무전해 Ni-P 도금막의 형성과 Turn over에 따른 막의 특성비교

Properties Comparison by Observing Metal Turn over of Electroless Plated Ni-P Films

Electroless Nickel(EN) plating method among the surface modification techniques is today one of the most fastly growing sectors in the material surface finishing industry. EN plating, in general, provides high precision functional coatings for industrial applications requiring; corrosion protection, high hardness, uniform thickness, less porosity, increased lubricity and wear resistance, etc. During EN plating, however, by-products of the chemical reaction, including orthophosphite, sodium sulfate, and ammonia, build up and decrease bath performance. As the concentrations of by-products increase, the nickel deposition rate decreases. In addition, the nickel plating becomes more porous and intrinsic-stressed, and its appearance becomes less lustrous. Physical properties such as magnetics and solderability may also be adversely affected. With the increase of metal turn over, the deposition rate, hardness and bath performance in the electro less plating are decreased, however, the corrosion behaviors of the electroless plated Ni-P films showed nearly low corrosion tendency. And the film morphology became from columnar to granular structure and the surface grain size decrease with the increase of metal turn over. On the other hand, the phosphorous content of electroless plated Ni-P films becomes increase, and the films tend to show more porous. Eventually, the properties comparison of the electroless plated Ni-P films can be explained by analyzing the content ratio of nickel and phosphorous, the grain size of surface, the morphology of cross section in the plated film in relation with metal turn over.