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Pits in acid copper plating

I have a buddy who is having a copper plating problem and was aware of the excellent forum you have going here so I thought I'd give you guys a try.

He is plating printed circuit boards with standard acid (sulfuric) copper sulphate ⇦this on eBay or Amazon [affil links] plating bath. He is getting perfectly round plating pits predominately along the traces and pads where they meet the dry film plating resist. Occasionally the pits will appear on the copper surface.

Other than these small, perfectly round pits, the copper appearance is good; uniform, bright and shiney.

The plating bath is air agitated. Could air bubbles be attaching to the resist at the beginning of the plating process? Does the plating process generate any gases at the plating site that can lead to this problem?

Any suggestions are appreciated.

Thanks,

Scott Campbell
- Tempe, Arizona, USA
2003

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First of three simultaneous responses --

In cases like you've described, it's usually a developer problem. Check the solution AND equipment.

James Totter, CEF
- Tallahassee, Florida
2003

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Second of three simultaneous responses -- 2003

THE PROBABLE REASONS ARE:

1. IN BALANCE brightener SYSTEM.
2. CHECK FOR ZINC CONTAMINATION(METALLIC CONTAMINATION)
3. LACK OF WETTER.
4. ORGANIC CONTAMINATION.

TAKE A LITER OF SOLUTION HEAT IT THEN ADD 2G/L potassium permanganate ⇦this on eBay or Amazon [affil links] , THEN ADD CARBON , SETTLE FOR OVER NIGHT (TILL CARBON SETTLES) THEN TRANSFER THE SOLUTION AND TAKE TRIALS.

Panjala Mukesh
fashion jewelry mfgr.
Hyderabad, India

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Third of three simultaneous responses --

Scott this is way too general of a question. I'll try to offer what I can. It would take a book to answer you. First he is buying a proprietary additive from a vendor. Hopefully a vendor that makes the additive and not a distributor. This additive allows bright plating and leveling of the copper thru holes. There are many parameters to control this bath. He should contact his vendor for assistance. He may have already. If they couldn't help, find another vendor.They have technical service engineers specifically for this. Second he should be utilizing a direct drive blower. If a Roots type blower is used oil will be introduced which could be the problem. Air is part of the process. Third it may be a dry film problem or preparation of same.

William F. Hemp
- Grand Rapids, Michigan
2003

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It sounds to me like your buddy has got gas bubbles trapped on the surface. This could be due to poor agitation, lack of wetting agent in the copper bath or possibly contamination of the substrate. If it is not gas bubbles, it could also be faulty dry film resist (how old is it?) or poor developing. Maybe even poor artwork. Perhaps a picture and more details may be advantageous. Do you scrub the tracks before processing them?

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2003

In general pitting is because of hydrogen evolution in vicinity of cathode surface. When cathode efficiency becomes poor this problem occurs. Why cathode efficiency is poor? Probably due to contamination in the plating bath. You will have to remove the contamination by corrugated dummy operation. Then check for the metal contents. If necessary optimize the bath. Air agitation will help reducing pitting and optimum concentration of wetting agent will take care of that problem.

Venkat Raja
- Kitchener, Ontario, Canada
2003

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RECENTLY WE HAD A SAME PROBLEM IN OUR BATHS SO WE TRIED AND INSTALLED A SEMI ABSOLUTE FILTER CARTRIDGE IN THE FILTER STREAM AND FOUND PIT FREE PLATING. HOPE THIS WILL SOLVE YOUR PROBLEM.

Syed Farooq Quadri
mfgr. of costume jewelry- Hyderabad, Andhra Pradesh, India
2003