As the two parts shown are normally a direct connection, the external source
of the arc is missing from the examination.

RL

On Fri, 1 May 2009 06:56:45 -0500, Steve Gregory
<[log in to unmask]> wrote:

>Hi Wee Mei!
> 
>Sorry it took me so long to get your pictures posted, but Homestead was
>down for server maintenance yesterday. I have your pictures posted now:
> 
>http://stevezeva.homestead.com/files/Q55-_burnt_site.JPG
> 
>http://stevezeva.homestead.com/files/Q55_-_remove.JPG
> 
>http://stevezeva.homestead.com/files/Q55_-_close_up.JPG
> 
>Yep, looks like some of the metal vaporized...pretty high temperature!
> 
>Steve
>
>________________________________
>
>From: Lum Wee Mei [mailto:[log in to unmask]] 
>Sent: Wednesday, April 29, 2009 8:35 PM
>To: Steve Gregory
>Subject: Is fusing current current?
>
>
>Dear All,
> 
>An engineer was trying to probe for a signal while he accidentally slip
>the probe pin and has it shorted between the MOSFET metal tab (power
>output) and the exposed area fill ( Chassis GND) beneath it. Ooop, up
>come the smoke and a small burnt site. The MOSFET is removed and found
>to be still functioning. The questions are :
> 
>1. To have the copper area blown up and fused look like we need a very
>high temperature. If that is the case, why we do not see any damage to
>the laminate epoxy glass fibre. We have a previous case, where the trace
>burnt and curled up and the laminate epoxy glass fibre burnt and become
>brittle.
> 
>2. As this PCBA is already fully populated and the damage does not seem
>bad, I was thinking or just sealed teh exposed laminate with epoxy,
>mount back a good part and use the PCBA as it is. Can I do that? or it
>would be good to re-mount the whole PCBA?
> 
>All the PCBAs are made from Nelco-4000-11.
> 
>Your kind opinion is greatly appreciated.
> 
>Steve : Would appreciate you can upload this pic for me and forward to
>TechNet for discussion.
> 
> 
>Thanks and Regards,
>~ Wee Mei ~
>
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