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Black/brown oil like contaminant in acid-copper plating solution

I am working as process engineer of copper plating line in a substrate manufacturing company. Recently we found black/brown oil like contaminant at the edge of our copper plating tank. We have collected the solution and after few days the oil like contaminant on the edge stick on it and turn into solid.At first we thought that it was oil leakage coming from the exhaust or the pipings or filter motor pumps on top of the tank but after checking the tank no leakage was found and the exhaust is dry and clean to cause this contamination. We are using acid-copper sulphate [on eBay or Amazon]plating solution and operating at 30 deg C. We also have additives and carrier in the solution.We have collected the sample with oil like contaminant and have done the hull cell but the result is shows no problem. We have also checked our product if there will be any peel test failure and bake test but still the result was passed. Our incoming tape have dry film laminated on the copper. I would like to ask if this is a possible chemical reaction? if yes, can you help to explain how this may happen? What other ways can we do to check the cause of this contaminant and to know what is this contaminant? Hope you can help me understand more acid-copper plating process.

Edith Liquido
Flex/TBGA Substrate manufacturing - Shatin, NT, HK


Hi Edith,
There are two possible causes that come to mind. The air lines for your air sparger may have oil in them. Most acid copper plating tanks have independent air compressors [adv: air compressors on eBay or Amazon] with oil trap (filters)in line before the tank. If you have one compressor for the entire plant, the lines have to bled of any compressor oil often.
The other possibility that comes to mind is that when some brightener systems breakdown, they can leave a residue that appears to be oily.
Dry film photoresist will normally flake off the edges of the part and be trapped on the filter cartridges. The resist you are using should be acid resistant and be suitable for acid copper solutions. As long as you don't have any resist breakdown issues (where resist peels from substrate material) you can probably rule out the resist. It would benefit you to run carbon cartridges in the filter system every month to keep organics at bay. I like to do a hot peroxide/batch carbon treatment at least once per year. Good Luck!

Mark Baker
Process Engineer - Syracuse, New York

Hi Mark,

I appreciate your inputs. Latest findings that we have is the brown oil inside the drain hose of the exhaust box which is nearly the same with the one we are observing in the solution (you may be right!). We have collected that sample to do FTIR to confirm the organic. I thank you for the time you have spent for my concern and for the advise. Good luck also and thanks again.

Edith Liquido
Flex/TBGA Substrate manufacturing - Shatin, NT, HK

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