Thermal ground planes (TGPs) are passive thermal management devices that utilize the phase-change of a working fluid to achieve high thermal conductivity and low thermal resistance. TGPs are flat, two-dimensional heat pipes—similar to vapor chambers—in which liquid is held within a capillary wick, and vapor is held in a sealed vapor layer. Heat is absorbed at an evaporator region, causing the liquid to evaporate. The heated vapor in the vapor core is carried via convection to a condenser region where it condenses as the heat is expelled from the TGP to an external heat sink. The condensed liquid is then pulled back to the evaporator via capillary forces in the wick. In numerous applications, mechanical flexibility of the TGP is required, as is low-cost manufacturing and viable integration routes with electronics. This work describes a flexible TGP (FTGP) fabricated using printed circuit board (PCB) technology, in which commercially available copper-cladded polyimide sheets are used as the casing material. The wick is composed of three layers of fine copper mesh electroplated or sintered together and coated with atomic layer deposited TiO2. A coarse nylon or polyether ether ketone (PEEK) mesh defines the vapor transport layer, and water is used as the working fluid. The perimeter of the device is heat-sealed with flouroethylene propylene (FEP), which has been found to provide a near-hermetic seal for several months and is suitable for flexible applications. This architecture allows the TGP to function with minimal reduction in heat transfer performance while bent by 90 deg, and full functionality is returned when the device is returned to its flat configuration. The FTGP's measured thermal resistance is about half that of an equivalent copper reference for input heat fluxes of 3–6 W/cm2. More than 30 copper-cladded polyimide FTGPs were fabricated and characterized using both simple qualitative and more involved quantitative test setups. The results show that the fabrication and assembly processes developed in this work are repeatable and the devices are durable.
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March 2017
Research-Article
Flexible Thermal Ground Planes Fabricated With Printed Circuit Board Technology
Li-Anne Liew,
Li-Anne Liew
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Li-Anne.Liew@colorado.edu
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Li-Anne.Liew@colorado.edu
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Ching-Yi Lin,
Ching-Yi Lin
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
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Ryan Lewis,
Ryan Lewis
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
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Susan Song,
Susan Song
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
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Qian Li,
Qian Li
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
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Ronggui Yang,
Ronggui Yang
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Ronggui.Yang@colorado.edu
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Ronggui.Yang@colorado.edu
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Y. C. Lee
Y. C. Lee
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Yung-Cheng.Lee@colorado.edu
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Yung-Cheng.Lee@colorado.edu
Search for other works by this author on:
Li-Anne Liew
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Li-Anne.Liew@colorado.edu
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Li-Anne.Liew@colorado.edu
Ching-Yi Lin
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
Ryan Lewis
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
Susan Song
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
Qian Li
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
University of Colorado at Boulder,
Boulder, CO 80309
Ronggui Yang
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Ronggui.Yang@colorado.edu
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Ronggui.Yang@colorado.edu
Y. C. Lee
Department of Mechanical Engineering,
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Yung-Cheng.Lee@colorado.edu
University of Colorado at Boulder,
Boulder, CO 80309
e-mail: Yung-Cheng.Lee@colorado.edu
Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received August 30, 2016; final manuscript received November 13, 2016; published online December 7, 2016. Assoc. Editor: Xiaobing Luo.
J. Electron. Packag. Mar 2017, 139(1): 011003 (10 pages)
Published Online: December 7, 2016
Article history
Received:
August 30, 2016
Revised:
November 13, 2016
Citation
Liew, L., Lin, C., Lewis, R., Song, S., Li, Q., Yang, R., and Lee, Y. C. (December 7, 2016). "Flexible Thermal Ground Planes Fabricated With Printed Circuit Board Technology." ASME. J. Electron. Packag. March 2017; 139(1): 011003. https://doi.org/10.1115/1.4035241
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