After looking at your profile, i cave a comment or two.
Preheat to 100°C is a good idea to drive off the volatiles in the paste. This will lessen the possibility of boiling flux causing the part to move, will also reduce the formation of solder balls. Heating to 450°C is much too high. Tin Lead eutectic solder melts at 183°C, and normal soldering temperature should be around 215° to 220°C. The profiles on the manufacturer datasheet are set up for belt furnace soldering. In that process, the board is on a steel belt that moves at precise speed through several tightly controlled temperature zones. The belt speed and the zone length determine the dwell time at each temperature. That said, I would guess that trying to get that type of profile in a reflow oven would be difficult. I am thinking that the thermal response would be too slow. Preheat and cool down would probably be better served outside the oven on a hotplate.
Harvey (the other one) Altstadter
