Gary,
The Purple stain probably is caused by the gold bath brightened.  Nickel and
Cobalt are used in varying degrees to produce different levels of hardness.
The Cobalt, I think, is absorbed into the laminate due to low resin content
and/or low bath plating efficiency.
The heat of Reflow, like magic, oxidizes it to a visible molecular state. To
my knowledge no one has been able to show any functionally detrimental
problems with this stain.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Gary Camac
Sent: Monday, August 28, 2000 2:45 PM
To: [log in to unmask]
Subject: [TN] Staining on edge connector


Good morning all,

I have come across something I have never seen before and thought it would
be a good idea
to see what my panel of experts have to say.  I have some assemblies that
are showing a
purple stain in the laminate around the gold contacts of a board edge
connector.  Under
the microscope,  I see no sign of anything on the laminate on the boards
from stock.   I
took a sample of the stock boards and ran them, unpopulated, through the
reflow oven and -
lo and behold - I've got a stain.  The stain seems to be in the epoxy.  A
little light
scratching with a knife blade takes off something purple.

Any ideas as to what I am looking at?

Gary Camac

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Keach Sasamori at [log in to unmask] or
847-509-9700 ext.5315
##############################################################