Study On The Electroless Nickel Plating Of Low-Phosphorous

Electroless nickel of low-phosphorous coatings have been widely applied in electronic fields because of its great solderability. Therefore, the study of electroless nickel plating technics of low-phosphorous is of great practical significance and value.In this paper, lactic acid and propionic acid system , citric acid and acetic acid, succinic acid and malic acid system which are the complexing agent systems were researched. The deposition rate is measured through weighing by electro-balance; the P content is analyzed by X-ray fluorescence spectrum(XRF); the porosity is determined by GB5935-86; surface morphology is observed by stereomicroscope and atom force microscope(AFM); the solderability is tested by immersion tin. Through compared the different complexing agent systems, lactic acid and propionic acid system is determined as the electroless nickel of low- phosphorous based system.After determined the based system, the effect of composition in the electrole nickel plating solution and process condition on deposition rate and P content is discussed. Through the research obtained that increase Ni2+/H2PO2― , the concentration of complexing agent and sodium acetate and pH is propitious to low-phosphorous coatings. At the same time the scale of process condition is confirmed. Through orthogonal test, gets the best formula of electroless nickel of low-phosphorous. The P content of the coating obtained from the satisfactory electroless nickel plating is 2.46 mass%.Based on the satisfactory electroless nickel plating technic of low-phosphorous, then study the effect of Triethanolamine, Propandioic, Succinic acid, Malic acid and Ethylene diamine on coating appearance, bath stability, porosity, deposition rate, P content and the surface microtopography. Through these research obtain that Succinic acid is suitable for the complexing agent of electroless nickel of low-phosphorous. The turnover test is made to detect the bath life and the performance of the bath. Then, LVC is applied to study the effect of complexing agent on the cathode polarization curves and anodic polarization curves, The results show that the Triethanolamine can cause sodium hypophosphite oxidation rate increase and then decrease,succinic acid can make sodium hypophosphite oxidation rate increase; triethanolamine and succinic acid can cause the nickel reduction potential is positively shifted and reducing current increased. But triethanolamine can make nickel reduction rate increase, succinic acid cause nickel reduction rate decrease and then increase.