"Andreas Jahn" <andreas_-_j...@t-online.de> writes: > Hello > >>I do not imagine cadmium bearing solder being easy to acquire. The >> Wikipedia entry for solder says Pb90Sn10 can be used as a replacement >> for Cd70Sn30 in low thermal EMF applications: >> >> http://en.wikipedia.org/wiki/Solder >> >> On Thu, 30 May 2013 04:00:19 +0200, Volker Esper <ail...@t-online.de> >> wrote: >> >>> >>>By the way: does anyone know, if Agilent uses special solder alloy? I've >>>heard that a cadmium containing solder is used to get extremely low >>>thermoelectric voltages (or voltage differences). >>> >>>Is that right? If so, which alloy has to be used? >>> >>>Thanks >>> >>>Volker >>> > > Within LT AN86 Cd60Sn40 is recommended for a limited temperature range > of 0 to around 40 degrees. > http://cds.linear.com/docs/en/application-note/an86f.pdf > > But: the thermal EMF is only zero against copper. > Most precision integrated (hermetical) cirquits use Kovar. (39uV/K > against copper) > Relay contacts will be either copper berillium or another material. > So in most cases a optimized solder for copper/copper connections will > not be useful.
I have never understood why it matters anyway. The conductors being soldered together end up in very good thermal contact. So there should be no thermocouple generated by the solder-conductor interfaces (since there is no temperature difference between the ends of the wires being soldered). So if you have copper-solder-copper, say, then the copper-solder junction is microns away from the solder-copper junction and is surrounded by metal. So surely they will be at the same temperature unless there is a huge heat flow. The referenced AN86 even suggests introducing balancing copper-solder-copper junctions, by cutting tracks and bridging with solder. [...] -- John Devereux _______________________________________________ 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.