Wear of gold electrodeposits: Effect of substrate and of nickel underplate

The adhesive and abrasive wear of electrodeposited gold was studied and the effect of a ductile hard underplate (nickel) and a hard substrate (beryllium copper) determined. Wearing conditions experienced by connector contacts were modeled with rider-on-flat apparatus. It was found that: (i) both the adhesive and abrasive wear of gold plate can be markedly reduced by hard substrates and underplates, (ii) thin film lubrication is effective when adhesive wear predominates, but is of little value in abrasive wear, (iii) there is a load-dependent minimum thickness of gold plate that will not wear through because of a change in mechanism which occurs during unlubricated sliding in the adhesive regime, (iv) sliding at mild conditions, as in the presence of a good boundary lubricant, occurs with lateral flow of gold which can close as-plated pores and wear-induced breaks produced early in a run, (v) pure (soft) gold platings may be able to resist abrasive wear at loads where hard golds fail by brittle fracture, and (vi) the prow formation mechanism adequately describes the adhesive wear of gold plate. Nickel underplate may be desirable on connector contacts to minimize the wear of gold plate, especially at high loads, with thin golds, where it is impractical to use lubricants and where abrasion is the dominant mechanism.