Rapid calculation method to evaluate thermal management of LED systems based on an improved multi-layer model

Abstract

An improved laminated structure model of LED systems is proposed. Besides the light-emitting diode (LED) chip, printed circuit board (PCB) substrate, heat sink, etc, additional interface layers are applied to model the non-ideal surface of thermal interface materials (TIMs). And a rapid calculation method is developed for temperature-related calculations. Through comparisons, the method is proved to be valid, and the execution time can be greatly reduced. It is found that the air gap at the TIM surface does hinder heat conduction but the effect is not obvious. The influence of LED chips on system thermal management is comprehensively analyzed. For a single LED chip, the junction temperature shows a linear relationship with its thermal resistance and heat power. The chip size, as well as the aspect ratio between the chip and the PCB substrate, has great effects on the junction temperature. For a multi-chip array, the impact of the chip quantity is suggested to be considered combined with the chip layout. The mutual thermal interaction among LED chips is of most concern, which will become more serious with an increasing number of chips. The work provides a rapid and flexible evaluation method for thermal management of LED systems.