The current trend in mobile electronics industry is towards development and commercialization of foldable electronic devices such as smartphones. Most of these devices employ organic light emitting diode (OLED) displays which show direct correlation between local temperature and luminescence intensity. It has been observed that 10% change in luminescence intensity which corresponds to approximately 1°C temperature change across an OLED surface could be detected by bare eyes rendering the device useless. In this work, we investigate the performance of three common strategies for thermal management of a sample smartphone with screen dimensions of 144 mm by 138.1 mm.
Three cases are studied using FEM simulations: graphite heat spreader with in plane thermal conductivity of 700W/m.k, two thermal ground planes (TGP) with a graphite hinge and a single large TGP. TGP is also known as vapor chamber or 2-D flat heat pipe. In the fully unfolded configuration, a significant difference is observed between different thermal management strategies. For design using a graphite heat spreader, the temperature distribution across the OLED display is about 13.1°C. For the design using two TGPs, the temperature distribution is about 5.4°C. Finally, for the design using a single large TGP, the temperature distribution is only 0.8°C. These results demonstrate that using a single large TGP can achieve the temperature uniformity required for a high-quality OLED display.