Preparation And Performance Control Of Cu Based Composites With High Thermal Conductivity And Electrical Insulation

At present,chips are developing towards miniaturization,integration,high efficiency and intelligence,how to improve the thermal conductivity of packaging substrate has become an urgent problem.In order to obtain substrate materials with high thermal conductivity and electrical insulation,this paper attempts to use mechanical ball milling method to coat insulating materials on the surfaces of Cu particles with high thermal conductivity,and then spark plasma sintering technology is used to prepare Cu based insulating composites with high thermal conductivity.By selecting different insulating coatings and adjusting process parameters,the performance of the composites is controlled.The research results are as follows:Four kinds of Cu based composites were prepared by mixing micron Cu powders with four kinds of nano insulating powders(Si C,MnO₂,Mg O and Al₂O₃,respectively)by ball milling and spark plasma sintering.Under the condition of the same mass ratio,the microstructures of the four composites were investigated,and it was found that the coating effect was quite different.Si C and Mg O could not be effectively coated on the surfaces of Cu powders due to their high brittleness and low interfacial adsorption,so the prepared Cu based composites had high thermal conductivity,but poor insulation.Although MnO₂ can be uniformly coated on the surface of Cu particles,the intrinsic resistivity of MnO₂ is low,which leads to poor insulation effect for the MnO₂/Cu composites.It is worth noting that the Al₂O₃/Cu composites also had an obviously uniform coating layer,and the electrical insulation of Al₂O₃ is excellent,so the prepared Cu based composites had high thermal conductivity and high insulation characteristics,which had the prospect of further exploration and application.Using micron Cu powders as matrix and nano Al₂O₃ powders as coating material,the effect of different Al₂O₃ content on the microstructure,electrical resistivity and thermal conductivity of the composites were studied.The results showed that the insulation layer thickened with the increase of Al₂O₃ content,and the resistivity increased continuously,while the thermal conductivity decreased.It is worth noting that when the content of Al₂O₃was more than 15.0 wt%,most of the Cu powders were separated by Al₂O₃,which greatly improved the resistivity of the composites while it exhibited high thermal conductivity.The effect of sintering temperature on the properties of the composite was studied by using the composite powders with 15%w(Al₂O₃)as the research object.It was found that the resistivity of the composites decreased with the increase of sintering temperature,while the thermal conductivity increased.Finally,the electrical/thermal properties of the sintered samples prepared by pre cold pressing and non-cold pressing are compared.The resistivity of the sintered samples prepared by the former was obviously lower than that of the sintered samples prepared by the latter,while the thermal conductivity was higher than that of the samples prepared by spark plasma sintering at the same sintering temperature.