Manufacture And Performance Of Flowing,high Thermal Conducting And Insulating Silicone Grease

The trend of microprocessor chips in electronic devices continuing to get smaller and smaller dramatically increases the problem of heat accumulation in electronic circuits.The large amount of heat generated during manufacturing will directly affect the reliability and service life of electronic devices if not released in time.The contact surface between the electronic and electrical components and the heating elements and heat dissipating devices which are coated with interface thermal conductive material plays an important role in solving the problem of heat accumulation in the electronic and the electrical devices.At present,the main types of interface thermal conductive materials include thermal grease,phase change materials,polymer filler materials,and carbon-based composite materials.The thermal grease has the advantages of excellent thermal conductivity,good insulation performance,good stability and reliability.Meanwhile,it’s easy to be processed and smeared,easy to be cleaned later,and is able to be maintained the grease stage under a working temperature of-50°C～250°C for a long time.Besides,it has great adaptability with different thermal interfaces.All these advantages make it become an ideal choice for interface thermal conductive materials.In the actual application process,to meet the needs of being exposed to the surface void under low pressure conditions,the thermal grease will minimize the thermal resistance between the contact surfaces and reduce the amount based on the premise of filling the gap between contact interfaces.It is also expected with as good fluidity as possible.Therefore,manufacturing a kind of flowing,high thermal conducting and insulating thermally conductive silicone grease has a highly practical value.Based on a polymer matrix with simethicone and surface treatment with γ-（methacryloxy）propyltrimethoxysilane KH-570 to the powder,this research studied on the effect of different types,dosages and compounding relationships on the performances of thermal grease.After comprehensively analyzing the testing results and relations between the formulation and the performances of silicone grease,a flowing thermal grease with both high thermal conductivity and insulation is generated thereby.The main contents of this research include:（1）It studied the effect of coupling agent in thermal conductive filler on the performances of thermal grease.The results show that the coupling agent KH-570 （γ-（methacryloyloxy）propyltrimethoxysilane）with the mass fraction of 1%can effectively improve the oil leakage of the thermal grease,and has the best effect on the thermal conductive filler.（2）It studied the effect of the particle size and morphology of the filler on the performances of thermal grease.The results show that the thermal coefficient produced by the angular Al₂O₃is normally higher than that of the spherical Al₂O₃at any of the same additional amounts.The angular Al₂O₃is difficult to achieve high filling capacity.The spherical shape has better fluidity than the non-spherical particles.The fluidity of the low surface area particles are better than that of the high surface area particles.And the large particle size filler has a higher thermal conductivity than the small particle size filler.（3）It studied on the effect of Al₂O₃and different fillers on the performances of thermal grease including the combination of spherical Al₂O₃with different compounding particles,and the combination of spherical Al₂O₃and Al N,BN,Si C,graphene,Al powder and Cu powder.It concluded that the optimal compounding ratio between spherical Al₂O₃is 6:3:1.When m（30μm）:m（5μm）:m（2μm）=6:3:1,the proportion of oil powder is 1:8.The ratio of thermal conductivity of the silicone grease is 2.21 W/（m·k）and the viscosity is 30900 m Pa·s.The Al N with a 20%proportion of the whole additional materials can increase the thermal conductivity and reduce the viscosity of the silicone grease meanwhile.The oil permeability of the silicone grease is greatly improved after adding Zn O.The AIN with a proportion of 3%of the whole additional materials can reduce the viscosity of the silicone grease and make the fluidity better.Besides,the graphene and Al₂O₃have a synergistic effect.Therefore,adding graphene with a proportion of 1%of the total filler content can significantly increase the thermal conductivity of silicone grease.Through the above researches,a flowing,high thermal conducting and insulating thermally conductive silicone grease is finally produced with the quality proportio of dimethyl silicone that is 2μm Zn O:5μm Al₂O₃:40μm Al₂O₃:2μm Al N:2μm Al,graphene=10.33%:7.23%:21.69%:43.39%:14.46%:2.17%:0.73%.It’s with a 3.46 W/（m·k） thermal conductivity,a 36700 m Pa·s viscosity,and a 1.67×10 14Ω·m volume resistivity.The silicone grease has excellent fluidity which satisfies the requirements of coating process of screen printing and thereby effectively controls the thickness of the thermal grease to achieve a more uniform and effective heat dissipation effect.