A circuit subassembly, comprising: a conductive layer, a dielectric layer formed from a thermosetting composition, wherein the thermosetting composition comprises, based on the total weight of the thermosetting composition a polybutadiene or polyisoprene resin, about 30 to about 70 percent by weight of a magnesium hydroxide having less than about 1000 ppm of ionic contaminants, and about 5 to about 15 percent by weight of a nitrogen-containing compound, wherein the nitrogen-containing compound comprises at least about 15 weight percent of nitrogen; and an adhesive layer disposed between and in intimate contact with the conductive layer and the dielectric layer, wherein the adhesive comprises a poly(arylene ether), wherein the circuit subassembly has a UL-94 rating of at least V-1.