[SI-LIST] Re: Soldermask Impact Microstrip Impedance
- From: Robert Haller <rhaller@xxxxxxxxxx>
- To: itasup@xxxxxx
- Date: Wed, 06 Apr 2005 11:03:07 -0400
Peter Pang, Giancarlo,
Not only do you need to take into account the the presence and value
of the solder mask dielectric, for high speed links you should include
the geometry that the soldermask is a conformal coating. Common in the
industry today is LPISM Liquid Photo-Imageable SolderMask that 'flows'
over the conductors. Many of todays popular field solvers do not provide
this capability to accurately model this geometry. It actually turns out
to have an impact, particularly on dielectric loss (which is important
for high frequency, low margin links).
regards,
Bob
--
Robert J. Haller (rhaller@xxxxxxxxxx)
Principal Consultant
Signal Integrity Software Inc.
6 Clock Tower Place, Suite 250
Maynard, MA 01754
Phone: (978) 461-0449, ext 15
Giancarlo Guida wrote:
> 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
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
