ohjeita:design_rules [TELOK ry]

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Track-to-track / pad-to-pad / pad-to-track clearance 8 mils (0.20 mm)

Track width 8 mils (0.20 mm)

Pad minimum annular ring 12 mils (0.30 mm)

These are minimum values. Always use largest sizes possible. Increase pad and track sizes individually when there is room for extra. 12 mil track/clearance and 16 mil annular ring recommended for most of the PCB.

You can try to do stuff below these minimum limits, but yield goes down very quickly and you have to be extra careful.

Annular ring is especially important in through-plated boards due to the tenting process - photoresist film must have enough area on all sides of the pad to adhere to, and you need to have extra for alignment mismatch. Sacrifice pad-to-pad / pad-to-track clearance on round pads to get larger pads - 6 mil / 0.15 mm clearance is doable in pin header / via rows. If you can ensure 12-16 mil (0.30-0.40 mm) annular ring by doing that, it's all good.

Use 18µm copper clad when you have used extended areas of 8 mil (0.20 mm) work to improve etching resolution. If you through-hole plate your boards, use 18 µm clad even with mainly 10 mil (0.25 mm) boards, because the plating increases the copper thickness by about 15 µm.