Check for exposed metal on your oxide racks;  if isolated copper areas 
     are grounded to metal, they won't oxidize.


______________________________ Reply Separator _________________________________
Subject: RE: Black-oxide layer turned red after pressing
Author:  [log in to unmask] at INET
Date:    3/13/97 11:09 AM


Darick,
     
The anomaly we experienced manifested itself in several forms. One of = 
the strangest was a reddish color on a single trace while all other = 
traces surrounding it were black. I have heard this referred to a = 
galvanization in the copper plating area but I'm not sure what causes = 
this in oxide. By the way, if anyone out there knows the specifics or = 
mechanics as to what causes this condition, I would like to know.
     
Thanks=20
     
Ed=20
     
----------
From:  Darik Leung[SMTP:[log in to unmask]] 
Sent:  Wednesday, March 12, 1997 1:42 PM 
To:  Ed Cosper
Subject:  Re: Black-oxide layer turned red after pressing
     
Ed Cosper wrote:
>=20
> Dear Darik,
>=20
> We experienced a similar problem a few years ago, we found that by = 
putting in a caustic pre-dip and changing it out weekly, we problem went = 
away.  When we would try to extend the bath, it would gradually return.  = 
However, usually we could see a reddish color streaking before we = 
pressed it. You might have to look close and angle the layer in a light = 
source.
>=20
> Hope this help,
>=20
> Ed Cosper
> Director, Quality Assurance and Engineering 
> Graphic Electronics, Inc.
>=20
> ----------
     
Thank you so much for your advice.  We will try to investigation this 
based on your suggestion.
Anyway, in your case, did it happened on all board design (not 
particularly those with thin outer layer), and did the red area confined 
near the edge of the platen? We did observed such symptoms.
     
Best Regards,
     
     
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