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What should you do with PLACE_BOUND_TOP if your component has no body?

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Let's say I have a component that doesn't have any body. For example, I made a footprint essentially consisting of a single plated through hole that I was going to solder a wire to. I wanted to have an explicit schematic component with a footprint to make sure I don't forget to add it.

The problem I am having is that even if I don't add a place bound top shape, Allegro will automatically add one when I place the footprint based on some other bounds in the shape. This has a few problems with it:

  1. The shape is too large.
  2. The shape will create a shape in the 3D viewer that shouldn't be there.
  3. This can cause unnecessary DRC errors that must be dealt with.

My next solution was to create my own place bound top but with a very small shape. The problems with this are:

  1. You get shapes on the assembly drawing that aren't actually there, even if they are small.
  2. Even if you set the height to 0, you still get rendering artifacts in the 3D viewer. For example, if the shape is over a hole, you can't actually see through the hole because the shape is blocking the view.
  3. If you wanted to argue that even something like a throughole for a wire should have some bound, I would think that a keepout would be more appropriate than a component shape.

Is there any way to deal with this that doesn't feel like a kludge or workaround?

  • 0

     Try creating footprint as mechanical symbol without place_bound shape. I tried it, and place_bound shape was not automatically generated after I placed the footprint.

  • +1

    Hi, since version 17.2 of Allegro, Allegro includes an option to automatically create a place bound top on symbols.

    To resolve your issue disable the automatic creation of the placebound if one does not exist on your symbol.

    Go to Setup > Design Parameters - Design Tab,  Un Check the box "Auto Create Place Bound"

    A little history. Originally the place bound top served two functions. One was for DRC Bounds checking such as component body spacing and the other was to provide
    a method to do an early 3d view of the footprint. The 3D View was enhanced so as to include step files. In addition to the placebound top there is also a DFA_Bound_Top
    that is part of the package geometry class. You could use this as a means for bounds checking also instead of the placebound within symbols you create.

    Let us know if that works for you.

    All the best.

  • 0 in reply to excellon1

    Thanks. This helps a lot. I'm new to Allegro, so I've been using DFA_Bound_Top for bounds checking already.

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