Re: gEDA-user: Using mm units in .pcb files

[Steve Meier <smeier@xxxxxxxxxxxxxxxxxxx>]

given the 0.01 mill base unit I would like to have a grid of 4 mills.

This would allow 4 mill traces and 4 mills of clearance between traces.

The grid error for 50 mill pitch components would be no greater then 2
mills the grid error for 1mm devices would be under 48 microns (~1.8
mills)

for the 50 mill pitch parts there will be a margin of 8.5 mills.
(25mills pad / 2) - worst case error - (trace width / 2)

12.5 - 2 - 2 = 8.5 mills

for the 1 mm pitch the margin

.25 mm - .048 mm - .0508 mm = 0.1512 mm

~6 mills



Steve Meier



On Tue, 2008-06-10 at 18:39 -0400, DJ Delorie wrote:
> > What unit should we define for PCB default units?
> 
> For compatibility, the default (no units specified) should remain 0.01
> mil.
> 
> 
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