i should have said

1 mil or greater INTEGER grid instead of 
'1 mil or greater grid'

Dennis Saputelli


Dennis Saputelli wrote:
> 
> earlier i had reported the following
> (the saga continues):
> 
> history
> i used virtual shorts without problems for > 1 year
> hundreds and hundreds of bds (turns out i was lucky)
> 
> one day a bd shop calls and offers to increase some tiny gaps ("no,
> thanks!")
> 
> later another shop 'fixes' them without calling, causing opens
> no big deal, a short run, blob a little solder
> 
> i investigate and conclude that using gerber 2.3 i too *could*
> see a 1 mil gap that they were seeing, but not always (i.e. not in every
> VS instance)
> 
> i conclude that the problem was that i had shifted the origin from pin 1
> to centroid in my VS part
> did some gerber viewing and shipped another one to yet another shop
> (it turns out this was almost the right conclusion)
> 
> a quick glance at the bds and they look fine
> testing begins and then power which was running is lost to one section
> the gap blew out, it was only maybe 800mA going thru a pretty beefy VS
> pad part
> 
> looking at the bd you could see what did not look like a gap but did
> look like a slight visual line in the solder plated pad
> 
> looking at the gerbers there was in 2 of 6 VS cases a 1 mil gap
> (don't know how i missed that, i thought it was nailed)
> i guess those guys can etch pretty good (i think i will start doing 1/1
> bds!)
> 
> new conclusion, this fix works i am pretty sure
> my original part had 60x75mil thruhole pads spaced at 75.005 mils apart
> (depending on the positioning the gerber rounding can be benign or not,
> this is why it always worked sometimes and sometimes worked other times)
> 
> my new part has 60x74.995 mil pads spaced at 75 mils apart
> maybe this is what Lomax recomended from the outset and i just caused
> myself some grief, i don't know
> 
> as long as the new part is placed on a 1 mil or greater grid i think the
> pads will always bleed together now
> 
> i did a test at gerber 2.5 and camtastic still reports 0 gap between
> objects using their inspection query tool
> (which is as it should be since 2.5 is .01 mil resolution)
> 
> another problem solved i hope!
> i am pursuing this because it is a very useful technique for certain
> situations
> 
> you can steer the currents and control trace widths on an otherwise
> common 'net'
> 
> i have made the schematic so that is not too messy by using a symbol
> that appears to be a wire but has pins at the opposite ends so the
> schematic reflects the intent
> it is not hard to read or as confusing as it would be if they appeared
> as 'jumpers'
> 
> i have not tried the other technique he has described of using a
> mechanical layer to create the shorts since making this VS work seems
> more integral to me
> 
> there is of course the option of drawing a trace at the end of the
> process and putting a wire in the schematic and sometimes this is the
> best choice for certain situations
> 
> Dennis Saputelli
> 
> --
> ___________________________________________________________________________
> www.integratedcontrolsinc.com            Integrated Controls, Inc.
>    tel: 415-647-0480                        2851 21st Street
>       fax: 415-647-3003                        San Francisco, CA 94110

-- 
___________________________________________________________________________
www.integratedcontrolsinc.com            Integrated Controls, Inc.    
   tel: 415-647-0480                        2851 21st Street          
      fax: 415-647-3003                        San Francisco, CA 94110

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