POROSITY OF ELECTROPLATED PALLADIUM, PALLADIUM-NICKEL AND COBALT HARD GOLD AS A FUNCTION OF SUBSTRATE ROUGHNESS AND DEPOSIT THICKNESS E. J. Kudrak J. A. Abys F. Humiec AT&T Bell Laboratories 600 Mountain Ave. Murray Hill, NJ Abstract The porosity of electroplated deposits is known to be related to certain substrate conditions, such as, inclusions, purity, and particularly, roughness. As few commercial substrates are polished smooth, a means of understanding the impact of surface finish was required. A comparison of porosity was made between electrodeposited palladium, palladium-nickel (80/20) and cobalt hard gold over varying degrees of substrate roughness and deposit thicknesses. OFHC copper disks were abraded to roughnesses which varied from 0.05 to 1.0 micron (center line average). These samples were then plated with individual layers of the metal of interest under controlled conditions using a Rotating Disk Electrode. Thicknesses ranged from 0.25 to 2.0 microns. Plating conditions were previously determined in order to produce low levels of intrinsic porosity from these specific chemistries. Porosity was determined by subjecting the plated disks to sulfurous acid vapor according to ASTM B 799-88 (Standard Test Method for Porosity in Gold and Palladium Coatings By Sulfurous Acid Vapor) and subsequently to vapors of ammonium sulfide. The pore corrosion was tallied and reported as a percentage of salt covered area for the various conditions.