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Donut pads

Question asked by Thomas.DeSmit on Dec 12, 2011
Latest reply on Dec 15, 2011 by hgk-layout

Hi all,

 

We use some SMT standoffs here, made by a well-known hardware maker. The recommended "footprint" for these is a donut-style pad, with a non-plated hole in the middle. We have created the cells for these in a number of different ways, none of which is ideal. Expedition does have a "donut" shaped pad, and I'm trying some test using that pad in a padstack/cell. The problem I'm running into is the fact that Expedition always insists on routing to the center of the pad/cell. In order for this to work as we'd like, the routing needs to end at the donut, not continue on into the center of the pad. The way it's working now, you'd end up with a trace across the area that we intend to be clear of copper (the small are between the inside diameter of the donut copper, and the non-plated drill).

 

I've tried doing this two different ways; in one, I made a "thru" padstack using the donut pad and a non-plated drill in the center. Expedition wants to route to the center.

 

Next, I tried making an SMT padstack with the donut pad and no drill. Then in the cell, I used this padstack, and added a non-plated mounting hole in the center. Expedition still insists on routing to the center.

 

So, does anyone know how to get Expedition to recognize the donut pad as a valid start/stop point for routing?

 

I know there are other ways to get what we want, and as I said earlier, we do have some things that work. I really want to try to find a way to make the donut pad work, as this seems like the exact scenario where that pad style would apply. It seems to me if the a donut pad is available, the software should recognize the copper donut as a valid stop/start for routing. If you have a "donut" pad, it seems you would not want copper routed through the "donut hole".

 

Open to ideas. Thanks.

 

Tom D

Aeroflex

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