Immersion Cooling of Light Emitting Diodes

Light emitting diodes (LEDs) historically have been used for indicators and produced low amounts of heat. The introduction of high brightness LEDs with white light and monochromatic colors has allowed them to penetrate specialty and general illumination applications. The increased electrical currents used to drive the LEDs have resulted in higher heat fluxes than those for average silicon CPUs. This has created a need to focus more attention on the thermal engineering of LED power packages. The output of a typical commercial high brightness 1mm² LED has exceeded 100 lumens at drives levels exceeding 300 W/cm². LEDs belong to the Solid State Lighting family, and are limited by their junction temperature (<;150 C). Temperature affects both performance and the reliability of the LED lighting systems. Immersion cooling has been studied for integrated circuits, and other consumer electronics for the last three decades. It is found that it can provide an order of magnitude higher heat fluxes removel than air-cooling due to the phase change heat transfer. This study explores the use of immersion cooling of LED chips in a unique light engine. An experimental and computational study has been carried out to obtain the thermal and optical performance of a multi chip LED light engine. Heat transfer has been kept at the single phase in dielectric fluids, which is compared to conduction in the conventional silicone capping material.