Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-03-31
2001-02-27
Gaffin, Jeffrey (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S756000, C361S801000, C361S802000, C361S788000, C174S034000, C174S034000, C174S051000
Reexamination Certificate
active
06195266
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates in general to the controlling electromagnetic emissions and in particular to a device and method for grounding high speed circuit electromagnetic emissions.
2. Background Art
The ever-increasing speed of modern computer processors or CPUs has given rise to increased electromagnetic interference (EMI) emissions. As a result, the need to develop better techniques and procedures for controlling EMI has also increased to keep pace with U.S. and European emission regulations.
In the prior art, high speed circuit electromagnetic emissions are typically eliminated or reduced via a direct ground connection which allows a return path for the high speed signals. The return paths are generally located close to the point of origin to reduce the length of the return paths and reduce the amount of radiating area that can
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release the emissions. The suppression of radiating signals can be accomplished through spring clips or conductive gaskets from the source to ground. As long as the processors remained close to the electrical or motherboard they were attached to, EMI reductions involving spring clips were not needed.
However, with the advent of new, ultra high speed slot-type processors, improved EMI reduction techniques are needed. Slot-type processors are pluggable in a vertical orientation with resect to the system motherboard, and are currently capable of speeds in the range of 300 to 750 MHZ. This problem is further compounded by the fact that the heatsinks used to cool the processors are the primary source of the CPU's radiated energy and emissions. Since the heatsinks are typically free-floating (i.e. not attached to the system planar board), the emissions are free to radiate throughout the system and out of the system enclosure.
SUMMARY OF THE INVENTION
A slot-type processor and one or more cache modules are incorporated into a vertically oriented, multiple chip module (MCM) that is mounted to a printed circuit board. The MCM operates at ultra high frequencies and very high temperatures. Each component of the MCM has a heatsink, a thermal plate, and a series of mounting clips and screws which combine to dissipate heat. The heatsinks and thermal plates generate most of the electromagnetic interference (EMI) since they are not attached or grounded to the board.
A series of alignment posts extend from the board and are used to individually and slidably mount each of the components to the board. Each thermal plate is grounded to the posts with grounding clips. The clips maintain contact with the thermal plate through wiping elements. Additional pressure is applied to the wiping elements through a post retaining bracket. The components are fully seated and retained in position with retaining cams.
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Electrical Grounding Arrangement—IBM Disclosure Bulletin (Nov. 1964).
Dials Edward N.
Hodges A. Lamond
Hunt Daniel J.
Owsley William D.
Padgett Russell S.
Dinh Tuan
Felsman Bradley Vaden Gunter & Dillon, LLP
Gaffin Jeffrey
International Business Machines - Corporation
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