What I meant to emphasize was that it's the PCB and not the oven that seems to make the most difference, and that's why the first or second pass at the PCB layout seldom works out. Further, what' seems to matter quite a bit is the precision with which the mask between the BGA and the PC foil is fabricated. More recently, there have been lots of experiments with filling the feed-throughs to the lower layers (most high-pin-count BGA's need 6 or 8 layers, if not more) with solder, copper plugs, etc, all of which adds considerably to the cost of the entire assembly, but mitigates the risk of solder bleeding away from the BGA and into the vias.

Yes, hobbyists seldom use those 432 or even 257-ball parts, but since the ball count can exceed 1200, it's worth knowing about the pitfalls in advance. Damaged solder balls are one problem, but certainly not the only one. If the PCB isn't evenly heated, the solder may not be totally melted in the inner portion of the BGA footprint, and if there's a lot of copper, i.e. feedthroughs to the power supply bypass members on the bottom of the board, that can draw heat away from the inner reaches of that footprint. Time, on one hand, is your friend, as it can allow the heat to spread evenly, but it also works against you, in that it can damage IC's. Even if the costly BGA can be salvaged, reballing is an added cost, and not readily available to hobbyists. With BGA application, it is critical that the board be VERY clean, so the solder will spread evenly, but not wick away. Too much time in the heat, and the solder will bleed under the mask, possibly drying a contact.

Fortunately, I've not had to use any low pin count (<80 contacts) devices that weren't also available in TQFP. I've had such good luck with TQFP's that I'm loath to move to BGA unless I really have to. The only problem I see with them is that it's difficult to find adapters that allow one to provide adequate local supply bypass. I do, after all, like to wire-wrap my onesies/twosies, rather than having to have boards made in the PRc. One certainly can't get reasonable PCB's in the U.S. at a reasonable price. For what it would have cost for high-quality prototype runs made locally, I was once able to get 2K boards, and I got them much more quickly, though only if I was willing to pay for the premium shipping. It would have cost more for a dozen of them made locally. That has evened out a bit more recently, but I still believe I can get 100 perfect boards from the PRC for what it would cost me in time and money for a dozen perfect boards made here.

RE