Expansion/evaporation cooling system for microelectronic devices

Apparatus for cooling a circuit component comprising:

• heat exchanger means in thermal contact with said circuit component and including a heat exchange surface;
• and
• an open loop cooling assembly comprising a source of fluid under pressure and expansion valve means for releasing a stream of expending gas from said source of fluid, said expansion valve means being positioned in proximity to said heat exchange surface so that said stream of expanding gas passes over said heat exchange surface and absorbs thermal energy from said heat exchange surface by thermal expansion cooling and then is released into the ambient environment, said heat exchange surface including a plurality of fins defining grooves which direct said stream of expanding gas outwardly away from said expansion valve means, said grooves having an axial dimension parallel to an initial direction of said stream of expanding gas as it is released through said expansion valve means, said initial direction being substantially perpendicular to said heat exchange surface, said grooves increasing in axial dimension with distance from said expansion valve means.