I have never really seen post drill bake cure or eliminate the anomaly
     pink ring.
     
     Although some may view pink ring as a strictly cosmetic defect, there
     is a fine line between pink ring and actual delamination from the 
     inner layer surface. 
     
     In most cases the root cause of the pink ring is the fracture of the
     epoxy interface due to incorrect feeds/speeds in the drilling 
     operation. This fracture then allows chemistry to wick back and 
     remove the black oxide treatment from the inner layer.
     
     If the fracture is severe enough... there is the potential for
     a dreaded defect referred to as "WV's" (wedge voids).
     
     The post dip processes of today can band-aid a great deal of this
     problem but not all.
     
     
     Terry Pearo
     Marcel Electronics, Int.
     
     
     
     


______________________________ Reply Separator _________________________________
Subject: Re[2]: Post Baking Process
Author:  [log in to unmask] at Internet
Date:    1/27/97 3:50 PM


     Will someone please clarify the paragraph below ?  It states that pink 
     ring can be eliminated with a post drill bake.  It then goes on to say 
     that it cannot reseal the crack and it is only a cosmetic fix.  Isn't 
     pink ring a cosmetic issue?  Why would it be a dangerous fix if it 
     works??
     
     Also, you can have the best innerlayer treatment out there and if the 
     drilling operation is unoptimized, it will not make a difference in 
     cracking of inner layers.
     
     
______________________________ Reply Separator _________________________________
Subject: Re: Post Baking Process
Author:  [log in to unmask] at corp
Date:    1/27/97 11:46 AM
     
     
     
Post-drill bake -  A bake after drill has been shown to eliminate pink ring.  
Our work shows this is a dangerous fix.  Pink ring is caused by a chemical 
attack on innerlayer surfaces that are exposed by cracks introduced at drill. 
The bake relaxes the epoxy enough to close the crack, but it cannot reseal the 
crack.  Thus it is at best a cosmetic fix.  However in addition, the bake 
hardens epoxy smear and makes it difficult to remove.  A much better solution 
to pink ring is to use a good innerlayer surface treatment that prevents 
cracking at drill.
     
     
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