Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Solder Mask on RF PCB Posted: Fri Jan 23, 2009 10:55 am
Joined: Wed Aug 16, 2006 8:20 am
I am designing a PCB to work
from 100KHz to 7 GHz. I was almost done with my Layout and the gerber was ready for fabrication when someone
mentioned to me that I should consider the effect of Solder mask.
He suggested that the Grounded CPW trace
width and separation I used were valid only when I had air as the dielectric over my traces. Using a Solder mask
would alter the impedance as it has a dielectric greater than air.
I quickly added a layer of Solder mask in
my simulation (using Er for Solder Mask as 3.3 and loss tangent as 0.04
I found that The VSWR of my trace
improved, however the trace was now more lossy.
I don't want to get rid of the solder mask as the Coplanar
GND plane is just 20 mil away from the RF trace and many (0402) size components need to be soldered on them. Since
I am not very good at soldering I am afraid that I would short the traces. My board is fairly large (10 inches by
7 inches) and has more than 500 components. Few traces are 1 inches long.
Has anyone faced a similar
problem or has any suggestions...
Design Engineer- RF
Post subject: Posted: Fri Jan 23, 2009 5:36 pm
Joined: Mon Jun 27,
2005 2:02 pm
Solder mask at frequencies higher than 4GHz is not recommended
because it adds insertion loss. Do not worry about soldering, once you start you will improve with time. But if
you will miss 1-2dB gain in your Tx chain it will be much harder to compensate...
Post subject: Posted: Sat Jan 24, 2009 4:44 am
Joined: Wed Aug 16,
2006 8:20 am
I am exploring the possibility of using Solder Dams
to restrict the flow of solder on the bare traces.
However for a board having more than 500 component, the
time required to create Solder dams along each pad would be large.
Along with the Solder mask another
issue that is driving me crazy is that of Board Surface finish. I have a choice of HASL and ENIG finish. I have
learnt that ENIG causes higher insertion loss and also degrades IMD performance.
Design Engineer- RF