Abstract An economical, high-performance flexible electrical insulating sheet is made by coating a thermosetting polybutadiene-epoxynitrile resin mixture onto the surface of a sheet of reinforcing fibrous material and curing the resin mixture to form a tough flexible resinous laminate. Where tear strength is not so important, the resin may be made into a self-supporting film without the inclusion of reinforcing materials. Because of its high dielectric strength, the flexible electrical insulating sheet may be used as a covering or as a substrate for flexible printed circuits. Where the flexible laminate is to be used as a printed circuit substrate, the fiber filled resin mixture is coated onto a thin metal foil and cured to form a tough flexible laminate, or in the alternative, the fiber filled resin mixture is cured in sheet form and metal coated by electroless plating. Photoresist materials applied to the metal foil surface render the laminate subject to the state-of-the-art printed circuit etching processes. Printed circuit boards can be fabricated by applying a layer of polybutadiene-epoxy-nitrile adhesive to the etched circuit pattern sheets, stacking the sheets, and thermally curing the adhesive. Alternatively, the flexible printed circuit sheets may be rolled and inserted in tubular connectors.
A FLEXIBLE ELECTRICALLY INSULATING SHEET COMPRISING: A. 90% BY WEIGHT OF POLYBUTADIENE-EPOXY ELASTOMERIC RESIN HAVING AN ORGANIC PEROXIDE HOMOGENEOUSLY DISPERSED THERETHROUGH AND HAVING A RATIO OF I. ONE EQUIVAENT OF HDROXY TERMINATED POLYBUTADIENE HOMOPOLYMER CONSISTING ESSENTIALLY OF AT LEAST 50% OF 1,2 -POLYBUTADIENEDIO II. NE GRAM MOLE OF AN AROMATIC ACID ANHYDRIDE, III. 1 TO 2 EQUIVALENT OF A POLYFUNCTIONAL EPOXY RESIN, AND B. 10% TO 5% BY WEIGHT OF A DICARBOXY TERMINATED BUTADIENEACRYLONITRILE COPOLYMER COMPRISING 16% TO 50% BY WEIGHT ACRYLONITRILE AND THE BALANCE BUTADIENE AND HAVING AN AVERAG MOLECULAR WEIGHT BETWEEN ABOUT O,000 AND ABOUT 34,000.
Claim 2
Dependent Claim
98 words
A FLEXIBLE ELECTRICALLY INSULATING SHEET COMPRISING: A. 90% BY WEIGHT OF POLYBUTADIENE-EPOXY ELASTOMERIC RESIN HAVING AN ORGANIC PEROXIDE HOMOGENEOUSLY DISPERSED THERETHROUGH AND HAVING A RATIO OF I. ONE EQUIVAENT OF HDROXY TERMINATED POLYBUTADIENE HOMOPOLYMER CONSISTING ESSENTIALLY OF AT LEAST 50% OF 1,2 -POLYBUTADIENEDIO II. NE GRAM MOLE OF AN AROMATIC ACID ANHYDRIDE, III. 1 TO 2 EQUIVALENT OF A POLYFUNCTIONAL EPOXY RESIN, AND B. 10% TO 5% BY WEIGHT OF A DICARBOXY TERMINATED BUTADIENEACRYLONITRILE COPOLYMER COMPRISING 16% TO 50% BY WEIGHT ACRYLONITRILE AND THE BALANCE BUTADIENE AND HAVING AN AVERAG MOLECULAR WEIGHT BETWEEN ABOUT O,000 AND ABOUT 34,000.
Claim 3
Dependent Claim
31 words
A flexible sheet according to claim 1 wherein said polyfunctional epoxy resin comprises up to 50% of a polyfunctional aliphatic epoxy resin and a polyfunctional aromatic epoxy resin for the remainder.
Claim 4
Dependent Claim
27 words
A flexible electrical laminate according to claim 2 wherein the polyfunctional epoxy resin comprises 10% to 30% by weight of a polyfunctional epoxy resin aliphatic epoxy resin.