Why should I need to resize a polygon? Most of the multi-layer PCB’s I made had a ground or power plane inside the PCB. In Altium it is possible to implement an internal plane but most designers I know (me as well) don’t like that approach as the copper does reach till the outside of the PCB shape. In most cases I use a polygon connected to ground as internal plane. This polygon is a scaled version of the board shape. To do this Altium Designer should provide the functionality to scale the polygon by a value or percentage. However, Altium does not provide this scaling functionality that’s why I wanted to share my tiny workaround to create the scaled version of the polygon.
(* Press (CTRL+h) and click on the wire to select the whole connection)
- Create the pcb border/shape using a mechanical layer or keep-out layer. For explanation purpose I created an weird example PCB shape.
- Select the board shape (*), Mine was on mechanical layer 1. To create a board shape in Altium press [Design/Board Shape/Define from selected objects] while selecting the objects.
- Copy the board shape ( mechanical 1) next to the the PCB.
- Select the copy of the board shape and convert the layer from mechanical 1 to top or bottom layer. It is important that it is a copper layer otherwise it would not work.
- Change the line width for example toward to 2 mm. This will set the scale factor of the polygon. Thicker lines (3mm, 4mm …) will create a smaller polygon inside this shape.
- Outline this thicker version of the board shape. Select it (*) and press [Tools/Outline]. The result will look like this figure.
- Select the thick line ( * ) as well as the outer version of the thin lines (*) an delete them. To create the scaled polygon only the inner lines are needed.
- Select these lines and press [Tools/Convert/Create Polygon from Selected Primitives]. The result is a polygon. You can change the layer of this polygon, as well as the net connection or if it is solid or hatched.
Copy this polygon back to the pcb board. You can see that it is a scaled version of the board shape. Resize it by using the same process as explained while changing the line width.