Study On Surface Stickiness Of Thermal Silicone Pads

Silicone rubber has perfect thermal resistance, viscoelasticity and electricinsulation. A kind of thermally conductive insulating thermal interface material can beprepared by mixing and heating the compound of vinyl silicone resins, hydrogensilicone resins, crosslinking agent and thermally conductive insulating inorganicpowders. Thermal silicone pad is one kind of the excellent thermal interface materialsand it has been widely used in electronic industry. But the reports about surfacestickiness of thermal silicone pads are still very rare. This paper selects five kinds ofthermally conductive inorganic fillers and four groups of silicone resins to fabricatethermal silicone pads. The resins are liquid addition-type silicone resins and the fillersare aluminium hydroxide and alumina which are low cost.Composition and chemical structure of silicone resins and particle size andmorphology of fillers have a great influence on mechanical property, heat-conductingproperty and surface stickiness of thermal silicone pads. So this paper analyzed thesilicone resins and inorganic fillers which were used to prepared the thermal siliconepads by a series of characterization methods. Microtopography, particle size, specificsurface area and crystal form of fillers were characterized by scanning electronmicroscope, laser particle size analyzer, BET specific surface area analyzer and X raydiffracmeter. The Structure, functional groups content, viscosity and molecular weightof silicone resins were characterized by Liquid nuclear magnetic resonancespectroscopy, rotational viscometer and gel permeation chromatograph.This paper investigated the effects of fillers, resins and crosslinking agent onmechanical property, heat-conducting property and surface stickiness of thermalsilicone pads. Focus on the influence of filler content and crosslinking agent contenton surface stickiness of thermal silicone pads and summarize the mechanism ofsurface stickiness. The peel strength was measured to characterize the bondingcondition between the thermal silicone pad and the release film. The results show that:The change of peel strength is not obvious when the content of filler is small. Butwith the further increasing of the filler content, peel strength increases first and thendecreases; Increasing the filler content helps to improve the heat conductivity coefficient of the thermal pads. The crosslinking density and elastic modulus of thethermal pads increase with the increasing of the content of crosslinking agent whenthe vinyl functional group content in the resin is excessed. The peel strength betweenthermal silicone pads and release film increases first and then decreases. In addition,filler content and cross linking agent content affect the peel strength between thermalsilicone pads and release film by influencing elastic modulus and surface tack of thepads.