[SI-LIST] Re: Conductor loss reduction at High Frequency

  • From: "Eric Bogatin" <eric@xxxxxxxxxxxxxxx>
  • To: "'agathon'" <hreidmarkailen@xxxxxxxxx>
  • Date: Fri, 31 Aug 2007 08:26:24 -0500

One of the best papers on rms roughness and skin depth was by Gary Brist,
Stephan Hall, Sidney Clouser and Tao Liang, presented at the ECEC 10
conference at IPC expo Designers Summit, 2005, "Non-classical conductor
losses due to copper foil roughness and treatment."
 

You can probably find a copy with a google search.

 

--eric

 

**************************************
Dr. Eric Bogatin, President
Bogatin Enterprises, LLC
Setting the Standard for Signal Integrity Training
26235 w 110th terr
Olathe, KS 66061
v: 913-393-1305
f: 913-393-0929
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 <http://www.bethesignal.com/> www.BeTheSignal.com 

Fall 2007 Signal Integrity Training Institute
EPSI, SIAA, BBDP
Oct 8-12, 2007, San Jose, CA
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  _____  

From: agathon [mailto:hreidmarkailen@xxxxxxxxx] 
Sent: Thursday, August 30, 2007 8:27 PM
To: eric@xxxxxxxxxxxxxxx
Cc: scott@xxxxxxxxxxxxx; jeff.loyer@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: Re: [SI-LIST] Re: Conductor loss reduction at High Frequency

 

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
26235 w 110th terr
Olathe, KS 66061
v: 913-393-1305
f: 913-393-0929
c:913-424-4333
e:eric@xxxxxxxxxxxxxxx
www.BeTheSignal.com
Fall 2007 Signal Integrity Training Institute
EPSI, SIAA, BBDP
Oct 8-12, 2007, San Jose, CA
**************************************** 
-----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  <mailto: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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