there is a 'issue' w/ the 'lomax short' of which you should be aware
it bit me!

(i forget if i already posted this)

after using the lomax short without probs on several jobs, one day a
board shop called and
reported that there was a small gap between some pads, should they 'fix'
it?
i said no and forgot about it

later on another job from a different shop they went ahead and 'fixed'
them so they were all open
(they didn't call to ask)

now i started to wonder
i examined the gerbers and sure enough i could see the small gap, but it
should have been too small to
render (dims as or similar to below)

i thought maybe i used gerber 2.4 or 2.5 or something, but even these
should have bled together

after a lot of futzing i figured it out
my original part had pin 1 as the origin
later while cleansing libs to all have centroids as origin i did that
one (the 'shorted' pads part) too

when the origin is the centroid the gerber plotter will back off to the 
nearest mil or tenth mil depending on 2.3 2.4 etc
this will create a gap
solution, change the origin back to pin 1 and they bled together on the
plot

Dennis Saputelli


[EMAIL PROTECTED] wrote:
> 
> In a message dated 5/14/2002 5:27:28 AM Eastern Daylight Time,
> [EMAIL PROTECTED] writes:
> 
> >   I am fine tuning the PCB on an amplifier circuit.
> > The circuit requires 'Kelvin' (or loner!) paths to
> > components on the same nets as other paths.
> > Obviously the autorouter puts them into the
> > shortest path and I was wondering if there is a
> > way to keep them seperate.
> >
> 
> This sounds like a perfect application for the "Lomax virtual short" which
> has been discussed on this board. Check the archives for details, but in a
> nutshell you create a part which has a gap which is too small to fabricate
> (i.e. 0.000002"), and set up a special design rule to allow a 0.000001"
> clearance between the pads involved. Place a jumper on the schematic to allow
> the two wires involved to be separate nets, and place the physical component
> described above to control the connection point between the two nets.
> 
> Steve Hendrix
> 

-- 
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