Hi Fred and all,

        From many of the other responses I have received off line a galvanic
reaction seems to be the most likely culprit.

> Hans; is there any chance that these plane layers have copper extending
> out to the edge of the panel? i.e. is there any exposed copper on the
> sheared or routed edge of the panel that potentially can make contact with
> your electroless basket?
>
        The thermal/ground plane layers have copper extending all the way
out to the panel edge.
        The panel edge is beveled after desmear so it is nice and smooth
before plating.

> Is there any chance of stray voltage (from a leaky heater, for example)?
> I have seen several times where this current sets up a higher
> electroglavanic potential that creates this exact problem.
>
        Yup.  The tank has a heater in it.
        In fact, we just replaced it because the last one went 'postal' and
burned out a week ago.

> It's not such a major problem with the surface copper foil since there is
> just so much of it compared to the amount on the inner layers that's
> exposed either in the holes or on the edges...
>
> SOLUTIONS:  make sure that there's no exposed copper planes on the edge of
> the panel and make sure you don't have any leaky heaters.  Teflon heaters
> are notorious for pinholes that leak current.
>
        Does anybody out there use coated plating baskets?
        Somebody else suggested a copper-less gap around the edge of the
panel,
        a more durable fix than some rubber coating.

        We'll see if I can issue a double ration of virtual grog after my
meeting on Monday.
        (And after the last episode of 'Horatio Hornblower' on A&E this
Sunday.)

        Have a great weekend folks!

        Hans

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