Why not provide a fuse to prevent deterioration of the PE trace on a PCB? Joking of course, but now that I have your attention, I would like to see this thread move away from the physics and discuss what practical reasons there are for using PC traces to provide earth fault circuits.
Lou Aiken, LaMer LLC 27109 Palmetto Drive Orange Beach, AL 36561 USA tel ++ 1 251 981 6786 fax ++ 1 251 981 3054 Cell ++ 1 251 979 4648 From: Peter L. Tarver <peter.tar...@sanmina-sci.com> To: <emc-p...@majordomo.ieee.org> Sent: Tuesday, February 04, 2003 9:53 AM Subject: RE: EN60950 protective conductor test (was Re: Circuit Breaker Tripping Dring Fault Tests) Not quite. I^2·t will tell you the let through current of the copper trace, but will not necessarily tell you if the construction will be compliant. The compliance criteria for this test include: * no damage to the trace (no lifting, probably no discoloration) * no damage to the PWB (no delamination, burning; I don't know if this includes burning off of solder mask) * before and after earthing impedance must comply with the 0.1 Ohm maximum impedance * no change in earthing impedance greater than 10% of the before and after earthing impedance results There is also the much more variable solder in the earthing path. While manufacturing techniques have come a long way in terms of consistency, the amount of solder in a joint and the quality of the joint itself can play a significant role. It should be expected that a lower melting point solder will perform less well than a higher melting point solder. Appropriate process controls will have a positive effect. These are some of the reasons some form of safety agency factory auditing of this type of construction is normal. Regards, Peter L. Tarver, PE Product Safety Manager Sanmina-SCI Homologation Services San Jose, CA peter.tar...@sanmina-sci.com > -----Original Message----- > From: Chris Maxwell > Sent: Tuesday, February 04, 2003 5:32 AM > > > Exactly! > > Chris Maxwell > > > > -----Original Message----- > > From: drcuthbert [SMTP:drcuthb...@micron.com] > > Sent: Monday, February 03, 2003 7:50 PM > > > > What is needed is the I squared t rating of the > breaker. Then the (I^2)(t) > > rating of the PCB. Then you know if the PCB can > take it. > > > > Dave Cuthbert This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
