Mounting Holes with KiCAD 7

[a4dev]

Hi,

A popular (I think) method for creating mounting holes with no copper or solder mask around the hole in KiCAD 6 involves adjusting the pad and solder mask clearance settings in the footprints properties dialog. It is easy to create a hole surrounded by bare FR4 such as can be seen on a raspberry pi PCB.

This no longer works in KiCAD 7. The solder mask clearance setting, renamed mask expansion, has no effect unless the pad has some metal in it.

Any suggestions about best way to do this in KiCAD 7? (I have a handful of PCB designs to migrate from v6.)

[retiredfeline]

Hmm, aren’t there mounting holes with no pads at all in the library? I’m sure I’ve used them in the past.

[a4dev]

There are! But they don’t exclude the solder mask around the hole.

[retiredfeline]

Hmm, I’m pretty sure those mounting hole footprints have soldermask holes and margins, otherwise the soldernask would bleed into the sides of the hole.

I looked at one of my boards with gerbview and suppressed the Cu layers. Here’s what it showed for one of my holes.

Or was your problem that you couldn’t adjust the margin?

[mf_ibfeew]

Any suggestions about best way to do this in KiCAD 7?

If you can wait a few weeks: this is already bugfixed (just checked with the current testing-version) and should be incorporated in the upcoming v7.0.3-version.

If you can’t wait: simple, fast and dirty solution: add a filled circle (with 5mm or any other desired diameter) on f.mask-layer at the centre of the mounting hole.

[a4dev]

Thanks! That solves it for me.

[a4dev]

Actually, for a mounting hole with no pad in from library, the solder mask does bleed into the hole on the finished PCB. Thanks for looking into this, apparently there is a change coming in v7.03

[retiredfeline]

Hmm, bleed never happened on the PCBs I have received. But you could always design your own NPTH hole footprint with a wider margin.

[a4dev]

I wonder if you have some custom mounting hole footprints? They seem different to the KiCAD library ones.

[retiredfeline]

Nope, just a standard 3.5 mm bare mounting hole from the library.

[eelik]

You can add “aperture pads”, i.e. pads having only mask or some other layer. They don’t have copper layers by definition. That way you can also control footprints which have mask holes different than the copper pad, either different shape or asymmetrically placed. Aperture pads don’t use mask or paste clearance values.