Inverse Displacement Deposition Of Ni-activated Layer On Copper Surface Study On The Properties Of Nickel Phosphorus Coating

Electroless nickel-palladium-gold plating is considered to be an ideal surface treatment technology to prevent copper tracks in printed circuit board from oxidation and corrosion.Because copper is inactive to hypophosphite owing to the high energy barrier of hypophosphite oxidation on copper,electroless Ni–P plating cannot occur on copper unless a palladium activation procedure is carried out first.However,because of the ever-increasing price of palladium and the over-plating phenomenon of palladium activation,it is of great significance to develop a facile and feasible procedure to prepare a low-cost activator to replace palladium activator.Nickel and cobalt have a good activation effect on electroless Ni–P plating.However,how to prepare nickel or cobalt activation layer on the copper surface has become a problem.In this project,nickel or cobalt activation layer has been prepared on copper by antigalvanic replacement deposition method.It is found that high iodine ion concentrations or deep eutectic solvent can reduce the actual potential of copper to be lower than that of nickel and cobalt,making it possible to deposit nickel and cobalt on copper by galvanic replacement reaction.The anti-galvanic replacement deposition solution composition and deposition process have a significant impact on the composition and structure of deposited nickel and cobalt layer on the copper surface.With the increase of iodine ion content in the anti-galvanic replacement deposition solution,the deposition rate of nickel layer is increased.Similarly,the increase in nickel and cobalt ions content can also lead to the rapid deposition of nickel and cobalt layers.In addition,the deposition temperature also significantly affects the anti-galvanic replacement deposition rate of the nickel layer.The higher the deposition temperature,the higher the deposition rate.When the deposition temperature is increased to 95 ℃,the nickel film can be obtained on the copper surface within 10 minutes.The activation performance of nickel,cobalt and palladium layers have been comparatively studied.It is found that the morphology,structure,density,thickness,deposition rate and corrosion resistance of nickel-phosphorus coatings deposited on nickel,cobalt and traditional palladium layers are basically the same,indicating that the nickel and cobalt layers have excellent activation ability.The anti-galvanic replacement deposited nickel and cobalt activation layers can replace the traditional palladium activation layer and become a novel method to activate electroless nickel-phosphorus plating on copper circuits in printed circuit boards.