Here are some before and after photos of our recent hot air soldering.
These are tiny SOT-23 package darlington transistors.
A blob of solder paste was put on each pad (manually using a small paintbrush). As you can see, the paste did spread onto parts of the board that we don't want soldering.
Apply some heat (300 deg, airflow about 1/3rd) and - ta-da!
Similarly, to solder the PIC 18F2455 SOIC SMT package neatly, first start by spreading solder paste all over the place:
Put the chip down with it's feet in the gunky stuff
Add the magic ingredient (heat) - and here's the finished job!
We tried to take a video showing the actual process, but fat fingers and moving parts close to the camera made the focus go all fuzzy. Here's a video from YouTube showing the same soldering process (but when heated from below rather than above).
Just like hot air soldering, it's pretty boring. Nothing much happens until about 1m:30 into the video. Then all of a sudden, the magic happens....