Solar-Thermal Synthesized Graphitic Heat Spreader for Thermally Enhanced Organic Substrates

Thermal management in electronic devices by efficient heat-spreading significantly impacts their overall performance. Various methods can synthesize graphitic material for heat spreaders. This work considers a green manufacturing approach using concentrated solar irradiation to convert organic substrates into a graphitic form directly. The process involves short-duration high-flux solar irradiation from a customized solar simulator, utilizing a 10 kWe xenon short arc lamp. The simulator produces a peak heated region approximately 3 cm in diameter with 4.5 MW/m 2 (4500 suns) peak heat flux. To optimize the graphite synthesis process, various parameters such as distance from the focal plane, irradiation duration, and optical power are adjusted to achieve a larger graphitic region size, improved uniformity, and substrate adhesion. Raman spectroscopy confirms the resulting synthesized region as graphitic. The thermal penetration depth of solar-thermal processing is studied by considering substrate thermal properties. The effective thermal conductivity of the substrate improves by more than 10 %, as observed through infrared thermography during the operation of a GaN chip bonded on an organic substrate via thermal compression bonding. This work marks a significant milestone in green manufacturing for the production of graphitic heat spreaders using solar energy.