Study On Preparation And Modification Of One-component Silicone Resin For LED Encapsulation

As a power LED packaging material,silicone resin has many advantages such as high light transmittance,good thermal stability,small thermal expansion coefficient,UV resistance and heat aging resistance,now it is one of the research hotspots in power LED encapsulation field.Different from the traditional two-component silicone resin research,in this thesis,a polyphenyl silicone resin containing both vinyl and hydrosilyl groups was designed,and a type of one-component silicone resin synthesized by hydrolysis and condensation reaction was cured to work as a power LED packaging curing silicone resin material.In the process of preparation,the synthesis process was optimized,and the curing behavior of the one-component silicone resin was also studied.At the same time,the silicone resin was modified by inorganic nano-oxides.Lastly,the prepared silicone resin basically meets the performance requirements of power LED packaging materials.The specific contents and achievements of this thesis are as follows:1)Using strong acid cation-exchange resin as the catalyst,vinyltrimethoxysilane(VTMS),diphenyldimethoxysilane(DPDS)and methyldiethoxysilane(MDES)as monomers,dimethyl dimethyl(DMDS)as chain extender and hexamethyldisiloxane(MM)as blocking agent,the target product was synthesized by heated hydrolysis and water-separation polycondensation in ethanol water.In this way,the influences between the addition amount of catalyst,DPDS,DMDS,solvent,the hydrolysis time and temperature,the water-separation time,blocking agent addition time and the refractive index,viscosity,monomer conversion rate of silicone resin were studied and optimized by single factor experiments.Tests on the clear and transparent one-component silicone resin indicated that the viscosity was about 1200 mPa · s,the refractive index was greater than 1.52,and the monomer conversion rate was not less than 85%.2)Using Karstedt catalyst as curing agent,n-level dynamical model was established.The non-isothermal DSC method was used to study the curing dynamics of four kinds of single-component silicone resin systems at different heating rates.The curing characteristic temperatures and reaction dynamical parameters were obtained.According to the curing characteristic temperatures,the curing gel behavior and the curing shrinkage and internal stress characteristics,the curing operation ladder temperature program of one-component silicone resin was set as 100?/lh and 140?/2h and 160?/0.5h.3)Three kinds of modified inorganic nano-oxides including silica,titania and lanthanum were respectively added into the single-component silicone resin with different contents.And the optical property,the thermal stability,mechanical property and resistance to liquid erosion of modified silicone resin systems were studied through horizontal and vertical comparative analysis.The addition of modified filler kept the silicone resin transparent with a high refractive index of 1.52 or more,and increased the thermal failure temperature of silicone resin systems by 74?82 ?,the maximum tensile load was 8.73?12.45MPa,the maximum elongation at break was 1.54?2.86%,the Shore hardness was over 52HD,the performance of resistance to acid,alkali and water erosion decreased slightly,but all the silicone resin systems maintained good hydrophobicity.Finally,the modified single-component silicone resin was in conformity with the performance requirements of high-power LED packaging materials.