Solder mask minimum width

My board house requires a minimum solder mask width of 0.2mm. I have a couple of QFN parts where the distance between pads is less than 0.2mm so they won’t accept my board.

I’ve tried setting “solder mask minimum width” to 0.2mm but this creates some really strange geometry on exported Gerbers. Is this setting broken in 5.1.9? Is there any DRC option so I can find and manually remove solder mask narrower than 0.2mm?


If the pads are too close to have solder mask between them you should not put it there.

Knowing technology you will use, you can modify footprints having that problem.

Footprints with a pitch of 0.2mm usually do not have any solder mask in between the pins.

If you fiddling with KiCad’s settings have strange consequences, it may well be because your settings distort the way some footprints are supposed to be used. To give us a better idea of what is going on, a few screenshots may help.

The pitch is 0.5mm, but the recommended footprint leaves 0.2mm between pads.

Here’s what the footprint looks like without any solder mask clearance or minimum width:

Here’s the same footprint with solder mask clearance set to 0.05mm and minimum width set to 0.22mm:

It leaves a bunch of tiny islands in the solder mask which are even worse than the bridges between pins. If I leave the mask clearance set to 0 it generates Gerbers that look OK, but don’t work in a bunch of online Gerber viewers.

My KiCad Version:
Application: Pcbnew
Version: 5.1.10-88a1d61d58~90~ubuntu20.04.1, release build
wxWidgets 3.0.4
libcurl/7.68.0 OpenSSL/1.1.1f zlib/1.2.11 brotli/1.0.7 libidn2/2.2.0 libpsl/0.21.0 (+libidn2/2.2.0) libssh/0.9.3/openssl/zlib nghttp2/1.40.0 librtmp/2.3
Platform: Linux 5.4.0-80-generic x86_64, 64 bit, Little endian, wxGTK
Build Info:
wxWidgets: 3.0.4 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
Boost: 1.71.0
OpenCASCADE Technology: 7.3.0
Curl: 7.68.0
Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:

I can not seem to change the solder mask parameters at all.

Got it to work Global on a simple project.

Well, now working as expected:

That was weird.

Solder mark rings, overhangs and min webs are tricky.
Would your fabricator accept a ‘one-to-one’ mask, where the ring is zero, the mask openings are exactly the same as the pads that must be open? A fabricator has CAM software that can deal with masks, and then they can tweak it to match their process.
Most fabricators prefer a one-to-one mask, and compensate for fabrication tolerances themselves.
Maybe you should ask him.

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