If a Solderdam does not help, why not an Amsterdam. Agree with you, we have
tried different coatings, globs and such thing and they all have an
influence on the microwave's field. Worst problem is that some works as
humidity absorbers and you'll get local changes added. If plenty of power
maybe no problem, but LNAs at millimeterwaves don't like to much glues on
lines. You can print a suitable short string of green mask or similar, but
see that it's placed on the right node of the wavelength.
Ingemar Hernefjord
Ericsson Microwave Systems
-----Original Message-----
From: Richard Weiner [mailto:[log in to unmask]]
Sent: den 16 januari 2001 22:40
To: [log in to unmask]
Subject: Re: [TN] RF Surface mount...
Barbara'
Bill is right on with this solution, As a PCB designer working many years
with RF layouts, we use this technique extensively. The solder mask will
definitely have an effect on the RF circuit. Our engineers say it is quite
lossy. Using these 10 to 15 mil soldermask lines as solder dams we are able
to contain the reflowed solder exactly where we need it resulting in a high
quality solder joint.
Richard Weiner
-----Original Message-----
From: Brooks,Bill [mailto:[log in to unmask]]
Sent: Thursday, January 11, 2001 9:02 AM
To: [log in to unmask]
Subject: Re: [TN] RF Surface mount...
Hi Barbara,
I have an answer to your soldering problem. Make solder 'Dam's' by creating
a soldermask that ONLY has small 10 - 15 mil lines of soldermask that cross
the conductor trace (at right angles) that leads away from the component pad
to prevent the solder from wicking away from the pad. It will be a line
barrier that will corral the solderpaste in reflow and won't affect the RF
circuit like a standard soldermask would because it is so minimal. All the
other circuitry can be exposed without a problem because you have restricted
the flow of the solder to just the component pad. It's a good compromise,
and I have used it before with great success! Good Luck with your board! I
know it will work out.
Bill Brooks
PCB Design Engineer
DATRON WORLD COMMUNICATIONS INC.
3030 Enterprise Court
Vista, CA 92083
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
mailto:[log in to unmask]
IPC Designers Council, San Diego Chapter
http://www.ipc.org/SanDiego/
http://home.fda.net/bbrooks/pca/pca.htm
-----Original Message-----
From: Barbara Burcham [mailto:[log in to unmask]]
Sent: Thursday, January 11, 2001 8:10 AM
To: [log in to unmask]
Subject: Re: [TN] RF Surface mount...
If Steve is dealing with a RF board, necking down the trace to create the
solder dam could destroy the impedence and RF characteristics of the
circuit.
You need to:
A) Talk to the client about adding the solder mask, perhaps researching why
they chose not to have a mask or finding a mask material that will
not degrade the circuit.
B) Hand assemble
Barbara
-----Original Message-----
From: Kathy Kuhlow [mailto:[log in to unmask]]
Sent: Thursday, January 11, 2001 9:42 AM
To: [log in to unmask]
Subject: Re: [TN] RF Surface mount...
Steve,
Ina very past life we produced a product similar. We were able to control
the solder running and maintain the solder tension at the pad site by having
the trace necked down considerably (bare minimum width) to force and create
as large a solder dam as possible.
Kathy
>>> [log in to unmask] 01/10/01 07:15PM >>>
Hey all,
We've got a job in here that's going to be a few RF assembies. It uses
surface mount in the design, but the board doesn't have any soldermask at
all
on the surface.
The last time I dealt with something such as this, and tried to print solder
paste, place components, and reflow, all I wound-up with is a bunch of
tomb-stones, and insufficient solder all over the board because the solder
wants to flow out all along the surface layer traces, and goes where-ever it
wants to go...because there's no soldermask to contain it.
I'll try to post a picture of what I'm getting ready to deal with on my
free-drive tomorrow...
This is not high volume at all, but from past experience it's my take that
we
should just hand solder stuff like this...because we'll wind-up touching-up
everything anyway...have any of you ever dealt with stuff like this before?
-Steve Gregory-
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