if do not have x-ray inspection machine, how to verify the 1st board out from the smt placer that the BGA is placed accurately onto the solder pads. the diameter of the solder ball is 1mm. could it self align during reflow?
BGA�s are known for their ability to self align and from own experiance they do. There�s enough documentation on this one available (...don�t have the links present like Dave but I�m sure he will give you enough to spend some evenings reading) To judge on the placement accuracy before and after soldering you don�t need X-ray, just look at the alignment of all 4 sides to verify that the device is aligned to your specification (or IPC spec). If your outer rows are well aligned your inner rows are too. That doesn�t tell you anything about the quality of your solder joints but for the question of alignment and maybe warp it tells you enough.
For the purpose of viewing the component sides I do have a moveable camerasystem at my reworkstation that allows for excellent sideviews without tilting and handling the boards during inspections.