Do you AOI your inner layers? Like Rudy said we are also seeing a lot of
minute foil resin spots on the copper that is not visible thru magnifying
glass but AOI catches them. Since it is only 5% I am assuming you have
already looked into clearance pads being large enough to cover any
misregistration or wobbly drilling. Also tiny webs(0.006") between
clearances can break loose and redeposit  during inner layer process causing
shorts.

Sona
Fineline Circuits Inc.

----- Original Message -----
From: "Krishnan C" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, September 18, 2003 3:29 AM
Subject: [TN] Inner Layer Ground Shorts


> Hi Technetters,
>
> Can any of the technical Gurus from the PWB Fab or related industry
> enlighten how & why the inner-layer power/GND shorts occur & how they can
> be detected after the boards have been laminated. Of course I do
understand
> that when you are building boards with very tight tolerances, fine lines
> thin cores the probability of these type of shorts occurring is quite
high.
> However we have days when we have zero GND shorts & days with upto 5%. We
> have looked into all potential problems, but maybe we are still missing
out
> something, so if someone out there can enlighten me it will be very much
> appreciated.
>
> Thanks,
> Krishnan.C
> Sanmina-SCI
>
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