A printed circuit board may include an aluminum nitride (AIN) substrate that includes an AIN thin film and a layer of high-frequency polymer as a carrier substrate of the AIN thin film. The AIN substrate forms a first layer of the printed circuit board. The AIN substrate comprises a heat spreader that laterally spreads out heat from a heat sink on the printed circuit board to form a thermal dissipation path parallel with a signal path on the printed circuit board. The printed circuit board may include a main substrate aligned to and bonded with the AIN substrate. The main substrate may include one or more additional layers of the printed circuit board.