Experimental study on thermal performance of SMD-LED chips under the effects of electric wire pattern and LED arrangement

Abstract

This paper presents an experimental study on the thermal performance of SMD-LEDs (Surface Mount Device-Light Emitting Diodes) mounted on plate-fin heat sink (HS) and effects of LED arrangement, HS size, particularly heat spreading effect by electric wire pattern in PCB. Various types of LED arrays and HS sizes were investigated for both wide and narrow electric wires. By calibrating the temperature from IR thermometry, novel correlations were proposed for estimating the temperature of various surface types where the emissivity is not known. Thermal coupling effects between LEDs are analyzed and explained comprehensively. Experimental results indicate that electric wire patterned PCB causes not only LED temperature but also affects the temperature difference between LEDs, and non-uniform temperature distribution. The maximum temperature deviation between wide and narrow wire patterns is approximate 26.3 degrees C for 2 x 2 LEDs. Novel correlations between maximum junction temperature and LED power density are proposed. The results obtained implicate that the electric wire pattern along with LED arrangement and HS size needs to be designed carefully in thermal management of SMD-LED packages.