what is your edx detector?  if it is windowless or polymer window,  
you might see C contamination at interface if you prepare your sample  
correctly.  If you have windowed detector, you are out of luck for  
the low elements detection (start Na and on words).  you possibly not  
see anything at all (remember the low element detection limit is few%  
range, if you have a lot of contamination, you might see it, even  
with windowless or polymer window - provide you have a decent SEM -  
LaB6 or FE gun - with low acceleration voltage).
my 2 cents.
        jk
On Sep 8, 2014, at 9:51 AM, Pradeep Menon wrote:

> Dear Sir,
>
> We have been coming across the phenomenon exactly as indicated in  
> the IPC 6012 document ( figure included below), where in we have a  
> clear black demarcation in the microsection between the base  
> copper / electroless copper and at times between the electroless  
> and plated copper. We did do an EDX analysis at the points, but are  
> not finding anything else, but copper. We are stuck with this and  
> do not know how to go about. We have consulted, both laminate and  
> chemical manufacturers , but have not got any good inputs so far.  
> Though this is acceptable as per IPC 6012, the same is not  
> acceptable as per the customer requirements. Any input on what are  
> the factors that contribute to it and why is it that this is  
> concluded as acceptable, even for class 3 boards
>
> [cid:[log in to unmask]]
>
> Rgds
>
> Pradeep
> [Logo]<http://www.micro-pack.com>
>
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