Sulfur-Rich Ageing Mechanism of Silicone Encapsulant Used in LED Packaging: An Experimental and Molecular Dynamic Simulation Study

In a light-emitting diode (LED) package, silicone encapsulant serves as chip protector and enables the light to transmit, since it exhibits advantages of high transmittance, refractive index, thermal stability. However, its reliability is still challenged under harsh operation conditions. this study, optical mechanical properties encapsulant, including appearance, Young’s modulus, tensile strength, were experimentally monitored during sulfur-rich ageing process. Meanwhile, Fourier transform infrared (FTIR) spectroscopy molecular dynamics (MD) simulation used reveal degradation mechanism. The results show that 1) in sulfur (S 8 )-rich process, severe vulcanization reaction occurred assisted only by temperature moisture, with existence H 2 S product O vapor. 2) Vulcanization characterized formation sulfhydryl (-SH) group lowered both encapsulant. 3) hydrolysis featured hydroxyl (-OH) decreased performances but brought slight harm performances.