[SI-LIST] Re: Conductor loss reduction at High Frequency
- From: "Eric Bogatin" <eric@xxxxxxxxxxxxxxx>
- To: <scott@xxxxxxxxxxxxx>, <jeff.loyer@xxxxxxxxx>
- Date: Wed, 29 Aug 2007 16:47:28 -0500
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
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Dr. Eric Bogatin, President
Bogatin Enterprises, LLC
Setting the Standard for Signal Integrity Training
26235 w 110th terr
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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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