Rich
Thanks for the info – which I had not realised before. However, even if I had known, I don’t think it would have helped much in that particular situation which involved a wide range of board designs and layouts produced in very small quantities of each – so we could not have tested every one even if we had had the right test facilities, which we did not. In the end, the “solution” was a different sort of pragmatic approach because the boards were always enclosed in hermetically sealed high pressure (10,000 psi+) / temperature (180C+) -resistant stainless steel tubes which have very little free air volume inside them. That means that there is very little free oxygen for component fires to use, and calculations proved that ignitions involving all the flammable material within the enclosures would exhaust that oxygen well before fires could develop, and also the way the enclosures are built and sealed means that flames or flammable material could not escape unless there had first also been very substantial external physical damage. PS: the problem with the V-1 boards was that the flame-retardants apparently break down over time at the high operating temperature in which the enclosures operate (down oil and gas drill holes), and the by-products then aggressively attack the components on the boards and cause them to fail. John E Allen W.London, UK From: Richard Nute [mailto:ri...@ieee.org] Sent: 21 May 2016 03:01 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] fire safety test methods for different country standards In my last job I tried to do something similar w.r.t. PWB materials for applications where V-1 or better materials aren’t any good because the retardants result in reduced service lives in hostile equipment environments, whereas some specific (and very special!) HB materials last much longer. A PWB with lots of copper will pass the 94V-1 or 94V-0 tests even if the base material is 94HB! The copper acts as a heat-sink and prevents oxygen from mixing with evolved gasses from the epoxy. Test in place (vertical or horizontal). Rich - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
