John,
Yes, you will need to scale 7-8 drill file.  My experience is that the
registration issues you face with a core that is drilled and plated is going
to offer challenges you don't see with respect to typical material movement
of the rest of the stack up.  7-8 may not be as predictable, or at least may
exhibit wider variation, lot to lot.  Nevertheless, it does sound like you
can be a lot closer to optimal than your current method of not scaling.  Keep
in mind there are other issues affecting registration of 7-8 pattern to
through pattern, than just scaling the drill file.  Once you have the scaling
worked out, that may become apparent.
Regards,
Mark Julstrom
Senior Process Engineer
Multek Irvine (closed)

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