Lorenz,

In my experience, pitting in acid copper plating more often then not is
caused by the presence of fine particulate matter in the bath (although a
number of other causes -- from improper pre-plate cleaning to contamination
-- are also possible).  You should be able to tell by plating a Hull cell
panel, filtering the solution through a < 5 micron filter, plating another
panel and comparing the two.

If filtration cures it -- make sure you filter cartridges in the working
tank are polypropylene, 5 micron or less and the solution turns at least 3
times/hour.  Better yet, if you have an extra tank available, filter the
solution into it, clean the tank/anode bags and filter it back into the
working tank.

If filtration doesn't improve the Hull cell panel -- use the Hull cell to
diagnose the cause (e.g., quickly carbon treat a small volume of the bath,
replenish the additives and plate a panel to check for organic
contamination/additive imbalance or check your working pre-clean chemistry
vs. freshly made-up, etc.).


Eric Yakobson
Alpha PC Fab






Albert Mok <[log in to unmask]> on 04/06/99 06:46:49 PM

To:   [log in to unmask]
cc:    (bcc: Eric Yakobson/AlphaPCFabUS/Cookson)
Subject:  Re: [TN] Pitting




Pitting is a process problem and is not workmanship defect like as solder
mask skipping.  Carbon treatment is the conventional way to resolve the
pitting problem. However, you must find the root cause where the organic
come come and how it accumulate?

____________________________________________________________


At 04:19 AM 1999/4/6 +0200, Smith Russell MSM LAPO US wrote:
>With reference to Air in the Solution , an overlooked area is the
>circulation systems. Make sure that the suction side of the pump has no
>leaks, and for best results put the filtration on the pressure side of
>the pump. this way you can eliminate cavitation of the impeller by
>providing a constant back pressure on the impeller. Also don't forget to
>pre-wet your filters to remove most of the air from them before you
>install them.
>        With todays fine feature technology I don't recommend increasing
>the filter rating  much beyond 50 micron absolute .
> ----------
>From: Gwerder Lorenz
>To: [log in to unmask]
>Subject: [TN] Pitting
>Date: Saturday, April 03, 1999 3:07AM
>
>We are a PCB manufacturer and are currently dealing with the "PITTING"
>problem. Small holes, craters in the electrolitic copper.
>Is there any acceptability guideline corresponding this problem. I did
>not find it in the IPC-A-600.
>
>
>Thanks for your help
>
>
>Lorenz Gwerder
>
>
>[log in to unmask] <mailto:[log in to unmask]>
>www.photochemie.ch <http://www.photochemie.ch>

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