Abstract: A circuit material, comprises a conductive layer; and a dielectric substrate disposed on the conductive layer, the dielectric substrate comprising, based on the total dielectric substrate composition, about 10 to about 60 vol. % of a fibrous web; and about 40 to about 90 vol. % of a cured resin system, wherein the resin system comprises up to 100 vol. % of a syndiotactic polybutadiene elastomer, and 0 to 40 vol. % of a particulate filler, based on the combined weight of the resin system and the particulate filler. Such circuit materials have improved tack and good mechanical and electrical properties.

Abstract: An electrical circuit material having a conductive layer disposed a substrate, wherein the substrate is formed from a thermosetting composition comprising a polybutadiene or polyisoprene resin; an optional, functionalized liquid polybutadiene or polyisoprene resin; an optional butadiene- or isoprene-containing copolymer; an optional low molecular weight polymer; an optional curing agent; a cross-linking agent; a particulate fluoropolymer; and about 20 to about 50 percent by weight, based on the total weight of the thermosetting composition, of a magnesium hydroxide having a low ionic content. Use of magnesium hydroxide allows the composition to attain a high level of flame retardancy without use of halogenated flame retardants, while maintaining good moisture absorption and other physical properties.

Abstract: A method of forming a circuit material comprises disposing an adhesion promoting elastomer composition between a conductive copper foil and a thermosetting composition; and laminating the copper foil, adhesion promoting composition, and thermosetting composition to form the circuit material. The adhesion promoting layer may be uncured or partially cured before contacting with the curable thermosetting composition. Preferably the adhesion promoting layer has electrical characteristics such as dissipation factor, dielectric breakdown strength, water absorption, and dielectric constant that are similar to and/or compatible with the electrical characteristics of the thermosetting composition.

Abstract: An electrical circuit material having a conductive layer disposed a substrate, wherein the substrate comprises an organic or inorganic polymer comprising a covalently bound polyhedral silsesquioxane (POSS). The substrate may further comprise an additional dispersed POSS, any other fillers including fibrous webs. Use of covalently bound POSS allows for flame retardancy in compositions having acceptable dielectric constants and dissipation factors.