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Research Papers

A Method for Thermal Performance Characterization of Ultrathin Vapor Chambers Cooled by Natural Convection

[+] Author and Article Information
Gaurav Patankar

Cooling Technologies Research Center,
an NSF I/UCRC,
School of Mechanical Engineering,
Purdue University,
585 Purdue Mall,
West Lafayette, IN 47907
e-mail: gpatank@purdue.edu

Simone Mancin

Cooling Technologies Research Center,
an NSF I/UCRC,
School of Mechanical Engineering,
Purdue University,
585 Purdue Mall,
West Lafayette, IN 47907
e-mail: simone.mancin@unipd.it

Justin A. Weibel

Cooling Technologies Research Center,
an NSF I/UCRC,
School of Mechanical Engineering,
Purdue University,
585 Purdue Mall,
West Lafayette, IN 47907
e-mail: jaweibel@purdue.edu

Suresh V. Garimella

Cooling Technologies Research Center,
an NSF I/UCRC,
School of Mechanical Engineering,
Purdue University,
585 Purdue Mall,
West Lafayette, IN 47907
e-mail: garimell@purdue.edu

Mark A. MacDonald

Intel Corporation,
5200 Elam Young Pkwy,
Hillsboro, OR 97124
e-mail: mark.macdonald@intel.com

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received September 12, 2015; final manuscript received November 16, 2015; published online March 10, 2016. Assoc. Editor: Ashish Gupta.

J. Electron. Packag 138(1), 010903 (Mar 10, 2016) (7 pages) Paper No: EP-15-1083; doi: 10.1115/1.4032345 History: Received September 12, 2015; Revised November 16, 2015

Vapor chamber technologies offer an attractive approach for passive cooling in portable electronic devices. Due to the market trends in device power consumption and thickness, vapor chamber effectiveness must be compared with alternative heat spreading materials at ultrathin form factors and low heat dissipation rates. A test facility is developed to experimentally characterize performance and analyze the behavior of ultrathin vapor chambers that must reject heat to the ambient via natural convection. The evaporator-side and ambient temperatures are measured directly; the condenser-side surface temperature distribution, which has critical ergonomics implications, is measured using an infrared (IR) camera calibrated pixel-by-pixel over the field of view and operating temperature range. The high thermal resistance imposed by natural convection in the vapor chamber heat dissipation pathway requires accurate prediction of the parasitic heat losses from the test facility using a combined experimental and numerical calibration procedure. Solid metal heat spreaders of known thermal conductivity are first tested, and the temperature distribution is reproduced using a numerical model for conduction in the heat spreader and thermal insulation by iteratively adjusting the external boundary conditions. A regression expression for the heat loss is developed as a function of measured operating conditions using the numerical model. A sample vapor chamber is tested for heat inputs below 2.5 W. Performance metrics are developed to characterize heat spreader performance in terms of the effective thermal resistance and the condenser-side temperature uniformity. The study offers a rigorous approach for testing and analysis of new vapor chamber designs, with accurate characterization of their performance relative to other heat spreaders.

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References

Figures

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Fig. 1

Schematic diagram of vapor chamber operation

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Fig. 5

Comparison of thermocouple temperatures obtained from experiments against those from the simulations at an electrical heat input of 1 W and ambient temperature of 298.2 K. Each bar is an average temperature from each grouping of thermocouples.

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Fig. 4

Exploded view of the numerical conduction model domain and boundary conditions

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Fig. 6

(a) Calibrated numerical model estimates of the heat loss and (b) junction-to-ambient temperature differences, as a function of input power for the copper and aluminum heat spreaders

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Fig. 10

Spreading metric for the prototype vapor chamber relative to the solid copper heat spreader as a function of device heat input

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Fig. 7

Thermal resistance as a function of power for the solid copper spreader and the vapor chamber

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Fig. 8

Contours of the condenser-side surface temperature for the (a) vapor chamber and (b) solid copper spreader at device heat inputs of approximately 1 W (left) and 2 W (right). Note the different temperature scales.

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Fig. 3

Photograph of the experimental facility

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Fig. 2

Schematic diagram of the test section (top inset shows the heater block assembly)

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Fig. 9

Condenser-side surface temperature difference from the mean, normalized by the device power (profile drawn along the length of the device passing through the center)

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