On 29 October 2016 at 14:51, NeonJohn <j...@neon-john.com> wrote: > > > On 10/28/2016 08:39 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: > > > I wonder how practical it is to weld test leads, so there's no solder or > > thermal EMF. > > > > I know that this will sound crazy, and probably is, but could one weld > > components to a PCB? > > Yes indeed. About 20 years ago I had a machine that made circuit board > by routing tiny wires and spot welding them to the connection. I can't > for the life of me remember that process name. > > Only problem is, if you weld two different metals together, even copper > with different compositions, you've still made a very rugged and durable > thermocouple. > > John >
But if one could use copper as the bond wire, rather than gold which is quite common, then it would give you very little thermal EMF I would have thought any impurities in copper wire, would be quite small, as it would reduce the electrical conductivity. Whilst I accept one is not going to get 100.0000000000000000000000 % pure copper, I would have thought the effect of any impurities at least an order of magnitude less than using solder. I'm only postulating this - I have no evidence to back it up, and have never studied the subject. Perhaps the person who was making the measurements on the solder, could try making a thermocouple by welding two bits of wire taken from different sources. I guess the problem would be preventing any impurities entering the weld. A quick Google suggests one needs argon gas when welding copper. Dave _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.