[PCB_FORUM] Re: high speed board material.
- From: Eric Hufstedler <ehufstedler@xxxxxxxxxxxxxxx>
- To: "'icu-pcb-forum@xxxxxxxxxxxxx'" <icu-pcb-forum@xxxxxxxxxxxxx>
- Date: Mon, 21 Feb 2005 10:07:06 -0800
> FR4 should be still ok, but if you are really worry about
> lossy and skin
> depth problem on critical traces, (on external layer only) try Gold
> plate it and
> leave the soldermask exposed on traces in question. Pls
> don't ask me why,
At high enough frequencies (we do 18 GHZ on rogers) the soldermask changes
the impedance of the line. Usually you simulate line impedance in air.
Additionally, i don't *think* board houses are all that good at controlling
the thickness of the soldermask, and even if they were, and the dielectric
constant of the mask was known, you would be faced with modeling the extra
layer.
And i wouldn't be surprised if soldermask was very lossy.
I can't say at exactly what freqs the soldermask effects kick in, but those
are the reasons i can think of at the moment.
-----------------------------------------------------------
To subscribe/unsubscribe:
Send a message to icu-pcb-forum-request@xxxxxxxxxxxxx
with a subject of subscribe or unsubscribe
To view the archives of this list please login at
//www.freelists.org. Our list name is icu-pcb-forum
or go to //www.freelists.org/archives/icu-pcb-forum/
Problems or Questions:
Send an email to icu-pcb-forum-admins@xxxxxxxxxxxxx
Want to post a job listing ? DON'T DO IT HERE!
Better yet, join our jobs listing forum.
SUBSCRIBE: icu-jobs-forum-subscribe@xxxxxxxxxx
POST: icu-jobs-forum@xxxxxxxxxx
-----------------------------------------------------------
Other related posts:
