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Donut Pad with Allegro Padstack Editor

PCBTech

The Donut shape for pads can be used for various components in your PCB Design flow. This pad geometry is intended for use commonly in Fiducials and Mounting Holes where contact with a chassis ground may be required. It got its name due to similarity in shape with the popular sweet treat Donut.

Cadence Allegro Padstack Editor provides the Donut shape to be selected as a pad geometry:

You need to define the outer and inner diameters to define your design layers:

Once a Donut pad is created, you can use this .pad file in your symbols and layout designs. After placing a symbol containing a Donut pad, Allegro PCB Editor provides two methods to add a connect line to it. The trace can go either to the center of the pad pin or to a specific user-defined location inside the Donut pad ring. This is because the Allegro Donut pad geometry uses a different connectivity model (touch vs. connect point) from all other pad geometries.

If you want to route your pad using a touch model, the Allegro Snap to connect point option must be disabled in the Options tab while routing.

Team PCBTech

Cadence Design Systems

  • Schulz Jordan

    Earlier I had come across a pad which is irregular pad like the one attached below. The blue & Red segments are pads & Green area has to be drilled out. How to proceed with donut padstack for such unique requirement ?

  • geda
    in reply to Schulz Jordan

    This seems like a very typical requirement. Is this a through-hole pad or an SMT pad? Wondering how the blue center pad stays when the green area gets drilled.

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