Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2001-05-16
2003-11-11
Chervinsky, Boris (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S689000, C361S699000, C361S698000, C361S701000, C361S704000, C361S700000, C174S015100, C165S080400, C165S104330, C062S064000, C062S259200
Reexamination Certificate
active
06646879
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to cooling of electronic equipment, and more particularly to the use of spray evaporative cooling to cool electronics components.
BACKGROUND INFORMATION
The demand for higher performance supercomputers continues to create challenging thermal and packaging design environments for today's computer packaging engineers. As the performance of CRAY supercomputers continues to grow exponentially, in general agreement with Moore's law (Bar-Cohen, et al, 1988), the thermal and packaging solutions continue to become more complex.
The increase of supercomputer performance over the last 30 years was initially achieved with an increase in the complexity of the computer's CPU by increasing the number of ICs within a CPU. The next step in performance was achieved by adding more gates per IC along with increasing the clock rate. Performance was further increased by the paralleling of CPUs and then the scaling of groups of CPUs. Now in order to continue on the path of Moore's law, we are again pushing the IC technology and ultimately the performance of each individual CPU. Die sizes are increasing, and power levels of these devices are increasing at rates approaching that of Moore's law for supercomputer performance.
One technology that hasn't been able to keep pace with the ICs is the printed circuit board (PCB) technology. The demands for component placement and IC net routings have exceeded the current state of the art in PCB technology.
One solution to this problem implements a multi-chip module with thin film routing layers (MCM-D) for the packaging of these high performance chip sets. This high density packaging design is, however, capable of producing heat fluxes on the ICs and MCM that approach values of 50 and 15 W/cm
2
, respectively. The control of the IC's junction temperature is important for its reliability and for the performance of two communicating devices. The amount of induced leakage “noise” that exists on an integrated circuit is also a function of its temperature.
A number of cooling methodologies have been described by Bar-Cohen (Bar-Cohen, A., “Thermal Management of Electronic Components with Dielectric Liquids”, JSME International Journal, Series B, vol. 36, No1,1993), by Simons (Simons, R. E., “Bibliography of Heat Transfer in Electronic Equipment”, 1989, IBM Corporation), by Incropera (Incropera, F. P., “Convection Heat Transfer in Electronic Equipment Cooling”, Journal of Heat Transfer, Nov. 1988, Vol. 110/1097) and by Bergles (Bergles, A. E., “Liquid Cooling for Electronic Equipment”, International Symposium on Cooling Technology for Electronic Equipment, March 1987). Studies by Chu and Chrysler (Chu, R. C., and Chrysler, G. M., “Electronic Module Coolability Analysis”, EEP-Vol. 19-2, Advances in Electronic Packaging-1997 Volume 2, ASME 1997) and by Nakayama (Nakayama, W., “Liquid-Cooling of Electronic Equipment: Where Does It Offer Viable Solutions?”, EEP-Vol. 19-2, Advances in Electronic Packaging-1997 Volume 2, ASME 1997), however, indicate that these approaches are no longer capable of satisfying today's high density packaging requirements (Chu and Chrysler, 1997), (Nakayama, 1997).
As heat flux continues to increase, the most promising methods are those that utilize direct liquid cooling with dielectric fluids. Direct liquid cooling circumvents the problems of high thermal interface resistance associated with conventional technologies and is capable of providing very high heat transfer rates (Bar-Cohen, 1993). A number of such direct liquid cooling techniques are described in, “Thermal Management of Multichip Modules with Evaporative Spray Cooling,” by G. W. Pautsch and A. Bar-Cohen, published in ASME Advances in Electronic Packaging 1999, EEP-Vol.26-2, 1453-1463, the discussion of which is incorporated herein by reference. That paper concluded that the method of choice for cooling high heat flux electronic components is described as “High Density, Pressure-Atomized Evaporative Spray Cooling”. This condition occurs when a fluid is sprayed on a surface at a rate that maintains a continuously wetted surface, whose temperature is less than 25° C. above the saturation temperature of the thermal coolant. This method, with the selection of an appropriate fluid, such as Fluorinert™ FC-72 which has a boiling point of 56° C. at standard atmospheric conditions, allows one to maintain high heat flux components at operating temperatures below 85° C.
Each of the above cooling approaches has its deficiencies. What is needed is a system and method for cooling electronics components that addresses these deficiencies.
SUMMARY OF THE INVENTION
To address the problems stated above, and to solve other problems which will become apparent in reading the specification and claims, a system and method for cooling electronic components is described. A liquid is heated to a temperature near its boiling point and directed against electronic components such that a portion of the heated liquid vaporizes, forming a mixed phase fluid. The mixed phase fluid is drawn away from the electronic components and the vapor is condensed back into a liquid.
According to another aspect of the present invention, an enclosure includes a plurality of electronics components, cooling means for cooling a gas and distribution means for directing the gas across the electronics components and the cooling means. The distribution means forms a closed system limiting the transfer of the gas both into and out of the distribution means.
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Antonetti, V., et al., “Bibliography of Heat Transfer in Electronic Equipment”,IEEE Transactions on Components, Hybrids, and Manufacturing Technology, CHMT-8 (2), pp. 289-295, (Jun. 1985).
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Chervinsky Boris
Cray Inc.
Schwegman Lundberg Woessner & Kluth P.A.
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