Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
1999-12-20
2001-11-13
Riley, Shawn (Department: 2838)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C361S818000
Reexamination Certificate
active
06316721
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and a device for shielding electronic components and in particular for shielding components mounted on a printed circuit board.
BACKGROUND OF THE INVENTION AND PRIOR ART
In many applications it is required to shield electronic components from the surrounding environment. Thus, in the fields of e.g. radio transmitters, radio receivers, computers and other electronic devices, it is highly desirable to provide an electromagnetic shield around components emitting and/or sensitive to absorbing electromagnetic radiation.
In order to provide the electromagnetic shield it is common to arrange a rectangular shaped device of a metallic material over the electronic components.
Such a device is disclosed in U.S. Pat. No. 5,175,395, which describes an electromagnetic shielding device formed by walls of an electrical conductive material. On top of the walls a cover of an electrically conducting material is provided.
However, electronic components have become smaller and smaller thereby allowing the circuit boards on which they are mounted to be smaller as well. Conventional shielding devices typically have a top of approximately a few tenth of a millimeter. In today's technique this represents quite a large part of the height available on the circuit board for many applications.
Also, there is often a requirement that the top should be possible to lift off in order to perform service or replacement of different circuits mounted on the printed circuit board. Conventional shielding devices having a top which can be lift off are expensive.
Thus, there is a need for a small shielding device, which adds as little as possible to the height of the printed circuit board, and having a top which can be removed for service purposes and the like.
SUMMARY
It is an object of the present invention to overcome the problem as outlined above and to provide a shielding device having small dimensions.
This object is obtained by a shielding device formed by a wall having a top edge arranged to fasten a foil comprising an electrically conducting material. In order to fasten the foil, the wall can be provided with teeth at its top section. Also the wall(s) can be formed with arbitrary angles with respect to each other when forming a whole shielding device.
The cover can be formed by one large or several smaller pieces. The cover is preferably fastened to the walls by means of an adhesive and an electrical contact is provided by the teeth projecting from the wall(s).
Thus, by forming the top of the shield by a foil the height of the electromagnetic shield can be reduced significantly. Further, since a foil is a flexible material it will follow the shape of the components on the printed circuit board. Thus, if a component would project higher up from the printed circuit board, there will be no problem, as would be the case if the top was made of an inflexible material or a material having a low flexibility.
Furthermore, the walls can be made more flexible, since the fastening means between the top and the wall does not require a particular shape of the top.
REFERENCES:
patent: 3809233 (1974-05-01), Gruszka
patent: 5175395 (1992-12-01), Moore
patent: 5335147 (1994-08-01), Weber
patent: 5880938 (1999-03-01), Johnsen et al.
patent: 6049468 (2000-04-01), Learmonth
patent: 296 12 557 U1 (1996-10-01), None
patent: 462944 B (1990-08-01), None
patent: 95/28075 A1 (1995-10-01), None
Koitsalu Evald
Persson Michael
Wallin Lars
Nixon & Vanderhye P.C.
Riley Shawn
Telefonaktiebolaget LM Ericsson
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