Well, I hate to say this, but this very thing was done at a company that makes fire alarm panels. If UL allowed that, they'll probably allow it in your application as well. Just remember that the i2t value of the trace can vary WIDELY. How wide? I think it was on the order of +/- 50%. Mark Hofmann -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Andrew Ingraham Sent: Wednesday, August 25, 2004 9:47 AM To: Si-List Subject: [SI-LIST] Re: Can a thin PCB trace be used as a reliable fuse I don't know the regulatory details here ... ... but I'd be very concerned about things like fire. When a trace blows, is there a flame? In a packaged fuse, it would be contained within the package. Not so with an open trace. Even if no flame, does something melt, and could it fall somewhere else? Are toxic materials released, due to the uncontained nature of your makeshift fuse? I would not think that a thin board trace would make a very reliable fuse with good repeatability, but that's not much more than a guess. External layers have loose tolerances on trace thickness, because of the way they are made and because it has minimal effect on Zo. Also I'd think that the heat sinking properties of the board might make it a rather slow acting fuse, and in the meantime a lot of the board "cooks" as well as all nearby components (you did say you are tight on space). Even attaching short lengths of nichrome wire might be better (if nichrome makes a good fuse)... Regards, Andy ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu