Adapted electrically conductive layer

Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition

Reexamination Certificate

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Details

C361S816000

Reexamination Certificate

active

06294730

ABSTRACT:

TECHNICAL AREA OF THE INVENTION
In order to screen against electromagnetic radiation and/or to drain electrical fields, e.g. static electricity, from ECD, electrical devices or from antenna elements or similar, for balancing of another antenna and/or draining and taking care of ground currents, electrically conductive layers of various types are currently used, which are located directly or indirectly in connection with a protective cover. This can be arranged by using various application methods for the layers, e.g. screen or tampon printing. Other methods, like spray painting and vacuum vaporisation of metallised material, are also used. Various types of metal foils or sheet metal can also be used and fitted as protectors for this purpose.
When using spray painting and vacuum metallising, one problem is that the material is spread around, in such a manner that a substantial portion thereof will not end up on the part to be supplied with the electrically conductive layer. This entails a large waste of material. Another problem concerning these methods is that the material will also end up on areas that are not to be metallised, such as openings, projections and fasteners. Parts and/or surfaces must then be masked before surface treatment, or the coating must be removed after the surface treatment. Furthermore, it is difficult for the material to reach into and build up layers in nooks and corners, resulting in lack of material there, which must then later be replenished so as not to impair the function. Alternatively, an excessively thick layer must be applied, to ensure coverage in these inaccessible areas. In some areas, such thick layers of material, as these methods will involuntarily cause are not necessary; consequently, this will also contribute to unnecessary material consumption. Thus, with these methods, a predetermined material thickness cannot be achieved with any high precision.
With screen and tampon printing it is possible to print a metallic layer on the surface of a component. Printing is however difficult on complicated surfaces that are very curved, surfaces located at sharp corners, surfaces located at openings and recesses, and surfaces located close to protrusions and abrupt elevations.
To manufacture prefabricated metal foils or sheets with the aim of producing the layer in question is expensive and time-consuming in production and, furthermore, they will be difficult to fit into a case.
SUMMARY
The object of the present invention is to eliminate the existing drawbacks with the above designs and to simplify and reduce the cost for providing cases with complete, functioning, electrically conductive layers and to create radio-frequent and conductive paths where the least damage is done or the highest benefit is achieved. The characterising features of the invention are stated in the appended patent claims.
Owing to the invention, an electrically screening and draining unit, without the above disadvantages, has been provided. According to the invention, the unit thus exhibits a network of electrically conductive paths of varying width, thickness, length and distribution along the case surface, creating a “Faraday cage”. The electrically conductive paths extend, according to the invention, along those predetermined surfaces where they most efficiently screen the electromagnetic radiation and where they drain the electricity, instead of providing, according to the present-day method, the entire case surface with a metallic layer. In a preferred embodiment, an electrically conductive pattern, creating paths, is tampon printed on e.g. the inner surface of a telephone case, in such a way that printing on curved surfaces, at holes, on protrusions, in recesses, sharp corners, etc. is avoided. The case is only provided with these electrically conductive paths at those locations where a metallic layer is necessary. In order to achieve improved conductive properties at selected locations, a wider and/or thicker path may be printed. In this manner, a large amount of material will be saved, where saving is possible. Furthermore, the difficulties arising from printing on inaccessible areas are avoided by allowing the paths to run beside such locations. In order to be able to print the paths on difficult areas, bridges may provide a base. Such bridges can level out corner radii as well as provide the base at e.g. annular formations around holes and protrusions. The paths may furthermore be placed at other suitable locations to provide adhesion against the underlying material. On the larger surfaces of the case, material may also be saved by printing paths in various network structures also here, e.g. shaped like a number of circles, squares, ellipses, rhomboids, triangles, octants, hexagons, loops, ending extensions towards e.g. holes, etc. or being of optional shape. By suitable reshaping of the layer, a good screening as well as a good adhesion of e.g. an adhesive on the underlying base surface, is obtainable.
The invention can also be applied by screen-printing the electrical unit onto a foil, or by stamping out a metal foil or metal sheet, configured as described above in the preferred embodiment of the invention, and subsequently fitting it into a case. Naturally, these methods may also be combined in the same electrical unit.
All types of cases can be screened and drained of electromagnetic radiation by means of the invention.
The invention will be described in more detail below by means of some preferred embodiment examples, with reference to the attached drawings.


REFERENCES:
patent: 5206796 (1993-04-01), Thompson et al.
patent: 5334800 (1994-08-01), Kenney
patent: 5360941 (1994-11-01), Roes
patent: 5596170 (1997-01-01), Barina et al.
patent: 2 298 387 (1996-09-01), None
patent: WO97/34459 (1997-09-01), None
Sandh, H.; International-Type Search Report, Feb. 19, 1999, pp. 1-3; Search Request No. SE98/00776.

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