Electroless Plating Of Ni-cu (co)-p Thin Film Technology And Performance

With the advent of electroless plating technology, multicomponent electroless nickel plating becomes a research hotspot in this area,which will expand the applications of electroless nickel plating greatly. Electroless Ni-P layer has very good features, such as high strength wear resistance, corrosion resistance, good electromagnetic properties.In order to meet the need of high hardness, heat resistance,corrosion resistance,the co-deposition of nickel and copper, cobalt, tungsten, etc are achieved, making plating Ni-P layer properties greatly improved.Properties of low-density, easily-strenthened, high-hardness, high conductivity, good thermal conductivity, easily-worked and good corrosion resistance made aluminums to be suitable for the requirements of electronics industry, so that aluminum is widely used. However, the surface of aluminum oxide film can be easily corroded in acidic and alkaline environment. Electroless Ni-Cu-P layer can well solve the shortcomings in this regard.The addition of Cu element led the Ni-Cu-P deposits a high crystallization temperature, thus making high thermal stability and weldability, also good conductivity and low remanence. As a ferromagnetic material, cobalt can improve the coercivity, reduce remanence of Ni-P coatings to achieve high corrosion resistance, strong electromagnetic shielding properties and light weight requirements, These are required for electronic products .As the bath composition, process conditions and other factors will affect the coating quality, so research in this area has become very important. At present, the studies of electroless Ni-Cu-P plating are mainly in the plating process, plating rate, crystallization behavior, hardness, corrosion resistance, weldability and so on. Influence of c(Cu²⁺) and pH value on the activation energy, structure on the magnetic magnetic performance are studied relatively little.Low plating rate, bath instability,large pH value fluctuations during plating and other issues can be observed. And non-metallic based Ni-Co-P chemical plating is relatively little researched. On the basis of the work of our predecessors, we study the substrate pre-treatment process, the plating bath composition and plating conditions in detail . Through the analysis of film composition, structure, etc., combined with the mechanism, we arrive at the following results.1. During Al pre-treatment, adding HF to the withdrawal solution of zinc in the HNO₃ solution(1HF + 3HNO3)can reduce the residual zinc ions at the interface after first zinc dipping,remove some metal impurity ions of the surface, enhance the higher binding capacity and corrosion resistance.2. When c(Cu²⁺) is 0.006 mol·L^-1 and pH value 8.5, the bath is stable, plating rate is moderate, obtained coating has good quality .3. The residual magnetization of Ni-Cu-P coating obtained under the datum plating bath is as low as about 1.0emu/g.4.When Co²⁺/Ni²⁺ is 1 and pH value 9 in the Ni-Co-P bath, the obtained coating is uniform compact, high hard, coercivity Hc and residual magnetization Mr is clearly enhanced after heat treatment at 400℃for 1h.