Tempco of PCB copper and solder regarding sense resistor?

[cupoftea]

Hi,
We are doing an overcurrent trip circuit for output of SMPS. (28V and 33A is nominal max output)

We are using sense resistor CSS2H2512RL500FE for sensing up to 45A. (also with INA195 sense amplifier) It is two terminal, and even though we have kelvin connected it, the resistance obviously varies depending on the amount of solder used on the pads (they are hand soldered).

Anyway, that’s maybe not a problem, as we can “calibrate” and get an “effective sense resistor value”.
Anyway, our “sense resistor” is obviously partly the CSS2H2512RL500FE part, and partly the PCB copper and solder. What is the tempco of the PCB copper and solder?

Looking at the CSS2H2512RL500FE datasheet, the tempco of the resistor is great… it is pretty much within 1% for -40to 150degC.

CSS2H2512RL500FE datasheet,

https://www.mouser.co.uk/datasheet/2/54/css2h-2512-1862180.pdf

 

[FvM]

Consider ~K resistance for pure metals (Cu, Sn) as a rough estimation, about 3300 ppm/K near ambient temp.

 

[KlausST]

Hi,

It´s shouldn´t be hard to find the copper´s tempco ... in times of internet.
The tempco of copper is huge, thus you rather may use it as temperature sensor than as precise resistor.

For solder: you have to contact the manufacturer, if it´s not listed in the datasheet. Different solder types will have different tempco.

If you see a lot of tempco whil you use kelvin wiring, then maybe your wiring technique is not optimal.
--> Post the part of the PCB layout.

Klaus