Heat exchange – With retainer for removable article – Electrical component
Reexamination Certificate
1998-09-11
2004-03-16
Flanigan, Allen (Department: 3743)
Heat exchange
With retainer for removable article
Electrical component
C165S185000, C165S905000, C361S704000
Reexamination Certificate
active
06705388
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates broadly to thermal management devices for electronic components, such as integrated circuit (IC) chips. More particularly, the invention relates to a non-electrically conductive, low profile thermal dissipator for attachment to the heat transfer surface of an electronic component for the conductive and/or convective cooling of the component.
Circuit designs for modern electronic devices such as televisions, radios, computers, medical instruments, business machines, communications equipment, and the like have become increasingly complex. For example, integrated circuits have been manufactured for these and other devices which contain the equivalent of hundreds of thousands of transistors. Although the complexity of the designs has increased, the size of the devices has continued to shrink with improvements in the ability to manufacture smaller electronic components and to pack more of these components in an ever smaller area.
As electronic components such as IC semiconductor chips or dies have become smaller and, in turn, more densely packed on printed circuit boards (PCBs), designers and manufacturers now are faced with the challenge of how to dissipate the heat which is ohmicly or otherwise generated by these components. Indeed, it is well known that many electronic components, and especially power semiconductor components such as transistors and microprocessors, are more prone to failure or malfunction at high temperatures. Thus, the ability to dissipate heat often is a limiting factor on the performance of the component.
In basic construction, and as is described in U.S. Pat. Nos. 5,488,254 and 5,359,768, semiconductor chips or dies typically are packaged by encapsulation in a ceramic or plastic chip carrier. External connections provided on the chip carrier allow for the chip to be mounted onto a PCB by wire bonding electrical leads on the carrier through a common mounting surface on the board, or by surface mounting the carrier directly to the mounting surface of the board. Recently, the industry trend has been away from ceramic chip carrier packages and toward plastic packages. Usually molded of an engineering thermoplastic material such as polyethylene terephthalate (PETP), polyphenylene sulfide (PPS), polyetherimide (PEI), polyetherether ketone (PEEK), polyetherketone (PEK), or polyimide (PI), or a thermosetting material such as an epoxy or an epoxy-phenolic composite, these plastic chip packages typically are less expensive than their ceramic counterparts. However, these plastic materials generally exhibit less efficient heat transfer characteristics as compare to other package materials, and therefore may raise additional thermal dissipation considerations.
Electronic components within integrated circuits traditionally have been cooled via forced or convective circulation of air within the housing of the device. In this regard, cooling fins have been provided as an integral part of the component package or as separately attached thereto for increasing the surface area of the package exposed to convectively-developed air currents. Electric fans additionally have been employed to increase the volume of air which is circulated within the housing. For high power circuits and the smaller but more densely packed circuits typical of current electronic designs, however, simple air circulation often has been found to be insufficient to adequately cool the circuit components. One approached has been to design integral metal or ceramic heat sinks into the die package or mounting assembly, such as is shown, for example, in U.S. Pat. Nos. 5,175,612; 5,608,267; 5,605,863; 5,525,835; 5,560,423; and 5,596,231.
Heat dissipation beyond that which is attainable by simple air circulation may be effected by the direct mounting of the electronic component to a thermal dissipation member such as a “cold plate” or other heat sink. The heat sink may be a dedicated, thermally-conductive metal plate, or simply the chassis or circuit board of the device. To improve the heat transfer efficiency through the interface, a layer of a thermally-conductive, electrically-insulating material typically is interposed between the heat sink and electronic component to fill in any surface irregularities and eliminate air pockets. Initially employed for this purpose were materials such as silicone grease or wax filled with a thermally-conductive filler such as aluminum oxide. Such materials usually are semi-liquid or solid at normal room temperature, but may liquefy or soften at elevated temperatures to flow and better conform to the irregularities of the interface surfaces.
For example, U.S. Pat. No. 4,299,715 discloses a wax-like, heat-conducting material which is combined with another heat-conducting material, such as a beryllium, zinc, or aluminum oxide powder, to form a mixture for completing a thermally-conductive path from a heated element to a heat sink. A preferred wax-like material is a mixture of ordinary petroleum jelly and a natural or synthetic wax, such as beeswax, palm wax, or mineral wax, which mixture melts or becomes plastic at a temperature above normal room temperature. The material can be excoriated or ablated by marking or rubbing, and adheres to the surface on which it was rubbed. In this regard, the material may be shaped into a rod, bar, or other extensible form which may be carried in a pencil-like dispenser for application.
U.S. Pat. No. 4,466,483 discloses a thermally-conductive, electrically-insulating gasket. The gasket includes a web or tape which is formed of a material which can be impregnated or loaded with an electrically-insulating, heat conducting material. The tape or web functions as a vehicle for holding the meltable material and heat conducting ingredient, if any, in a gasket-like form. For example, a central layer of a solid plastic material may be provided, both sides of which are coated with a meltable mixture of wax, zinc oxide, and a fire retardant.
U.S. Pat. No. 4,473,113 discloses a thermally-conductive, electrically-insulating sheet for application to the surface of an electronic apparatus. The sheet is provided as having a coating on each side thereof a material which changes state from a solid to a liquid within the operating temperature range of the electronic apparatus. The material may be formulated as a meltable mixture of wax and zinc oxide.
U.S. Pat. No. 4,764,845 discloses a thermally-cooled electronic assembly which includes a housing containing electronic components. A heat sink material fills the housing in direct contact with the electronic components for conducting heat therefrom. The heat sink material comprises a paste-like mixture of particulate microcrystalline material such as diamond, boron nitride, or sapphire, and a filler material such as a fluorocarbon or paraffin. The greases and waxes of the aforementioned types heretofore known in the art, however, generally are not self-supporting or otherwise form stable at room temperature and are considered to be messy to apply to the interface surface of the heat sink or electronic component. Moreover, use of such materials typically involves hand application or lay-up by the electronics assembler which increases manufacturing costs.
Another approach has been to substitute a cured, sheet-like material or pad for the silicone grease or wax material. Such materials may be compounded as containing one or more thermally-conductive particulate fillers dispersed within a polymeric binder, and may be provided in the form of cured sheets, tapes, pads, or films. Typical binder materials include silicones, urethanes, thermoplastic rubbers, and other elastomers, with typical fillers including aluminum oxide, magnesium oxide, zinc oxide, boron nitride, and aluminum nitride.
Exemplary of the aforesaid interface materials is an alumina or boron nitride-filled silicone or urethane elastomer which is marketed under the name CHO-THERM® by the Chomerics Division of Parker-Hannifin Corp., 77 Dragon Court, Woburn, Mass. 01888. Additionally, U.S. Pat. No. 4,
Flanigan Allen
Molnar, Jr. John A.
Parker-Hannifin Corporation
LandOfFree
Non-electrically conductive thermal dissipator for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Non-electrically conductive thermal dissipator for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-electrically conductive thermal dissipator for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3208510