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.