How to design the safety spacing of PCB?
Electricity-related safety spacing
1. Spacing between circuit.
For the processing capacity, the minimum spacing between wires should be no less than 4mil. The mini line spacing is the distance from line to line and line to pad. For the production, it’s bigger and better, usually it’s 10mil.
2. Pad’s hole diameter and width
The diameter of the pad shall not be less than 0.2mm if the hole is mechanically drilled, and not less than 4mil if the hole is laser drilled. And the hole diameter tolerance is slightly different according to the plate, generally can be controlled within 0.05mm, the minimum width of the pad shall not be less than 0.2mm.
3. Spacing between Pads
The spacing should be not less than 0.2mm from pad to pad.
4. Spacing between copper and the edge of board
The distance between copper and PCB edge should be no less than 0.3mm. Set the item spacing rule in the Design-Rules-Board outline page
If the copper is laid on a large area, there should be a shrinking distance between the board and the edge, which is usually set to 20mil.In the PCB design and manufacturing industry, in general, for the sake of the mechanical aspects of the finished circuit board, or to avoid the occurrence of coiling or electrical short circuit due to the copper skin exposed on the edge of the board, engineers often reduce the copper block with a large area by 20mil relative to the edge of the board, instead of laying the copper skin all the way to the edge of the board.
There are many ways to do this, such as drawing a keepout layer on the edge of the board and setting the keepout distance. A simple method is introduced here, that is, different safety distances are set for copper-laying objects. For example, if the safety spacing of the whole plate is set to 10mil, and the copper laying is set to 20mil, the effect of shrinking 20mil inside the plate edge can be achieved, and dead copper that may appear in the device can also be removed.