Could you describe the process in a bit more detail? How did you put the solder paste on? Were you able to do the chip separately from the other smd parts?
Sure. First of all, I didn't use paste. My understanding is that you don't with BGA parts. The little balls on the part that are in the images I uploaded are solder. So all I did was flux the board (see board for footprint), flux the bottom of the part, made sure ball 1 was in the right corner, placed it on the board, held it down lightly with the point of my tweezers, and put my hot air gun (this tool: https://www.sparkfun.com/products/10706
) on the part, rapidly moving it back and forth so as to heated evenly. I had the gun at 400C. This is hotter than what you use in reflow ovens but it has been working great for me so far with all surface mount parts. You don't need to apply this amount of heat for long. Anyway, when my intuition told me the part was probably nice and melty (very scientific!), I pointed the gun away and nudge the part very, very slightly. The part then returned to its pads based on surface tension. This tells you with most surface mount parts that you got it right. Anyway, like I said in the original post, it wasn't quite right and two pins were joined. So second time I just fluxed the top of the chip to help spread the heat and hit it again, again nudging it a bit. This time, all pins behave correctly. For all the other surface mount parts on this board what I did was flux the pads, apply a bit of solder to the pads from fine diameter solder (Kester), flux it again, hit it with the hot air gun until it melts, and then apply the part with tweezers. Then I usually hit it again and nudge it to see how it behaves, usually it lines up very well with the pads. The through-hole stuff I did in the normal fashion.