Carl;
In my previous employment we built several small daughter boards, and used
the plated castellation type of connection on a couple of small ones, for
something the size you are talking about we used preformed leads from NAS
Interplex, you may want to look into their products. The only thing I can
say about this approach is due to the nature of the RF circuitry you may not
be able to use a lead of this type. If not, I can see many problems trying
to keep a board of this size flat, especially if a shield can is installed.
Yes, you will need to use a high temp solder to assembly the board and
attach the can. I had experience with some filter assemblies where the
manufacturer didn't do this and we had a mess when we reflowed them on to
our microstrip assemblies. The parts inside the filters reflowed and
shifted effecting the performance of the filters. Cleaning under a
castellated board of this size would be a nightmare also.
Keith S. Calhoun
Product Engineer
SoPark Corporation
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl VanWormer
Sent: Monday, November 03, 2008 10:01 AM
To: [log in to unmask]
Subject: [TN] Looking for design guidance FR-4 module for PCB surface
mounting
We are creating a small (20x30mm) radio module that is intended to be
surface mounted on other PC boards. We are using surface mounted parts
on only one side, with "half pads" around the edges for our contact
points. The "half pads" have plating in the "half vias", and have
plating on the top and bottom of the board to allow for inspection of
the mounted solder joints. The board will probably be made of 0.032"
FR-4, and will have a metal shield covering most of the top side of the
board. We are planning on RoHS compliance.
I have seen other small RF modules that were built like this. I am
hoping to learn where the problems might be hiding, from people who have
"been there, done that".
I am looking for guidance for the following issues:
1. How do we maintain co-planarity for our board? (to allow for reliable
soldering to the target PC board)
2. Is special processing needed for our board? (since it will go through
another surface mount process when mounted on the target PC board)
3. Is special solder needed for our assembly? (high temperature?)
4. Is there any way to design the board to aid the cleaning process,
after it is mounted to the target PC board? (slots, risers, etc.?)
5. What other things should I worry about?
Thanks,
Carl
Carl Van Wormer, P.E.
Senior Hardware Engineer
Cipher Systems
1800 NW 169th Place, Suite B-100
Beaverton, OR 97006
Cipher Systems (503) 617-7447
Direct Line (503) 425-5163
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