Moisture diffusion and integrated stress analysis in LED module

The moisture diffusion phenomenon and moisture stress in a specific LED module was studied in this paper. Firstly, the finite element model of the LED module was built. The moisture diffusion distribution at operation condition with 25°C ~ 85°C, was analyzed. Secondly, the temperature distribution and moisture distribution of the LED module during reflow soldering process were simulated at the initial moisture condition of 85%RH. The thermal stress, moisture stress were analyzed, respectively. The simulation shows that maximum thermal stress in the LED module was 30.1 MPa and the maximum moisture stress was 7.8 MPa. Furthermore, integrated vapor pressure, moisture stress and thermal stress modeling of LED module during reflow were established. The resulting maximum integrated stress was up to 178 MPa. Thirdly, a curing process at the condition of 125°C which was assumed to dry out the moisture in the LED package before reflow process was modeled and the corresponding moisture diffusion distribution was obtained.