Numerical analysis of temperature and humidity effects on the reliability of high power light emitting diode

High power light emitting diode (HP-LED) as solid-state Lighting (SSL) is a promising light source, and one of the important factors for its wide acceptance is its reliability. [1]Temperature and humidity are two key factors which affect the reliability of HP-LED. Based on the three-dimension model of Multi-chips integrated module LED (MCIM-LED), the effects of temperature and humidity on the reliability of HP-LED are numerically investigated in this paper. The status of thermal conduction and humidity diffusion and the distribution of thermal stress and humidity stress are obtained by the simulation of thermal and humidity respectively. The temperature field reaches equilibrium state in short time, while the stable time of humidity field is dozens of day. In the normal working status, the humidity stress is less than the thermal stress. The results suggest that thermal stress plays a dominant role can be used for the further study on the effects of thermal-humidity coupled on the reliability of HP-LED.

1 Introduction

High power light emitting diode (HP-LED) is generally considered to be the light sources for the new generation illumination. HP-LED, which offers many advantages over the conventional light sources, such as lower power consumption, faster response time, better spectral purity, environment friendly and so on, has been widely used in car taillights, LCD backlight and lighting area.[2] However, the reliability of HP-LED should be improved in order to implement semiconductor illumination. Otherwise the application of HP-LED will be restricted by the high maintenance cost. Temperature and humidity are two key factors which affect the reliability of HP-LED. The luminous efficiency and lifetime of HP-LED significantly decrease with increasing working temperature. So the temperature should be controlled below a certain value. In the air, the relative humidity (RH) changes frequently, and some HP-LED packaging materials which consist of macromolecules may absorb the moisture. The moisture diffused into the packaging structure will cause multiple problems. [3] So studying on the impacts of temperature and humidity on HP-LED is good for the reliability of HP-LED