Complex antipad shape

 Glad to finally see others getting advanced antipads in their designs.  We've been doing it for years and your method is spot on.  We use a custom antipad on each layer for a specific stackup.

You need to tweak the origin of the complex shape over in the shape -- just use the design setup menu.  One of the issues with the padstack editor is cacheing so what I do is name each revision of the complex pad with name_n where n increments and Allegro replaces everything.  Once it's all working I clean up what I need to and enter everything in the master library.

Thanks for your reply.  I've been thinking about this since I posted my question and I had pretty much come to the conclusion that what I had to do was change the origin.  Can you give me some insight into why the origin might be wrong (obviously you've had this same problem) and what general procedure I would use to determine what it should be?  Also, when I instantiate this pad in a component symbol, the antipad is not visible.  I think this is because the component symbol doesn't have any net connections yet so, if I see anything, it would probably be the thermal relief on that layer.  But I might not see anything except the normal pad on that layer until I attach a net to it (by using it in a power or ground plane).  Does that make sense?

 Also, I see that you are using a custom antipad for each layer, as you said.  So that means that when I define my padstack I should define it with the same stackup my board will eventually have (and fixed layers, I guess) rather than using the generic internal layers that can be defined in the padstack editor.  Which also means that I have to define new padstacks for every board stackup I use, right?

 As far as being able to view the anitpad in the component -- your understanding is correct.  It has to be pulled into a board.

As far as the origin ---  there are lots of little things that can contribute to the offeset becoming a big issue.  I can't completely answer your question without looking at the specific instance.  It probably has to do with where the actual geometric center is located...

What I do is set up the board, import a "normal" via, edit the "local" via which now contains the stackup, and then rename it with a custom name for my RF signals.  That way only where I use the custom via does it come in to play.  The "normal" via can be used for regular signal vias that don't require the custom antipads.

Does that help?

Yes, thank you, that does help.  I thought the padstack editor might be inventing its own origin for the antipad because it has an asymmetrical shape.  That's probably what it's doing.

I've been able to draw keepout areas in Autocad (much easier than using the native Cadence drafting tools) and bring them into my part symbol, and the origins stay where I put them in Autocad even when the shapes aren't symmetrical.  But maybe the padstack editor works differently.

I understand your procedure for using the vias and that makes sense to me.  I can do it the same way on my board.

Thanks for your help with this.  I appreciate your taking the time to respond.

John