Preparation And Properties Of Addition-cured Thermal Conductive Silicone Encapsulant

With the rapid development of electronic technology and electronic industry, electronic components tend to be smaller and smaller, of which the heat dissipation will affect the service life of the instrument and the stability of performance. Therefore, the thermal conductive polymer composite materials have attracted the attention of a great many people. The thermal conductivity of the polymer material itself is bad, by changing the molecular structur e to improve the thermal conductivity of the polymer composite materials is difficult and the cost is high. So, at present, the thermal conductivity of the polymer materials is improved both at home and abroad mainly through filling modification, adding inorganic filler of high thermal conductivity. Moistureproof, dustproof. shockproof, and good in heat resistance, electronic pouring sealant pouring sealant is widely used in the electronics industry.In the process of this topic research, taking vinyl silicone oil as matrix, orga- nohydrogenpolysiloxane as crosslinking agent, chloroplatinic acid-V4 as catalyst and SiC, Al2O3, SiCw, CNT as thermal conductive filler, by controlling the content and the particle size distribution of the filler and adding fibrous high thermal conductivity filler to improve the performance of thermal conductivity of pouring sealant, we produced composite of molding liquid pouring sealant of thermal conductivity. Through the material thermal conductivity, viscosity, scanning electro n microscopy(SEM), volume resistivity, dielectric constant, thermal stability, mechanical properties, characterization and analysis in the thermal conductivity, the dispersion in the matrix, electrical insulating properties, mechanical properties and thermal stability were tested. The results showed that:When SiC and Al2O3 are the thermal conductive fillers, with the increase of SiC and Al2O3, the thermal conductivity of silicone encapsulant are increased. When the SiC particles filler content was 33.3 vol.%, the thermal conductivity of the silicon reached 0.771 W/(m?k), which was improved by 370 % compared with pure encapsulant. When the Al2O3 particles filler content was 33.3 vol.%, the thermal conductivity of the silicon reached 0.750 W/(m?k), which was improved by 357% compared with pure encapsulant.SiC is better than Al2O3 in improving the thermal conductivity of silicone encapsulant. At the same time, the dielectric constant of the system increases, but the volume resistivity decreases; Adding SiC and Al2O3 can improve the thermal stability and mechanical properties of materials; Adding filler makes the silicone encapsulant viscosity rise. When the filler is more than 33.3Vol.%, the pouring sealant liquidity is poorer.Comparing different SiC particle size on the silicone encapsulant in the influence of the thermal conductivity of the composite material, the results shows that, under the same amount filling, the thermal conductivity of silicone encapsulant with large size particles filled is higher than the small diameter filling. With the increase of fillers, the viscosity of silicone encapsulant increases, and the growth rate increases with the increase of adding amount, and the smaller the particle size of the SiC is, the bigger the influence on silicone encapsulant is. The tensile strength and hardness of the composites increases but elongation at break is gradually reduced. Under the same content, the smaller the filler particle size is, the greater the tensile strength of composite material is and the higher the elongation at break is. When 15μm and 30μm SiC filled with different mixing ratio, the thermal conductivity and mechanical properties of composite material is higher than the single filler.Then we discuss the effect of SiC w and CNT on thermal conductivity of silicone encapsulant. When the amount of SiCw is 12 Vol.%, the thermal conductivity of the the silicone encapsulant increases from 0.473W/(m·K) to 0.577W/(m·K), increases by 22%; When the amount of CNT is 0.38 Vol.%, the thermal conductivity of the silicon reaches 0.525W/(m?k), increases by 10%. What can be seen from the SEM figure are as follows. the fillers are uniformly dispersed in the matrix, and the mechanical performance are greater than those not added. On the other hand, CNT is a good conductor of electricity, because of the adding quantity is not high, the volume resistivity of the silicone encapsulant composite material is low, but the insulation performance of composite materials is better.The stability properties of the silicone encapsulant composites is superior to the pure silicone encapsulant, and the higher the filler’s volume fraction is, the better the thermal stability is.