Julie,
           I think what the problem might be is this. When laminating dry
     film a small amount is squeezed into the hole. This can be
     exascerbated if the holes aren't completely dry. The other part of the
     problem if you are running your developer conveyor at the high end of
     the speed. What this does is leave a ring of resist just inside the
     hole below the knee. This of course does not plate up with either
     copper or tin/lead. When the board is stripped the resist is removed
     and there you have a ring of copper waiting to be etched.

     Hope this helps.

     Mike Doty
     P.E. Hadco TCE


______________________________ Reply Separator _________________________________
Subject: [TN] Ring Voids
Author:  Julie Dixon <[log in to unmask]> at smtplink-hadco
Date:    12/14/99 8:42 AM


Dear TechNet,

What would cause a perfect ring void just under the knee of the hole, with
the knee
intact? Drill, DML, Dry film, light scrub, Pre plate clean- acid cleaner & Na
Persulfate Etch 10-15 micro inches, Acid CU, Acid bright Tin, Mono DF strip,
Ammoniacal
Etch. Job specific to 1 part # all other product running along side is
perfect.
All material Std. .062 Fr-4 1/1. Longtime runner w/ no probs in past.

Thanks,

Julie Dixon

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