I would check to see if any metal parts didn't have a via keepout underneath
them, and when they assembled the PCB the vias shorted to the metal case ?

Karl

Bock Ming Gai Joanne wrote:

> Hi all,
>
> Currently I'm facing a problem at work. I have a few 6 layers of PCBs
> that are perfectly alright, meaning that they passed the ET. However,
> when our engineers did some testing after board assembly, problem
> surface. When they tighten the board with mounting screws, they found
> that one of the supply trace was shorted to the Gnd. This was not shown
> during the ET because PCB suppliers only did the test on the bare
> boards. So now I am looking into what could possibly cause them to short
> together.
>
> I appreciate anyone who can help to provide me with a solution.
>
> Thanks & Best Regards!
> Joanne Bock
>
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