I didn't build your boards, but I build them for a living. After reading
numerous comments, I offer the following:

Be careful about specifying the materials. If you spec the glue into the
middle, as you say, then you increase the cost of the boards with no real
benefit. It is cheaper and just as reliable to build the boards with a
single double-sided core and prepreg on both sides against foil
outerlayers. This is the preferred method of manufacture... it costs less
because it is easier to build and the materials are cheaper, but the
pricess itself is every bit as good as the "old way".

The best oxides are no longer black in appearance. If your traces on layer
2 are silver-colored now, this is probably a good thing. Your supplier may
be just improving his quality and forgot to brag about it.

The new oxides are now lighter than the treatment used by laminate
manufacturers. Laminators use a treatment that is tan or reddish colored.
When it was contrasted by black-oxided traces, it appeared light. But now,
against the silver of the new oxides, and covered with soldermask, it can
seem quite dark.




At 08:59 AM 2/26/02 -0600, you wrote:
>Hi,
>We just received a new rev of a PWB in house.  It has not been populated
>yet.  It looks like it has been built correctly - the right layer order,
>connections, etc - but it looks different than the rest of our 4 layer
>boards.  Normally the traces on the inner layer that is closest to the
>surface appear dark in colour and the deeper layer appears lighter.  This
>board is the opposite.  The layer closest to the surface is light in colour
>and the deeper layer is dark.  Also, the FR4 seems much easier to see
>through than usual.
>
>Any thoughts or explanations for this?
>Thanks for your time.
>
>Genny Gibbard (mailto:[log in to unmask])
>
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