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Shielding from Nearby Heat-Any Tricks

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Shielding from Nearby Heat-Any Tricks | 24 December, 2008

Put on your thinking caps for this one......We are trying to remove a BGA (10 x 10mm, plastic, 0.8mm pitch) which is approx 3 mm next to another BGA (5 x 5mm, plastic, 0.8mm pitch). The challenge is this second device is underfilled with a softening point of 160C. If you get above this temp for more than 1 minute (it takes about 1.5minutes to remove the first lead free BGA) To complicate further both are connected to roughly the same extent to a common ground plane which readily conducts the heat. Approaches we have tried include: a heat sink on the 2nd BGA and cooling of the 2nd BGA via air. Any novel ideas anyone would try?

Regards and Happy Holidays


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Shielding from Nearby Heat-Any Tricks | 24 December, 2008

If they share a common ground plane you are in for some difficulty in trying to prevent the second part from heating too much.

What happens to the underfill material when it is softened by being heated beyond the 160C? Does it harden up again, or become useless?

You could remove both parts, and help assure that you are not causing any compromise in the second component by replacing the first one.

You could "nuke" the one you are removing using a heat gun with a focused tip, and keep ahead of the heat spreading, but that provides you with no means to resolder the new part down without facing the same issues.

Tough spot. If cost were not an issue I would replace both parts. If cost is the barrier, well, you're up against it.

Most important though, is the reheating of the underfill product a real problem? Maybe you should go with it, and flux both parts during the process of removal, and the second part during the replcement of the first part.

Good Luck and Happy Holidays


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Shielding from Nearby Heat-Any Tricks | 5 January, 2009

If you can use a IR desoldering station, you could try covering the second BGA with aluminum tape. The tape shouldnt touch the second BGA, it should form a 'roof'over it that reflects the IR waves.

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