Just a warning to remember to take into account creepage distance when
you have chassis ground on board. In other words, the distance between
chassis ground and all the other copper is typically greater than the
spacing used generally in order to maintain safety during faults (and
therefore electrical safety testing). For example, typically on the
boards I design I use 0.2 mm spacing, but with chassis ground (when
present) I make the spacing 0.85 mm. That way, if the internal
circuitry suddenly finds itself at a high voltage relative to chassis
ground during a fault, anyone touching the metal casing at the time wont
have their socks blown off.
Now in some respects having bolt holes connected to chassis ground in
the schematic will help you here, because in the board layout you just
make the chassis ground track spacing the relevant amount (in my case
0.85 mm), and Kicad does the rest. However, there is a gotcha. I've
not found a way to tell Kicad to maintain a safe distance /through/ the
board. That means one has to manually maintain the distance between
chassis ground and the layers beneath it ... and that's really easy to
screw up. Does anyone know a way to automate that?
Regards,
Robert.
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