WHy do you believe that using a toaster to solder to a PCB would work any better than the factory production equipment? I agree that, if the PCB is "right", then the toaster will probably work as well as anything, but ... as they say ... there's many a slip 'twixt cup and lip ... which means that it's still easy to make a mistake. Unfortunately, the only way to "check" to see whether the BGA is properly soldered is to x-ray the chip. Most prototype houses in the U.S. can't/won't hold tolerances on solder mask, or, for that matter, registration between layers, sufficiently tight to allow the use of BGA packages. Further, they can't/won't drill small enough holes, because those small-enough-holes (.0035") (vias) are smaller than their minimal tolerance(=/-0.003" = 0.006", worst case) and the ring is therefore too large to allow an escape route on a mid-size (~400-ball) BGA. Only with multiple respins can U.S. board houses "get it right" enough to produce one in ten usable boards. I one orders only 6 prototypes, it's likely, in fact, VERY likely, that they'll all be unusable.

If one has a "proper" BGA-to-through-hole adapter, it probably has been worked out such that one can, indeed use a toaster-oven to solder the thing, provided, of course, the toaster-oven is sufficiently hot. Without precisely located solder mask, however, all bets are off.

If one has boards made in the PRC, Taiwan, or Korea, it's very likely they'll be right the first time, although, there, one will have to deal with a direct competitor within weeks, since their cultural attitude toward IP differs from ours. The only realistic protection one has from that pitfall is programming during receiving inspection when the boards are assembled. Unfortunately, U.S. prototype assembly facilities also only are capable of producing about a 10% yield, so, once again, one has to have the work done in the PRC, where, if any one makes even one mistake, their reusable body parts are subsequently sold into the Asian medical tourism industry in order to recover the cost of correcting the mistake. It would be terrific if such policies were followed here in the U.S. There would be vast and immediate improvement in quality!

RE