| The silicon revolution, that began nearly four decades ago, has been characterized by an exponential increase in the number of transistors incorporated onto a single piece of silicon. The increased density and ever-faster operation of these transistors has resulted in current heat fluxes that exceed 25 W/cm2 and are expected to reach 100 W/cm2 by the end of this decade. Recent years have witnessed the emergence of a new microelectronic paradigm, System-On-A-Package or SOP, which is expected to revolutionize microelectronic systems. SOP uses a thin, intermediate interconnect layer on top of a printed circuit board, to integrate multiple microelectronic, photonic, and microwave devices into a single microsystem. It is anticipated that passive, low cost cooling techniques will be needed to commercialize high performance SOP packages, with very high local power dissipations and requirements for precise temperature control of several distinct types of devices.; The present study addressed direct liquid cooling of a simulated, high performance SOP, capable of reaching a heat flux of 100 W/cm2. Thermal management was provided by pool boiling heat transfer from the package to a contained dielectric liquids (FC-72, FC-40, HFE-7100, HFE-7200) and focused on enhancements of the Critical Heat Flux, or the upper limit of nucleate pool boiling.; Experimental studies of nucleate pool boiling and CHF were performed with Sandia's ATC2.6 chip package immersed in dielectric liquids at various pressures and temperatures. The previously observed beneficial role of liquid subcooling, leading to an increase in CHF with higher subcoolings, was confirmed. When the pressure was elevated above atmospheric conditions, higher CHF values were obtained. Possible CHF enhancement via the use of an additive liquid was investigated in FC-72/FC-40 mixtures. CHF enhancement with micro-porous coatings was investigated for ATC2.6 chips coated with synthetic diamond particles. An experimental study of pool boiling heat transfer with Novec—a new family of dielectric liquids—was also performed. These results revealed that judicious combinations of passive enhancement techniques may be capable of raising the pool boiling CHF for the candidate dielectric liquids to the range of 50 W/cm2 to 75 W/cm2.; Use of ebullient cooling in SOP and other electronic systems will require modeling approaches and correlations that can be: used to determine the CHF with acceptable precision. In addition to the effects of fluid properties, liquid pressure, and liquid subcooling, prior work at this TME laboratory has revealed that CHF increases asymptotically with the product of the heater thickness and the square root of thermal effusivity, (ρck)h, reflecting the beneficial role of transient thermal conduction in smoothing the surface temperature variations. (Abstract shortened by UMI.)... |
