Submitted by: Submitted by ricola
Views: 376
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Pages: 19
Category: Spirituality
Date Submitted: 03/28/2012 02:00 AM
Minhua Lu
Larry Mok
IBM T.J. Watson Research Center,
1101 Kitchawan Road,
Yorktown Heights, NY 10598
R. J. Bezama
IBM Microelectronics Division,
Route 52,
Hopewell Junction, NY 12533
A Graphite Foams Based Vapor
Chamber for Chip Heat Spreading
A vapor chamber using high thermal conductivity and permeability graphite foam as a
wick has been designed, built, and tested. With ethanol as the working fluid, the vapor
chamber has been demonstrated at a heat flux of 80 W / cm2. The effects of the capillary
limit, the boiling limit, and the thermal resistance in restricting the overall performance
of a vapor chamber have been analyzed. Because of the high thermal conductivity of the
graphite foams, the modeling results show that the performance of a vapor chamber
using a graphite foam is about twice that of one using a copper wick structure. Furthermore, if water is used as the working fluid instead of ethanol, the performance of the
vapor chamber will be increased further. Graphite foam vapor chambers with water as
the working fluid can be made by treating the graphite foam with an oxygen plasma to
improve the wetting of the graphite by the water. DOI: 10.1115/1.2351908
Keywords: vapor chamber, graphite foam, heat spreader, chip cooling
Introduction
As a result of CMOS scaling, the circuit density and power
density of semiconductor chips are increasing. According to the
2004 update of The International Technology Roadmap for Semiconductors ITRS , the average power density of a chip may soar
to nearly 140 W / cm2 in a few years 1 and the average power
density of high-performance chips, especially at the hot spots,
could be even higher. Because of this high heat flux, it seems
inevitable that the use of liquid cooling will increase. However,
the engineering complexity as well as the costs associated with
liquid cooling makes it difficult to implement in products 2 .
Extensive efforts to extend the limits of air cooling are underway,
where...