Patty - good reading material - unfortunately haven't read till u mentioned.
would like to dispute Lenny's views - have seen too many cross sections to
know otherwise. Whenever pinkring occurrs - look at those cross sections
carefully - u will notice some sort of copper folding after plating - means
had to be minor space - most llikely filled with air - then solution -
whether plain shifting or whatever - the wall has either a gough in it - or
minute fracture in the oxide layer. Reduced oxide is nice - but is the oxide
layer reduced chemically or is it being chemically etched back - be careful
when ur chemical supplier says " we have reduced oxide".Can SERA determine
breakdown product is left in? When does the reducer have to be changed? And
when we speak about multi-layers - 4 - 6 - 8 - 10 - what happens on 16 layer
boards - 20 layers? Saw some occurances happen this year on some pretty thick
boards - hydrolization of the reducer - ain't a pretty sight when a 20 layer
board seperates. Final conclusion as to how and why? Will know in a month or
so .... will try to remember to pass info on. Little pressed for time these
days .... once i get freed up will try to forward this info through the net.
Yes - reduced oxide does help out when using DM - to an extent - but drilling
is still where it starts - from there - your guess is as good as mine as to
where the acid attack occurrs.
best regards
Richard Fudalewski
Atotech Canada Ltd
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