Tom Bruhns had an interesting article published in the 11.17.08 edition of Electronic Design. His point was that the positive tempco of copper traces was beneficial in design over fixed resistors. Not trying to reduce his fine article but it is interesting to note that the 10mV drop that he depicted is approaching the limit in trace voltage drop before heating of the trace's center hotspot will be greater than 5 degrees centigrade and the PC boys will do their Henny Penny renditions. Copper traces fail at 1000C and we allow resistors to reach 150C but 5C rise in a trace will bring out a flock of H.P. bird dogs. Most designers of PC traces, less than 2 inches, worry about max current but max voltage drop is more indicative of trace heating. Keeping all PC traces less than 12mV guarantees all trace hotspots will have less than a 5C rise. Cheers, Harry
- posted
15 years ago