Maintenance and Control on Acid Copper Plating

The concentration of copper sulfate or copper fluoborate can be approximated by specific gravity measurements, but the contribution of sulfuric acid to the specific gravity of the sulfate bath must be taken into account. The acid concentration of fluoborate bath is controlled by measuring pH, using colorimetric pH papers.

The concentration of addition agents is usually controlled by empirical methods, such as evaluating the appearance of deposits on special bent or sloping cathodes immersed in breaker samples of the plating solution. An analytical method based on a brominating reaction was developed for determining the concentration of phenol of phenolsulfonic acid.

Filtration requirements depend on the dirt load of the air, any dirt brought in by the work, and the amount of detached anode sludge particles. If the cathodes are steel and if they are incompletely protected with copper or nickel strike, particles that become detached from immersion deposits will also contribute to the filtration requirements. Although it is possible to maintain acceptably smooth deposits with only occasional batch filtration, continuous filtration is usually preferred. Cellulosic filter aids are satisfactory, but siliceous filter aids should be avoided when the flouborate solution is filtered papers are satisfactorily.