[SI-LIST] Re: Soldermask Impact Microstrip Impedance
- From: "Giancarlo Guida" <itasup@xxxxxx>
- To: <pangning2000@xxxxxxxxx>, "SI-LIST" <si-list@xxxxxxxxxxxxx>
- Date: Wed, 6 Apr 2005 15:27:33 +0200
Hi Pang,
of course the impedance will change
because as you point out
the dielectric configuration around the strip
changes for the presence of the solder mask.
If you want have a quantitative measure of the change you should use a
simulator that take in to account the presence of any dielectric and not
only the substrate.
To have an idea about the change in the capacitance
you may wanto to download Maxwell Sv fro Ansoft site
www.ansoft.com
Take in to account that there are also other effect that
could change the impedance of a microstrip
what about the effect of the placement of the microstrip on the center of
gnd plane or close to an edge....
again a good simulator could you also indicate if for your particular design
you have to be afraid or not by the edege effects....
giancarlo
----- Original Message -----
From: "Pang Ning" <pangning2000@xxxxxxxxx>
To: "SI-LIST" <si-list@xxxxxxxxxxxxx>
Cc: "Yang Wanguo(Tony)" <tony_yang@xxxxxxxxxxxxxxxx>; "Tang Lan(Stella)"
<stella_tang@xxxxxxxxxxxxxxxx>
Sent: Wednesday, April 06, 2005 3:21 PM
Subject: [SI-LIST] Soldermask Impact Microstrip Impedance
Dear experts,
I have a simple question for you about microstrip impedance. As you know,
many impedance calculation tools didn't consider soldermask influence when
counting microstrip impedance. Maybe the trace should be called as coated
microstrip or embeded microstrip. Because the dielectric constant of
soldermask is much bigger than air, and soldermask thickness is about
0.5mil~1mil, the real impedance on PCB will be smaller than the calculation
results from simulation tools. So would you please let me know how to deal
with this issue? Should the soldermask influence be taken into consideration
when calculating microstrip impedance? Thanks for your comments.
Thanks,
Best Regards,
Peter Pang
XGI Technology Inc.
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