Study of the Au-Co alloy electrodeposition mechanism from acid bath and the effect of Tl+ on the deposition properties

Hard gold electrodeposits have a wide application in the microelectronics, opto-electronics and micro system technologies.Cobalt hardened gold electrodeposits are used in the electronics industry due to magnetic properties of cobalt. The obtained coatings have high internal tension, good wear resistance, and low contact resistance [1]. Addition of trace quantities (ppm) of heavy metal ions such as Tl+ to gold baths induced a cathode depolarization that extends the current density range in which bright, fine grained deposits can be obtained. Hydrogen incorporation was identified as the single most important source of mechanical problems in Auelectrodeposits. These problems are addressed by addition of heavy metal salts (Tl+) [2-3]. A mechanistic study of these systems is still lacking.