Fabrication Of Insulating Thermally Conductive Inorganic Coating Upon The Copper Surface

Copper as one of the most important industrial raw materials is widely used in industrial and electronic integrated circuits because of its good electrical conductivity,thermal conductivity and anti fatigue.However,copper products will be oxidized easily at more than 400°C,the strength and service life will be reduced.Moreover,the noninsulated surface of copper product limits its use in the circuit.In order to solve those problems,the glass coating was prepared on the surface of copper.The copper coated with composite coating with good oxidation resistance,insulating property and thermal properties could be used in the high temperature environment.In this paper,glass coating was prepared on the surface of copper using liquid phase sintering technology.The Li₂O-B₂O₃-SiO₂-based glass was adopted as the main raw material,Na₂SiO₃·5H₂O as binder,anhydrous alcohol as carrier.The preparation of the glass coating was explored,and the wettability of the molten glass on the copper surface was solved.Nano ZrO₂,nano?-Al₂O₃ and 45S5 expansion glass powder as reinforcement,mixed with glass raw material respectively,formed the slurry with a suitable viscosity,and coated on the surface of copper using dip coating method,a composite coating was formed after heat treatment.The microstructure,composition,oxidation resistance,adhesion,wear resistance,breakdown field strength and thermal conductivity of the coating were studied.The results showed that a Cu₂O transition layer was formed on the copper surface during heat treatment in the few oxygen atmosphere,and molten glass could be spread on the surface uniformly.The surface of transparent coating was smooth and dense,the thickness was uniform.The existence of Cu₂O transition layer could improve the wettability of the glass on the copper surface effectively.Moreover,the copper infiltrated into the glass,the coating and the substrate were firmly bonded.ZrO₂/glass composite coating was prepared on the surface of copper with nano ZrO₂ as reinforcement,the surfa ceof the coating was smooth and compact,and the thickness was uniform.The copper coated with ZrO₂/glass composite coating was oxidized at 400°C for 61h in the air,the copper has no obvious oxidation.The adhesion between coating and substrate was strong.With the increase of the content of ZrO₂,the wear resistance of the coating increased remarkably.When the content of ZrO₂ was 5%,the breakdown field strength of the coating was up to 27.4 kV/mm,the addition of ZrO₂ was beneficial to increase the thermal conductivity of the coating.Al₂O₃/glass composite coating was prepared on the surface of copper by nano?-Al₂O₃ as reinforcement.By adjusting the content of the reinforcing body,the composition of the coating was changed.The results show that the composite coating prepared on the copper surface was smooth and compact,and the thickness was uniform.The copper coated with Al₂O₃/glass composite coating was oxidized at400°C for 61h in the air,the copper has no obvious oxidation.With the content of Al2O3 increased to 20%,the wear resistance of the coating was significantly enhanced,and the breakdown field strength of the coating was up to 35.1 kV/mm,the thermal diffusion coefficient of the coating increased obviously,the addition of Al2O3 could improve the thermal conductivity of the coating significantly.The 45S5 glass/glass composite coating was formed with 45S5 high expansion glass powder as reinforcement.The results showed that the 45S5 glass had no obvious influence on the surface smoothness of the coating,the internal crack of the coating was obviously reduced,the coating thickness was uniform and dense,and the oxidation resistance of the coating was good.The 45S5 glass could enhance the wear resistance significantly and improve the thermal conductivity of the coating,but have no effect on the breakdown field strength.