Plated over parts should not use ftir for detection. IR is reflective to metallic surface, and in active to the metallic or in organic surface. You might need to use sims - dynamic. Use one without discoloration as reference. You might have uncured epoxy filling in the via hole that react with plating solution (amino acid if epoxy curing agent is acid based), changed local chemistry of the surface pth. My 2 cents. You might want to wash the flux away from the site if there is any prior to analysis. (Not cheap, but MAY provide the answer you seek)
--------------------------
Sent using BlackBerry
----- Original Message -----
From: Inge Hernefjord [mailto:[log in to unmask]]
Sent: Saturday, October 22, 2011 10:30 AM
To: [log in to unmask] <[log in to unmask]>
Subject: Re: [TN] Discoloration on plated over vias
l'oeil est fraudé ? Peut-être. I believe something is bleeding out from the
adjacent components. Check if there are any more sites with exactly the same
parts, but with no discoloration. If the answer is negative, I think even
stronger, that the issue is connected with the two packages.
seulement une proposition
Inge
On 21 October 2011 22:26, Ioan Tempea <[log in to unmask]> wrote:
> Dear Technos and Smarts,
>
>
>
> I got this issue, see http://ipc-technet.groupsite.com/gallery/21662
>
>
>
> So 6 layer, 2oz Cu per layer PCB, epoxy filled vias and plated over. After
> assembly we see 4-5 vias having reddish stains, on most boards. Had it
> analyzed, no trouble with via integrity, no cracks in cover plating, no
> migration of fluids from inside out. FTIR does not detect any surface
> contamination.
>
>
>
> Au plating thickness stands at 2.09 micro inches.
>
>
>
> Nothing special detected in the stains, so the lab concluded what we see is
> an optical effect due to a certain roughness of the Cu. The logical
> conclusion is no issue, cosmetic defect.
>
>
>
> However, our end customer, high reliability, want to know what the stains
> are and want absolute confirmation that long term reliability is not
> affected. Also, we've been warned that no such issues will be tolerated on
> future lots.
>
>
>
> My questions to your infinite knowledge is: have you seen this before? How
> can I convince the customer everything is OK? What is the root cause and how
> can I get rid of the issue?
>
>
>
> Many thanks,
>
>
>
> Ioan Tempea, ing.
> Ingénieur Principal de Fabrication / Senior Manufacturing Engineer
> T | 450.967.7100 ext.244
> E | [log in to unmask] <mailto:[log in to unmask]>
> W | www.digico.cc <http://www.digico.cc/>
>
>
> N'imprimer que si nécessaire - Print only if you must
>
>
>
>
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