How are Mask and Paste generated/drawn around pads?

Layout
1

I’m sure this is a simple question, but it’s been causing me some confusion. (Stable version 4.07).

I’m designing with a TPS63070 which has a VQFN package and some fairly specific solder mask recommendations. So, I downloaded a footprint from SnapEDA to use as a starting point, with the intention of checking it carefully and fixing up to my satisfaction.
Unfortunately, I’ve become stuck because Mask, and Paste are inflated to be much larger than the pads, both in default and OpenGL canvases. (Cairo, which I don’t typically use, seems much more reasonable?)

When I generate the Gerbers, this effect is reproduced, so it’s not just a viewing artifact.

If I just draw new pads, they seem ok so, of course, I could just draw the whole thing from scratch and be done with it. But, I want to understand where/how these pads have become set up to have this excessive enlargement of these layers. I can’t find anywhere to set them back to default… In the footprint editor/pad editor, the Mask and Paste clearances are set to 0. In the footprint editor/dimensions/pad settings the local clearances are set to 0.

I must be missing a setting somewhere. Any suggestions?
Thx
Doug

2

Masl and clearance can be set in 3 different places:

  1. Pad level
  2. Footprint level
  3. Global level

Maybe you have them set to 0 at footprint level but not at pad level. Edit each pad with the problem and set clearances to zero.

3

Since you got the footprint outside of KiCad, I would suggest you read and examine the footprint file in a text editor.

4

Thanks Pedro,
Yes, I think I checked it in all three places (unless I’m being stupid…).

5

Hi Sprig,
I actually did look in a text editor, but I’m not familiar with the syntax so I may have been missing something problematic. Near the start of the file, there are entries saying
.SolderMask 0
.SolderPaste 0
which I presumed were the (global?) settings. Here it is if you’re curious and/or have time to educate me.
Doug

TPS63070RNMR.mod (4.7 KB)

6

I went ahead and created a new part in the library editor and changed some settings. This is the result:

(module test (layer F.Cu) (tedit 59CC347D)
(fp_text reference REF** (at 0 0.381) (layer F.SilkS)
(effects (font (size 0.762 0.762) (thickness 0.127)))
)
(fp_text value %R (at 0 -0.381) (layer F.Fab)
(effects (font (size 0.762 0.762) (thickness 0.127)))
)
(pad 1 smd rect (at -1.397 0) (size 1.524 1.524) (layers F.Cu F.Paste F.Mask)
(solder_mask_margin 5.08) (solder_paste_margin -12.7))
(pad 2 smd circle (at 1.27 0) (size 1.524 1.524) (layers F.Cu F.Paste F.Mask))
)
The formatting does not look anything alike.

It does take a little time to learn how to create your own footprints; but it really is not all that hard. Then, if one needs a footprint that is not in the library, they can make their own fairly quickly with a little practice.

7

Yes, I can certainly draw if from scratch, as I said in the first post, and I’ll probably do that.
I was hoping to figure out how to fix this one, just to add to my understanding of the Kicad system.
Thx. Doug

8

I believe your file is an out-of-date, obsolete, syntax used by KiCAD prior to the version 4.0.x releases. Understanding this syntax may be a useful mental exercise, and source of personal satisfaction, but not especially valuable in the long term. I recall some tools to convert this type of footprint to the current format and syntax but I can’t locate them.

Dale

9

Ok, fair enough. I’ll just remake the footprint and not worry about weirdness with this old file format.
Doug

10

the footprint editor takes it’s global setting from PCBnew.

11

This is version dependent. (Nightly differs from stable.)
In the stable release (at least 4.0.6 under fedora) it is always 0.2mm unless footprint specific settings are applied.

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