A circuit breaker includes a molded housing, separable contacts, an operating mechanism adapted to open and close the separable contacts, and a trip circuit cooperating with the operating mechanism to trip open the separable contacts. The molded housing includes two molded halves. The trip circuit includes a pair of arc fault printed circuit boards which cooperate with the corresponding molded halves to form an external composite structure. That external composite structure includes the printed circuit boards and an over-molding material, such as, for example, a thermally conductive epoxy coating disposed thereon.