I was looking at using the raytac MDBT50Q-UATMS radio module for a personal project. I am still investigating exactly which module I will use, but I expect it to be similar to this one.
Looking at the recommened solder pad layout, we can see that this is a no-lead part, and the pads are located under the part. For a regular microchip one could hand solder this using some solder paste and a hot air gun. The problem is that this part is not a chip, but rather a whole PCB with lots of little parts on it.
From experience I would say that this isn't going to be 10 seconds of light air. I would need to hit it with a lot of air for quite a while to get the solder on the bottom to melt onto the pads. Pre heating the host PCB can help. But if I shoot that much air at it, there is a real possibility of little parts moving around which would make the module unusable.
So, the question then becomes, what method can be used to solder a small SMD radio module (that has lots of little parts on it) to a PCB without a reflow oven?
This particular module has an RF shield over a lot of the parts, and that helps. But I am interested in a general answer that works with any kind of SMD module with small exposed parts on the top side.
One option is to find a SMD module that has uses castellated edges for the connections (avoiding hidden pads altogether). I could then just solder each connection with a soldering iron as normal. But looking around I have been unable to find a module in that format that also has the range I want and a connection for an external antenna (it's going in a metal box so the antenna must be external, and it's going outside pretty far away so it needs long range).
My first guess would be to design the host PCB with a little clearance around the module. Then cut and bend a small piece of 30-gauge scrap sheet metal into a small box (like 12 x 17 x 10 mm) that fits around the module. Finally drill a small hole in the side to stick in a thermocouple. I could then shoot hot air at the outside of the box and the inside would heat up like it was in an oven. But since there is no airflow (other than convection inside the box), no parts get blown around.
I hope someone else has some good answers for this.