[SI-LIST] Re: Conductor loss reduction at High Frequency
- From: agathon <hreidmarkailen@xxxxxxxxx>
- To: eric@xxxxxxxxxxxxxxx
- Date: Thu, 30 Aug 2007 18:26:43 -0700
Eric or others,
YIKES! I would like to enquire about:
* references for the 2x resistance increase, dependent on roughness/skin
depth ratio.
* suggestions for simulating this ... cannot just hack a tabular rlgc or
sparam file [??]
since the R is really R(f), unless answer to the 1st question gets me a
R(f) indirectly.
Need to consider this. Very serious. For 10G.
Please help!
Regards,
Agathon
On 8/29/07, Eric Bogatin <eric@xxxxxxxxxxxxxxx> wrote:
>
> I second Scott's important point. Above 1 GHz, skin depth is less than 2
> microns in copper. When the RMS surface roughness is larger than the skin
> depth, it affects conductor loss.
>
> Above 3 GHz, surface roughness can almost double conductor loss. In fact,
> the commonly used approximations for the impact from conductor loss,
> saturate at a factor of 2 increase to the resistance when the surface
> roughness is about 3 x skin depth.
>
> This means, even though your line width is 5 mils, it would have the
> conductor loss equivalent of a 2.5 mil wide line. The conductor loss can
> easily swamp the dissipation factor of even FR4, negating any benefit for
> low loss materials unless you are using very wide lines.
>
> If you want the biggest bang for the buck in evaluating conductors, try
> looking at surface treatments that allow smoother copper foils.
>
> --eric
>
> **************************************
> Dr. Eric Bogatin, President
> Bogatin Enterprises, LLC
> Setting the Standard for Signal Integrity Training
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> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On
> Behalf Of Scott McMorrow
> Sent: Wednesday, August 29, 2007 4:11 PM
> To: jeff.loyer@xxxxxxxxx
> Cc: sridharam@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Conductor loss reduction at High Frequency
>
> Surface roughness is the largest contributor we've measured for
> conductor loss. There are certain low loss materials that are
> constructed with high tooth copper for maximum adhesion, which show
> enough loss to absolutely negate any benefit that the low loss (low tan
> delta) material would have had over materials with twice the dielectric
> loss.
>
> Interesting stuff.
>
> Scott McMorrow
> Teraspeed Consulting Group LLC
> 121 North River Drive
> Narragansett, RI 02882
> (401) 284-1827 Business
> (401) 284-1840 Fax
>
> http://www.teraspeed.com
>
> TeraspeedR is the registered service mark of
> Teraspeed Consulting Group LLC
>
>
>
> Loyer, Jeff wrote:
> > My 2 cents available in the article below:
> >
> > http://pcdandm.com/cms/content/view/2572/95/
> >
> >
> > Jeff Loyer
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of M Sridhar
> > Sent: Wednesday, August 29, 2007 5:08 AM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Conductor loss reduction at High Frequency
> >
> > Hi Members,
> >
> > What are the methods by which we can reduce the conductor losses at high
> > frequency?(Loss due to skin effect, Dielectric losses etc.)
> > Which is the best conductor at higher frequency? in the range of 1-5 GHz
> >
> > Thanks,
> > Sridhar
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