Rick,

We had a problem early this year when our heated rinse water wasn't heated
and
panels in the pre plate were hitting 58 F rinses and a 68 F sulfuric dip then
smutting
when hitting a 74 F acid copper plating bath. I used a thermal scanner from
the
dry film room and noticed the panels were 68 F also when hitting the bath. We
drained the rinses, filled with warm water 98 F (the temp of the cooling
water from
the etcher), and all other conditions exactly the same, the panels plated
perfect.

When the occasional smut monster sneaks into our plant it can usually be tamed
by increasing the ASF to 35-40 ASF for the first 5 minutes of plating. We
metered
the amps at the rack spline. Only thing being, on this particular panel the
copper
area was way uneven. We split the layup in half so all the copper area
wouldn't be
on one side of the panel. But it was a weird balance then,too, as the front
half was
very heavy, the far half very light; and just the opposite on the other side
of the panel.
Thus, I wondered how this affected the overall distribution of ASF across the
panel.

This whole smut thing is only a very occasional experience when conditions
must
be ripe. From what we experience, contributing factors are 2 trips through
the DML
line, aging preplate, cold weather, organics creeping in the plating bath.
Still within
our pm windows but sometimes there appears to be another factor we can't
finger
which throws us out. The net has suggested pd in microetches to be a factor
and
over and under etching in general to be issues in smut. I think we'll try a
proprietary
microetch my DML advisor is suggesting which is supposed to eliminate smut for
ever. Believe that? I just use a generic now, so I'm going to try it. I'll
let you all know
how it works out.

Thanks for your input,
Julie

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