pcb-rnd knowledge pool
Polygon vs. polygon clearance
poly_clr_poly by Tibor 'Igor2' Palinkas on 2016-09-24
Tags: howto, polygon, clearance, thick, wide, current
Abstract: Some boards need a lot of copper: so much that it looks like if the whole bottom layer was just copper with a few gaps drawn to form islands. A new way of drawing this with pcb-rnd is enabling polygon-vs-polygon clearance. This way thick polygon islands can be formed within a polygon pour without shorting the islands to the pour.
This enables polygons to make clearance around themsleves the same way as lines or arcs do. Speaking in technical terms, the new flag, PCB_FLAG_CLEARPOLYPOLY is the polygon alternative to the clear-line flag used on lines and arcs.
The real reason for adding this feature was to support arbitrary shaped smd pads with subcircuits - the smd pad needs to be able to clear other polygons. Being able to draw these thick islands in a ground plane is just a bonus.