Dave The use of PCB traces as a fuse is highly unreliable. During my stint at Racal-Vadic in the early 80's I was assigned the task of determining the reliablility of PCB traces as a fuse. The tests were made under very controlled conditions. We had each of our 6 PCB vendors make 10 boards each. Each PCB had a number of different trace widths connected to the RJ-11's. The resulting variations in the fusing action was so wide and varied we abandoned the concept and wrote an edict "Thou shall not use PCB traces as a fuse." Just the variation in opening up the trace to over current was totally unusable. Not to mention the problem of shorting to other traces and components when a trace buckled and peeled from the PCB. This was the case even with MIL grade material and PCB design specs.
The best argument against this idea: The company is finacially libel for all injuries, damages and the board becomes a throw away. It's simply best to use a fuse. I would be surprised if UL would accept a trace as a fuse anyway. I think it's a false economy. Duane Marcroft Telecom Consultant ___________________________________________________ On Mon, 29 Jul 1996, Dave Spalding wrote: > Hi TREG - > > We have the "opportunity" to purchase a cheaper transformer which will meet > the requirements of UL 1459 instead of UL 1950. I understand that we can > comply with either standard until March 2000 or 2001 and UL 1459 is getting > talked about around here. Our product is an ISA card that will fit into a > PC. I would rather go with UL 1950 because the PC would be tested to that > (right?), because I have heard that we would need to install a fuse in the > front end to comply with UL 1459 and because UL 1950 is more compatible with > international standards.. My boss is looking to save cost so he wants UL > 1459 and answers my desire with the fact that we will have multiple boards > (one for USA/Canada, one for international), so we could use this transformer > for the domestic board, although the issue of whether Canada would accept UL > 1459 is not resolved. Also, the "fuse", he says, would be the etch on the > board because they would just peel off with the overvoltage testing of UL > 1459. I am not comfortable with that, though. Anyway, I want to go with UL > 1950 but I need ammunition. I was wondering if you could help me understand > the difference between UL 1459 and UL 1950 and also give me your > recommendation on which to test to. Any help that you can give would be > greatly appreciated. Thanks in advance. > > - Dave Spalding > > > David Spalding > Motorola ISG > 20 Cabot Boulevard > M2-250 > Mansfield, MA 02048-1193 > Phone: (508) 261-4742 > FAX: (508) 339-2346 > EMail: [email protected] >
