Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Patent
1997-08-22
1999-03-09
Picard, Leo P.
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
361748, 361800, 174 35R, H05K 900
Patent
active
058809384
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a circuit board and more particularly, but not exclusively, to circuit boards of the kind that are comprised of a plurality of superposed electrically conductive layers such as to form conductive patterns, and electrically insulating layers there between.
More particularly, the present invention is concerned with the construction of a circuit board that includes surface-related electrically conductive layers which screen against electromagnetic interference, wherein one such outermost conductive layer is provided with a plurality of coordinated connection islands where selected islands are adapted for electrical and mechanical coaction with connection conductors, connection pads, connection pins or the like or a discrete surface-mounted component.
DESCRIPTION OF THE BACKGROUND ART
Several different designs of such circuit boards are known to the art.
The latest development within electronic equipment tends towards increasing signal speed and towards increasing the compactness of discrete circuits on circuit boards. These measures has led to problems relating to electromagnetic interference (EMI).
Various measures have also been proposed in endeavours to reduce or fully eliminate the electromagnetic interferences that result primarily from higher signal rates and short switch-over times.
Concerns other than EMI are related to electromagnetic compatibility (EMC) and electromagnetic discharge (EMD).
It is also known to fully "cover" or enclose circuits of this kind in an electrically conductive material so as to obtain effective screening to and from the surroundings.
It is also known to fully encapsulate circuit boards in a metallic casing and to provide delimited holes in the casing through which cables and conductors can be connected to the circuit board.
In the case of circuit boards, it is known to attempt to "cover" and enclose the signal-carrying conductors formed in one or more electrically conductive layers in the form of copper foils inwardly of a circuit board having external earth-potential related electrically conductive layers.
An example of this technique is given in publication EP-A2-0 238 267.
Such measures are taken in order to prevent external electromagnetic interference fields from obtaining access to the interior of the circuit board and also to prevent the emission of electromagnetic fields generated by board components as interference fields.
It is also known in circuit boards to endeavour to utilize mutually opposing external electrically conductive layers and to connect said layers to earth potential such as to give said layers a screening function.
However, such circuit boards normally require electric conductors to be included in these screening layers.
The provision of such conductors requires conductor-related foil sections to be isolated from the electrically conductive layer or from the remainder of the foil, wherein it is known to form said conductors by etching away selected sections of the metal foil, such as to enable the conductors to be formed without contact with the remainder of the metal foil.
In this regard, it is known to permit that part or those parts of the metal foil or the outer copper layers that have not been used as conductors for connection purposes and which have not been etched away to remain on the circuit board and to connect this part or these parts to earth, so that the layer will obtain a partial screening function.
It is quite natural that screening layers etched in this manner are unable to provide a complete or a maximum screen, since several different conductor patterns have been formed therein with peripheral exposure of the metal foil.
Even though encapsulation forms part of the earlier standpoint of techniques in preventing electromagnetic interference, this technique will not be described for the sake of simplicity.
The earlier standpoint of techniques also includes the realization that screening problems are heightened with increasing frequencies of electromagnetic fields and interference f
REFERENCES:
patent: 4758896 (1988-07-01), Ito
patent: 4801489 (1989-01-01), Nakagawa et al.
patent: 5006667 (1991-04-01), Lonka
patent: 5043526 (1991-08-01), Nakagawa et al.
patent: 5140110 (1992-08-01), Nakagawa et al.
patent: 5274193 (1993-12-01), Bailey et al.
patent: 5323299 (1994-06-01), Weber
patent: 5335147 (1994-08-01), Weber
patent: 5341274 (1994-08-01), Nakatani et al.
patent: 5428506 (1995-06-01), Brown et al.
patent: 5430933 (1995-07-01), Marx et al.
Johnsen Helge Bodahl
Timgren Mats Olov
Gandhi Jayprakash N.
Picard Leo P.
Telefonaktiebolaget LM Ericsson
LandOfFree
Circuit board with screening arrangement against electromagnetic does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circuit board with screening arrangement against electromagnetic, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuit board with screening arrangement against electromagnetic will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1327407