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 ~ > >--------------------------------------------------- >Technet Mail List provided as a service by IPC using LISTSERV 15.0 >To unsubscribe, send a message to [log in to unmask] with following text in >the BODY (NOT the subject field): SIGNOFF Technet >To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) >To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest >Search the archives of previous posts at: http://listserv.ipc.org/archives >Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 >----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------