Performance Of High-power Light-emitting Diodes Research Articles

Performance of Chemical Vapor Deposited Boron-Doped AlN Thin Film as Thermal Interface Materials for 3-W LED: Thermal and Optical Analysis

Boron-doped aluminum nitride (B-AlN) thin films were synthesized on Al substrates by using chemical vapor deposition method by changing the synthesis parameters and were used as thermal interface material for high power light emitting diode (LED). The B-AlN thin film-coated Al substrate was used as heat sink and studied the performance of high power LED at various driving currents. The recorded transient cooling curve was evaluated to study the rise in junction temperature (T j), total thermal resistance (R th-tot) and the substrate thermal resistance (R th-sub) of the given LED. From the results, the B-AlN thin film (prepared at process 4) interfaced LED showed low R th-tot and T j value for all driving currents and observed high difference in R th-tot (ΔR th-tot = 2.2 K/W) at 700 mA when compared with the R th-tot of LED attached on bare Al substrates (LED/Al). The T j of LED was reduced considerably and observed 4.7 °C as ΔT j for the film prepared using process 4 condition when compared with LED/Al boundary condition at 700 mA. The optical performance of LED was also tested for all boundary conditions and showed improved lux values for the given LED at 700 mA where B-AlN thin film was synthesized using optimized flow of Al, B and N sources with minimized B and N content. The other optical parameters such as color correlated temperature and color rendering index were also measured and observed low difference for all boundary conditions. The observed results are suggested to use B-AlN thin film as efficient solid thin film thermal interface materials in high power LED.

Heat Transfer Enhancement of the Liquid-Cooled LED Illumination Module

High-power light emitting diode (LED) modules offer several advantages over conventional light sources, but require effective thermal management for optimal performance, such as liquid cooling or thermoelectric cooling (TEC). This study compared the thermal performance of high-power LEDs with liquid cooling and TEC using both the finite element method and experiments. We considered a mutichip module in which the LEDs are immersed in one of three different cooling fluids in a metal enclosure with passive cooling or a TEC module. In the experiments, temperatures were measured by thermocouples. The temperature and flow fields of the liquid-cooled package inside the enclosure were analyzed in detail using a numerical model, and the results were validated against the experimental measurements. In this paper, we discuss the major design considerations when using liquid cooling and TEC. Our results show that for the illumination module considered in this study, appropriate heat sink design is crucial to optimizing performance with TEC, which can enhance the heat dissipation for small and compact LED modules.