Not that I'm trying to discourage you, but what would be the end use of this, exactly?
To me, it sounds like you want to basically duplicate the use of a guy holding a soldering iron and feeding solder in with a robot. While a neat idea (If impractical, at least to me), there are some terrible complexities to this that are simplified by the human doing it without them realizing, but are terrible hard to reproduce with a robot, mainly telling when a solder joint has 1) Enough solder and 2) is connected properly. Appropriate soldering time and amount depends on: How clean the tip is, soldering iron orientation, Temperature, amount of connected copper on both the pin and the connecting traces, and size of the pad.