[SOLVED] What is the resistance and temperature coefficient of solder?

Hi,

I would like to add a resistor based on solder characteristics to emulate solder joints to some simulations and haven't found any documentation online yet that provides all the information I'm looking for. Either that or I haven't understood it. I can't find this info on the manufacturer's spec. sheet or Googling "the solder type + resistance + temp co + company name." I know I can emulate the 1oz copper pcb tracks using online tools to calculate their resistance and temp co., when I get to that part.

One document View attachment 5aafaad2d3f1a2d5b47f962ef994840fd591.pdf says:
"b The alloy exhibited Ohmic behavior and has electrical resistivity 24.6 μΩ.cm at room temperature.
c The resistivity increased linearly with temperature and the temperature coefficient of resistivity was calculated and found to be 11x 10 ^-3 C-1."

Others, related to metal conductivity and resistivity don't seem to cover the specific solder I use.

engineering toolbox website says:

solder is: - ρ - (ohm m2/m) (Ω m) 15 x 10-8

This edaBoard thread says "solder has about tenfold resistivity of copper"

Which of these are sufficient for a simple model, and what about the temp co. aspect?

Is it unlikely to get such an exact match, and do you have to use general solder characteristics?

For Sn60Pb38Cu2, or just SnPb solder does anyone know of any helpful webs/tools/documents to obtain both parameters: resistance and temperature coefficient?

Thanks.

The data in the scientific paper looks reliable to me. Eutectic SnPb alloy should refer to Sn63Pb37. I don't remember the source of the "tenfold conductivity of copper" estimation. It may belong to Sn60Pb38Cu2, but not sure if it's accurate.

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Reviewing datasheets, the 24.6 µΩcm specification seems too high. 15 to 17 µΩcm (11.5 downto 10% IACS, annealed copper conductivity) is the range of datasheet specifications for both Sn60Pb40 and Sn63Pb37.

More data in this paper Dependence of Electrical Resistivity on Temperature and Sn Content in Pb-Sn Solders, Journal of ELECTRONIC MATERIALS, Vol. 40, No. 2, 2011

...

Hi,

Could someone check these calculations are correct. I'm unwilling to believe 1mm³ or 2mm³ of solder create such a high resistance value as 1.5Ω and 0.75Ω, respectively. Maybe I made a mistake somewhere doing the sums.

Must add first, after doing more research, found a table that says "solder" has a resistivity of 15 * (10^-8), the same 10^-8 as copper and tin, so not sure which to go with.

Anyway, let's say, solder has a resistivity of 15uOhm/cm, the solder blob could be 1mm³ or 2mm³.

For 3D shapes, Resistance is ρ * (L/(W * t))
(Length, Width, thickness)

These are calculated in metres. e.g. 2mm is 0.002m, 15µΩ/cm * 100 is 0.0015Ω/m

2mm³ solder resistance = 0.0015Ω * (0.002m/(0.002m * 0.002m))
= 0.0015Ω * (0.002m/0.000004m)
= 0.0015Ω * 500
= 0.75 Ω

1mm³ solder resistance = 0.0015Ω * (0.001m/(0.001m * 0.001m))
= 0.0015Ω * (0.001m/0.000001m)
= 0.0015Ω * 1000
= 1.5 Ω

This seems very high to me, compared to the e.g. 0.00122Ω a 2cm * 1cm bit of PCB track causes, ...which is why it would be nice to know if the calculations are correct or the 10^-8 figure may be the more accurate one..

Also, why does 1mm work out as having more resistance than 2mm, when it is smaller on every side and in volume?

Apart, but related: To choose the ppm/ºC for solder, with nothing much to go on for solder specifically, is it best to use the worst ppm value of Sn Pb Cu, which is the tin that has a ppm/ºC of +4,700 (copper is +3,930; lead is +3,400)?

Thanks.

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d123 said:

Also, why does 1mm work out as having more resistance than 2mm, when it is smaller on every side and in volume?

Click to expand...

I really asked that question... Slight mental disconnect between increasing wiring gauge for greater current and little sums about blobs of solder... Embarrassing.

You start with confused resistivity units. Solder resistivity is 15 µΩ*cm or 15e-8 Ω*m, not Ω/m. Respectively all calculation results are wrong as well.

The 1 mm cube has a resistance of 150 µΩ, the 2mm cube 75 µΩ. A 1 m cube 0.15 µΩ.