Experimental, Numerical and Analytical Investigation of Thermal Resistance in High Brightness LED Arrays

Abstract

Thermal performance of a commercial LED array module has been studied by experimental, numerical and analytical approaches to find the dominant thermal resistance in the thermal circuit. The light quality, lifetime and reliability of the LED modules depend strongly on the junction temperature which can be obtained and modified by a suitable thermal resistance model. Analytical models for the first level packaging (Die) and second level packaging (PCB and heat sink) have been developed with special attention to the thermal spreading resistance. Numerical modeling has been performed using commercial finite element software (COMSOL) and the results are in good agreement with the analytical models. An LED array module has also been studied experimentally by measuring the temperature field in the PCB and heat sink using thermocouples and infrared thermography. The results of the experimental part are used to validate the numerical and analytical models. It is shown that more than 50% of the total thermal resistance is caused by the heat sink while the PCB and LED package each share 25% of the total thermal resistance.