I have a need to produce a replacement H.T. regulator panel for a vintage 1967 BRC2000 colour TV set, and it is connected into circuit with an edge connector that fits on the PCB direct – how do I make sure there is no solder–mask over the edge–connector contact fingers?
Add top and bottom solder resist layers in Design Tech. Then add a rectangular shape of solder resist over top and bottom pads as Iain explained above. (This is "negative" solder resist i.e. void of solder resist!). You should then be able to see the area of solder resist you've added in the pcb editor. Finally check Gerber files with a definitive Gerber viewer (www.https://gerber.ucamco.com/) to ensure all is as you expect.
I measured the size of each edge–connector finger from a little piece of scrap PCB from the colour TV concerned, made this as a rectangular SMD pad, replicated this 16 times, add the pads with the sides chamfered at each end to form connections 1 and 18 of the edge connection, then group and duplicate these, change layer to "Bottom Resist" (the board is single –sided so a "top resist" layer isn't needed), then drop them exactly over the "bottom copper" edge–connector fingers – have I got this right?
Not really, -but it's probably one (very complicated) way of skinning the cat. The edge connector should preferebly be one component but could be made up of 18 separate fingers. All you have to do is add one large area of bottom solder resist which covers all 18 connector fingers. Job done!