How to set track width size of differential pairs?


#1

I am using the differential pair router (just started learn how to use it) but cannot figure out to set the track width size. Can someone give tell me how to do it?

The problem I am having now is that the pair’s width size is less than 5 mil, causing DRC errors of too thin tracks.


#2

Set the track width and trace gap from the main menu Dimensions -> Differential Pairs.

Remember that the differential track width must not be smaller than the global minimum track width you set in Design Rules -> Design Rules then choose Global Design Rules.

And also there is a default net class which includes both width and clearance, so if you do not assign the nets to a custom net class, the differential gap must not be smaller than the clearance set in Design Rules -> Design Rules, Net Classes Editor tab. You can also assign the differential signals to their own net class.


#3

Thanks @Andy_P! I was able to change it after reading your reply.


#4

I should mention that I had to set the gap of the differential pair wider than that of the default track clearance, for example, the gap = 0.009 mil, the default tack clearance = 0.008 mil. Otherwise, the ERC reported errors like “track too close”, even the gap = 0.008, the default track clearance = 0.008, would get the ERC errors.


#5

This is a known bug.


#6

One example on the bugtracker:
https://bugs.launchpad.net/kicad/+bug/1533551

The last post shows that this bug is worked on.