A study on corrosion resistance of electroplated Gold over Nanocrystalline Ni-W for contact applications

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In this work gold and nanocrystalline Ni-W with nickel sulfamate was electroplated on beryllium-copper. This sample was compared with the baseline coupon in which the electroplating was done with gold and nickel on beryllium-copper. Both samples were passed through the environments of (a) 85% relative humidity at 85oC for 24 hours (b) 85% relative humidity at 85oC for 96 hours and (c) Salt spray treatment for 24 hours, (d) nitric acid vapors for 30 minutes. After passing through these environments, the effect on electrical, mechanical and materials properties of samples were investigated through Force Deflection Resistance, Life-cycle test, Scanning electron microscopy, Energy dispersive X-Ray spectroscopy and X-Ray. Thicknesses of electroplating layers are 0.9 µm, 1.8 µm, 1.9 µm and 0.5 µm of gold, nanocrystalline Ni-W, Ni sulfamate and Ni strike respectively. In the case of Au/Ni sulfamate sample, during the compression cycle the spring force increased from 2.1 oz to 11.3 oz and during the extension the spring force reduced from 5.2 oz to 1.1 oz. During the compression and extension the resistance was constantly measured, which varied from 9 mΩ to 4 mΩ during compression and from 6 mΩ to 12 mΩ during extension. In LCT, the resistance was measured under a stroke length of 0.09 inch and a life cycle of 10,000 at a test current of 0.025 amps with cycle rate of 4 cycles/sec. The rate of increase in resistance with number of cycles is higher in the case of Au/Ni sulfamate than Au/nc Ni-W/ Ni sulfamate.