Doesn't it depend on the purpose of the fuse? If the circuitry is non-telco and voltages are < 42V you have wide design latiitude. Even if the agencies do not care, you should characterize the performance under abnormal conditions. At least one company uses printed fuses on PC accessory cards to prevent runaway combustion (fires) when ceramic by-pass capacitors crack and short. The cards were recognized by well-known US and European safety agencies. Mains and telco have special IEC-950 rules and testing likely has poor ROI. Since the 'fuse' is not a recognized component, sufficient characterization may be a problem with most safety agencies. David Sterner Ademco, Syosset NY -----Original Message----- From: Joshua Wiseman [mailto:[email protected]] Sent: Friday, September 15, 2000 2:42 PM To: Emc-Pstc (E-mail) Subject: PCB fuse trace
Hi group, I am sure that Ken appreciates all the pointers, but no one is answering his question. He is asking for a reference to a standard that allows him to do this. If I knew one I would certainly tell him. Josh -----Original Message----- From: [email protected] [ mailto:[email protected] <mailto:[email protected]> ] Sent: Friday, September 15, 2000 8:30 AM To: E Eszlari Cc: [email protected]; [email protected]; [email protected]; [email protected] Subject: Re: RE: PCB fuse trace Keep in mind the possibility of the trace shorting to dead metal parts before vaporizing creating a momentary high leakage current. Bob E Eszlari <[email protected]> wrote: > Ken, >From my experience with UL, if a trace opens during a fault test, the first test you must pass is the hipot, then UL will jump the portion of the trace that opened and perform the same test. If the trace opens in another location the same process is repeated (I guess until there is no longer a trace to open or if another device fails and protects the unit). If some other device (unapproved) protects the unit, you will have to repeat the fault 3 times with the same result in order for it to be acceptable. If the trace opens up to the input, you may discover that you really should have designed in a protective device. Ed >From: "Matsuda, Ken" >Reply-To: "Matsuda, Ken" >To: "'Jim Freeman'" , Peter Tarver > >CC: "Matsuda, Ken" , [email protected] >Subject: RE: PCB fuse trace >Date: Thu, 14 Sep 2000 17:09:07 -0400 > > >Thank you all for responding to my inquiry thus far. Here is an update on >my findings. I have since had the opportunity to discuss this issue with a >few different NRTLs in regards to particular standards. The uniform >concensus thus far from these agencies are that they test to standards, not >necessary impose restirctions that are not in the standards. Thus many >agencies have agreed that a fuse trace, although discouraged, can be used >as >a primary means of protection, unless specifically referenced not allowing >such use. But once again, this comes down to the particular standard that >you apply too. Some may require abnormal tests, etc... > >-----Original Message----- >From: Jim Freeman [ mailto:[email protected] <mailto:[email protected]> ] >Sent: Thursday, September 14, 2000 11:38 AM >To: Peter Tarver >Cc: Matsuda, Ken; [email protected] >Subject: Re: PCB fuse trace > > >In all of this discussion, no one has mentioned the possibility of fire >from >blowing a PCB trace fuse. I know that there are flame retardants in the PCB >material that protect to a certain flashpoint but to rely on that mechanism >for fire prevention is a bit far fetched. From my limite experience with >fuses, there is generally a large structure that is enclosed in sand to >prevent a fire from spreading. > >Jim Freeman > > > >Peter Tarver wrote: > > > > >My experience with safety agencies is they do not want to rely on traces >opening to act as fuses and no standards have been developed, that I am >aware of, to address this issue. Fuses certification gets involved in the >metallic alloys used, to the fraction of a percent, the conductor size, >additional construction features, such as heat sinking elements for time >delay characteristics, tension loading for fast action, blah, blah, blah. > > >Most of these issues are far too difficult to control for pwb traces, >especially considering the etching processes don't lend themselves to the >level of control necessary to be a reliable fuse of specific ratings. >Additionally, the heat sinking from pwb layout of one product to another or >varying copper thicknesses in a product line, adding or subtracting ground >planes for emc, the variability of soldering processes and location/thermal >capacity of components on the pwb make this seem far too cumbersome to want >to work with. > > >BTW, this is a very different world from "repeated twice, same result" >single-fault testing, where a pwb trace opens. > > >Regards, > > >Peter L. Tarver, PE >[email protected] > > >-----Original Message----- >From: Matsuda, Ken [ mailto:[email protected] <mailto:[email protected]> > ] >Sent: Thursday, September 14, 2000 7:02 AM >To: [email protected] >Subject: PCB fuse trace > > > >I was wondering if anyone knew a standard for the US, Canada, and Europe >that covers PCB board traces that can be used as fuses? > > > > >Thanks for the help, > > >Ken > > >------------------------------------------- >This message is from the IEEE EMC Society Product Safety >Technical Committee emc-pstc discussion list. > > >To cancel your subscription, send mail to: > [email protected] >with the single line: > unsubscribe emc-pstc > > >For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > > >For policy questions, send mail to: > Richard Nute: [email protected] > > > >------------------------------------------- >This message is from the IEEE EMC Society Product Safety >Technical Committee emc-pstc discussion list. > >To cancel your subscription, send mail to: > [email protected] >with the single line: > unsubscribe emc-pstc > >For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > >For policy questions, send mail to: > Richard Nute: [email protected] > > _________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com <http://www.hotmail.com> . Share information about yourself, create your own public profile at http://profiles.msn.com <http://profiles.msn.com> . ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected] ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
