Stress analysis of LED bulb under thermal and humid environment

LED luminaires is wildly used in global. In the heat and wet condition, the LED bulb is easy to failure. But the thermal and humidity stress in it is seldom studied. In terms of LED devices, study on the thermal and humidity reliability was on the thermal or humidity diffusion simulation, as well as material thermal or wet expansion stress. Coupling of heat-moisture study is few. In this paper, finite element software is used to simulate the steady-state thermal distribution and thermal stress distribution of LED bulb. Also simulate the humidity diffusion of LED bulb stored under 60°C/60RH environment for 168h. Couple the temperature field and the wet field by Klapper Long equation and calculate the vapor pressure. The result proves that the stress generated by the vapor pressure is low but is still important. The thermal stress generated at the edge of substrate which is likely to cause poor contact. The vapor pressure generated at the edge of chip which is likely to cause chip crack or poor contract. That will lead to the lighting fade. Air tightness for the body and the shade of LED bulb is very important.