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August 2000

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Subject:
From:
Chuck Brummer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 9 Aug 2000 08:47:14 -0700
Content-Type:
text/plain
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text/plain (62 lines)
Guenter,
It may be just an oxide spot on the copper.  The solder mask will not adhere well to the copper oxide and can even get a small gas bubble between.  It may not be a big problem, if the oxide is not an
acidic contaminant then the trace will probably not be a reliability problem.  It could also be an organic contaminant, also not a problem if it has not already caused a failure.

Look at it under high power (like 200X) and if the copper is full height forget about the spot.

Chuck Brummer


Guenter Grossmann wrote:

> Hi all
>
> I have a case here where I am not sure what I see.
> - There are dark spots visible below the solder mask on the surface of the traces on a PCB. I attached 2 Pictures in JPEG that show a view onto the surface of the traces with 10x and 40x magnification.
> - In microsections we see clearly a cavity between the traces and the soldermask.
> - EDX is hopeless, since the dark layer is so thin that the background covers all but the copper peak.
>
> Before I start to work with TOF SIMS, Spectroscopy and other expensive analysis methods I'd like to ask whether one of you knows what the dark spots are.
>
> Thanks in advance. Have a great day.
>
> Guenter
>
> Guenter Grossmann
> Swiss Federal Institute for Materials Testing and Research EMPA
> Centre for Reliability
> 8600 Duebendorf
> Switzerland
>
> Phone: xx41 1 823 4279
> Fax :      xx41 1823 4054
> mail:     [log in to unmask]
>
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