What is the appropriate resistance of a ZERO-OHM resistor?

[buenos]

Hi

I have recently noticed that on my board on one of the power-link zero ohm resistors I got 12mV voltage drop. It is a memory VTT power rail that goes through this 0402/0R resistor. It provides debug isolation for design bringup. The current might be 2-3A (unknown), so it leads to 4-6mR. I have measured it with a normal multimeter which is not very accurate, and it says 0.1 ohm.
So what should I expect? I though it should be as good as 0.1mR or less.

 

[prestonee]

Typically the resistance measurements of a multimeter will read .1 or .01 depending on its accuracy. as far as whats appropriate? it depends on your application, and what loss you can deal with ( obviously there is no such thing as 0 ohms, even superconductive material has some resistance). chances are the resistive routing on your board the 0 ohm resistor is attached to, and the solder joints are going to be more resistive then a 0 ohm resistor(which is essentially a block of conductive metal). If this is really important for you you could fork out some money and grab a more expensive more accurate multimeter.

Hi

I have recently noticed that on my board on one of the power-link zero ohm resistors I got 12mV voltage drop. It is a memory VTT power rail that goes through this 0402/0R resistor. It provides debug isolation for design bringup. The current might be 2-3A (unknown), so it leads to 4-6mR. I have measured it with a normal multimeter which is not very accurate, and it says 0.1 ohm.
So what should I expect? I though it should be as good as 0.1mR or less.

 

[buenos]

The issue is not the multimeter nor the fact that R>0, but how much is too much for a component like this. I thought 4-100mR is too much, and 0.1mR would not be too much. Is it a quality issue?

 

[keith1200rs]

Bourns zero ohm 0402 resistor is specified as <50m ohms. If you are seeing 12mV drop with 2-3A then that is pretty good. If you don't want a significant voltage drop don't use such a small resistor. 0603 would be <10m ohms from Bourns for example. Another alternative is "solder jumpers" where you use pads which are shorted with solder then required i.e. with no component.

Keith.

 

[mtwieg]

Unless the manufacturer says specifically what resistance is expected, I wouldn't make any assumptions. Most manufacturers will at least give a current rating for the jumpers. 2-3A sounds like a great deal for a 0402 size jumper, you may want to change to 0603.

 

[buenos]

OK, Thanks.