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Removing non-functional pads - Lesson 6 of Advanced PCB Layout

Tom Yunghans , 06-12-2020, 09:07 PM
Hi Robert,

I understood you to say in Lesson 6 of "Advanced PCB Layout", that non-functional pads (pads which have no connections on a layer) are never placed on the Altium plane layers. The Rex Module has vias with 0.2mm holes and 0.45mm pads. In the video you showed (and I confirmed) that on both L4 and L9 (both plane layers assigned to ground) that these pads were indeed removed and the hole in the plane ended up being 0.4mm in diameter( the hole being 0.2mm in diameter and the standard clearance being 0.1mm), I am questioning if that hole in the plane is large enough. I assume a 0.45mm pad was selected to account for "wander" of the drill bit to avoid "breakouts". If that is true, wouldn't we need a hole in the plane layer that is at least 0.45mm in diameter?

On the signal layers with power/ground polygons (L2, L5-L8, and L11), you created a few new rules to allow smaller clearances from the pads of the vias to the polygon, under the assumption that the PWB manufacturer was going to remove these non-functional pads on those layers, and this smaller clearance would allow more copper to flow between the vias on those layers The latest version of Altium has a command which removes the non-functional pads ("Tools/Remove Unused Pad Shapes") and when you repour the polygons after executing this command, you get the smaller holes in the polygon that you desired. If you expect the PCB vendor to remove those non-functional pads in those layers, why wouldn't you just remove them in Altium using this command? Was that command not available in Altium when you created the course, or is there some other reason you didn't remove them in the artwork?
robertferanec , 06-15-2020, 02:56 AM
- yes, that command was not available ... still I do not really use it.
- hmm, good point about the power planes. Especially, because standard PCB manufacturing requirement is copper clearance at least 0.2mm from PTH hole. When I will be manufacturing PCBs next time, I will ask about this. Interesting.
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