What is the best way to agitate a plating solution? Is the use of eductors recommended? G.B.
The classic way to agitate plating solutions has been either air agitation or, to a lesser extent, cathode reciprocation. A paper, Exploitation of Eductors Agitation in Copper Electroplating, D. R. Gabe, M. Ward and J.N. Crosby, presented at the June 1999 Sur/Fin®, American Electroplaters & Surface Finishers Society, www.aesf.org, addresses these questions. Using a mathematical relationship, which we needn’t concern ourselves with here, the following enhancement factors were determined.
As can be seen from the data, the agitation method used does make a difference. Surprisingly, the two standard methods, cathode reciprocation and air agitation, give similar enhancement factors. The data above also indicates that the vibratory and turbulent flow methods of agitation offer real improvements over the two classic methods. The vibratory method is not used in the plating industry, however, the turbulent flow method is used.
The use of eductors will give you a turbulent flow environment and, based on the information in the table, much better mixing compared to cathode reciprocation or air agitation. An eductor is a specially designed nozzle that causes liquid pumped through the nozzle to exit at high velocity. This in turn pulls additional solution from the surrounding region through the nozzle.
Yes, I recommend eductor-based agitation systems. More information on the process and vendors who sell the eductor nozzles can be found at the PF Online Supplier Database, www.pfonline.com/suppliers.html.