A printed circuit board (PCB) has a multi-layered substrate including a plurality of signal lines and a ground voltage plate disposed below the signal lines and by which a common ground voltage is applied to the signal lines, a heat sink disposed on the multi-layered substrate, and thermal interface material interposed between the signal lines and the heat sink to transfer heat from the multi-layered substrate to the heat sink. The heat sink thus dissipates the heat generating from the multi-layered substrate and along with the ground voltage plate suppresses electromagnetic interference of signal transmitted through adjacent ones of the signal lines. The thermal interface material also serves in the design phase as a means to tune the impedance of the signal lines.