Abstract: A heat sink board structure includes a thermal/structural base having a composite core layer of a mass of graphitized carbon fibers infiltrated with a first resin material matrix. The graphitized carbon fibers of the composite core are substantially unidirectional and oriented parallel to the face of the composite core layer. Transverse reinforcement layers are bonded to the oppositely disposed faces of the composite core layer. Each transverse reinforcement layer is formed of carbon fibers embedded in a resin material matrix, with the carbon fibers lying substantially in a plane of the transverse reinforcement layer and perpendicular to the carbon fibers in the composite layer. Heat generating and heat dissipating components are bonded to the thermal/structural base. Metallic contact strips are bonded to the surfaces of the transverse reinforcement layers.