Thermal management system and computer arrangement
It is the object of the present invention to provide a low weight, compact, low vertical profile thermal management system for removing heat from electronic components. The thermal management system comprises of a plurality of “flow-through” type cooling devices, a source of filtered pressurized fluid suitable for use as a coolant, and a fluid delivering device that supplies the cooling devices with fluid. A preferred fluid is air, such as a filtered pressurized air. The cooling device is comprised of a high conductivity metal matrix composite heat spreader, a miniature heat sink, preferably of the same material, a permeable heat exchanger with high specific surface, and a closure that provides structural integrity of the cooling device.
This application claims the benefit of U.S. Provisional Application No. 60/591,254, filed on Jul. 26, 2004 and U.S. Provisional Application No. 60/560,382, filed on Apr. 7, 2004. The entire teachings of the above applications are incorporated herein by reference.
FIELD OF INVENTIONThe present invention relates to a thermal management system, especially electronics cooling and computer arrangement, and more particularly, to high performance electronics thermal management device that achieves high heat dissipation rates and provides a compact arrangement in which the electronic components are disposed with maximized space and weight efficiency.
BACKGROUND OF THE INVENTIONHigh power electronic components continue to have an increasing demand for higher power dissipating waste heat generated during computer operating within a relatively confined space. A major thermal management challenge is to adjust the constantly increasing heat emission from the electronic components to the constantly reducing weight and size of the computer arrangement. Conventionally used electronics cooling materials and technologies often become beyond of demands of modern computer idea. The further computer miniaturization requires the development of fundamentally new thermal management technologies and materials able to meet a combined requirement of high thermal conductivity, miniature performance, high heat dissipating rate, and low cost.
A variety of thermal management techniques are known in the prior art. In general, the thermal management cycle for electronics comprises two phases: the heat removal phase and heat dissipation phase. The heat removal stage can be performed by the following heat transfer methods:
a conductive heat transfer in solids
a convection heat transfer in fluids
a mixed phase change—convection heat transfer
a heat transfer accompanied thermal electric effects
These heat removal methods are used in the prior art and provided with the corresponding design embodiments such as solid-state high conductivity heat spreaders (often coupled with heat sink), close-loop circulation systems for fluids, phase change heat pipes, and thermal electrical cooling devices. The purpose for all of the above listed heat removal methods is the dislocation of the heat energy from a heat emitting component to a heat dissipating device, which mostly is an air cooled heat sink. Functional and designing division onto the heat removal and heat dissipating parts becomes typical for the modern computer architecture because the currently used cooling material and technologies can no longer manage the increased heat flux being coupled in one thermal management device. Commonly used heat pipes in notebooks, heat spreaders, and recently developed liquid cooling system are examples of such a functional dividing.
Unfortunately, the currently used solutions are not free from the drawbacks. The solid-state conductivity heat removal devices are heavy and their thermal conductivity often is beyond of what is required. Another disadvantage of the commonly used aluminum and cooper heat spreaders is the CTE mismatch with CTEs of semiconductor materials by the factor 2-3. The liquid cooling close-loop systems are heavy, roomy, and expensive in manufacturing. Heat pipes are often bulky and fragile. Thermoelectric cooling devices are heavy and bulky; their energy consumption is in a range that puts them outside of battery-driven applications.
The finned heat sinks are the most usable heat dissipating devices in computers.
Conventional heat sink-fan tandems produce a large amount of high velocity air flow that is the main source of computer noise. A large amount of air pumped through the computer causes deposition of contaminations on the surface of electronic components that reduces heat exchange additionally. Use of air filtration devices for fan air movers is limited because of the air pressure developed by air fans do not meet the pressure drop conditions in the air filtration systems. A large volume air flows produced by fans are used in inefficient way in computer systems. A simple calculation made on the basis of energy balance shows that the same amount of waste heat energy can be removed from a computer by an air flow that constitutes only 4-6% of the flow produced by conventional fans. Thus, the heat accumulating capacity of air flow is used only on 4-6% in the thermal solutions of the prior art. To achieve such energetic efficiency a condition of a quasi—total entropy heat exchange must be provided. Under this condition temperature of exhausting air should be close to temperature of heat sink. In turn, this high efficiency condition requires use of high thermal conductive materials and heat exchangers with extremely high specific surface. Unfortunately, the prior art does not disclose solutions able to meet these requirements. Still another disadvantage of the common design heat sinks is that they occupy too much physical volume to be practical in extremely confined applications. In view of the foregoing, it would be highly desirable to provide a compact electronics cooling device with high heat dissipating capacity, low noise, low energy consumption, harsh environment protected, and a low vertical profile to insure its compatibility with compact electronic equipment.
It is a continuing need in the prior art to provide low thermal impedance, stress avoiding heat spreaders and substrates that are thermal-mechanical compatible with the semiconductor materials. Commonly used ceramic substrates have thermal expansion coefficients similar to that of the semiconductor chip. However, recent remarkable progress in the semiconductor industry has promoted larger heat emission. Under such conditions, ceramic substrate becomes the most thermal resistive component in the heat transmitting path “semiconductor-substrate-heat sink” because of relative low thermal conductivity of ceramics. With the condition of close thermal-mechanical properties, high thermal conductivity metal matrix composite materials can be used in a beneficial method of the direct chip attachment to the high conductivity heat spreader becomes practicable.
In order to satisfy requirements of low thermal expansion the variety of metal matrix composites have been developed. The U.S. Pat. No. 5,167,697 discloses W—Cu, W—Ag, Mo—Cu and Mo—Ag materials and substrates of these materials made by sintering powders of tungsten or molybdenum with following infiltration of sintered preforms with copper or silver alloys. The heterogeneous microstructure of such composite materials combines the specific properties of both its components—high thermal conductivity of copper and silver and low thermal expansion of tungsten and molybdenum. The substrates with relative low CTE are provided by use of aluminum-silicon carbide composite materials. However, the mentioned metal matrix composite materials do not provide exact harmony with the CTE of such semiconductor materials as silicon or gallium arsenide. Besides, the conventionally used sintering and die casting manufacturing technologies do not provide production of the net-shape, net-size components with fine details. Additional machining is requires for theses difficult-to-machine materials that adds to their cost. A manufacturing process is still in need able to produce net-shape and net-size parts and micro-parts of metal matrix composite with adjustable thermal-mechanical properties.
Generally, computer systems are comprised of a cabinet or housing, that contains a plurality of components or subsystems, such as processors, memory, power supply, video cards, audio cards, disk drivers, and the like. Each of these components generates some heat, and collectively, the computer system can be considered as a thermal device requiring a fine thermal management.
Further, individual components, such as a microprocessor, may produce significant heat emission in very local areas. This waste heat is typically dissipated by a heat sink mounted directly on the individual component. As computer systems have become more complex and powerful, the individual components generate more heat. Increasing the number and size of the fins located on the heat sinks has generally provided increased cooling. Unfortunately, as the number of fins has increased, airflow provided by the fans has been inadequate to penetrate the now relatively dense fin structure, limiting the ability to cool the component. Increasing air flow to a sufficiently high level has proven problematic because fans tend to be noisy, consume substantial electrical power and increase their size consuming valuable real estate in the computer housing. As consequence, modern computer systems have added a small auxiliary fan adjacent to the overheating component. Quantity of auxiliary fans in modern computers reaches 9 pieces at the time of composing this patent application. These auxiliary fans have provided some relief but they have created additional problems. For example, increase of the number of auxiliary fans adds to the cost and complicity of the computer system. Further, with the growing complexity of modern computer systems, more and more individual components require additional cooling capacity. As the number of components grows, the problem associated with installing additional auxiliary fans is compounded. A plurality of auxiliary fans create a plurality of separate air flows within compressed space of a computer case. This creates an additional problem of air flows matching, which often becomes an obstacle for further miniaturization of computer systems.
Conventionally, computer components, such as those of “desktop” computers, are disposed within an exterior housing such that various computer components are stacked one over the other in a generally horizontal manner within the housing. Depending on the system requirements, heat dissipation is controlled using typically air fan—heat sink thermal management structures. The fans take up valuable space within the housing, increase costs and noise, and are particularly susceptible to failure due to their mechanical nature. The fans and heat sinks also complicate the general layout of the components within the housing, hampering overall size of the computer. To resolve this problem, conventional arrangements have relied on a less compact layout, such the components, while taking up less space, still provide sufficient heat removal.
SUMMARY OF THE INVENTIONIt is the object of the present invention to provide a low weight, compact, low vertical profile thermal management system for removing heat from electronic components. The thermal management system comprises of a plurality of “flow-through” type cooling devices, a source of filtered pressurized fluid suitable for use as a coolant, and a fluid delivering device that supplies the cooling devices with fluid. A preferred fluid is air, such as a filtered pressurized air. The cooling device is comprised of a high conductivity metal matrix composite heat spreader, a miniature heat sink, preferably of the same material, a permeable heat exchanger with high specific surface, and a closure that provides structural integrity of the cooling device.
It is the further object of the present invention to provide a source of pressurized filtered air for use in the flow-through cooling devices. The source of pressurized air (air port) is comprised of a miniature air mover, an air filter, an air distribution device, and a plurality of flexible hoses that connect the air port with a plurality of the flow-through cooling devices.
It is the further object of the present invention to provide a self-cleaning air filtering system in which the self-cleaning effect is provided by use of two air filters and a cyclical air flow directivity change. Within this system the filters are self-cleaning by turn by means of expulsion of the filter by exhausted air.
It is the further object of the present invention to provide a miniature air mover capable of overcoming the hydraulic resistance of the air filtration device and a plurality of the flow-through cooling devices.
It is the further object of the present invention to provide a Coefficient of Thermal Expansion (CTE) controlled heat spreader applicable for direct and non-direct chip attachment. More particularly, an improved thermal conductivity heat spreader with an adjustable CTE within 4.0-6.5 PPM is provided.
It is the further object of the present invention to provide a high conductivity, CTE controlled heat spreader that is integrated metallurgically with a ceramic substrate, on which an electronic device can be placed using conventional technique. Thus, an ideal thermal contact between the ceramic substrate and a heat removal structure is created, and use of the low thermal conductivity interface materials is avoided.
It is the further object of the present invention to provide an electronic device with an integrated cooling system within which a silicon die integrated metallurgically into the flow-through cooling structure to form a single whole thermally uninterrupted body.
It is the further object of the present invention to provide a flow-by type electronics cooling device that unites a CTE controlled high thermal conductivity heat spreader and a miniature metal matrix composite heat sink in one thermally interrupted item.
It is the further object of the present invention to provide a computer arrangement in which one or more electronic components can be arranged in any desirable order and orientation without concern of air flow directivity, components proximity, gravitation, and electro magnetic influence. New computer arrangement comprises the encapsulated modules with electronic components and the thermal management system on the basis the flow-through cooling devices and a supply of filtered pressurized air. New computer arrangement provides freedom in layout for electronic devices and protection from exterior contamination factors.
It is the further object of the present invention to provide micro composite and macro composite high thermal conductivity materials applicable for the electronics cooling devices.
It is the further object of the present invention to provide a method for manufacturing the components of “flow-through” cooling devices in high volume and low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
A description of preferred embodiments of the invention follows.
Illustrative embodiments of the thermal management system for electronics and computer arrangement according to the present invention are shown in
The present invention provides a high thermal conductivity micro composite and macro composite heat spreaders that absorb waste heat generated by an electronic component distribute heat onto larger surface area, and transfers heat to a heat dissipating structure. According to the present invention, the heat spreader can be provided as a separate item or in a combination with a heat dissipating unit. Turning to
A heat spreader, preferably macro composite super thermal conductivity heat spreader, is shown on
Another arrangement for macro composite heat spreader according to the present invention is shown on
Still another arrangement for macro composite heat spreader according to the present invention is shown on
Further another arrangement for macro composite heat spreader 22 combined with a flexible heat connector 28 is shown on
Suitable materials for manufacturing the coolers of the invention include graphite foam (about 70 w/mK), pitch graphite fabric (up to about 1,100 w/mK), and pyrographite (1,400 w/mK). The conduits for controlling fluid flow can be made of, for example, steel, PVC or other material. The device can be encapsulated in a shell made of, for example, a macrocomposite material.
Turning to
While the relative sizes of the components can vary substantially depending upon the materials and fluids selected and the volume of air flow employed, in one example, the electronic component can have a surface area of about 50 mm2; the heat spreader can have a surface area of about 5 cm2; the micro heat sink can have a surface area of about 120 cm2; and the permeable heat exchange of up to about 50 m2 or more.
Further heat comes to heat sinks 33, for example a net of miniature heat sinks, which are metallurgically connected to the heat spreader 32 forming a single body with uninterrupted heat flux (
In one embodiment, the present invention provides a source of filtered and pressurized air for the flow-through cooling devices. The principal advantage of the pressurized air supply is that it enables miniaturized heat exchangers with extremely high heat dissipating capacity, but having a significant hydraulic resistance and pressure drop. By this, use of pressurized air enables basically new electronics cooling concept, one core principle of which is the use of miniature permeable heat exchangers with extremely large heat exchanging surface. Another advantage is that pressurized air has enough power to overcome hydraulic resistance of air filtering devices that produce clean contamination—free air flow and prevents contaminating impurity of the permeable heat exchanging media.
In contrast to fans, compressors and vacuum pumps produce high air pressure sufficient to overcome hydraulic resistance in both, flow-through cooling devices and air filtering devices (See
The flow-through cooling device in a combination with the source of filtered pressurized air represents a number of advantages before the commonly used finned heat sink-fan structures. This new electronics cooling solution provides a significantly greater heat dissipating capacity than solutions of the prior art. See
Expected air requirements for different computer applications include an air flow between about 3-6 l/min at about 0.01-0.015 atm for a mobile personal computer; between about 5-10 l/min at about 0.015-0.03 atm for a desktop personal computer; and between about 10-20 l/min at about 0.025-0.05 atm for a performance computer;
An especially important advantage is low weight and miniature arrangement for cooling devices. Comparing to conventional solutions based on finned heat sinks, the flow-through cooling devices of the invention are lighter by 4-8 times and smaller by 3-5 times (
A flow-by brush-type heat sink 77 is shown on
The present invention provides a CTE controlled heat spreaders and substrates that can be made as a separate item or as a joint item that comprises a heat spreader, a heat sink, a ceramic substrate, and a permeable heat exchanger. The CTE controlled heat spreader and substrate 50 is a macro composite article comprising a CTE controlling core 51, which has CTE close that of the electronic component, and a shell 57 that three-dimensionally envelopes the core 51 (
Due to different properties of the core 51 and shell 57, a thermal mechanical conflict takes place within the CTE controlling substrate 50 during manufacturing process and over time following service in an electronic device. During fabrication a residual tensile stress 59 and a residual compressive stress 58 are purposely created in the shell 57 by braking shrinkage according to the manufacturing process of the present invention. Magnitude and directivity of residual tensile stress 58 and residual compression stress 59 in shell 57 can be specified and managed by a proper disposition of through holes 55 in core 51 (
Generally, the core 51 is subjected mostly to compressive stress 59, while metal matrix composite shell 57 is subjected to tensile stress 58. Generally, materials better withstand against compressive loads than against tensile load. Therefore the shell 57 is not able to compress the core 51 when temperature comes down. Further, the shell 57 cannot withstand against expansion of core 51 when temperature rises. Being a weaker structure, shell 57 follows to thermal mechanical behaving of the core 51. Since the CTE of the core material 51 is selected similar to the CTE of electronic component, the CTE controlled substrate 50 becomes thermal-mechanically matched with the electronic component 52. The thermal-mechanical matching method according to the present invention provides the electronic supporting and cooling components with useful properties as it shown in the following embodiment examples.
Turning to
Turning now to
The electronic components 101, 102, 103, and 104 lie on the flow-through cooling device 107 which is connected with the air port 106 by mean of flexible hoses 105. Although only four cooled electronic devices shown on
The air compressor 110 sucks cold air 116 through the air filter 111 entrapping contamination particles and preventing the pollution deposition within the flow-through cooling devices 107 and clogging the porous heat exchange media. The flow path of slightly pressurized cold air starts in the air filter 111 and the micro compressor 110 is powered by an electrical motor 109. Further purified air passes the air distributor 114, in which air flow is divided on a plurality of flows destined to cool electronic components 111, 112, 113, and 115 by flowing through cooling devices 107, on which the electronic devices are mounted. Within the permeable media of the cooling devices 107 the heat exchange between cold air and a heat exchanging structure takes place as it explained in more details below. Cold air removes heat from the heat exchanging structure and passes out of the cooling devices 107. Further hot air 117 exiting different cooling devices 107 is collected in the air collector 121, transferred to a definite location beyond the bounds of the computer case 115 and then exhausted to atmosphere. Alternatively, exiting hot air 117 can be exhausted into atmosphere in the destined points within the computer case 115 by connecting the air outlets of the flow-through cooling devices 107 and desirable exhausting points with the flexible hoses 105 (not shown).
In both such embodiments, while the figures may suggest that a single cooling device is matched with an electronic component. While this configuration may be convenient, other configurations are also possible. For example, a single cooling device may service two or more electronic components or all of the electronic components. Indeed, even the units of the cooling devices can be combined. For example, a single micro heat sink can service two or more heat spreaders.
In one embodiment, the air mover is a vane machine, preferably a toroidal vane machine. Suitable vane machines include but are not limited to those embraced by U.S. Pat. No. 5,233,954, U.S. Published application 2003/0111040 and U.S. applications entitled “Improvements in Intersecting Vane Machines” U.S. Ser. No. 10/744,230 filed Dec. 22, 2003 as Atty. Docket number 4004-3001; “Improvements in Sealing Intersecting Vane Machines” U.S. Ser. No. 10/744,229 filed Dec. 22, 2003 as Atty. Docket No. 4004-3004; and “The Use of Intersecting Vane Machines in Combination with Wind Turbines” U.S. Ser. No. 10/744,232 filed Dec. 22, 2003. The entire teachings of the aforementioned patents and patent applications are incorporated herein by reference. The toroidal vane machine is capable of serving as a micro compressor or vacuum pump which can be scaled to meet a variety of dimensional requirements. In one embodiment the toroidal intersecting machine is a micro air mover capable of being used in small computer applications, such as but not limited to, in computer “notebooks”, desktop computers or servers. Other suitable air movers are known to those skilled in the art.
Turning to the following drawings, a vertical (
A thermal-mechanical matching method according to the present invention provides the electronic supporting and cooling components with useful properties as it shown in the following embodiment examples. Turning to
Turning to
Turning to
Turning to
While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.
Claims
1. A thermal heat management system comprising flow-through cooling device, a source of filtered pressurized air and a closure that provides structural integrity of the cooling device.
2. The thermal heat management system of claim 1 further comprising a heat spreader, a heat sink, a substrate and a permeable heat exchanger.
3. A thermal heat management system for removing heat from electronic components comprising:
- a) a plurality of flow-through type cooling devices;
- b) a source of pressurized air; and
- c) an air delivering device wherein the cooling device of (a) further comprises a heat spreader, a heat sink, a substrate and a heat exchanger.
4. The thermal heat management system of claim 3, wherein the source of pressurized air of (b) is filtered.
5. The thermal heat management system of claim 3, wherein the heat exchanger is permeable.
6. The thermal heat management system of claim 3, wherein the heat spreader is metal matrix.
7. The thermal heat management system of claim 6, wherein the metal matrix possesses high conductivity.
8. The thermal heat management system of claim 6, wherein the heat spreader is a microcomposite heat spreader.
9. The heat spreader of claim 8, wherein the thermal conductivity and the CTE are isotropic.
10. The thermal heat management system of claim 6, wherein the heat spreader is a macrocomposite heat spreader.
11. The thermal heat management system of claim 3, wherein the heat spreader is made of material selected from the group consisting of graphite foams, metal foams, ceramic foams, graphic fabrics, porous metals and nanotubes.
12. The thermal heat management system of claim 3, wherein the heat sink is ceramic.
13. The thermal heat management system of claim 3, wherein the heat sink is made of the same material as the heat spreader.
14. The thermal heat management system of claim 3, wherein the substrate has a thermal expansion coefficient compatible with semiconductor materials.
15. The thermal heat management system of claim 14, wherein the substrate is ceramic.
16. The thermal heat management system of claim 3, wherein the substrate is a metal matrix composite.
17. The thermal heat management system of claim 16, wherein the metal matrix composite possess high thermal conductivity.
18. The thermal heat management system of claim 3, wherein the heat exchanger is permeable.
19. The heat exchanger of claim 18 having a high specific surface area.
20. The heat exchanger of claim 18 further comprising a high thermal conductivity.
21. The heat exchanger of claim 18 further comprising porosity in range of about 50 to about 60 percent.
22. The heat exchanger of claim 18 further comprising graphite foams, metal foams, ceramic foams, graphic fabrics, and porous metals.
23. The heat exchanger of claim 18 further comprising carbon nanotubes.
24. The heat exchanger of claim 3, wherein the heat exchanger is a labyrinth type heat exchanger.
25. The labyrinth type heat exchanger of claim 24, wherein the heat exchange is branched.
26. A method of producing an integrated cooling system comprising forming a silicon die integrated metallurgically into the flow-through cooling structure to form a single whole thermally uninterrupted body.
Type: Application
Filed: Apr 7, 2005
Publication Date: Jan 19, 2006
Inventor: Viktor Frul (N. Attleboro, MA)
Application Number: 11/101,372
International Classification: F28F 7/00 (20060101); B22F 9/00 (20060101); C22C 5/00 (20060101);