The demand for efficient thermal management has increased substantially over
the last decade in every imaginable area, be it a formula 1 racing car suddenly
braking to decelerate from 200 to 50 mph going around a sharp corner, a
space shuttle entering the earth’s atmosphere, or an advanced microprocessor
operating at a very high speed. The temperatures at the hot junctions
are extremely high and the thermal flux can reach values higher than a few
hundred to a thousand watts/cm2 in these applications. To take a specific
example of the microelectronics area, the chip heat flux for CMOS microprocessors,
though moderate compared to the numbers mentioned above have
already reached values close to 100 W/cm2, and are projected to increase
above 200 W/cm2 over the next few years. Although the thermal management
strategies for microprocessors do involve power optimization through
improved design, it is extremely difficult to eliminate “hot spots” completely.
This is where high thermal conductivity materials find most of their applications,
as “heat spreaders”. The high thermal conductivity of these materials
allows the heat to be carried away from the “hot spots” very quickly in all
directions thereby “spreading” the heat. Heat spreading reduces the heat flux
density, and thus makes it possible to cool systems using standard cooling
solutions like finned heat sinks with forced air cooling. A quick review of
the available information indicates that the microprocessors heat fluxes are
quickly reaching the 100 W/cm2 values, which makes it very difficult to use
conventional air cooling (see for example, “Thermal challenges in microprocessor
testing”, by P. Tadayan et al. Intel Technology Journal, Q3, 2000, and
Chu, R., and Joshi, Y., Eds. “NEMI Technology Roadmap, National Electronics
Manufacturing Initiative”, Herndon, VA, 2002).
the last decade in every imaginable area, be it a formula 1 racing car suddenly
braking to decelerate from 200 to 50 mph going around a sharp corner, a
space shuttle entering the earth’s atmosphere, or an advanced microprocessor
operating at a very high speed. The temperatures at the hot junctions
are extremely high and the thermal flux can reach values higher than a few
hundred to a thousand watts/cm2 in these applications. To take a specific
example of the microelectronics area, the chip heat flux for CMOS microprocessors,
though moderate compared to the numbers mentioned above have
already reached values close to 100 W/cm2, and are projected to increase
above 200 W/cm2 over the next few years. Although the thermal management
strategies for microprocessors do involve power optimization through
improved design, it is extremely difficult to eliminate “hot spots” completely.
This is where high thermal conductivity materials find most of their applications,
as “heat spreaders”. The high thermal conductivity of these materials
allows the heat to be carried away from the “hot spots” very quickly in all
directions thereby “spreading” the heat. Heat spreading reduces the heat flux
density, and thus makes it possible to cool systems using standard cooling
solutions like finned heat sinks with forced air cooling. A quick review of
the available information indicates that the microprocessors heat fluxes are
quickly reaching the 100 W/cm2 values, which makes it very difficult to use
conventional air cooling (see for example, “Thermal challenges in microprocessor
testing”, by P. Tadayan et al. Intel Technology Journal, Q3, 2000, and
Chu, R., and Joshi, Y., Eds. “NEMI Technology Roadmap, National Electronics
Manufacturing Initiative”, Herndon, VA, 2002).
