Hi 

new to the forum, although in a previous life I used it quite a lot!

We use the Freescale MPC860DTCZQ50D4 in one of our designs, we've had a few issues with soldering at our sub-contractor which has got worse as we just don't seem to be able to lock down the root cause.
We have other BGA's on the boards (different pitches) which solder ok

The problem is always the outer pins in the corners , I've a lot of infor on the tests we have done, but I had seem a post about contamination of the balls on the Motorola package, which to be frank I hadn't considered

I've also seen some info about substrate changes which I'm wondering if it also was connected