Preparation Of Core-shell Structured Copper/silver Composite Powder And Its Application In Electronic Paste

At present,from the electronic slurry used in the microelectronics industry,the electrical conductive phase is mainly silver powder,which needs to consume a large amount of precious metal silver,and the silver slurry conductive film may also have the phenomenon of silver migration in the process of use,which causes the circuit board short circuit to cause the equipment failure.Copper/silver composite powder with nuclear shell structure,as a new type of conductive composite powder,has both advantages and disadvantages.It is an ideal substitute for silver powder,which can be used in the related fields such as electronic slurry,conductive ink and catalyst.Therefore,the research on the preparation of copper/silver composite powder with core and shell structure provides a theoretical basis for the development of high value-added and high quality microelectronic industrial conductor slurry,saving precious metals for the conductor sizing products and reducing the cost with great value and significance.In this paper,a copper/silver composite powder with high dispersion and high antioxidant capacity and suitable for low temperature conductor slurry was prepared by chemical reduction method.The effects of the pretreatment process,the type of dispersant,the temperature and pH value of the bath and the ultrasonic stirring time before silver plating on the properties of copper/silver composite powder were studied.The prepared Copper/silver composite powder is conductive phase,epoxy resin and phenolic resin as the main raw material,and low temperature composite polymer conductor slurry is prepared.The effects of Copper/silver composite powder content,epoxy resin and phenolic resin mass ratio,curing time and curing temperature on the conductivity of slurry were studied.The structure and properties of copper/silver composite powder with different silver content were analyzed and compared by SEM,XRD,TG and EDS,and the antioxidant stability and comprehensive properties of copper/silver composite powder and pure silver paste with different silver content were analyzed.The results of the study show that:(1)the optimum processing conditions for the preparation of copper/silver composite powder are:silver nitrate:9.45?10.5 g/L;three ethylene four amine:22.5 to 25 ml/L;glucose:12.0 to 13.3 g/L;Z-I dispersant:0.25?0.28 g/L;pH:8.0?8.5;the reaction temperature is:Reaction for 30 minutes under 50?conditions,Reaction for 30 minutes under 60? conditions;drying temperature:degrees;50?;Bulk Technology;Z-I dispersant + mechanical agitation + ultrasonic agitation.(2)the use of Z-I dispersant as the dispersant of the plating solution can effectively reduce the surface tension of the copper particles,improve the wettability,adjust the deposition rate of the silver particles on the surface of the copper particles,and make the silver coating more compact and smooth.The shape and the density of the copper/silver composite powder are mainly determined by the properties of the original copper powder and in the silver layer.The thickness of the coating will affect the size distribution of copper/silver composite powder.With the increase of silver content in the coating,the grain size(D50)of copper/silver composite powder increases,and the effect of silver coating on the resistance of copper/silver composite powder is also larger.When the content of copper/silver composite powder is low,the resistance of the sheet is with the silver content.As the silver content is more than 30%,the reduction of sheet resistance tends to be smooth and stable.(3)the thermal stability of Copper/silver composite powder is different from that of silver powder.The thermal stability of copper/silver composite powder with low Ag content is lower than that of high Ag content.When the silver content is over 30%,the silver coating has already covered the copper powder particles completely,and the coating layer is continuous,compact,good uniformity,and has good thermal stability.(4)when the curing time of the copper/silver composite powder conductor size is 30 min,the curing temperature is 150,the content of the conductive phase is 75%and the mass ratio of the epoxy resin and the phenolic resin is 2:3,the printing property of the slurry is good and the conductivity is better.It has no oxidation phenomenon in the process of preparation,and has little change in resistance,good stability and good oxidation resistance.(5)the preparation of copper/silver composite powder and pure silver slurry under the same ratio,the square resistance of the silver pulp is 13.07m?/?,the change rate of the resistance resistance is 4%,the adhesion of the conductive film is not shedding,the stability of the silver pulp is good,and the square resistance of the copper/silver composite powder with 50%and 40%silver content is 15.90m?/? and 16.46 m?/?,and the change rate of the resistance resistance is 5%,and the adhesion force is not detected on the surface of the conductive film,and its performance index is up to the requirement.In order to reduce the cost of silver and production,the copper/silver composite powder with silver content of 40%can replace silver powder in the preparation of low temperature composite polymer conductor slurry,which has a good application prospect.