Preparation And Properties Of High Thermal Conductivity And Insulating Grease

With the miniaturization, efficient and the demand of electronic components cooling of the electronic products rising, it requires a thermally conductive material with superior thermal conductivity and insulation properties. Due to thermal grease does not thicken at low temperature, unchanged dilute at high temperature, and non-volatile, non-curing, also can be long-term grease state at a temperature of -50 ℃～+230 ℃, be adapted to different thermal interface and easy coated, easy clean up late, it is widely used between electronic components and the heat radiating plate or heat sink.Therefore, the development of good thermal conductivity and insulatiing grease has high practical significance.The high-temperature insulating silicone grease was prepared by using polydimethyl siloxane as substrate, using methyltrimethoxysilane(JHN311) as coupling agent, andusing Al2O3, ZnO, SiaN4 BN, AlN, carbon nanotubes and homemade Al2O3-AIN as filler, adjusting the component ratio of each experimental group, filtering fillers at a lower cost. The main contents are:(1) The type and content of coupling agent effect for the surface of thermally conductive filler was researched, filler treated by silane coupling agent effect the performance of thermal grease, and coupling effect.The results showed that:a silane coupling agent JHN311, the optimum amount is 1.3%, surface treatment work is best, after the filler surface-treated, sedimentation rate and permeability status of thermal grease condition is very good, the thermal conductivity of thermal grease composite materials is improved.(2) Studying the impact of different thermally conductive filler complex to the performance of thermal grease, including complex Al2O3 and ZnO, Al2O3 and AlN mixed complex, irregular alumina complex, spherical alumina complex. As filler obtainedincreasing, the viscosity and thermal conductivity of thermal grease is also increasing; the ratio of 3 μm irregular alumina and alumina 10 μm is 2:8, the highest thermal conductivity grease is 1.360 W/(m·k); The size ratio of 3 μm spherical alumina and alumina 10 μm is 4:6, the largest thermal conductivity grease is 1.089W/(m·k).(3) The same mass fraction of Al2O3-filled, amorphous Al2O3 were higher than sphere Al2O3 on thermal conductivity and viscosity amorphous, but amorphous Al2O3 was difficult to reach highly filled; the 70 μm Al2O3 was beneficial to higher thermal conductivity and lower viscosity than small particle size filler. When the filling fraction of hybrid Al2O3 was 92%(wt), the thermal conductivity reached 3.98 W/(mk), the viscosity was 20000 mPas, and the volume resistivity reached 9.13×1016Ωcm, which showed high thermal conductivity and good flow properties.(4) It studies the preparation of thermal grease filled by homemaded spherical alumina-aluminum nitride powder, and successfully prepared spherical alumina-aluminum nitride powder, diameter is about 14.153 μm; The resulting manufacture alumina-aluminum nitride powder replace 10 μm of Al2O3 in the Al2O3 70 μm:10 μm:3 μm:1 μm ZnO= 2.1:2.94:1.96:3 to prepare thermal grease, the thermal conductivity reached 4.35 W/(m·k), the viscosity was 35000 mPa·s, and the volume resistivity reached 3.16 × 1015Ω·cm.