Analysis of the use of uniform Semi-Porous heat s+
ANALYSIS OF THE USE OF UNIFORM SEMI-POROUS HEAT SINK MEDIAS FOR
CHIP THERMAL MANAGEMENT WITH FREE CONVECTION by
Eric R. Savery
A Project submitted in partial fulfillment of the requirements for the degree of
Masters of Engineering
Rensselaer Polytechnic Institute
2011
Approved by ___________________________________________________
Ernesto Guiteerez-Mirravette, Engineering Project Advisor
Rensselaer Polytechnic Institute
Groton, Connecticut
September, 2011
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CONTENTS
2
List of Tables
3
List of Figures
4
Nomenclature
5
Acknowledgement
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1.
Abstract
This work presents a numerical investigation of the use of metallic porous materials, as a semiconductor heatsink. Specifically a comparison of how a heatsink made of porous material compares to a traditional fin heatsink. The modeled heatsinks will use the same volume mass of material, material thermal conductivity
(ie Material) and have the same dimensional footprint. The heat source (ie Processor) will be held at a constant temperature and by varying the heatsinks porosity the amount of energy that is able to be transferred to the atmosphere will be analyzed.
The results of the each heatsink are then compared and analyzed against each other to determine the affect of porous material as a heatsink.
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2.
Introduction
Since the discovery of the microprocessor computing power has been becoming more powerful and consequently been creating more heat. The heat which more powerful processors create is required to be dissipated else the processor will become less reliable or fail 1 . For every 10ºc that you are able to reduce a transistors
temperature the failure of the electronic component is halved 1 . Therefore the more
heat that is able to be removed from the transistor the greater the reliability is. To transfer the waste heat from the transistor to the environment requires the use of a heatsink. A heatsink is a device which dissipates energy from a component to ambient air by use of natural or forced convection. The heatsink’s ability to dissipate the heat energy is a function of the material properties, geometry and the environmental conditions
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. Increasing the amount of heat energy which is able to be dissipated by the heat sink will allow for higher processing speeds at a lower temp.
Below is an example of a simple fin heat sink that would be used on a typical integrated circuit.
Figure 1: Fin Heat Sink
This paper looks how the use of semi-porous media with a significant amount of surface area affects the efficiency of the heat sink to dissipate heat energy from a computer chip. With the use of a numerical analysis this paper will compare the efficiency of the standard fin heatsink against a heatsink that uses a semi-porous material.
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3.
Problem Description:
The design of a heatsink is dependant on the physical space, cooling needs and cost of the component. In a semiconductor application increasing capabilities results in the need for additional cooling, increase cooling requires a larger heat sink and as a result increases the overall size and cost of the final component. For portable electronics the goal is to provide the most capability, in the smallest package for the lowest cost. Using a semi-porous material for a heat-sink may provide increased cooling per cubic inch of space resulting in a smaller and more capable device at a lower cost when compared to a traditional fin heat sink.
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4.
Methodology/Approach:
A systematic approach will be used to build and analyze 3 different heat sinks.
Those heat sinks will be all be made of the same material and will have the following geometry; a block, fin, and porous block. Each heatsink will be made from the same base material to ensure that the differences in the results are not due to base material differences. The following basic heatsink shape will be anaylyzed.
Block Fin Porous
Modeling: Using Comsol a heat sink and the semi conductor that it is attatched will be modeled similar to Figure 2 below.
Heat Sink
Semi Conductor
Energy in (Watts)
Figure 2: Model
The heat sink will consist of three forms Foam, Fin and Block. Along with three different forms each form will consist of 4 different arrangements as described in
Reference (3) and Reference (4). Arrangements are provided below in Table 1.
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Foam
5 Pores Per Inch (PPI)
10 PPI
20 PPI
40 PPI
Table 1: Forms and Arrangements
Fin
4 Fins per inch
6 Fins per inch
8 Fins per inch
10 Fins per inch block
1 Fins Per Square Inch (FPSI)
Using accepted values of heat transfer coefficients (Reference 3), the Comsol models will updated. Each one of the heat sink models will then be subject to a standard heat input which is to be determined. The models will be analyzed to determine the affect of each heat sink arrangement on the semiconductor base. Using the resulting data it will be determined which heat sink has the potential of transferring the most heat.
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5.
Results/Discussion:
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6.
Conclusion:
References
1 Fundamentals of Thermal-Fluid Sciences; Second Edition, Yunus A. Cengel & Robert H. Turner, © 2005
2 http://en.wikipedia.org/wiki/Heat_sink
3 Medal Foam and Finned Metal Foam Heat Sinks for Electronic Cooling in Buoyancy-Induced
Convection. A. Bhattacharya & R.L Mahajan, © 2006
4 An analytical study of local thermal equilibrium in porous heat sinks using fin theory. Tzer-Ming Jeng,
Sheng-Chung Tzeng, Ying-Huei Hung; © January 10, 2006
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