Refrigeration – Structural installation – With electrical component cooling
Reexamination Certificate
1999-08-23
2001-02-27
Doerrler, William (Department: 3744)
Refrigeration
Structural installation
With electrical component cooling
Reexamination Certificate
active
06192701
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to cooling technology for electronic packaging for computer systems, and, more particularly, relates to means for cooling and preventing the formation of condensation on cooled components within a computer system.
The high circuit densities and operating frequencies in modern integrated circuit devices and multi-chip modules of today's computer systems has resulted in a significant increase in the power dissipated by such chip and module components. No matter how fast one wishes to operate a given electronic circuit chip, there almost always is the potential for running it faster if the chip were to be cooled further and more thermal energy is removed during its operation. This is true of computer processor circuit chips and more particularly of such chips disposed within multi-chip modules that generate significant amounts of heat. Because of the demand to run processor modules at increasingly higher speeds, the clock frequencies at which the devices must operate also increases. Power generation correspondingly rises in proportion to the clock frequency, generating thermal demands in terms of energy which must be removed for faster, safer, and more reliable circuit operation. It is required that cooling arrangements be provided so that the heat generated by the operation of these components be effectively and efficiently removed in order to maintain the temperature of the devices within the limits that will keep the operating parameters of the devices in a predetermined range, and, that will keep the operating parameters of the devices in a predetermined range, and, further, to prevent the damage or destruction of the integrated circuit devices by overheating from the high temperatures generated.
Using refrigeration technology, integrated circuit chips and multi-chip modules readily can be cooled to appropriately low temperatures. In addition, however, to the essential of cooling to prevent damage from overheating, it is also recognized that cooling offers marked advantages in circuit speed, system throughput, and component reliability. For example, it is known that a CMOS circuit will operate at higher clock speeds as the circuit temperature is lowered, and, it has been reported that the processor frequencing of a CMOS processor has been improved by nearly threefold by cooling the processor to temperatures around −200° C.
Various techniques for the cooling of integrated circuit electronic devices are known and many have been implemented with success. Some practiced techniques involve conventional methods such as by directing ambient air onto the components to be cooled; by sealing the computer cabinet and refrigerating the interior of the cabinet; as well as by immersing components in coolants such as liquid nitrogen. Individual integrated chip or multi-chip module components also have been cooled through specialized devices such as hollow cold plates which are attached to the components to be cooled. Liquid coolants can be circulated through the hollow cold plates to effect cooling of the attached components.
However, cooling of the electronic components to a temperature below the ambient environment dew point results in condensation problems in that moisture will condensate on the cooled components and the structures and components to which the cooled components may be attached. This condensation can damage and literally destroy the electronic circuitry associated with the integrated chip or multi-chip module and the circuit board on which it is mounted.
Accordingly, a cooling system is needed for an integrated chip or multi-chip module device which can effectively reduce the temperature of the device to below ambient dew point without causing damage to the device through the effects of condensation.
SUMMARY OF THE INVENTION
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the present invention.
Now, an improved system for cooling integrated circuit devices within a computer system has been developed whereby condensation is prevented from forming on the cooled devices. According to the present invention, a cooling system is provided which comprises a cooling evaporator unit having a thermal interface in thermal communication with an integrated circuit device mounted on a substrate within a computer system. The integrated circuit device typically is a multi-chip module (MCM) mounted on a planar circuit board contained within the cabinet of a computer system. The evaporator, generally comprising a thermal block, typically copper or aluminum, having coolant flow passages through its mass, is connected to a refrigeration unit to circulate coolant through the evaporator to cool the integrated circuit device to a desired temperature. To optimize performance of the chip device, it generally is cooled to a temperature below the dew point of the surrounding atmosphere. Typically, the device is cooled to a temperature ranging from about −10° C. to about +10° C.
The refrigeration unit typically includes a compressor, condenser, and expansion device connected in a closed refrigeration loop with the coolant flow passages in the thermal block. The coolant used may be any coolant fluid; R134A and R507, standard refrigerants known and used in the art, are preferred because of their environmentally friendly composition.
The cooling evaporator is enclosed within a housing. The evaporator block is attached, through a thermal grease layer, to the cover or hat of the integrated circuit devices. The integrated circuit devices are mounted on a printed circuit board substrate via solder interconnections. The cooling evaporator unit and the integrated circuit devices with which it is in thermal communication both are enclosed within the evaporator housing. The housing typically comprises a sealed aluminum chassis to which the thermal block is attached by suitable screws and insulating spacers. The thermal block in turn is attached to the integrated chip device, such as a MCM, by a series of bolts passing through the thermal block into the MCM cover or hat. The housing is designed to seal to the substrate so as to enclose the evaporator unit and the MCM mounted on the substrate. The seal between the housing and the substrate typically is accomplished through a suitable compliant gasket member, preferably a c-shaped gasket. A preferred gasket material is a butyl rubber. The housing is designed to form an airtight enclosure for the evaporator unit and the integrated circuit device when the housing is sealed to the substrate.
The housing is fitted with various sealed ports which connect to the evaporator unit. These ports provide flow communication for the coolant in and out of the evaporator from the refrigeration unit, and also include flow communication from a vacuum source to an air cavity around the MCM and evaporator. The vacuum source can be activated to reduce the pressure within the enclosure. This pressure reduction serves to draw off any moisture trapped within the enclosure during attachment of the housing enclosure to the substrate. A pressure detection device also is provided in communication with the enclosure in order to determine that the reduced pressure within the enclosure is maintained after the vacuum source is deactivated. The maintenance of the reduced pressure evidences the accomplishment of an airtight condition within the enclosure. A pressurized dry gas system, typically pressurized dry air, also is in flow communication with the enclosed evaporator, so that, once the airtight condition of the enclosure is verified, a positive pressure of dry gas can be maintained within the enclosure during operation of the cooling system. Preferably, the source of dry gas can be air drawn from the blower system of the computer cabinet, first passed through a desiccant canister to remove moisture.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following
Goth Gary F.
Loparco John J.
Singh Prabjit
Cantor & Colburn LLP
Doerrler William
Gonzalez Floyd A.
International Business Machines - Corporation
Shulman Mark
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