Plastic and nonmetallic article shaping or treating: processes – Forming electrical articles by shaping electroconductive... – Conductive carbon containing
Reexamination Certificate
2001-01-31
2004-01-20
Aftergut, Jeff H. (Department: 1733)
Plastic and nonmetallic article shaping or treating: processes
Forming electrical articles by shaping electroconductive...
Conductive carbon containing
C264S271100, C264S272150, C257S720000
Reexamination Certificate
active
06680015
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to the cooling of heat generating surfaces and objects. More specifically, the present invention relates to apparatuses for dissipating heat generated by such objects. In addition, the present invention relates to cooling of heat generating objects by use of composite materials and devices without the use of external fans to assist in cooling.
In industry, there are various parts and components that generate heat during operation. For example, in the electronics and computer industries, it is well known that computer components generate heat during operation. Various types of electronic device packages and integrated circuit chips, such as the PENTIUM central processing unit chip (CPU) manufactured by Intel Corporation and RAM (random access memory) chips are such devices that generate heat. These integrated circuit devices, particularly the CPU microprocessor chips, generate a great deal of heat during operation which must be removed to prevent adverse effects on operation of the system into which the device is installed. For example, a PENTIUM microprocessor, containing millions of transistors, is highly susceptible to overheating which could destroy the microprocessor device itself or other components proximal to the microprocessor.
There are a number of prior art methods to cool heat generating components and objects to avoid device failure and overheating, as discussed above. A block heat sink or heat spreader is commonly placed into communication with the heat generating surface of the object to dissipate the heat therefrom. Such a heat sink typically includes a base member with a number of individual cooling members, such as fins, posts or pins, to assist in the dissipation of heat. The geometry of the cooling members is designed to improve the surface area of the heat sink with the ambient air for optimal heat dissipation. The use of such fins, posts of pins in an optimal geometrical configuration greatly enhances heat dissipation compared to devices with no such additional cooling members, such as a flat heat spreader.
To further enhance air flow and resultant heat dissipation, fans and devices have been used, either internally or externally. However, these external devices consume power and have numerous moving parts. As a result, heat sink assemblies with active devices are subject to failure and are much less reliable than a device which is solely passive in nature.
It has been discovered that more efficient cooling of electronics can be obtained through the use of passive devices which require no external power source and contain no moving parts. It is very common in the electronics industry to have many electronic devices on a single circuit board, such as a motherboard, modem, or “processor card” such as the Celeron board manufactured by Intel Corporation. For example, video cards, which are capable of processing millions of polygons per second, are also susceptible to overheating and need efficient and effective cooling as do the CPUs discussed above. Video cards typically have at least one chip thereon that runs extremely hot to necessitate a video card cooling system.
There have been prior art attempts to provide effective and efficient cooling to microprocessors, electronic components, other heat generating components, and the like. The devices of the prior art are simply the technology previously used for CPUs and other heat generating components. In particular, machined block heat sinks of metal have been typically used for cooling CPU chips, such as the Pentium processor, as described above. These block heat sinks have been modified in size to match the size of the semiconductor device package to be cooled. Since the prior art heat sinks are made of metal, it must be machined to achieve the desired fin configuration. Since the machining process is limited, the geometry of the fin configuration of a machined heat sink is inherently limited.
In the heat sink industries, it has been well known to employ metallic materials for thermal conductivity applications, such as heat dissipation for cooling semiconductor device packages. For these applications, such as heat sinks, the metallic material typically is tooled or machined from bulk metals into the desired configuration. However, such metallic conductive articles are typically very heavy, costly to machine and are susceptible to corrosion. Further, the geometries of machined metallic heat dissipating articles are very limited to the inherent limitations associated with the machining or tooling process. As a result, the requirement of use of metallic materials which are machined into the desired form, place severe limitations on heat sink design particular when it is known that certain geometries, simply by virtue of their design, would realize better efficiency but are not attainable due to the limitations in machining metallic articles.
It is widely known in the prior art that improving the overall geometry of a heat dissipating article, can greatly enhance the overall performance of the article even if the material is the same. Therefore, the need for improved heat sink geometries necessitated an alternative to the machining of bulk metallic materials. To meet this need, attempts have been made in the prior art to provide molded compositions that include conductive filler material therein to provide the necessary thermal conductivity. The ability to mold a conductive composite enabled the design of more complex part geometries to realize improved performance of the part.
As a result, optimal geometries cannot be achieved with a machined metal heat sink. To compensate for these limitations, active cooling, such as by powered fans, must be employed to achieve the requisite cooling to prevent device failure.
In view of the foregoing, there is a demand for a heat sink assembly that is capable of dissipating heat. There is a demand for a passive heat sink assembly with no moving parts that can provide heat dissipation without the use of active components. In addition, there is a demand for a complete heat sink assembly that can provide greatly enhanced heat dissipation over prior art passive devices with improved heat sink geometry. There is a demand for a heat sink assembly that can provide heat dissipation in a low profile configuration. There is a further demand for a net-shape molded heat sink assembly that is well suited for a wide array of heat generating electronic devices, such as microprocessors and video cards.
SUMMARY OF THE INVENTION
The present invention preserves the advantages of prior art heat dissipation devices, heat sinks and heat spreaders. In addition, it provides new advantages not found in currently available devices and overcomes many disadvantages of such currently available devices.
The invention is generally directed to the novel and unique molded heat sink that is net-shape molded of a thermally conductive polymer composition. The present invention relates to a molded heat sink for dissipating heat from a heat generating source, such as a computer semiconductor chip or electronic components on a computer circuit board, such as a video card.
The molded heat sink of the present invention has many advantages over prior art heat sinks in that it is injection molded from the thermally conductive polymer materials which enables the part to be made in complex geometries. These complex geometries enable the heat sink fin configuration to be optimized to be more efficient thus dissipating more heat. As a result, the molded heat sink is freely convecting through the part which makes it more efficient. The ability to injection mold the heat sink permits the optimal configuration to be realized and achieved. A carbon-carbon matrix plate core is embedded within the molded heat sink to greatly improve the overall thermally conductivity of the heat sink while still enabling the heat sink to be molded into complex geometries. With the present molded heat sink, the heat sink can be designed to what is thermally best while not being
Aftergut Jeff H.
Barlow Josephs & Holmes, Ltd.
Cool Options, Inc.
Musser Barbara J
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