Study On Preparation Technology And Properties Of Diamond/Ag Composites

With the development of electronic devices towards miniaturization,integration and high power,the current heat dissipation materials can no longer meet the requirements of high power devices,especially in the field of military electronic radar packaging.The high thermal conductivity of diamond/Ag composite can meet the heat dissipation requirements of high-power devices.However,due to the high equipment cost and complex preparation process of the current preparation method,it has become a research hot spot to prepare the diamond/Ag composite with low cost.In this paper,low-cost non-pressure infiltration and high pressure infiltration methods are used to study the properties and preparation process of composite materials,which also involve the analysis of raw materials,high-temperature damage analysis of diamond,etc.The main research contents and results are as follows:(1)The oxygen absorption phenomenon of silver,the volume ratio of diamond in different stacking modes and the heat transfer mode of composite materials were studied.The effect of pressure on the density of silver was investigated by die casting.The volume ratio of diamond under natural and vibration stacking conditions is compared.The heat transfer mechanism of diamond/Ag composite was studied.The experimental results show that the density and thermal conductivity of the silver block without pressure can be increased by11.4% and 41.4% by using the die casting process for the molten solidified silver.Compared with natural deposition,the volume ratio of diamond with different particle sizes is larger in vibration deposition.As the number of diamond mesh increases gradually,the volume ratio of diamond increases first and then decreases.The maximum volume ratio of vibrating diamond is 59.7% at 120 mesh,and the maximum volume ratio of natural diamond is 58.0% at 120 mesh.Electron and phonon are the modes of heat transfer in the composite.The heat transfer efficiency can be improved by increasing the volume ratio of diamond in the composite.(2)Diamond will undergo oxidation reaction at high temperature,resulting in mass loss.The residual ratio of diamond particles with different mesh sizes after burning at 1000 °C was investigated,and the effect of protective gas on residual ratio of diamond was analyzed.Finally,the diamond particles cauterized by protective gas were prepared into diamond/Al composite and the effect of cauterized diamond on the properties of composites was studied.The experimental results show that in the range of 40-1000 mesh,the larger the number of diamond mesh,the smaller the residual rate,and the minimum residual rate is 23%.The quality loss of diamond can be effectively reduced by introducing protective gas,and the residual rate of 40-320 mesh is above 90%.The thermal conductivity of diamond/Al composite prepared by high-temperature sintered diamond increases by 10.7%,which is due to the micro ablation of diamond surface caused by high temperature,which increases the surface roughness of diamond,which is conducive to the combination with metal liquid.(3)Study on the technology of diamond/Ag composite prepared by non-pressure infiltration method.The silver liquid penetrates into diamond particles only by its own gravity and capillary force,and the composite prepared by it has poor density and thermal conductivity of 173 W/(m·K).In the molten state,the silver atoms will be affected by its surface tension,which makes the silver atoms shrink into clusters with each other.Moreover,there is infiltration Angle between silver and diamond particles,and there are pores in the composite material,which greatly affects the thermal conductivity.(4)Formed a stable high pressure infiltration process route: mold loading-molten silver-casting-high pressure infiltration-cooling-stripping.The effects of different temperature,pressure and diamond particle size to volume ratio on the properties of composites were compared in high pressure infiltration.The results show that the optimum preparation parameters of high pressure infiltration are as follows: temperature 1050 °C,infiltration pressure 50 MPa,diamond particle size 40 mesh;The best properties of the composite prepared by high pressure infiltration are 630 W/(m·K)thermal conductivity and 5.7 ppm/K thermal expansion.In this paper,the technology of high pressure infiltration for the preparation of diamond/Ag composite was innovatively studied,and the mold and heating device were designed.The process is characterized by low cost,short preparation cycle,high efficiency and simple process,and the prepared diamond/Ag composite have uniform texture,high compactness,high thermal conductivity and thermal expansion coefficient suitable for the chip,which lays a foundation for the industrial production of diamond/Ag composite.