[PCB_FORUM] Re: nets shorted to gnd plane

Sam, anything you don't set-up in constraint manager has a default setting, 
even if it is zero.  If you don't set something up, you are bound to have 
problems since the tool doesn't know what you want.  It is always a good idea 
to have a "golden" board (or a technology file exported from it) that you have 
triple-checked to have everything you need set-up, then start with that board 
(or import that technology file).

The good thing about using a  tech file is that you can read it again at any 
time, even just before shipping, and look for DRCs.  You could even have a 
different tech file for each manufacturer, although I do NOT recommend this 
practice.

This keeps the loose nut on the keyboard from falling off and shorting 
something :)

--
George Patrick
Tektronix, Inc.
Central Engineering, EDS Applications Support
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
* 503-627-5272 (voice)     * 503-627-5587 (fax)
http://www.tektronix.com<http://www.tektronix.com/>    
http://www.pcb-designer.com<http://www.pcb-designer.com/>

"Off-Grid and Proud of it!"

-----Original Message-----
From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of sjchar3@xxxxxxxxxxxx
Sent: Tuesday, July 21, 2009 15:16
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] Re: nets shorted to gnd plane


George, your right about the nut behind the keyboard. I didn't set up the 
constraint spacing for vias, but why didn't the drc report catch this, thats 
whats bothering me..I'm on to the next board and i did a better visual check...
Thanks for all your responses
Sam

-----Original Message-----
From: george.h.patrick@xxxxxxxxxxxxx
To: icu-pcb-forum@xxxxxxxxxxxxx
Sent: Mon, Jul 20, 2009 4:42 pm
Subject: [PCB_FORUM] Re: nets shorted to gnd plane



Oh, geeezzzz....  Next thing you know, the "Use positive planes" crowd will be 
rolling out, warning everyone that them newfangled negative planes just don't 
work  :)  If you don't use a feature you are never going to work the bugs out 
of your process.

In 12+ years working with RS274X, I have never seen a short in the board that 
wasn't caused by a loose nut on the keyboard (often the one I see in the 
mirror).  Look carefully and I'll bet you find a bad thermal size, vector based 
pad behavior turned off, or one of the things the others were talking about.

While we are on it, beware of Valor.  It sometimes gives you false shorts and b 
rokens (usually brokens) when you run the netlist analyzer.  When you dig in 
and really look at them, you find they are bogus or (again) loose nut on the 
keyboard stuff (damn, forgot to set those drill depths again).  This happens 
much more with the direct extract from Allegro, much less often when importing 
gerbers.


--
George Patrick
Tektronix, Inc.
Central Engineering, EDS Applications Support
P.O. Box 500, M/S 39-512
Beaverton, OR 97077-0001
* 503-627-5272 (voice)     * 503-627-5587 (fax)
http://www.tektronix.com<http://www.tektronix.com/>&nbs p;   
http://www.pcb-designer.com<http://www.pcb-designer.com/>

"Off-Grid and Proud of it!"

-----Original Message-----
From: 
icu-pcb-forum-bounce@xxxxxxxxxxxxx<mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx> 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx<mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx?>]
 On Behalf Of Dale Rasmusen
Sent: Monday, July 20, 2009 16:17
To: icu-pcb-forum@xxxxxxxxxxxxx<mailto:icu-pcb-forum@xxxxxxxxxxxxx>
Subject: [PCB_FORUM] Re: nets shorted to gnd plane


Hi Sam,

We have had problems in the past with 274X formats where they will have nets 
shorted to planes.  You won't see the short=2 0in Allegro, but you can 
definitely view it in a gerber viewer and it is very random.  We currently use 
the 274D format and that works just fine, we just don't have the embedded 
apertures.  It is no big thing to the board house, they will use the 
photoplot.log that is generated for apertures.

Dale Rasmusen
CAD Manager
TEKNOVUS

  _____




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