Copyright: 1996 - 2024
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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My Hobby Website:
Solder Mask on RF PCB - RF Cafe Forums
RF Cafe Forums closed its virtual doors in 2012 mainly due to other social media
platforms dominating public commenting venues. RF Cafe Forums began sometime around
August of 2003 and was quite well-attended for many years. By 2010, Facebook and
Twitter were overwhelmingly dominating online personal interaction, and RF Cafe
Forums activity dropped off precipitously. If the folks at
phpBB would release a version with integrated
sign-in from the major social media platforms, I would resurrect the RF Cafe Forums,
but until then it is probably not worth the effort. Regardless, there are still
lots of great posts in the archive that ware worth looking at.
Below are the old forum threads, including responses to the original posts.
|-- Amateur Radio
Gripes & Humor
-- CAE, CAD, &
Test & Measurement
Post subject: Solder Mask on RF PCB Posted: Fri Jan
23, 2009 10:55 am
Joined: Wed Aug 16, 2006
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.
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
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