Rudy Sedlak mentions that a reduction in oxide thickness from black to
brown to red in color assists in deterring wedge voids.

This trend could lead to a cosmetic difficulty.  Am I correct?

Matt Byrne states that reduced oxide helps:  Here I take this to be
reduction from cupric to cuprous ions which Rudy Sedlak confirms.

Richard Fudalewski states that reduced oxide brings in a problem of its
own, but I am uncertain which definition that Sedlak mentioned he is
referring.

****

New question:  At what minimal thickness does one entertain cupric ion
post oxide reduction with DMAB?  What are the trade offs cosmetically
versus functionality (w.r.t. wv's)?

Again thanks,
Josep

P.S.  In direct answer to Byrne's question of reduction problem,  we see
wv problems intermittently.  The goal is to strive for a cosmetic black
coating.  Thickness entering DMAB is typically 0.28mg/cm2 (black not
brown before immersion).  Acid resistance (10% HCl) is greater than 2
hours.  

These wv issues are not related to layer counts.  I cannot as yet pin
the mechanism down but have not ruled out materials such as prepreg.

I'd like to understand more about the contact mechanism of prepreg
during lamination, whether other's verify Tg of lots, and if this has
ever been an issue in wv troubleshooting.

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