Preparation And Performance Of Silicone Materials For LED Encapsulation

Light-Emitting Diode(LED)has become one of the fastest developing industries in the field of new energy.LEDs have attracted great attention owing to their outstanding features,such as low power consumption,long service life,versatility of multi-colors,environmental friendliness and high luminosity at low current and voltage.With the continuous development of the manufacturing technology,the performance of LED packaging materials,such as optical properties(refractive index,light transmittance),high temperature resistant,mechanical properties,bonding performance and so on,is put forward higher requirements.The shortage of research and application about high power LED packaging materials in domestic market severely restricts the development of LED industry in our country.Based on this situation,this paper studies the thermal properties of the addition curing silicone resins to obtain high performance for LED packaging materials.The addition curing liquid silicone resins become an ideal material for LED encapsulation because of their excellent thermal resistance,aging resistance and high transmittance.In order to investigate the changes of mechanical properties,transmittance and adhesive properties of LED packing materials at high temperatures,addition curing liquid silicone resins with low refractive index,medium refractive index and high refractive index were prepared through the design of formula in the paper.And the mechanical properties,transmittance and adhesive properties after aging at high temperature have been characterized.The test results of addition curing liquid silicone resins with different refractive indexes in the process of aging have certain theory value and application value.Fumed silica can be used to enhance the mechanical properties and heat resistance for silicone resins.And the addition of organic phenolic antioxidants can also greatly improve the thermal resistance of the liquid silicone resins.Adding a small amount(0.5%)of organic phenolic antioxidants to the low refractive index LED encapsulation materials can effectively inhibit the pyrolysis reaction of free radicals for silicone resins without affecting their mechanical properties,light transmittance and adhesive properties,and improve its anti-aging ability.A highly anti-thermal aging silicone oil was synthesized by hydrolysis and co-condensation method from dimethoxydiphenylsilane,octamethylcyclotetrasiloxane(D4)and 2,4,6,8-tetramethylcyclotetrasiloxane(D4H),and used to prepare anencapsulation material for high-power LED-filament.The cured silicone materials were characterized by thermogravimetric analysis(TGA)and thermal aging test under180 °C and 250 °C.The results demonstrated that the thermal stability of the cured silicone resins with short-chain phenyl silicone as a crosslinker was higher than that with long-chain methyl silicone oil crosslinker.Owing to the excellent thermal stability,appropriate hardness,high transparency and photoelectric efficiency,this LED encapsulation material is a promising candidate for high-power LED package.