Pitting Problem in Acid Copper Plating

Sanjay,

The following may help.

1) Check the level of both Brightener and Carrier .
2) Chloride levels. Recheck the chloride using fresh reagents.
3) Do a simple Bent Panel test in a beaker and see if the pitting results can be replicated.
4) Assuming your solution is not contaminated with resin from the boards, or Oil , or that there is no form of chrome in the bath , it is then safe to assume the pitting is possibly organic contamination.

In which case draw 5 liters of bath, treat with potassium permanganate ⇦ this on eBay or Amazon [affil links] @ 1 gram / lit, hot at 60- centigrade, Carbon at 3 g/l stir for an hour at 60 then settle for 6 hours and decant .

Filtering the actual bath over Carbon cartridges is a good idea replacing the 6 hour wait, messy carbon handling.. In which case no carbon need be added to bath.

Make up the solution with additives, and run Hull cell panels with a proper anode, with air. Check.

The pitting , if caused by a organic impurities will go away.

Excess additives enhance the tendency pit.

So does lack of wetter.

It is advisable to check wetter content and surface tension at this point of time. 40 Dynes per cm is a suggested middle number. Check with your supplier too for accurate numbers. Some PCB systems have additional wetters.

Good luck.

It is possible that the preparation for acid copper plating does not remove all the soils. Anything left on the surface may cause pitting. I suggest an experiment: Wet sand a panel using 600 grit emery, rinse, acid dip, D.I. rinse and plate in the acid copper bath. Sanding should remove the type of imperfections that cause pitting. If no pitting, reevaluate your entire cleaning and preparation cycle. Look especially for traces of photo resist or other resist residues.