Electroless nickel-phosphorus plating on copper substrates by nickel strike activation

Abstract

Deposition of nickel layer onto copper substrate was investigated. The normal plating process which is cleaning, soft etching, pre-dipping, acid dipping and lastly electroless nickel plating have been performed onto copper substrates. No deposition of nickel layer onto the surface of copper surface when negative deposition speed -2.513 µm/h was obtained from our first trial. Nickel strike activation was introduced towards normal plating process in which nickel layers can be seen deposited on the surface of copper. The deposition speed of the nickel layer is 4.965 µm/h with semi-bright appearance. Optimization of the experimental parameters such as pH value, temperature and plating time were performed as they affected the deposition of nickel layer. The values for those parameters are 4.0-5.0, 90.0℃ and 20 mins, respectively. The optimum current density for nickel strike activation is 10 A/dm². The copper substrate was then characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) which showed the topography and chemical composition of the copper substrate. The result from these characterizations showed that copper substrates without nickel strike activation have irregular shape at several areas on the surface of copper and contain about 96.8 wt.% of copper, 2.8 wt.% of carbon and 0.4 wt.% of oxygen. While, for the copper substrate with nickel strike activation, discoidal shape of particle can be seen over the entire surface of the copper. The chemical composition of this copper substrate is a bit difference from the previous copper substrates where about 85.0 wt.% of nickel, 12.4 wt.% of phosphorus, 2.3 wt.% of carbon and 0.3 wt.% of oxygen were found in this substrate