mairomaster , 02-03-2017, 02:32 AM
You should at least have an idea about the manufacturing specifications (min track/gap, via properties, etc). Then you can use bigger track widths than supposedly they will actually be, so that you can shrink them later to achieve the right tolerance. As you said yourself, I wouldn't route the differential signals before having the stackup, since you will need to re-route them later.