BGA require placement accuracy of only 0.3mm (�12 thou), compared with a required placement accuracy of 0.08mm (�3 thou) for fine pitch devices. Even with this level of misalignment, plastic BGA self-center / self-correct during reflow due to symmetry of solderable surfaces and the surface tension of solder. So, only standard pick & place [P&P] machine capability is required, without need for vision. Although, some people use the vision system on their P&P machine to inspect for missing balls.
These are fly-weight [relative to their pad area], 50 pitch devices yer putting on the board!!! The PBGA exhibits such a strong self centering effect that precise alignment is not critical. Just get �em on the board bug down and focus on other stuff.
Good luck with your BGA assembly adventure. We SMTneters stand on ready alert to assist.
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