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Lifted Lead



Lifted Lead | 10 September, 2004

We have recently faced lifted lead problem that happened on our 20 mil pitch QFP. We have infact pushed it back to the incoming quality, but still I have a few questions to bring up :

1) what is the typical coplanarity tolerance that ICs' manufacturer is controlling now ? +/- 2 mil ? +/-4 mil 2) By overprint the solder paste (elongate the stencil aperture), can this help? The logic of this proposal is to get better reflowed solder height so that the risk of lifted or non-contact is minimal. 3) What are other things that you guys would suggest for me to look at apart from improving the handling?

Thanks in advance.

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Lifted Lead | 13 September, 2004

Suggest looking at the packaging,is it sufficient to prevent damage to the QFP?.

What way are these components stored when received?.Are the reels stored in boxes or racks?.Storage in boxes may cause damage from stacking the reels on top of each other.

Are these QFP's being flashed/programmed before use?.If a probe has to be placed on a lead for this,it could be the root cause of the lifted legs.

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Lifted Lead | 14 September, 2004

The general control on QFP fine-pitch coplanarity is +3mils.

suggest to look at the re-use of thrown out component from SMT machine. If the component pack in std pack, then most probably the lifted is due to processing, not incoming as the packaging control of IC is std.

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