At 11:26 AM 11/12/01 -0700, Bob Fearon wrote:
>     Sorry to mislead, the additional cost came from routing the boards out of
>the panels
>     and then plating.

Ah. *That's why it was so expensive.* A whole extra step to be performed on 
a bunch of small boards instead of on the panel. I'd really try to avoid 
doing it that way. It would not only be two additional plating steps but 
also the top and bottom surfaces would have to be masked.

Instead, I'd determine a few places, if possible, where an opening in the 
edge plating would be tolerable and leave those as tabs. The internal 
routing would be done before electroless copper, so all the edges would be 
plated in the same step as the holes.

>  Mindful that edgr plating is not a "linear" or accurate as
>     thru hole plating.

That does not make sense to me. Plating of a copper-free board surface is 
done by first using electroless copper which chemically deposits a *very* 
thin film of copper on the surface, then it is electroplated up, typically 
to one ounce added copper in order to get about 1 mil of copper minimum in 
the holes. The rest of the board gets about 1.4 mils. The holes do not 
plate as easily or as reliably as the board surface, and this gets worse 
the smaller the holes. So edge plating should be pretty good, being more 
like board surface than like the interior of holes.

But the accuracy of the plating would not be of much importance. Even small 
voids in the plating might be harmless. The largest difficulty in plating 
the edges would be the roughness of the edges, the smoother the edges 
before plating, the more uniform the plating. Still, I'd think that plating 
accuracy would be better than in the holes.

Abdulrahman Lomax
Easthampton, Massachusetts USA

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