Thermal EMF of lead free solders?

[splin]

Does anyone have any figures for the most common lead free solders against copper and kovar? I did spend some time looking around but couldn't find any numbers.

[helius]

"Unfortunately, the thermal EMF coefficient of Kovar against copper is one of the highest among the alloys used in electronics (-35µV/°C)."
"the thermal EMF value for copper vs. platinum (7.6µV/°C)"
(http://www.vishaypg.com/docs/49871/theremf.pdf)

The Seebeck coefficient is determined by the composition of a single material. There is no thermoelectric effect caused by "different materials against one another". Nevertheless, the figures are quoted relative to a common alloy because that is the way they are measured. By subtracting the contribution from the common alloy (which is determined using a chemical method) you can find the Absolute Thermoelectric Power of the alloy under test.

The ATP of copper is +1.94 µV/K, which makes the ATP of Fernico I -33 µV/K, and the ATP of platinum -5.7µV/K.
I've seen papers that place the ATP of SAC407 at -1.2 µV/K, but that isn't a common lead free solder. In any case it seems to be lower in magnitude than the ATP of Sn63Pb37 at -4.8 µV/K.

One reason that the Seebeck coefficients of solders are rarely printed may be that they are irrelevant to properly designed circuits.