Processing quality results for electroless/electroplating of high-aspect ratio plated through holes in industrially produced printed circuit boards

The plating quality results of high-aspect ratio through holes in industrially produced and sized printed circuit boards are reported in this paper. Test panels with 32,000 PTHs were processed on an existing industrial production line in order to test the possibilities of modifying the line for panels with higher aspect-ratio plated through holes. Depending on the process parameters different types of faults in the plating of these plated through holes were detected, varying from gas bubbles stuck inside the plated through hole, rough and non-plated glass fibers caused by the drilling of the holes, to parts of resist stuck inside the through holes. The type of error occurring is dependent on the processing used. Because each individual processing step can influence the following processing steps, an integrated quality approach has to be considered. Most of these problems could be solved by small changes in process parameters. Making a quantitative analysis of the type of errors resulted in a drastic reduction in the number of unplated through holes on industrial panels. This was done by identifying and classifying the type of error occurring. Aspect ratio's of 10.7 could be plated with a high yield on an existing vertical electroless plating line.