Clearance in PCB design is the gap enforced between conductors of different nets, and between copper and drills, board edges or keepouts. Fabricators set a manufacturing minimum, commonly 0.1 to 0.15 mm (4 to 6 mils) on standard work and finer for HDI, while safety rules for mains-connected boards demand millimetres of creepage and clearance rather than mils. Clearance is checked by the design rule check and again by the fabricator's DFM review.
Default clearance is 6 mil, but make it 8 mm across the isolation barrier between the mains side and the low-voltage side.
Also heard as
- spacing
- air gap
Related terms
DRC
Design rule check: automated scan of a layout for spacing, width, drill and connectivity violations.
Keepout
Region of a board where copper, parts, vias or routing are forbidden by a design rule.
Sliver
Very narrow strip of copper or soldermask in the artwork that can peel loose during fabrication.
Trace
Copper conductor path etched on a board layer, connecting pads, vias and planes.