Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


BGA Assembly Misalignment

Philip A. Reyes

#6655

BGA Assembly Misalignment | 22 May, 2001

Hi to all!!

For those who have current process of Placing BGA package (SMT using BGA package), do you have any idea what is the acceptable misalignment of the balls on the pads of PCB? I have here with me the IPC 7095 BGA Assembly and Design but its not stated there... pls advise for those who have the info....

Thanks, Philip

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#6658

BGA Assembly Misalignment | 22 May, 2001

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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Brian Sloth Bentzen

#6703

BGA Assembly Misalignment | 26 May, 2001

Dear Philip.

BGA�s are very forgiven components when it comes to misplacement. In my experience, 1.27 mm ball pitch BGA�s, can be misplaces by up to 50% of the solder pad. They can easily be placed using only backlighted vision. It will however be a good idea adding some corner markes on the PCB for easy visual inspection of the placement accuracy.

You might check out my article on PBGA packages on:

www.smtinfocus.com/technical_papers_list.html

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