I’m running into some confusion about the F.Cu layer for BGA pads. When working with the LBGA-169 footprint, the F.Cu layer seems to indicate that pads are overlapping.
The representation of the pad in the footprint editor is what I expect.
However, when placing a footprint in Pcbnew, it seems as if the pads on the F.Cu layer is being displayed as two concentric circles and I’m unclear as to what the outer circle is.
It’s almost as if the F.Paste and F.Mask layers are correct, but the F.Cu layer as being displayed as an annular ring. If I toggle the F.Cu layer visibility in F.Cu, the larger outer ring around a pad disappears, leaving the F.Mask and F.Paste layers looking as I expected.
Is the outer ring a keep-out, and if so, where is that dimension specified?
Attached are screenshots showing this with the LFBGA-169_16x12mm_Layout28x14_P0.5mm_Ball0.3_Pad0.3mm_NSMD footprint included with the standard KiCad libraries.
Note that in the Footprint Editor (top), we see that H14 is 0.3mm and the toggling the visibility of the F.Cu, F.Mask, and F.Paste layers all indicate this.
However, if we look at this footprint placed in Pcbnew (bottom), the F.Cu layer seems to show the pads as these two concentric rings. The F.Mask and F.Paste layers seem to be correct, but I’m confused as to why the F.Cu layer for the BGA pads look different.
My KiCAD version is 5.0.1-3 for Windows.
(1) Can someone else reproduce this with the LFBGA-169 footprint?
(2) Can you explain what I’m seeing here? Based on what I’m seeing it looks like the LFBGA-169 footprint is not possible to use due to overlap, or I’m just not understanding the UI (quite likely).