Nickel Plating For Enhanced Corrosion Resistance In Connector Applications

Connectors are widely used in our daily life,as electronic industry has been changing with each passing day,the reliability of electronic devices are more critical than ever.The performance of connectors depends on its electrical properties,mechanical behaviors and environmental performances.In terms of environmental performance,the corrosion resistance is of great importance.Traditional way to improve the corrosion resistance is to plat gold on nickel with the substrate of copper alloy.However,with the rising gold price,plating excessive gold as the contact surface will not be a profitable way to go.In order to cut down the use of gold and the prime cost of connectors,this work researches on electrodeposition of nickel and nickel-tungsten alloy for connectors with good corrosion resistance.The microstructure and chemical properties of the commercial nickel coatings were studied.The direct and pulse current was applied on electrodeposition of nickel coating and their influence was studied.In order to observe the microstructure,samples were grinded to get cross-section view and XFM was applied to measure the thickness of the coating.Composition of coatings were analyzed by EDS,XRD,XPS.Microstructure such as grain size and orientation was investigated by XRD.The mechanical properties and surface roughness were investigated by nano hardness tester and AFM respectively.Characterization of corrosion resistance of coatings was measured by potentiodynamic polarization tests and electrochemical impedance spectroscopy.Corrosion resistance of nickel is affected by its microstructure,including grain size,crystal orientation and morphology.Firstly,the grain size,crystal orientation and corrosion resistance of commercialized Ni deposit were measured,which is helpful to adjust strategy for further research of the work: finer grain size,smoother morphology and easy to get passivated.Parameters,components of the bath of electrodeposition were adjusted to realize the purpose of this work.Pulse plating technique was employed to eliminate the intercolonial boundaries of micron-scale structural elements that exist in nano-crystalline materials produce by electrodeposition,which significantly influence the electrochemical corrosion.A method was developed to further enhance the corrosion resistance by electrodepositing nickel-tungsten alloy film on top of nickel/gold by reverse pulse current.As it is known that,nickel-tungsten alloy has excellent wear resistance and corrosion resistance but relatively bad ductility,a thin film is the right way to solve this problem.So in the bath without nickel ions,reverse pulse current was applied to dissolve a tiny amount of nickel and then be re-plated together with tungsten.This method is also been considered to fil the pits of gold which is also be attempted in this research.