David,

I have found there are two major contributing factors to this problem. Low amperage and/or
low tin concentration. Either one of these can result in peripheral voids at the knee. Other issues I have found is a lack of attention to brightner adds.  We have found it best to make the adds based on amp hours rather than all at once in the morning. Since it is difficult to check brightner except for hull cells, the hull does not really reflect what could be happening at the knee. I have heard some shops make adds in the morning or at start of shift without regard to amp hours. In any case, these are the items that we have found to be problematic in the past. We have good controls over this things now and have not seen this problem in over a year. You might also want to watch the bath temperature. I have heard that this can also be a problem

Have you talked to your supplier?

Hope this helps,

Ed Cosper
Director Quality Assurance and Engineering
Graphic Electronics, Inc
Tulsa, OK

----------
From:  David Creager [SMTP:[log in to unmask]]
Sent:  Monday, April 07, 1997 7:02 AM
To:  [log in to unmask]
Subject:  Annular ring failure, and Tin plating problems

In the past year, we have had problems with our tin tank not plating
properly. It has caused problems that resulted in annular ring failure
at the knee. I was wondering, can anyone provide inside into what to
check, and an reliable way to check the amount of brightners/wetting
agents in the bath. I am looking for tests (besides hull cell) that
doesn't cost a fortune.

If there is a way of testing the wetting agents on the Hull cell (full
bright), could someone please give some insight?

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