There is significant current interest in new technologies for IC
(Integrated Circuit) cooling, driven by the rapid increase in power
densities in ICs and the trend towards high-density electronic packaging
for applications throughout civilian and military markets. In accordance
with Moore's Law, the number of transistors on 6 Intel Pentium
microprocessors has increased from 7.5 x10 in 1997 (Pentium II) to 6 55
x10 in 2002 (Pentium 4). Considering the rapid increase in the
integration density, thermal management must be well designed to ensure
proper functionality of these high-speed, high-power chips. Forced air
convection has been traditionally used to remove the heat through a
finned heat sink and fan module. 2 Currently, with 82 W power
dissipation rate, approximately 62 W/cm heat flux, from a Pentium 4
processor with 3.06 GHz core frequency, the noise generated from high
rotating speed fans is approaching the limit of acceptable level for
humans. However, the power dissipation from a single cost-performance
chip is 2 expected to exceed 100 W/cm by the year 2005, when the air
cooling has to be replaced by new cooling technologies. Among
alternative cooling methods, the two-phase microchannel heat sink is one
of the most promising solutions. Understanding the boiling process and
the two-phase flow behavior in microchannels is the key to successful
implementation of such a device.