[volt-nuts] cadmium solder alloy for low thermal emf?

[m k]

Hi Volker,

Look carefully at the graph axis text, it is temperature difference between the two leads, not 0Centigrade to 40 centigrade room temps.

M K

> From: Andreas_-_Jahn at t-online.de
> To: volt-nuts at febo.com
> Date: Thu, 30 May 2013 11:05:42 +0200
> Subject: Re: [volt-nuts] cadmium solder alloy for low thermal emf?
> 
> 
> 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 <ailer2 at 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.
> 
> On the other side Cd containing solders create very poisonous damps when 
> being heated.
> 
> With best regards
> 
> Andreas
> 
> 
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