Research On High-performance Silicone Resins For LED Packaging

High-power light-emitting diodes (LEDs) have attracted great attention from scientists and engineers worldwide in recent years owing to their many desirable advantages, including long lifespan, low energy consumption, small size, high efficiency, and environmentally friendly characteristics. High power LED, especially the white LED excited by a ultraviolet ray or a near-ultraviolet ray, has higher luminescence intensity, but it also produces more heat and stronger short-wavelength radiation, meaning that the lifetime of high power LED tends to be easily shortened by UV and heat radiations. Therefore, the packaging materials for high power white LED should possess high UV light shielding efficiency to prevent the leakage of ultraviolet light, while maintaining high visible light transparency, high thermal conductivity and ultraviolet irradiation resistance.Silicone resins show a great potentiality for high power LED packaging owing to their outstanding integrated properties such as very low ionic impurities and moisture absorption, a wide range of service temperature, and stable thermo-optical property; however, their thermal conductivity and ultraviolet irradiation resistance need to be improved to completely meet the requirements of high power LED. This thesis includes two parts of investigations.First, in order to develop a new kind of transparent packaging material for LED chips with high UV-shielding efficiency, new transparent ZnO/silicone nanocomposites with outstanding integrated properties were designed and prepared, and the integrated properties of the ZnO/silicone nanocomposites were systematically investigated. Results show that the integrated properties of composites are closely related with the size, content and surface nature of ZnO. The organic nano-ZnO prepared by 3-methacryloxypropyltrimethoxysilane can increase the dispersion of nano-ZnO in silicone resin, and improve the interfacial adhesion between inorganic and organic phases. Besides,the increase of the content and size of ZnO in composites can endow the composites with high thermal conductivities and UV light shielding efficiency but lower visible light transparency, so there is an optimum content and size of ZnO in composites to obtain the best integrated properties. Specifically, the nanocomposite containing 0.03 wt% nano-ZnO(K) with an average size of 46±0.4 nm not only has high visible light transparency, UV light shielding efficiency and thermal conductivity, but also possesses low dielectric constant and loss, meeting the requirements of high performance electronic packaging for high power LED.Second, in order to find the possibility whether"new packaging materials"can replace the"traditional phosphors + packaging materials", ZnO quantum dots (ZnO-QD) with about 3 nm particle size were successfully synthesized, and transparent ZnO-QD/silicone nanocomposites were subsequently prepared via in-situ polymerization. The integrated properties of composites are closely related with the size, content and surface nature of ZnO-QD. The ZnO-QD/silicone nanocomposites show outstanding integrated properties, and a broad fluorescent emission peak at 520 nm are observed, and the intensity of the fluorescent peak increases monotonically with increasing the content of ZnO-QD.