IN-SITU PHOTOTHERMAL SPECTROSCOPY METHOD FOR INVESTIGATING SURFACE CHANGES DURING ELECTROPLATING OF NICKEL

A PTS method was used to monitor in situ the variations in surface structure during the early stages of nickel plating on a copper electrode. It was found that the changes in the photothermal signal indicated the existence of an intermediate state with a relatively rough surface before a smooth plating layer is formed. On the basis of these results combined with SEM data, the following process for the initial stages of nickel plating was suggested. First, a smooth copper surface is transformed into a relatively rough surface; with continuous plating, this changes into a well-distributed surface. The minimum thickness for a nickel plating layer with a uniform stable surface structure is about 536 monolayers at a current density of 8 mA/cm2. © 1993.