Of Mlcc Electrode Ultrafine Nickel Powder Side Electrode With Ultrafine Copper Powder Modified

In resent years, the ever-growing price of precious metals has promoted the widespread use of ultrafine nickel and copper powders in the internal electrodes and end terminations of multilayer ceramic capacitor (MLCC). Howerver, there are two problems in using nickel as an electrode material, which are partial oxidation of nickel and shrinkage mismatch between nickel layer and BaTiO3. In the firing process of end termination, the copper powder can be oxidated easily and its sintering temperature is high. In this paper, the ultrafine nickel and copper powders are modified respectively in order to solve these problems.During the experimentation of modification of nickel, the composite nickel powder coated with oxigen-resistant Ni-B-O system film is prepared by NaBH₄ reduction method. The effects of different conditions on anti-oxidation of the modified nickel powder are investigated. The optimal reaction conditions, such as the dosage of nickel 10g, the concentration of NaBH4 0.6mol·L^-1, the reaction temperature 45℃, pH=11, the flux of NaBH₄ 3ml·min^-1, the reaction time 30 minutes and the stir speed 200 r·min(-1), are determined by single factor analysis method. The initial oxidation temperature of the modified nickel powder modified under the optimal conditions is 355℃, which is 78℃higher than that of the original nickel powder. In addition, its sintering shrinkage property is promoted, and its electric conductivity is also good as well as its tap density.During the experimentation of modification of copper, the Cu-Ag bimetallic powder is prepared by chemical plating silver method after the original copper powder is sensitized and acted. The effects of different conditions on anti-oxidation of the Cu-Ag bimetallic powder are investigated. The optimal reaction conditions, such as the dosage of copper 2.5g, the concentration of argentamine 0.5mol.L^-1, the concentration of hydrazine hydrate 2.5 mol.L^-1, the dosage of PVP 0.75g, the reaction temperature 50℃, the pH=11, the flux of argentamine 3mL'min^-1, the reaction time 30min and the stir speed 100r·min^-1, are determined by single factor analysis method. In the optimal conditions, the full-package Cu-Ag bimetallic powder is prepared by coating the actived copper powder with silver twice. As a result, the oxidation ratio of the twice coated Cu-Ag bimetallic powder is 4.5% when it is heated in the atmosphere at 400℃for 30 minutes, which is 47.2% lower than that of the original copper powder in the same condition. In addition, its sintering temperature decreases greatly and its electric conductivity is better than that of the original copper powder.