> From: j...@devereux.me.uk > To: volt-nuts@febo.com > Date: Fri, 31 May 2013 14:05:39 +0100 > Subject: Re: [volt-nuts] cadmium solder alloy for low thermal emf? > > "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. > > [...] > >
But then why does it make a difference to stop the air currents around sensitive/accurate circuits? MK > -- > > 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. _______________________________________________ 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.