Homebrew PCBs

Stefan Trethan <stefan_trethan@...> writes:
> I believe when you draw 1 mil in your PCB software, the printer
> driver, printer resolution, transfer process, and etching process make
> something significantly wider out of it.

I know with my HP laserjet and PS, when I print a line N thou across,
I end up with a line N+1.67 thou across - the printer draws a row of
dots intersecting the edge, as well as a fill.  So a 1,3,5 mil line
would be 2.7, 4.7, and 6.7 mil.  Then you have to round up to printer
pixels - it ends up being 3.3, 5, and 6.7 mil.

I have to tell pcb to "bloat" all edges by -0.83 mil to get the print
to come out accurate, but I still choose (or chose, since I do photo
mask now) line sizes that were multiples of the printer resolution for
consistency.