Re: [SI-LIST] : Effects of thieving on SI and EMC.....

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From: Ravi Kiran (rkiran@iprg.nokia.com)
Date: Tue Aug 08 2000 - 14:24:55 PDT


Scott,

When we stich this to Ground I agree that will reduce the resonance effects
but what about the impedance of the traces. what will be the effect on the
characteristic impedance?

Ravi

Scott McMorrow wrote:

> Hey ... a good place to apply the 20H rule
>
> i.e. non signal related metalic structures should be
> spaced a minimum of 20 times the height of the
> trace to plane spacing away from all active
> signaling lines to reduce parasitic coupling.
>
> As Pat has also pointed out, any large structure
> should be stitched to ground to reduce resonance
> effects. The distance between stitch vias should
> be smaller than lambda/10 of the highest frequency
> component that one wants to rid freespace of.
> (Or keep from entering through freespace.)
>
> regards,
>
> scott
>
> --
> Scott McMorrow
> Principal Engineer
> SiQual, Signal Quality Engineering
> 18735 SW Boones Ferry Road
> Tualatin, OR 97062-3090
> (503) 885-1231
> http://www.siqual.com
>
> Chris Padilla wrote:
>
> > Michael,
> >
> > From an EMI perspective, I have yet to notice any
> > measurable difference between "thieved" and "non-
> > thieved" boards.
> >
> > We tell our fab vendor to keep the pattern at least
> > 400 mils away from any trace, via, pad, part, etc.
> >
> > As you point out, thieving increases manufacturability
> > by minimizing warping of the board.
> >
> > ----->Chris
> >
> > >A thieving pattern is a bunch of very small shapes
> > >added to a layer that helps equalize the plating
> > >across a given layer (increases manufacturability).
> > >An auto thieving utility or program uses a set of
> > >criteria to determine how and where to put these
> > >shapes. Unfortunately these programs are almost
> > >exclusively focussed on mfg issues and not SI or
> > >EMC issues.
> > >
> > >Usually if you see a bunch of 1/16" width diamonds
> > >on an artwork layer, this is thieving.
> > >
> > >FYI
> > >
> > >MG
> > >
> > >-----Original Message-----
> > >From: Ray Anderson [mailto:raymonda@radium.eng.sun.com]
> > >Sent: Monday, July 31, 2000 11:12 AM
> > >To: Greim, Michael
> > >Cc: SI LIST
> > >Subject: Re: [SI-LIST] : Effects of thieving on SI and EMC.....
> > >
> > >
> > >OK, I'll bite. Educate me, what is a thieving pattern,
> > >and an auto-thiever ????
> > >
> > >
> > >-Ray
> > >
> > >
> > > > Does anyone out there have a tool or reference
> > > > that would allow one to calculate the effects of
> > > > thieving patterns on signal integrity and EMC.
> > > >
> > > > I am trying to come up with appropriate rule sets
> > > > for driving an auto-thiever utility.
> > > >
> > > > Thanks for the help.
> > > >
> > > > MG
> > > >
> > >
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>
> --
> Scott McMorrow
> Principal Engineer
> SiQual, Signal Quality Engineering
> 18735 SW Boones Ferry Road
> Tualatin, OR 97062-3090
> (503) 885-1231
> http://www.siqual.com
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
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> ****

--
Ravi Kiran     1-650-625-2225
Sr. Hardware Engineer
Nokia IP Routing Group
313 Fairchild Drive
Mountain View,  CA  94043


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