Electroform it right the first time

Q: I am experiencing blistering when I electroform copper over aluminum substrate. What could be the root cause? 

A: This question came from a company producing tight tolerance parts for radio applications. Before I answer what the root cause was I think it prudent to do a quick overview of the electroform process, shown below. By nature of the process, rework is very expensive; As soon as the aluminum is dissolved the part can no longer be stripped and replated and a new mandrel must be made. Therefore it is critical to ensure that all chemical processes are working properly. By focusing on improving first pass yield the cost of manufacturing can be significantly reduced.

 In this particular case we discovered that oil contamination was the culprit. Although the manufacturer had focused on improving their alkaline cleaning process, drag-out propagated the issue throughout all the plating tanks. Only when proper rinsing (i.e. cascading overflow rinses) was practiced throughout the whole line was the issue resolved.

Adhesion problems bright copper

Q: I plate nickel over acid copper and am having trouble getting the nickel to adhere to the copper plate. The surface needs to be bright as possible as this is for a decorative application. 

A: Excessive brighter level can cause real adhesion problems with many deposits. Whether you are doing bright copper or bright nickel the components that make up the additives tend to inhibit any post treatment, including more plating. I would recommend using a reverse electroclean for 30 seconds followed by an acid dip to remove the brighteners and activate the surface. This will allow you to plate over the copper or nickel without sacrificing aesthetics. You won’t see this problem with chromium systems as the chromic acid will do this job for you.