Hi Richard -
Give me a more detailed explanation of what type of breakdown products
your SERA question refers to (I am confused by the term "breakdown
product"). SERA testing gives details about metal finishes and how
those surfaces get altered by various processing steps. The test
method doesn't analyze chemical residues.
Dave Hillman
Rockwell Collins
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______________________________ Reply Separator _________________________________
Subject: Re: Re[2]: Mechanism of Wedge Void Formation
Author: [log in to unmask] at ccmgw1
Date: 7/17/97 6:26 PM
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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