Studies On Adhesion Enhancement Of Flame Retardant Thermal Conductive Silicone Encapsulant

The characteristics of addition-cured liquid silicone rubber are that no by-products wereproduced in the process of sulfide, minimum contractibility rate,deep vulcanization.Therefore,as ahigh grade glue,addition curing liquid silicone rubber has higher product technology content,and added value, rapidly developed in recent years.However, in the practical application，theliquid silicone rubber exists deficiencies, such as the poor bonding capacity of the othermaterials,poor thermal conductivity, flammability.These shortcomings make the liquidsilicone rubber extremely restricted in applications,including potting of electroniccomponents, materials bonding, solar module encapsulation.Based on retrieving at home and abroad researches on the liquid silicone rubberapplicated in electronic potting, this article infiltrated by blending the epoxy group-containingsilane homemade adhesion promoter, thermal conductive filler alumina, flame retardant filleraluminum hydroxide, and investigated the influence of adhesion promoter on the propertiesof the thermal conductivity flame retardant silicone rubber.We prepared the thermalconductivity and flame retardant electronic encapsulants with bonding, and discussed themechanism of enhancing the adhesive performance of the silicone.The main researchcontents and achievements as following:Firstly, we selected a vinyl trimethoxy silane （A171）, γ-methacryloxypropyl trimethoxysilane coupling agent （KH570）, γ-glycidoxypropyl trimethoxy silane （KH560） asenhancer,and produced homemade bond enhancer by hydrolysis condensation with A171andKH560. We studied the effect of these bonding enhancers on the performances of thesilicone.The results showed that A171and KH570were able to substantially increase theadhesive performance of the potting.When the amount of the two was1.8%wt, potting shearstrength was up respectively to0.85MPa,0.88MPa, while KH560could not significantlyimprove the potting adhesive performance;when the amount of the homemade bond enhancerwas0.6%wt, the potting shear strength was up to0.58MPa, so that homemade enhancersreduced the amount of bonding, and laid the foundation for the preparation of highperformance bonding enhancer. Secondly,we selected acrylate-2-hydroxyethyl acrylate （HEA）, tetraethyl orthosilicate（TEOS） and KH560as raw materials, and enhancer vinyl/ester group/epoxy group-containingadhesive and enhancer B containing ethyleneyl/ester/alkoxy were prepared by thetransesterification reaction.The results showed that bonding enhancer A was significantlybetter than the same amount of bonding enhancer B,and when the amount of the promoterwith epoxy group was0.6%wt, shear strength was1.21MPa, increased by670%than thatwithout adhesion promoter.Finally,based on the heat conductive filler Al₂O₃, flame-retardant filler Al（OH）₃and theamount of fixed displacement m （Al₂O₃）/m（Al（OH）₃）=140:60,we studied that the effect ofthe amount of bonding enhancer A on performances of this thermal conductivity retardantsilicone encapsulants.The results show that the enhancer A basically has not effect retardantproperties of the potting, thermal conductivity first increased and then decreased with theincrease of the amount of the enhancer; when the amount of the enhancer was0.4%wt, theshear intensity of the potting reached a maximum, which was1.50MPa.