FE analysis of cure-process-induced residual stress in light emitting diode encapsulant silicone resin considering mechanical property evolution

The silicone resin recently attracts great attention as the high power LED encapsulant material due to the good thermal stability and the optical properties. However, there have been only a few reports for the silicone resin mechanical properties which are necessary for evaluating the thermo-mechanical behavior during the curing and cooling of silicone resin. In the present investigation, the cure kinetics model for the silicone resin was evaluated based on the DSC (Differential Scanning Calorimetry) test and applied to the FE analysis of the curing for predicting the cure-process-induced shrinkage and the residual stress. In addition to the curing, the FE analysis of the cooling was conducted to predict the thermal residual stresses and strains. Based on the experimentally measured surface profile of the fully cured silicon resin, the actual elastic modulus was examined as a function of DOC (Degree of Cure). FE simulation result implies that the process of the curing as well as the cooling should be designed carefully so as to reduce the residual stresses and strains although the cooling plays the bigger role than the curing in determining the final residual stress. It is supposed that the FE analysis of the cure process, composed of the curing and the cooling, can be utilized to predict the residual stress-induced optical property degradation (e.g., birefringence) as well as the mechanical problems (e.g., warpage) in the silicone resin encapsulant.