Gary
I have heard this phenomena referred to as "Purple of Cassius". (Something
the old guy did to jewellery before he took to mugging??)
It occurs when gold plating solutions are absorbed into the laminate which
is then exposed to elevated temperatures. In the distant past, I recall that
it appeared after tin/lead plated boards were processed through an IR Reflow
oven. I believe that 10% sulphuric acid was reasonably successful in
removing it.

Alistair Murray
-----Original Message-----
From: Gary Camac [mailto:[log in to unmask]]
Sent: 29 August 2000 15:46
To: [log in to unmask]
Subject: Re: [TN] Staining on edge connector


Brian,

I am only seeing this problem on the gold fingers of one assembly.  Haven't
had any luck removing it with the solvents I have in house.  You can scratch
it off - it seems to be in outer surface of the epoxy.

Gary

Brian Holt wrote:

> Might need to clean the oven.  Could be flux, or some kind of grease or
oil dripping off the inside of the oven.  Can it be washed off?  Is it just
on the gold fingers?  Is it on just that particular type of board?
>
> -----Original Message-----
> From:   Gary Camac [SMTP:[log in to unmask]]
> Sent:   Monday, August 28, 2000 12:45 PM
> To:     [log in to unmask]
> Subject:        [TN] Staining on edge connector
>
>  << File: gcamac.vcf >> 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
>
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