Diffusion Study of Electrodeposited Copper-Nickel Multilayer

Abstract

Copper and Nickel multilayer composites have been prepared by electrodeposition of nickel on copper substrate from Watt’s bath, producing Ni layer of low thickness and then subsequent deposition of copper on Ni by acidic sulfate bath, leading to electroplating of a thin Cu layer. Since adherent Nickel deposit cannot be deposited directly from conventional baths, copper substrate serves as an ideal undercoat for obtaining adherent Ni layer deposit with improved metal distribution and reduced critical cleaning & polishing requirements. Plating parameters such as current density and plating time are kept constant whereas the other bath compositions differ. This is done alternatively to generate alternate Cu-Ni metal multilayer. Magnetic stirring was applied during deposition process in order to produce homogeneous, smooth and adherent coatings of nickel. Characterization and surface morphology analysis is done using FESEM and optical imaging and thus, the thickness of the layers is obtained. The Cu-Ni multilayered composite is then subjected to vacuum heating so as to obtain the Time Temperature profile and the extent of interlayer diffusion. This vacuum furnace heating was carried out in the presence of Argon gas, at different temperatures (773K, 973K, 1173K) and the samples are held at these temperatures each for different time intervals (1 hr, 2hrs, 3hrs). The resultant hardness, microstructure and the diffusion effects are then investigated and studied. The diffusion coefficients for Cu in Ni and Ni in Cu at the above mentioned temperatures was studied from theoretical calculation and subsequently compared with actual diffusion coefficients measured from the Energy Dispersive Spectroscopy (EDS) line scan.