Footprint editor - Solder paste ratio clearance issues

[Art]

I was trying to enter solder paste clearance issues manually and was getting puzzling results. Definitely not the value I entered until I realized that default value of ratio clearance wasn't zero. So both of those values were driving the actual clearance. You need to zero out one if another one is manually changed.

BTW,you are using ratio for clearance as a negative value. By definition, ratio can't be negative. Its that pesky math thing.

[Art (diametrix)]

A better approach than zeroing the other field out, would be recalculating its value based on the new value entered.

[Art (diametrix)]

This way you can always use the sign from the "Solder paste clearance" line even though the ratio is positive.

[Rene Poeschl (poeschlr)]

I suspect this is simply a case of misunderstanding how the solderpaste is calculated. It might be a bit unintuitive that the different settings add up instead of being alternative ways to enter the value.

This might need better communication via the dialog or a rethink of the system itself. (I am not certain if there is a usecase to enter both at the same time and expect them to add up like the current implementation allows. If the answer is that a rethink is required then there would need to be a footprint format change and some way to map footprints that use this setting to the new system.)

[Art (diametrix)]

Another thing that is wrong is the sign. You are expected to enter a sign in the field (default value is -0.00), yet only negative values are allowed. If you enter a positive paste clearance, it is still counted as negative and is subtracted from the pad size. There are cases when you need to create paste aperture bigger than the pad size.

[Wayne Stambaugh (stambaughw)]

AFAIK, KiCad has always used the sum of both settings. I suppose it could be confusing but most users will use either the fix or the ratio paste clearance. Changing it may break existing designs. I agree that the negative ratio is a bit non-standard. I'm thinking, a ratio less than one makes the mask aperture smaller and a ratio greater than one makes the mask aperture larger. I also noticed that there was no warning in the footprint editor dialog when adding a positive solder mask ratio. The ratio is always reset to 0 at least in the master branch.

[KiCad Janitor (kicad-janitor)]

Fixed in revision d1b2a6ea70a75079a7510d6128631480037953ea
https://git.launchpad.net/kicad/patch/?id=d1b2a6ea70a75079a7510d6128631480037953ea