Hi Steve - yes, you have enough physical details that a lab that routinely
conducts FA work on electronic assemblies (there are several who are part
of Technet) would have a reasonable chance of finding the root cause. At a
very minimum with the details you have on this issue, the laboratory should
be able to rule out possible root causes even if they can't find a specific
root cause. I didn't see any dendritic shorting - is the belief that the
shorting is internal to the pwb?

Dave Hillman
Rockwell Collins
[log in to unmask]


On Fri, Apr 8, 2016 at 11:00 AM, Steve Gregory <[log in to unmask]> wrote:

> Good Morning All,
>
> We have an assembly that we build here for a customer that we built for
> some time, over 2,000 assemblies. There have been some failures that our
> customer has had field returns with that are beginning to escalate. There
> have been 12 field failures that we know of. The failures are avionic
> assemblies that have been in the field ranging from 111 days to 472 days.
> The actual failures are internal +12V to -12V shorts and we need to know
> why. I have two failed assemblies here. Here are a couple of external
> photos of a via that shows the short:
>
> http://stevezeva.homestead.com/Internal_Short.jpg
>
> http://stevezeva.homestead.com/Internal_Short_Close.jpg
>
> So my question is, can a lab take these boards and examine them to
> determine what the root cause actually is from the two assemblies that I
> have, or does there need to be more samples? What is the range we should
> expect to pay for this type of analysis?
>
> We're trying to work with our PCB vendor on this issue, but I have also
> been asked by my boss to pursue this with a third party.
>
> Thanks!
>
> Steve
>
>
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