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i think clearance is a minimal, that defined in CES via to via
I think that would be the issue
Let's asume that you want the distance between the two via's of a differential pair to be 0.5mm.
- Create a Netclass "LVDS" for the LVDS signals and add the appropriate nets.
- Create a clearance rule and give it a meaningful name "0.5 mm", set the via to via clearance to 0.5mm
- Add a class - class clearance for LVDS to LVDS and set it to the 0.5mm clearance rule
If you switch layers, the differential via will be placed at the clearance defined in the 0.5mm rule
In the same way, you can control the distance between the differential pairs.
This is dead on with the way the software works today. We do have some requests to allow the user to define a Diffpair Via Spacing just like we support for DiffPair Trace spacing today so the user does not have to go through the complexity of setting up class to class rules.
In VX.2 we support something called a Crankshaft pattern for HDI vias. So the user defines a set of HDI vias in a pattern including the clearances between theses vias in an ASCII file, then during Plow they can select this pattern to more easily move between layers with complex HDI via patterns. We are kicking around do the same for DiffPair allowing the user to define a DiffPair via model that includes the distance between the vias for each leg of the diffpair but also complex via patterns, shedding vias, plane obstructs, ... Then while routing the DiffPiar you can call up one of these patterns to be placed. If you would like to see this, vote it up on the Ideas Site if you would like us to implement this idea: Diff Pair Via Patterns