The Study Of Coating Mo Particles With Cu By Electroless Plating

Molybdenum is a kind of strategically important rare metal. Its melting point, strength and hardness level are high. It owns a good abrasion resistance and a good thermal conductivity. Although molybdenum is classified as "heavy metals" it is as important as nonmetallic elements. In addition, the alloy of molybdenum has a small expansion coefficient and a good corrosion resistance. Molybdenum-copper composite materials have a good thermal conductivity and heat resistance. And the thermal expansion coefficient and processing performance is similar to silicon, ceramics and other semiconductor device. Because of its high conductive thermal conductivity, low thermal expansion coefficient and good heat resistance, etc. it can be used as a substrate in the large scale integrated circuit, and it also can be used as high power microwave devices, embedded block, fittings and heat dissipation component, etc. The technology, principle and equipment of the electroless plating are introduced in this paper. When the technological parameters changed the influences are also studied.Mo powder with size of2um is used in the experiments. Before plating pretreatment was carried out on the molybdenum powder. Preprocessing step are washing, coarsening, activate the sensitization (colloidal palladium activation method), dispergation. Pretreatment is critical in the electroless plating. The success of pretreatments is the key of the electroless plating. When we do the activation sensitization, activation sensitizing liquid should not be placed too long. Otherwise it will decompose, and the effect of activation of sensitizing liquid will be less than expected. Then orthogonal experiment method is used to obtain the best formula of the electroless copper plating. The solution is:CuSO4·5H2O18g/L, EDTA-2Na25g/L, CHOH30ml/L, triethanolamine (TEA)22ml/L, ferrous potassium cyanide (K4[Fe(CN6)]-3H2O)20mg/L, CH3OH112ml/L.The best temperature is50℃, and the best pH is11.5. The influence factors of electroless plating are pH, temperature, loadage, formaldehyde content and salt content, etc. This article will study the relationship of plating speed, gestating time, weight increment, morphology of the composite powders with these factors. Through researching it can be found that these three factors-pH value, temperature, formaldehyde content have bigger influence on the chemical plating speed. Temperature and pH value are the main factors which affect gestating time. The influence of loadage and the main salt content on copper content is bigger. The weight increment of composite powder is mainly influenced by the content of CuSO4·5H2O and the pH value. Because of the size of molybdenum powder particle is small, they are easy to unite. Therefore, the scattering processing of the molybdenum powder particles is necessary. Acetone is used to clean the molybdenum powder particles in the experiments. At the same time, we have found that the molybdenum powder mixed in acetone can also play the role of dispersing them. Coarsening is in hydrofluoric acid, and its consistence is20ml/L. Activation of sensitizing liquid is easy to decompose. And along with the increase in use, activation of sensitizing liquid effective substances also gradually lost, activation of sensitizing effect is reduced. In this case in order to save time and materials, we can add lost ingredients to the sensitizing liquid. By this way we can realize the reuse of activation sensitizing liquid. In electroless plating we adopted double complexing agent triethanolamine and ethylenediamine tetraacetic acid disodium. The experiments proved that using the two complexing agent can obtain a good plating effect.