Charles Barker
04/09/97 07:47 AM

What type of "electroless" process did your PWB maker employ on your
boards?





TechNet @ ipc.org
04/08/97 09:02 PM


To:   technet @ ipc.org
cc:    (bcc: Charles Barker/IO-US)
Subject:  Etchback





The purpose of this request is to solicited some opinions as to the
merits of etchback.


My company has recently had some field returns which analysis has
disclosed that the failures are a result of post separation. The PWB
supplier ,when contacted, suggested that if our drawing had required
etchback there would have been a less of a chance for a failure of this
nature to occur.


My company uses both IPC-RB-276 (IPC-6011&IPC-6012) and
MIL-STD-55110E as procurement specifications and it so happens we
have experienced failures in PWB's procured using both
specifications. The guidance furnished by either is not definitive
just if the Master Drawing say do it the etchback has to fall within
certain limits.


We have always gone with only a chemical desmear (permanganate) with
no apparent epoxy removal. We have never specified a chemical
etchback for fear of latent defects from residual chemicals. Our PWB
supplier tells us there is now available plasma etchback/chemical
desmear (permanganate) which we are told eliminates the potential
for the latent defect problem.


Does anyone have data which would provide information as to which
process would make the more reliable product. Any and all replies and
opinions welcome.

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