  Efficient thermal management in high-power electronics cooling can be
achieved using phase-change heat transfer devices, such as vapor chambers.
Traditional vapor chambers use wicks to transport condensate for efficient
thermal exchange and to prevent "dry-out" of the evaporator. However, wicks in
vapor chambers present significant design challenges arising out of large
pressure drops across the wicking material, which slows down condensate
transport rates and increases the chances for dry-out. Thicker wicks add to
overall thermal resistance, while deterring the development of thinner devices
by limiting the total thickness of the vapor chamber. Wickless vapor chambers
eliminate the use of metal wicks entirely, by incorporating complementary
wettability-patterned flat plates on both the evaporator and the condenser
side. Such surface modifications enhance fluid transport on the evaporator
side, while allowing the chambers to be virtually as thin as imaginable,
thereby permitting design of thermally efficient thin electronic cooling
devices. While wick-free vapor chambers have been studied and efficient design
strategies have been suggested, we delve into real-life applications of
wick-free vapor chambers in forced air cooling of high-power electronics. An
experimental setup is developed wherein two Si-based MOSFETs of TO-247-3
packaging having high conduction resistance, are connected in parallel and
switched at 100 kHz, to emulate high frequency power electronics operations. A
rectangular copper wick-free vapor chamber spreads heat laterally over a
surface 13 times larger than the heating area. This chamber is cooled
externally by a fan that circulates air at room temperature. The present
experimental setup extends our previous work on wick-free vapor chambers, while
demonstrating the effectiveness of low-cost air cooling in vapor-chamber
enhanced high-power electronics applications.
