Hi - I’ve noticed that Eagle DRC check gets upset if a trace is less than 40mil from the edge of a board. This number is definable in the distance tab in the DRC settings. But it made me worry - is there a reason the default setting is so big? Can Sparkfun handle traces being right on the edge of the board? Or should we allow the 8 mil seperation? Thanks!
I believe the minimum spacing is 8 mil, just like any other distance. I have had 3 boards pass DRC with 10 mil between the edge of the board and any copper.
There was a thread about this before too. If you put your traces / copper right to the edge, the top and bottom layers could bridge together when the board is cut. This is especially bad if you have your + voltage on the top and GND on the bottom (GND plane perhaps).
Its actually more important when you are referring to more than two layer boards because without a pullback, its very likely to happen that bridging occurs between layers. Personally, I have been using a 10mil pullback without any problems so far.