM Research GmbH, Rüschlikon 8803, Switzerland

D. Poulikakos1

Department of Mechanical and Process Engineering, Laboratory of Thermodynamics in Emerging Technologies, ETH Zurich, Zurich 8092, Switzerlanddimos.poulikakos@ethz.ch

1

Corresponding author.

J. Heat Transfer 132(8), 081402 (Jun 02, 2010) (10 pages) doi:10.1115/1.4001306 History: Received May 27, 2009; Revised January 28, 2010; Published June 02, 2010; Online June 02, 2010

## Abstract

We report an experimental investigation of a novel, high performance ultrathin manifold microchannel heat sink. The heat sink consists of impinging liquid slot-jets on a structured surface fed with liquid coolant by an overlying two-dimensional manifold. We developed a fabrication and packaging procedure to manufacture prototypes by means of standard microprocessing. A closed fluid loop for precise hydrodynamic and thermal characterization of six different test vehicles was built. We studied the influence of the number of manifold systems, the width of the heat transfer microchannels, the volumetric flow rate, and the pumping power on the hydrodynamic and thermal performance of the heat sink. A design with 12.5 manifold systems and $25 μm$ wide microchannels as the heat transfer structure provided the optimum choice of design parameters. For a volumetric flow rate of 1.3 l/min we demonstrated a total thermal resistance between the maximum heater temperature and fluid inlet temperature of $0.09 cm2 K/W$ with a pressure drop of 0.22 bar on a $2×2 cm2$ chip. This allows for cooling power densities of more than $700 W/cm2$ for a maximum temperature difference between the chip and the fluid inlet of 65 K. The total height of the heat sink did not exceed 2 mm, and includes a $500 μm$ thick thermal test chip structured by $300 μm$ deep microchannels for heat transfer. Furthermore, we discuss the influence of elevated fluid inlet temperatures, allowing possible reuse of the thermal energy, and demonstrate an enhancement of the heat sink cooling efficiency of more than 40% for a temperature rise of 50 K.

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Copyright © 2010 by American Society of Mechanical Engineers
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## Figures

Figure 1

Schematic of a manifold microchannel heat sink: (a) top view of the manifold with K=9.5; (b) isometric section view

Figure 2

(a) 3D CAD drawing—isometric view on a test vehicle; (b) backside of the HT-chip showing the thin film metal heater with embedded RTDs

Figure 3

(a) 3D CAD drawing of the test section; (b) Schematic of the flow loop

Figure 4

(a) Spatial temperature distribution of a section of the heater being measured by an IR camera: the arrow indicates the flow direction in the manifold system; (b) top part: temperature distribution in the y-direction being averaged along the x-direction, bottom part: Temperature distribution in the x-direction being averaged along the y-direction

Figure 5

(a) Isometric section view indicating a unit cell of the heat sink; (b) computational domain of a unit cell of the manifold microchannel heat sink; (c) normalized velocity vectors at the XZ-center plane of the inlet manifold channel around a bracing; and (d) top part: relative volume flux distribution along the manifold system in the porous media, bottom part: comparison of the experimentally and theoretically determined maximum heater temperatures along the manifold system

Figure 6

Local maximum heater temperature for three different flow rates: arrows indicate the range for determination of the absolute maximum heater temperature

Figure 7

(a) Total pressure drop across the heat sink and (b) maximum total thermal resistance as a function of the volumetric flow rate for all six test vehicles

Figure 8

Comparison of the experimentally and theoretically determined (a) total pressure drop across the heat sink as a function of the number of manifold systems for varying channel width wHT,ch and (b) maximum total thermal resistance as a function of the channel width wHT,ch for K=9.5 and a volumetric flow rate of 1.08 l/min

Figure 9

Maximum total thermal resistance as a function of the pumping power for varying channel width wHT,ch and K=9.5

Figure 10

(a) Total pressure drop (squares) and maximum total thermal resistance (circles) and (b) relative COP as a function of the fluid inlet temperature for wHT,ch=25 μm, K=12.5, q̇heater″=100 W/cm2, and V̇=1 l/min

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