I've been using a hot plate technique (with a PID controller / thermocouple / SSR setup) to get into making SMD boards. I had an interesting experience earlier today, and I was hoping some more experienced individuals might be able to help me understand what caused it and what I can do to avoid repeat performances.
I applied (non-lead-free) solder paste to my board using a stencil, put it on the hot plate (with a lid on), and started heating up the plate slowly (maybe 1.5 degrees C / second), to "soak" the board prior to turning it up to the melting point. Way before I got to the melting point (maybe around 110C), I witnessed an incredible phenomenon. A variety (but not all) of my components started jumping off the board like popcorn. Some (e.g. D-PAK voltage regulators) just kind of flipped over, others (e.g. 0603 resistors) literally propelled upward and bounded off the lid.
In my earlier attempts I didn't see anything like this happen, and I'm not really sure what I might have done differently on this particular instance. Can anyone explain the circumstances under which this type of outcome might take place and what one can do to mitigate it?