I whole-heartedly agree with you. Wet process can be the cause of pink 
     ring, but it is also highly probable that something abnormal happens 
     during lamination/drilling, causing the pinkring/wedgevoid formation. 
     The reason people usually look at the wet processes when pinkring 
     occur is because the wet processes "BRING OUT" the defect.
     
     If the oxide is not reduced or is not allowed enough time to be 
     reduced, the next thing is that the acid resistance test fail 
     misarably, and every hole comes out of SES will be pink. The oxide 
     reduction is one major variable in wet processes that will cause 
     wedgevoids.
     
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: Re[2]: Mechanism of Wedge Void Formation
Author:  [log in to unmask] at corp
Date:    7/15/97 2:11 PM


     We found that a reduced oxide helped quite a bit.  This means that the 
     inner layer processing is involved in the formation of wedge voids.  
     I'll bet that lamination cycles can adversely affect the boards too.  
     Drilling is, of course involved, & wet process brings out the defect.
     
     What problems do you have with reduced oxide?
     
     Matt Byrne
     HADCO-Owego
     
     
______________________________ Reply Separator _________________________________
Subject: Re: Mechanism of Wedge Void Formation
Author:  [log in to unmask] at SMTPLINK-HADCO 
Date:    7/15/97 06:37 AM
     
     
wedge voids are usually a start of shotty drilling - then seepage of solution 
through the voids and that solution then starts attacking oxide layer - which 
inturn leads to pinkring. Dm will not make a difference - actually if 
drilling is still primary cause - will be the same or worse - since Dm is 
thinner coating. A reduced oxide layer can eliviate problem to a certain 
degree - but then - reduced oxide brings in a problem of it's own.
     
regards
     
Richard Fudalewski
     
Atotech Canada
     
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