Keep Out and Keep Off the Grass

The part land patterns in your CAD package parts library should all come with a valid keep-out area defined. That’s the theory anyway. However, theory and practice don’t always match up so well. I’ve written a lot about such things as verifying that the actual footprint matches the physical part. That’s important. But it’s not all that’s important.

Sometimes the footprint will match up just fine, but the body of the part won’t. This might be because you’re using a different variant of the same part or perhaps a different part altogether that just happens to have the same footprint.

It’s common practice to modify an existing library component for a new part, but if you do that, make sure you consider the physical dimensions of the part body too. Sometimes you can get away with the keep-out area being different, but as shown in this image, not always.

Duane Benson

One thought on “Keep Out and Keep Off the Grass

  1. This is interesting, I’ve come across it before when someone makes a library parts and uses a footprint that physically works but the keeput is for something similar but different. My only take on this is DON’T DO IT!

    It makes sense to make sure that any part you use has the proper footprint, including the keepout defined. It’s the best way and for the long term, the only way! It does mean you can hace some simliar but different footprints, but as long as their maked logically it should be easy to use.

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