Hi Sheila,
     Not sure whether you have a long term reliability problem or not.

     By your description, I am assuming the NPT holes are being drilled in
     after the panels have been through the final etching process, and that
     things like drill feeds and speeds, routing speeds, tools, etc. have
     been optimized for this material.  I am also assuming this is pure
     polyimide.  Unsupported polyimide material will fracture quite readily
     during machining.  This condition can be minimized, if not eliminated,
     by performing these secondary drilling/routing operations prior to
     etching the base copper from the material.  Also, the polyimide/epoxy
     blended resins (Tg around 220 deg C) machine much better the  pure
     poly.

     Hope this helps...Andy Slade



______________________________ Reply Separator _________________________________
Subject: [TN] Unplated thru holes
Author:  Sheila Smith <[log in to unmask]> at SMTPLink-Hadco
Date:    06/22/98 10:58 AM


Hi TechNet!

Does anyone know of any guidance, specifications, design practice etc regarding
acceptability of drilled thru holes and routed slots which are not plated?  We
have observed haloing and glass fiber intrusion in & around some of the holes &
slots at the bare board level.  Our concern is processing chemistries wicking
into the laminate during assembly which includes wave solder followed by hand
soldering of a number of components and several trips thru the semiaqueous and
vapor phase cleaners.  The unplated holes are for hardware & mechanical uses,
not electrical, but there are active circuitry traces nearby.  These are double
sided polyimide boards.  Anyone have any suggestions or similar experiences?

Thanks in advance.

Sheila @ Tracor AES

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