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

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From: Scott McMorrow (scott@vasthorizons.com)
Date: Tue Aug 08 2000 - 13:00:06 PDT


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 > > > > > > >**** To unsubscribe from si-list or si-list-digest: send e-mail to > >majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > >si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > >si-list archives are accessible at http://www.qsl.net/wb6tpu > >**** > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > ****

-- 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 majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu ****


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