What is the preferred way for writing a circular dot on the silk screen?
This would be, for example, for indicating the pads n°1 of a chip.
I could not find a clear and clean answer for this question on the forum.
Often, the circle is small. So, draw a graphical circle with a line width enough to close in the center of the circle on the F.Silk layer. Hopefully your board house doesn’t choke on circles/arcs in the gerbers. If they do, you may want to suspect them of other issues (maybe there are several reasons they are so cheap) and choose a different vendor.
Is it sensible to draw a segment with a large thickness (say 0.17 mm) but a very small length (say 0.01 mm) ?
I checked that KiCAD refuses to draw segments of zero length.
I have always used this approach.
I don’t know whether the observation (the vendor is not fully compliant to the Gerber spec) supports the conclusion (find a vendor who doesn’t display this particular shortcoming), but that is how I would approach it.
Give it a try and see how it looks in the Gerber. The worst I can imagine is that an over-zealous DFM check by your vendor may decide it’s an unintended segment, and delete it.
For a filled circle, I use a standard circle with thickness=desired radius, and drawn radius=half of the desired radius. For example, a 100 mil filled circle is drawn as a 100 mil thickness 50 mil (unfilled) circle.
This has the added bonus of being self-documenting, and less likely to be deleted at Gerber check.