Research On Preparation Of Cu/Ni/Ag Core/shell Powder And Its Resistance To High Temperature

Silver-coated copper powder has excellent physical and chemical properties, such as high electrical conductivity and good oxidation resistance. At the same time it can avoid the electronic migration faults of silver powder and reduce cost by implementing the base metal instead of precious metals. It has gained wide attention of many researchers. It is widely used in electronic pastes to produce integrated circuits, resistor,capacitor and other electronic components. It is involved in chemical industry, printing,military industry and other fields. However, there are many problems in the preparation of silver-coated copper powder. It is easy to be oxidized under high temperature. This defect limits its application scope seriously. Aiming at this problem, we adopt the method of adding nickel base metal transition layer to prepare Cu@Ni@Ag core/shell powder. The powder prepared by this way has good high temperature oxidation resistance.The effect factors of nickel-coated copper powder was studied. The coating layer is incomplete and oxidation resistance is poor when the nickel plating quantity is too small.The conductive performance is poor when the nickel plating quantity is too large.Reunion phenomenon of powder is serious when dispersant is too little. The coating effect is poor when dispersant is too much. The reductant ability is weak with small p H value. It is easy to produce nickel hydroxide precipitation when the p H is too big. In this paper, it is concluded that the best preparation technology are as follows: 30% nickel plating, 5% PVP58000, reducing agent A and Ni2+ mole ratio of 1:1, p H value of solution between 10 to 11, sixty degrees reaction.The effect factors of Cu@Ni@Ag powder’s preparation and performance was studied. The coating effect is better with more plating times and the oxidation resistance is better with large amount of silver plating. The coated layer is loose with small p H value. It is easy to produce silver oxide precipitation with large p H value. It can improve the surface density of silver with wet ball milling method. In this paper, it is concluded that the best preparation technology are as follows: reducing agent B, the amount of silver plating was 30% with the method of two plating, silver plating quantity was 45% with the method of three plating, nickel-coated copper powder dispersed in ethanol/water as 1:4 mixed solution, then adding the reducing agent and silver ammonia solution, adjusting p H between 10 and 11, ultrasound and mechanical stirring, fifty five degrees reaction.Characterization testing of the Cu@Ni@Ag powder is done by XRD and SEM/EDX methods. Results showed that the Cu@Ni@Ag powder consists of threelayers structure, the innermost for copper, middle tier for nickel and the outermost layer for silver. In addition, the powder granularity, vibrated and apparent density were tested.The results show that the Cu@Ni@Ag powder has certain reunion, but the reunion is not obvious. Vibrated and apparent density can meet the industrial application well.The powder was sintered at high temperature and the oxidation resistance performance of Cu@Ni@Ag powder was characterized by SEM, XRD and TG methods.Powder’s conductivity was also tested. The data shows that there is no obvious oxidation phenomenon for the powder of 30% silver plating quantity with two plating below 450℃ and its resistance changes little. For 45% silver plating quantity with three plating powder, there is no obvious oxidation phenomenon below 500℃ and the resistance changes little.