Hello Kevin 

  Lets re-define 'inside'.  If its mask pigment It could easily be
trapped in the pours of the laminate on the outside surface and not
easily cleaned off.  Does it appear to be on (or very close to) the
outer surface, or does it appear deeper in the material?  I find
depth-of-field on a microscope a useful aid in establishing relative
depth of features...

If it's only a discolouration on (or close to) the surface of the
laminate I would use the boards and lightly grill the supplier.  If it
appears on the copper or silkscreens or seems deeper inside I would
demand a much more comprehensive analysis prior to use.

  Again, my first suspect would be the black soldermask -- this stuff
can be brutal to fabricators (and I'm a fabricator that uses black mask
with regularity)



Ian

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
Sent: Friday, September 28, 2007 10:19 AM
To: [log in to unmask]
Subject: Re: [TN] Copper Staining in PCB laminate

It appears to be inside - it doesn't clean off.
 


Kevin Glidden
Manufacturing Engineer
Luminescent Systems Inc.
4 Lucent Drive
Lebanon, NH 03766
(603) 643-7766 x3152
 

-----Original Message-----
From: Ian Hanna [mailto:[log in to unmask]] 
Sent: Friday, September 28, 2007 10:07 AM
To: TechNet E-Mail Forum; Kevin Glidden
Subject: RE: [TN] Copper Staining in PCB laminate

IS this staining on the surface of the laminate or does it appear to be
inside.  Is there any indication of residue on the copper surface.  My
first
guess would be pigment from the black solder-mask, but that's just a
first
guess...Ian

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
Sent: Friday, September 28, 2007 9:06 AM
To: [log in to unmask]
Subject: [TN] Copper Staining in PCB laminate

We recently received a shipment of PCBs where the exposed outer layer
laminate has staining that looks like copper. I have a photo -
<http://tinyurl.com/yp9za2> http://tinyurl.com/yp9za2 My question is
what
would cause this?  I've never seen it before, but I am thinking
something in
the Copper plating process.  The vendor is telling us it is staining but
it
is an asthetic issue only. What would cause it?
Is it
an asthetic issue only?  It seems to me if the staining was caused by
some
plating chemistry, then it would effect the laminate properties,
particularly the insulation resistance.
 
Thanks!
 
Kevin Glidden
Manufacturing Engineer
Luminescent Systems Inc.
 
 
 

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