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Netlines Not Disappearing When Routed (Diff Pairs)

Question asked by cassini on Sep 24, 2019
Latest reply on Sep 26, 2019 by cassini

I am attempting to route a PCB with a lot of differential pairs. There are series resistors and spurs off the diff pairs in some circumstances (for a variant) and this has led to some problems in routing them but my main problem now is that the netlines are not disappearing even when a diff pair is clearly routed to completion. 


Weirder, I found one diff pair where one side had removed a netline upon being routed, but the other hadn't. You can see R106 to U16 pin 12 no longer has a netline, but despite being routed all other netlines on that diff pair are still visible. I did pick up a difference in the R106 net contraints over R107 net constraints, in that R106-to-U16 pin11 net was not 'ordered' in the constraints manager whereas the corresponding R107 net was, but changing the R107/U16 pin 11 net to 'MST' topology (instead of 'custom') and losing the 'ordered' constraint has not resulted in disappearance of the netline. BTW there are other similar diff pairs to this and despite also being routed they show ALL netlines still present.


I can't figure out what's causing the netlines to still be present. Any ideas?diff pair with termination/protection resistors (R9, R106, R107) with most netlines still visible