Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2003-02-07
2004-03-30
Chervinsky, Boris (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S707000, C361S718000, C361S719000, C257S718000, C257S722000, C174S016300, C165S080300, C165S185000
Reexamination Certificate
active
06714414
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to transferring heat from heat-generating electrical components to heat sinks and, more particularly, to spring spacer assemblies for urging heat-generating electrical components into contact with thermal transfer surfaces of heat sinks.
2. Discussion of the Related Art
Many various products incorporate electrical components that become heated during operation. Commonly used electrical components such as FETs (field effect transitors), for example, generate heat during operation which, if not dissipated, may result in damage to the electrical components. Accordingly, many electrical components may be considered heat-generating electrical components that may be impaired when heated above certain temperatures. Overheating of heat-generating electrical components may cause the electrical components to operate improperly or even fail, with the result that the associated products may also operate improperly or fail.
Given the need to protect heat-generating electrical components from overheating, heat sinks are usually used in conjunction with heat-generating electrical components to absorb and dissipate heat therefrom. Typical heat sinks are made from a thermally conductive material to absorb heat from heat-generating electrical components positioned in contact with thermal transfer surfaces of the heat sinks. Oftentimes the heat sinks are configured with fins or other structure to enhance dissipation of the absorbed heat and thereby maximize the thermal capacity of the heat sinks. Since heat sinks are ordinarily made from metal, the thermal transfer surfaces often comprise thermal interfaces made of thermally conductive but non-electrically conductive material secured on surfaces of the heat sinks. The thermal interfaces electrically insulate the heat-generating electrical components from the metal heat sinks while still promoting thermal transfer from the heat-generating electrical components to the heat sinks.
The degree to which heat sinks are effective in absorbing heat from heat-generating electrical components depends in large parton the integrity of the thermal contact maintained between the heat-generating electrical components and the thermal transfer surfaces of the heat sinks. To maximize heat transfer from the heat-generating electrical components, it is desirable to maximize the surface area of the heat-generating electrical components in contact with the thermal transfer surfaces. In addition, it is desirable for the heat-generating electrical components to be forcefully urged into contact with the thermal transfer surfaces with sufficient force applied at locations conducive to maintaining good thermal contact without causing portions of the heat-generating electrical components to move away from the thermal transfer surfaces.
Various mechanical devices have been proposed for maintaining heat-generating electrical components in contact with thermal transfer surfaces of heat sinks as represented by U.S. Pat. No. 2,740,075 to Walker et al, U.S. Pat. Nos. 4,845,590, 4,922,601 and 4,923,179 to Mikolajczak, U.S. Pat. No. 5,321,582 to Casperson, U.S. Pat. No. 5,363,552 to Coniff, U.S. Pat. No. 5,383,092 to Liberati, U.S. Pat. No. 5,450,284 to Wekell, U.S. Pat. No. 5,466,970 to Smithers, U.S. Pat. No. 5,483,103 to Blickhan et al, U.S. Pat. No. 5,648,889 to Bosli, U.S. Pat. No. 5,991,151 to Capriz, U.S. Pat. No. 6,049,459 to Edmonds et al, U.S. Pat. No. 6,084,773 to Nelson et al, U.S. Pat. No.6,088,226 to Rearick, and U.S. Pat. No. 6,313,995 B1 to Koide et al, and bythe thermal management clips of Thermashield LLC and The Max Clip System™ of AAVID Thermalloy.
As shown by several of the aforementioned references, the heat-generating electrical components may be mounted on printed circuit boards, the heat-generating electrical components typically being disposed along one side of the printed circuit boards with leads of the heat-generating electrical components extending through the printed circuit boards for soldering to the opposite side thereof. The heat sinks are positioned so that the heat-generating electrical components may be placed in contact with the thermal transfer surfaces of the heat sinks. A single printed circuit board may have many heat-generating electrical components mounted thereon, and frequently the heat-generating electrical components are disposed along or near peripheral edges of the printed circuit boards.
Many prior mechanical devices for maintaining heat-generating electrical components in contact with the thermal transfer surfaces of heat sinks operate by forcefully urging the heat-generating electrical components into contact with the thermal transfer surfaces of the heat sinks, but have numerous disadvantages. For example, a single printed circuit board having a plurality of heat-generating electrical components mounted thereon may require a separate mechanical device for each heat-generating electrical component, resulting in additional parts and costs. It is difficult to properly align many prior mechanical devices with the heat-generating electrical components to account for variations in the way that the heat-generating electrical components are mounted to the printed circuit boards. It is difficult to disassemble or remove many conventional mechanical devices from the printed circuit boards, the heat sinks and/or the heat-generating electrical components such that many devices are essentially non-removable or permanent, thereby limiting future repair or replacement. Many mechanical devices for maintaining heat-generating electrical components in contact with the thermal transfer surfaces of heat sinks require highly customized heat sinks to accommodate the devices so that the use of less costly heat sinks is precluded. In addition, it is common for conventional mechanical devices to require larger size heat sinks in order to mount the mechanical devices, and the need for larger heat sinks increases the cost and size of the associated products. Products in which conventional mechanical devices are used to maintain heat-generating electrical components in contact with the thermal transfer surfaces of heat sinks will generally have a larger size footprint due to the presence of the mechanical devices. Where the mechanical devices comprise clips, the clips ordinarily extend beyond the periphery of the printed circuit boards, resulting in a larger footprint. Larger size footprints may be unsuitable for many applications, such as those in which the associated products must fit on pre-fabricated, standard size mounting panels and assemblies. Clips and other prior mechanical devices may also significantly increase the height or depth of the assemblies formed by the printed circuit boards, the heat sinks and the clips or other mechanical devices, and such size increases are usually undesirable.
Many conventional mechanical devices provide inferior thermal contact between the heat-generating electrical components and the thermal transfer surfaces of the heat sinks due to insufficient forces applied to the heat-generating electrical components, the application of non-uniform forces and/or the application of forces at undesirable locations causing portions of the heat-generating electrical components to move away from the thermal transfer surfaces. Examples of mechanical devices having this drawback are those comprising screws or other threaded fasteners extending through the heat-generating electrical components into the heat sinks and capable of being tightened to urge the heat-generating electrical components into contact with the thermal transfer surfaces of the heat sinks. The screws or other threaded fasteners, one of which is needed for each heat-generating electrical component, add to the cost and labor intensiveness of assembly. Furthermore, consistent, repeatable torque control of screws and threaded fasteners is difficult to attain. Under-tightening or under-torqueing the screws or other threaded fasteners results in insufficient force being appli
Dubovsky Stephen M.
Mellema William
Chervinsky Boris
Morningstar Corporation
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