Study On Preparation And Properties Of Diamond Filler Thermal Conductivity Adhesive

In order to improve the internal heat dissipation of electronic equipment,it is necessary to use thermal conductivity adhesive to connect the heat dissipation electronic components with the heat dissipation device,and transfer the heat to the outside world through the heat dissipation device.At present,there are problems of low thermal conductivity and poor aging resistance in thermal conductivity adhesive products.In this paper,diamond micropowders were used as filler.By etching and modifying the surface of the diamond micropowders,the filling amount of the filler and the binding effect between the filler and the matrix were improved,and the thermal conductivity of the thermal conductivity adhesive was improved.In this experiment,sodium silicate and epoxy resin were used as thermal conductivity adhesive matrix,and the variation rule of thermal conductivity adhesive performance was studied by comparing the two as thermal conductivity adhesive matrix.Diamond micropowders with D₅₀ of 10μm,20μm and 60μm were used as fillers.Diamond micropowders with D₅₀ of 60μm were etched to increase the specific surface area.The surface modification of diamond micropowders with silane coupling agent was carried out.The diamond micropowders of different particle sizes were added into two different matrixes according to different mass ratio.The effects of surface etching,surface coupling,different particle size ratio,different diamond micropowders content and other factors on the properties of different matrix thermal conductivity adhesives were studied.The effect of lignin addition on the anti-aging property of epoxy resin was also studied.The results of the study are as following:（1）The surface etching degree of diamond micropowders are related to temperature and holding time.When the diamond micropowders are held at 950℃for 60 min,the surface etching degree of the diamond micropowders is moderate,which is the most suitable for the thermal conductivity adhesive filler.The surface modification effect of silane coupling agent on diamond micropowders is related to the PH value during hydrolysis of silane coupling agent.When PH value is 4.5,the silane coupling agent has the best surface modification effect on the diamond micropowders,and the coupling agent is uniformly grafted to the surface of the diamond micropowders.The thermal conductivity adhesive prepared by sodium silicate matrix has better aging resistance than epoxy resin based thermal conductivity adhesive.When 5 wt.%lignin is added,the weight loss rate of epoxy resin is reduced by 15%,and the anti-aging property is improved.（2）The thermal conductivity and bonding properties of the thermal conductivity adhesive are better when diamond micropowders of different particle sizes are mixed than that of single particle size diamond micropowders.D₅₀ different diamond micropowders are mixed and filled according to the mass ratio of 60μm:20μm:10μm 6:2:1,the thermal conductivity of the thermal conductivity adhesive is the best.When the content of diamond micropowders is 50 wt.%,the thermal conductivity of the thermal adhesive prepared by sodium silicate matrix is 3.23 W/（m·K）.After the diamond micropowders were etched,the maximum bonding strength of the thermal conductivity adhesive prepared by sodium silicate matrix and the thermal conductivity adhesive prepared by epoxy resin matrix increased by 23.7%and 15.7%respectively,and their maximum thermal conductivity increased by 80.5%and86.9%,respectively.After diamond micropowders coupling treatment,the bonding strength of the thermal conductivity adhesive prepared by sodium silicate matrix and epoxy resin matrix increased by 2.6%and 6.8%,respectively,and their thermal conductivity increased by 8.4%and 11.6%,respectively.（3）With the increase of diamond micropowders content,the curing temperature,insulation properties and thermal stability of the thermal conductive adhesives prepared by the two matrixes were improved.But the thermal conductivity,density and thermal expansion coefficient all showed a trend of increasing first and then decreasing.However,the changes in the bonding properties of the thermal conductivity adhesives prepared by the two matrixes are different.The bonding properties of the thermal conductivity adhesives prepared by the sodium silicate matrix first increase and then decrease,while those prepared by the epoxy resin matrix gradually decrease.（4）When the diamond content is 50 wt.%,the thermal conductivity of the sodium silicate based thermal conductivity adhesive reaches the optimal value of 6.32 W/（m·K）.When the diamond content is 60 wt.%,the tensile shear strength of the thermal conductivity adhesive is 1.98 MPa,and the bonding performance is the best.When the diamond content reaches 80wt.%,the thermal conductivity of the thermal conductivity adhesive prepared by epoxy resin matrix is the highest,and the thermal conductivity is 5.234 W/（m·K）.At this time,the bonding property is still good,and the tensile shear strength is 3.52 MPa.The research shows that the thermal conductivity of the thermal conductivity adhesive prepared by sodium silicate matrix is better than that prepared by epoxy resin matrix,but the bonding and insulation properties of the thermal conductivity adhesive prepared by sodium silicate matrix are lower than those prepared by epoxy resin matrix.