Research on test method of thermal resistance and junction temperature for LED modules

Until now, there has not yet been a standardized method for the LED module thermal resistance measurements. This directly affects the lifetime assessment of the LED modules. By testing and studying the temperature coefficient of the LED modules with different structures, it is found that the temperature coefficient of the LED module follows a linear relationship with voltage when an appropriate test current is applied. In this paper, we investigate the feasibility of measuring the thermal resistance of the LED module as a whole. Furthermore, we propose a method to estimate the junction temperature of the LED module based on the thermal resistances of each of its individual LED and the module itself. This method provides an important basis for the junction temperature calculation in the assessment of the lifetimes of the LED module. However, since the LED module usually has a large surface, the uncertainties existing in the materials and fabricating process will result in a distributed temperature within the LED module. And in most cases, the first failure occurs in the chip with the highest junction temperature. Therefore, the next step of our research will focus on the evaluation of the maximum junction temperature of the LED module based on the proposed method.