Thermal Behavior of Nominally Flat Silicon-Based Heat Spreaders

[+] Author and Article Information
Ta-Wei Lin, Ming-Chang Wu, Cheng-Hsien Peng, Po-Li Chen

Department of Power Mechanical Engineering,  National Tsing Hua University, Hsinchu 30013, Taiwan

Ying-Huei Hung2

Department of Power Mechanical Engineering,  National Tsing Hua University, Hsinchu 30013, Taiwanyhhung@pme.nthu.edu.tw


Corresponding author.

J. Electron. Packag 128(4), 370-379 (Dec 24, 2005) (10 pages) doi:10.1115/1.2351902 History: Received May 23, 2005; Revised December 24, 2005

Thermal characteristics for a horizontal heated chip mounted with three types of nominally flat silicon-based heat spreaders have been systematically investigated. They include the natural convective and radiative heat transfer from the top surface of the heat spreaders to the external ambient, external thermal resistance, and maximum overall thermal resistance. In the aspect of natural convection, an axisymmetric bowl-shaped profile of local Nusselt number is achieved, and the highest convective heat transfer performance occurs at the location near the rim of the heat spreader. The effect of surface roughness on both local and average natural convective heat transfer behaviors from nominally flat silicon-based spreader surfaces to the external ambient is not significant. Two new generalized correlations of local and average Nusselt numbers for various heat spreader surfaces are presented. The contributions of convection and radiation on the total heat dissipated from the top surface of the heat spreader to the ambient are about 72% and 28%, respectively. The effect of surface roughness on external thermal resistance for nominally flat silicon-based surfaces is not significant. The influence of the conductive thermal resistance within the silicon-based heat spreader on the maximum thermal resistance is not significant. The maximum thermal resistance is mainly dominated by external thermal resistance for flat nominally silicon-based heat spreaders.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Overall experimental setup with relevant measuring system

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Figure 2

Schematic of test assembly

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Figure 3

Definition of roughness

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Figure 4

Emissivity on top surface of heat spreaders

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Figure 5

Comparisons of the experimental data measured between IR and thermocouple measurements

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Figure 6

Local Nusselt number distribution for nominally flat silicon-based heat spreaders

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Figure 7

Smoke visualization for the natural convection from a horizontal nominally flat silicon-based heat spreader

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Figure 8

Distributions of local Nusselt number for various nominally flat silicon-based heat spreaders

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Figure 9

Relationships between Nu¯ and GrT in natural convection

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Figure 10

External thermal resistance

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Figure 11

Maximum overall thermal resistance




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