[SI-LIST] Re: Microstrip line loss on Rogers 4350
- From: Ming Tsai <ming.tsai@xxxxxxxxxx>
- To: Ed Sayre III <esayre3@xxxxxxxx>
- Date: Mon, 21 Mar 2005 10:23:18 -0800
Hi Ed,
Thanks for your message. I did think about solder mask, so I went back to lab
and took off the solder, but I did not see any effect. The curve on NWA was
right on each other.
I will also consult with PCB house to find out any fabrication issues. Thanks!
Ming
Ed Sayre III wrote:
> Ming,
> I have seen these elevated losses for materials after processing. As a
> first cut at your results I have to ask if you have you taken the solder
> mask into account (if you have any)??? That being said this may not be the
> only contributor to the difference. Make sure you have the exact losses
> for the core or prepreg you are using in your stack. Then you will be able
> to go from there.
> We have found that some fabricators can help you with these loss term
> differences since they are based on any variations that the fabricator may
> see.
>
> Best Regards
> -Ed Sayre
>
> At 06:07 PM 3/18/2005 -0800, Ming Tsai wrote:
> >Hi All,
> >
> >I am studying the microstrip line loss on 10 mil Rogers 4350 (Er = 3.48,
> >loss tangent = 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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--
Ming J. Tsai, Ph.D.
Staff Hardware Development Engineer
Product Technology - Hardware Design Group
XILINX
Telephone: 408-626-6260
E-Mail: ming.tsai@xxxxxxxxxx
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