Re: gEDA-user: Metric, Imperial, Rounding, DRC, and board houses

[Kai-Martin Knaak <kmk@xxxxxxxxxxxx>]

Russell Dill wrote:

> In addition, my board house rounds everything to
> 2.4 format (0.1 mil). I can envision several scenarios where my design
> meets DRC in PCB, but fails when I send it to the board house.
> 
> What is my best option?

Time to change the board house? 


> Just use imperial units and cope with weird grids?
> 
> Use metric spacing, but recalculate DRC based on worst case rounding?

I'd choose the second option. PCB internal units are 0.01 mil. This adds 
maximum 10% to the rounding error, the board house introduces anyway. If 
you do grids that fit the board house metric the rounding error will still 
happen.  The 1mm pitch will make some balls off by 0.05 mill.  
The internal units are 254 nm. I sincerely doubt that a design better to 
be etched in 35 Âm copper can be that critical. 

---<)kaimartin(>---
-- 
Kai-Martin Knaak
Email: kmk@xxxxxxxxxxxxxxx
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