Synthesis And Electrical Performance Of Silica-coated Copper Electronic Pastes For Low Temperature Co-fired Ceramic

Electronic pastes as the basic material of electronic components have an increasing demand.The precious metal resources are insufficient and the prices continue to rise.Copper electronic paste is favored by researchers due to high conductivity,low cost and anti-migration.Therefore,developing a silica coated copper electronic paste,which is dense with good electrical conductivity and connects well with the low-temperature co-firing ceramic substrates after sintering,is very promising for the microelectronics packaging technology.In this paper,different content silica was coated on the copper powder by the sol-gel route.The silica-coated copper powders were mixed with organic vehicle to prepare copper pastes.The pastes were screen-printed on low temperature co-fired ceramic substrate?LTCCs?to form copper films.The printed samples were sintered at910°C for 1 h under N₂ atmosphere.The morphology of silica-coated copper powder,copper film surface and cross-section were observed through SEM.The phase composition and elements distribution were studied by XRD and EDS.The resistance of the copper film was measured by RTS-9 four-point probes sheet resistance meter.In addition,the shrinkage of copper films was also discussed.It was found that the increasing of TEOS content increased the rate of hydrolysis and condensation.The silica network was interwoven on the surface of the copper powder,and the coating layer became thicker,but excessive TEOS resulted in an increase in the number of silica with independent nucleation.The increasing of ammonia concentration and the increasing of reaction temperature all accelerated the hydrolysis and condensation of TEOS.However,too much ammonia or too high reaction temperature caused the copper powder reacted with ammonia and oxygen to form ammoniacal copper complex.When the coating amount of silica was 0-2 wt%,the connection between the copper film and LTCC was more compact with the coating amount increasing.When the coating amount was more than 3 wt%,the unsintered silica coated copper powder increased,and the film density decreased.When the content of organic vehicle was 20wt%,the viscosity of the paste was larger,the copper film was grid-like after sintering.When the content was increased to 25 wt%,the copper film was more compact.When the content was increased to 30 wt%,copper particles grew up and existed alone,and the copper film was not conductive.In addition,the higher the number of printed layers,the worse the copper film density.As for the same layer,the higher the density,the lower the resistance of the copper film.The optimum coating amount was 2 wt%for untreated copper powder.In the sol-gel process,the amount of ammonia was 0.5 mL and the reaction time was 1 h at25°C.The coated copper powder was collected by evaporation and concentration.The optimum weight ratio of silica-coated copper powder to organic vehicle was 75:25,and the sintering temperature was 910°C for 60 min.The sintered copper film was compact and bonded with LTCC substrate well.The conductivity was well with the resistance of 6 m?/?.