Q. We are running high-speed, reel-to-reel plating of gold-nickel-tin and palladium-nickel, and using bipolar cleaning. I am somewhat confused about electrical connections in bipolar cleaning systems. –R.Q.
A. I assume by bipolar cleaning you are referring to periodic reverse electrocleaning. In this case, you will alternate reverse or anodic electrocleaning with direct or cathodic electrocleaning. You will generally start with the cathodic cleaning in which the workpiece is made the cathode. This has the advantage of generating twice as many gas bubbles, since hydrogen is created at the workpiece. You will then reverse the current in order to make the workpiece anodic. This generates oxygen at the workpiece and has the advantage of dissolving base metal and oxides. This process can be repeated several times and typically ends with the anodic or reverse process to insure deposits from the cleaning tank are not redeposited on the workpiece.