Resistance of TO220 resistor leg?

[cupoftea]

Hi,
Do you know the resistance of one leg of this TO220 resistor?

TO220 resistor

https://www.farnell.com/datasheets/2710536.pdf

Depending on what material it is made of (datasheet doesnt say), the resistance coudl be from 46.5uOhms, to 1.91mR ?

m	m	m
TO220 LEG RES	E-F				mm	m^2
width	thick	length		MAT'L	RHO	L	AREA	RES
7.80E-04​	5.10E-04​	0.00975​		copper	1.68E-08​	1.38E-02​	4.97E-06​	4.65E-05​
7.80E-04​	5.10E-04​	0.00975​		tin	1.09E-07​	1.38E-02​	4.97E-06​	3.01E-04​
7.80E-04​	5.10E-04​	0.00975​		GOE steel	4.60E-07​	1.38E-02​	4.97E-06​	1.27E-03​
7.80E-04​	5.10E-04​	0.00975​		s steel	6.90E-07​	1.38E-02​	4.97E-06​	1.91E-03​

..So i realise the qu is "what is a res leg made of"?

 

[shlooky]

Hi,

you can actually measure it using kelvin connection (4 wire measurement)
I would expect a value in mOhms...

Shlooky

 

[KlausST]

Hi,

I defintely expect them to be less than a milliohm.

If you go for high accuracy, low resistance, high current, you also should use short legs and kelvin wiring on the PCB.

Klaus

 

[dick_freebird]

I'd expect most of the resistance to be in the bond wire(s),
you could probably figure rough pin material resistance as
dimensional copper with a pair of calipers. Crack a package
and see what the wire bond looks like, for length and diameter,
and there's tables for that.

 

[c_mitra]

​

..So i realise the qu is "what is a res leg made of"?

They are copper plated with tin. Tin gets covered with an oxide layer but this oxide is soluble in the solder flux.

Tin alloys well with copper and the connection is ohmic.

The lead resistance will be in the microohm range (10-100 microohm)

This is close to the value of a well soldered PCB connection.

1. It is not tin because tin cannot stand soldering temp
2. It is not SS because stainless steel cannot take solder
3. Is it steel? you can check with a magnet.