I read in !emc-pstc that [email protected] wrote (in <200212040412.gB44C [email protected]>) about '48V supply on VoIP' on Wed, 4 Dec 2002:
>Is there any safety or reliability concern with 48V possibly permanently >across >0.02" spaced pads on a PCB surface? I believe safety-wise it is okay, but I am >not sure if electromigration or something else may cause long-term problems, >since the phones are more-less permanently connected. It's 2400 V/in or 95 V/mm. Yes, electromigration can occur with less field than that, especially if the atmosphere is salty or polluted. Can you put slots or holes in the board so that there is no surface for the migration to spread over? Otherwise, varnish or even conformal coating might be advisable. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! ------------------------------------------- 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
