Genny,
Sounds like your board supplier is using various types of materials and
processes if you are recieving boards from the same supplier. As you
explained
if your inner cores are lighter in color they probably used an oxide
replacement
or double treat copper which will not give you the "black oxide" or very
dark
coloration. If your traces on the outside appear darker they may have
switched
to an adhesion promoter for the soldermask, but usually you would not see
this unless the board has ENIG, white tin, or other aggresive finish which
do in fact
attack the mask.
Tony Steinke
Process Engineer
AIT-Atlanta Inc.(multi-wire lives on)
[log in to unmask]
----- Original Message -----
From: Genny Gibbard <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, February 26, 2002 6:59 AM
Subject: [TN] The board looks funny...


> 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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