[SI-LIST] Re: Microstrip line loss on Rogers 4350
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>, "Jeff Loyer" <jeff.loyer@xxxxxxxxx>, ming.tsai@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Mon, 21 Mar 2005 08:59:11 -0800
Guess I should check my typing before I hit send! That should have read:
The irregular shape of surfaces traces, due to plating and etching, is
> enough that I don't use surface traces for any controlled impedance work.
> Any buried layer is better, even buried microstrip. In fact, buried
> microstrip can be made to behave electrically just like stripline-
velocity
> cross talk, impedance all the same.
Lee W. Ritchey
Speeding Edge
P. O. Box 2194
Glen Ellen, CA 95442
Phone- 707-568-3983
FAX- 707-568-3504
I just used the energy it took to be angry to write some blues.
Count Basie
> [Original Message]
> From: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
> To: Jeff Loyer <jeff.loyer@xxxxxxxxx>; <ming.tsai@xxxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
> Date: 3/21/2005 8:49:05 AM
> Subject: [SI-LIST] Re: Microstrip line loss on Rogers 4350
>
> The irregular show of surfaces traces, due to platin gand etching, is
> enough that I don't use surface traces for any controlled impedance work.
> ANy buried layer is better, even buried microstrip. In fact, bureid
> microstrip can be made to behave electically jsut like stripling- velocity
> cross talk, impedance.
>
> Lee W. Ritchey
> Speeding Edge
> P. O. Box 2194
> Glen Ellen, CA 95442
> Phone- 707-568-3983
> FAX- 707-568-3504
>
> I just used the energy it took to be angry to write some blues.
> Count Basie
>
>
> > [Original Message]
> > From: Loyer, Jeff <jeff.loyer@xxxxxxxxx>
> > To: <ming.tsai@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
> > Date: 3/21/2005 8:15:49 AM
> > Subject: [SI-LIST] Re: Microstrip line loss on Rogers 4350
> >
> > I had similar results on FR4 when I played around with several
> > configurations (single-ended and differential microstrip, single-ended
> > asymmetric stripline, and differential symmetric stripline), trying to
> > correlate different tools to actual measurements. I could get good
> > broadband correlation for all but the single-ended microstrip (and I did
> > have well setup TRL structures for all). For single-ended microstrip, I
> > couldn't get good correlation at all frequencies with any tool (though
> > this wasn't an in-depth study). I suspect that, for this case, the
> > trace geometries are complex enough that all the subtleties must be
> > properly represented. For instance, neither a simple rectangle nor
> > trapezoid is sufficient - the plating process makes the trace appear as
> > more of a "mushroom". This complex shape might have significant effect
> > on cross sectional area, and how the fields surround the trace (how much
> > energy is in dielectric vs. air). I think you might have to
> > cross-section your traces to determine their actual complex geometry, or
> > take a best guess, based on info. from your fab vendor.
> >
> > I'm surprised that removing the soldermask didn't have any effect.
> > While I haven't done that on actual boards, simulations show it does
> > have a significant effect. And, I've added soldermask (putting a layer
> > of Kapton tape over a trace), and seen significant effects.
> >
> > My 2 cents.
> >
> > Jeff Loyer
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> > On Behalf Of Ming Tsai
> > Sent: Friday, March 18, 2005 6:08 PM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Microstrip line loss on Rogers 4350
> >
> > Hi All,
> >
> > I am studying the microstrip line loss on 10 mil Rogers 4350 (Er =3D =
> > 3.48,
> > loss tangent =3D 0.004 @ 10 GHz). The trace width is 22 mils, with half
=
> > oz
> > copper. From some transmission line calculator I expect to see 0.25dB
> > /inch loss @ 10 GHz. However I measured under network analyzer and I got
> > the loss up to 0.5dB/inch @ 10 GHz.
> >
> > I did not have well-setup TRL calibration on board, but I took 3
> > separate measurements from 3", 5" and 7.5" long microstrip lines, and
> > estimated the delta to get 0.5dB/in loss. So I assume the edge-mounted
> > SMA connector is not a factor. Also checked under TDR I saw 48 ohms of
> > line impedance, which is within the spec. I also scratched out the
> > solder mask which did not have any effect. I used full-wave tool to
> > verify the radiation as well as skin effect, but no surprise the
> > simulation showed that I should get about 0.25dB/in loss.
> >
> > Does anyone have similar experience or any suggestion? Thanks!
> >
> > Regards,
> >
> > Ming
> > --
> > Ming. Tsai
> > Staff Hardware Development Engineer
> > Product Technology - Hardware Design Group
> > XILINX
> >
> >
> >
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