The only problems I am aware of are plating voids which go all the way
around the hole when some direct metalization processes are used.  Some
metalization processes (maybe all?) require an etch step after
metalization.  The etch removes the metalization from any copper surfaces
because of poor adhesion to the copper.  This leaves the metalization only
on the epoxy.  Unfortunately, the etchant can also etch the edge of the
nail head exposing the non-metalized epoxy underneath.  Results in a
circumferential void.  Critical Defect!

Does not happen with electroless copper.



>     I would like to see IPC's response on this subject because I'm under
>     the assumption that nailheading is no longer a reason for rejection.
>     (I've also been told that somewhere somebody ran tests and found
>     increased holewall adhesion due to the nailheading<increased cu to cu
>     plated sites>)(?????)
>     I would think that only in the case of positive etchback requirements
>     would nailheading really create an issue.
>     Am I correct or wrong in my thinking?
>
>     Groovy
>
>
>______________________________ Reply Separator
>_________________________________
>Subject: Nailheading
>Author:  [log in to unmask]
>Date:    1/31/96 12:19 PM
>
>
>Simple Question:
>
>Has anybody found a functional defect in multilayer pwb's due to nailheading???
>
>D.Rooke
>([log in to unmask])
>
>
>
>






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