an electronic structure includes an electronic device , and a heat sink assembly in thermal contact with the electronic device . the heat sink assembly is formed of a piece of pyrolytic graphite embedded within a metallic casing and intimately contacting an interior wall of the metallic casing . the heat sink assembly is substantially fully dense . the heat sink assembly is fabricated by assembling the piece of pyrolytic graphite within the disassembled elements of the metallic casing , and then simultaneously heating and pressing the initial assembly until it is substantially fully dense .