Electric heating – Metal heating – By arc
Patent
1991-09-10
1994-01-11
Albritton, C. L.
Electric heating
Metal heating
By arc
21912169, 21912182, B23K 2600
Patent
active
052783855
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of producing printed circuits, in particular flexible printed circuits, by removing material on a blank comprising a dielectric substrate, flat metallic conductors bonded to an upper face of the substrate and an insulating coating covering substantially the entire extent of the printed circuit, in which material covering at least one defined zone of a conductor is removed so as to expose at least one of its faces.
The invention also relates to a printed circuit produced by this method.
Finally, the invention relates to a device for carrying out this method of producing printed circuits, in particular flexible printed circuits, by removing material on a blank comprising a dielectric substrate, flat metallic conductors bonded to an upper face of the substrate and an insulating coating covering substantially the entire extent of the printed circuit, this removed material being that covering at least one defined zone of a conductor, so as to expose at least one of its faces, the device comprising a support for a blank, a machining head designed to machine the blank by removing material and control and displacement means to activate the machining head and displace the latter and the blank relative to one another.
In a conventional method of producing printed circuits, in particular flexible printed circuits, the latter are coated with an insulating film which is held by an adhesive and covers the entire substrate and the conductors, except over connection zones and zones provided on the conductors and to the side of the latter for connecting or mounting electrical components. The insulating film is prepared before being placed on a substrate provided with a series of printed circuits. The preparation of the insulating film consists of cutting it into sizes covering several circuits and in punching, drilling or milling holes therein which will leave clear the connection and bare zones. The prepared insulating film is then manually positioned on the substrate by means of visual marks or using a template. It is held in position by adhesive bonding at several points, after which the assembly is hot-pressed so as to make the insulator adhere perfectly over its entire surface. The result is thus a strip of circuits ready to be cut up. This method, which uses manual positioning, is not very productive, particularly if the connection zones and the bare zones are numerous and have a small surface area.
A more efficient method, as defined in the introduction, is described in the Japanese publication Sho. 58 132 996. It consists of applying the insulating film over approximately the entire surface of the substrate, then removing it from the zones to be exposed by means of tools employing lateral ultrasonic vibration. One disadvantage of this method is that it is rather slow if a simple tool is used, otherwise a highly complex set of tools has to be available for each circuit type. Nor is the precision obtained sufficient for fine tracks. A further disadvantage which is inherent in this type of method is that, due to the projecting position of the conductors on the substrate, it does not allow the zones of the substrate which are adjacent to a conductor or located between two adjacent conductors to be cleared, and this clearing process is necessary to ensure good electrical contact between the conductor and the corresponding connector element.
The object of the present invention is therefore is provide a method which enables the above-mentioned disadvantages to be avoided and both the conductor zones and the adjacent zones on the substrate to be precisely and quickly exposed, without requiring a specific set of tools for each type of part which is processed.
With the object in view, the invention provides a method of the type specified in the introduction which is charaterised in that material is removed by heat by means of at least one laser beam from at least one defined zone of a conductor and/or at least one zone adjacent to a conductor.
The power of the laser beam is preferabl
REFERENCES:
patent: 4769523 (1988-09-01), Tanimoto et al.
patent: 4894115 (1990-01-01), Eschelberger et al.
patent: 4907341 (1990-03-01), Chapel, Jr. et al.
Electronic Packaging and Production. vol. 28, No. 8, Aug. 8, 1988, Newton, Massachusetts pp. 32-34; Fjelstad: "Design guidelines for flexible circuits".
Ambrose Jean-Jacques
Gerome Jacques
Albritton C. L.
Nicolitch S.A.
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