there is a trick to getting the chip on there… you hold the chip right in line of heat gun so the chip pre heats. then once the pads are liquid you set the chip ont there and if all is well it flows right into place self-centering!
OK, so you've pre-tinned the pads (or have solder already on there from the old chip). Then you hold the chip with tweezer or something? And then hold it just above the board, so the air stream is heating the chip and the pads at the same time? I think I don't have the right mental picture.
