kicad-developers team mailing list archive

[Cheng Sheng <jeru.sheng@xxxxxxxxx>]

Random thought: Make some positive thing to subtract away.
1. What about drawing a small dot under each pad? It is surely subtracted
but you still have some positive images so you don't have a negative-only
film to be "corrected".
2. What about picking some empty region to add a dot then subtract it?

Isn't necessarily easier than your suggestion to not generate the mask
negative. Depending on how easy it is to judge no silk is inside the edge
cutting boundary.

On Thu, Jun 16, 2016 at 6:51 AM, Chris Pavlina <pavlina.chris@xxxxxxxxx>
wrote:

> A warning to anyone making PCBs - and maybe to get some devs thinking, I'm
> not
> sure if there's a better way to do this:
>
> For those who didn't know, "subtract soldermask from silkscreen", for
> Gerber,
> is implemented by plotting the silkscreen, then switching plot modes to
> 'clear'
> with the %LPC*% command and plotting the mask over the top. This is like
> "drawing" the mask with an eraser, clearing out the silk layer.
>
> I sent a board off yesterday, to Elecrow, which had an empty back
> silkscreen. I
> sent the file anyway, to make sure they were aware I indeed wanted it
> empty and
> didn't just forget the file.
>
> Got an email a few minutes ago telling me my silk and mask layers were the
> same
> and asking me to check them. Checked the files I sent them and confirmed
> this
> wasn't the case, my files were fine - though I was led on a wild goose
> chase by
> the fact that the silk layer contained the whole mask layer in negative.
> What I
> believe happened is that their software saw a layer with all negative
> drawing,
> and automatically inverted it.  Probably meant to detect gerbers generated
> by
> old-fashioned EDA packages or packages with old-fashioned settings that
> output
> power plane layers in negative.
>
> Something to watch out for - if your silk layer is empty, either don't
> send it,
> or don't use "subtract soldermask from silkscreen". I wonder if we can do
> anything about this from the software side, like not generating the mask
> negative if the silk is empty.
>
> --
> Chris
>
>
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