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

  • From: Bill Wurst <billw@xxxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Tue, 04 Sep 2007 07:39:54 -0500

One of the characteristics missing from this discussion on conductor 
roughness is what is known as the "toothing profile," mentioned in 
Howard Johnson's "High-Speed Signal Propagation - Advanced Black Magic" 
book, section 2.11 (see also, 
http://signalintegrity.com/Pubs/edn/SurfaceRoughness.htm).  The toothing 
profile is the surface landscape that results from a variety of surface 
treatments, whether the reverse-treat foil process, the double-treat 
process, or something else.  In addition to peak-to-valley and rms 
roughness measurements, this additional characteristic could account for 
significant differences in conductor loss.  Dr. Johnson postulates that 
the double-treat process may result in both good surface adhesion as 
well as lower conductor loss, but it does not appear that much if any 
research has been done exploring the loss differences between different 
surface treatments.


      /         billw@xxxxxxxxxxx         /
     /                                   /
    / Advanced Electronic Concepts, LLC /
   /           www.aec-lab.com         /
Yuriy Shlepnev wrote:
> We also did some investigations of the roughness effect in
> http://pcdandm.com/cms/content/view/3620/95/  RMS value for roughness was 1
> um in the PCB example both for the strip and plane. In the packaging
> example, planes and one side of the strip had 1 um RMS. The top strip
> surface (that is closer to the plane) was assumed to be flat. Dielectric
> polarization losses and dispersion were not included in the analysis to
> focus only on the conductor-related effects. Though we did also computations
> for the same configurations taking into account the polarization loss and
> dispersion effects and it correlated well with the published experimental
> data.
> Yuriy Shlepnev
> Simberian Inc.
> www.simberian.com
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of olaney@xxxxxxxx
> Sent: Friday, August 31, 2007 9:50 AM
> To: hreidmarkailen@xxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Conductor loss reduction at High Frequency
> Here is a link to the paper that Dr. Bogatin pointed out:
> http://www.gouldelectronics.com/papers/CopperSurfaceLoss.pdf
> Orin
> On Thu, 30 Aug 2007 18:26:43 -0700 agathon <hreidmarkailen@xxxxxxxxx>
> writes:
>>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!
>>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
>>>saturate at a factor of 2 increase to the resistance when the
>>>roughness is about 3 x skin depth.
>>>This means, even though your line width is 5 mils, it would have
>>>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.
>>>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
>>>Fall 2007 Signal Integrity Training Institute EPSI, SIAA, BBDP Oct 
>>>8-12, 2007, San Jose, CA
>>>-----Original Message-----
>>>From: si-list-bounce@xxxxxxxxxxxxx
>>>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
>>>enough loss to absolutely negate any benefit that the low loss
>>(low tan
>>>delta) material would have had over materials with twice the
>>>Interesting stuff.
>>>Scott McMorrow
>>>Teraspeed Consulting Group LLC
>>>121 North River Drive
>>>Narragansett, RI 02882
>>>(401) 284-1827 Business
>>>(401) 284-1840 Fax
>>>TeraspeedR is the registered service mark of Teraspeed Consulting 
>>>Group LLC
>>>Loyer, Jeff wrote:
>>>>My 2 cents available in the article below:
>>>>Jeff Loyer
>>>>-----Original Message-----
>>>>From: 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
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