POROSITY OF COMPOSITE PALLADIUM, PALLADIUM-NICKEL AND GOLD ELECTRODEPOSITS

The porosity of palladium and palladium-nickel electrodeposits, in a composite contact finish, was investigated. This evaluation was performed on electronic connector pins plated at low current densities in a barrel pilot line, under conditions similar to a manufacturing environment. The composite finish, commonly known as Gold-Flashed Palladium (GFPd) or Gold-Flashed Palladium-Nickel (GFPdNi), typically consists of a nickel sub-plate (4.0-mu-m), a palladium or palladium-nickel layer (0.25 to 2.5-mu-m) and a flash of cobalt hard gold. A novel acid palladium strike process was also examined. The composite finishes were compared to equal thicknesses of standard hard gold (HG) over nickel. Results obtained for the GFPd and HG were between 0.25 and 1.5-mu-m, while the GFPdNi produced markedly lower porosity. The proprietary acid palladium strike, originally developed to enhance adhesion, reduced the porosity to a nearly pore-free finish for the GFPd, even at thicknesses below 1.0-mu-m.