Preparation And Properties Of Thermal Conductive And Transparent Silicon Encapsulant

Silicone material has excellent flexibility, heat and ultraviolet aging resistance, whichgradually replaces epoxy resin and is a new generation of LED packaging material. Based onthe rapid development of GaN-based and power-type white LED, more strict requirements onthe performance of LED encapsulant are suggested. So LED encapsulant needs to havefavorable mechanical properties, adhesive properties and thermal conductive properties.Currently thermal conductive insulation silicone encapsulant is often prepared by fillingthermal conductive filler, which will greatly affect the transparency of encapsulant. Therefore,emphasis and difficulty of this topic is that silicone encapsulant must have excellent thermalconductivity and transparency.This topic is aiming at the development of power-type LED and studys structuralcharacteristics of vinyl silicone oil and hydrogen-containing silicone oil, compatibilitybetween vinyl silicone oil and reinforcing filler, type of tackifier and so on. Then siliconeencapsulant with favorable mechanical properties, optical properties and adhesive propertiesis prepared. In addition, the effect of VMQ silicone resin, nano-silica, tackifier etc. onproperties of encapsulant is studied. On this basis, this paper prepares silicone encapsulantwith favorable mechanical properties, optical properties and thermal conductive properties byfilling nano-alumina and nano-zinc oxide. Moreover, the effect of nano-particle, couplingagent etc. on properties of encapsulant is studied. The main research contents andachievements as following:Firstly, LED silicone encapsulant was prepared and has the best performance when themass ratio of vinyl-terminated silicone oil with viscosity of19mPa·s and3000mPa·s is8/100, the mass fraction of Si-H group of hydrogen-containing silicone oil is0.8%, the molarratio of Si-H/Si-Vi is1.2, the amount of VMQ silicone resin is30phr and the amount ofnano-silica modified by KH-570.Secondly, tackifier DA, DAVE and DAVM were synthesized by allyl glycidyl ether,tetramethylcyclotetrasiloxane, vinyl-trimethoxy-silane and vinyl-triethoxy-silane. LEDsilicone encapsulant with tackifier DAVM is prepared and has the best adhesive propertiesand optical properties. Thirdly, thermal conductive and transparent silicone encapsulant was prepared byfilling nano-alumina and nano-zinc oxide modified by coupling agent. With the increase in theamount of modified nano-particle, encapsulant’s thermal conductivity and refractive indexhave a gradual rise. Furthermore, its heat aging resistance has improved greatly. However,transparency, CTE and volume resistivity of encapsulant decrease gradually. Considering therequirement of optical properties and thermal conductive properties, LED siliconeencapsulant has the best performance when the amount of nano-alumina modified by KH151is0.75phr.