Improvement of thermal and optical behavior of multi-chip LEDs package

Abstract

Thermal management of light emitting diodes (LEDs) packages is indispensable to maintain lower operating temperature. The present paper reports a numerical analysis of 45W LEDs module. Two forms of substrate and chips are compared. Results show that circular chips mounted on circular substrate provide lower junction temperature of the package thanks to the elimination of slide effects. Moreover, the disposition of chips is studied. In fact, junction temperature decreases by 8.72% when the pitch increases from 1 to 14 mm in the rectangular design, and it decreases by 7.46% when increasing the pitch from 1 to 12 mm in the circular design. However, it is found for both rectangular and circular configurations that the chips spacing causes a temperature difference between chips of the same package. The latter does not affect the light output but it causes a significant difference of chips lifetime: a difference of 1354 h between central and outer chips is noted with rectangular configuration, and 1331 h with circular configuration. This may cause a drop of the light output of the lamp when central chips fail and result in an optical discomfort for users.