Gaby,
If the BGAs are OK, and your is process OK, then I can't see better
solution than search for a better board supplier.

 You'd better send some pics on the cross sections. You told us nothing
about the failure freqency per position, per board, batch dependency,
and variations by time. To change supplier is of course a question of
what the failures cost you. 

Inge

-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Gabriela Bogdan
Skickat: den 28 oktober 2005 09:37
Till: [log in to unmask]
Ämne: [TN] BGA failure and assembly repair

Dear Technetters!

We sometimes receive failed boards from the field with failures on BGA's
for  repair.
Supposing there is no problem with the BGA as a component, supposing
that the X-ray test (feinfocus tiger) does not reveal any problems in
the solder joints (with exception to cracks which are very hard to
detect), what procedure would you suggest?
We are concerned with the following:
Reliability
Cost: the assemblies are still our responsability
We are considering:
Scrap
Repair by reflow and electrical test
Repair by installing a new component and electrical test- this includes
the possibility of visual inspection of the area under the failed
component and finding more out about the failure mechanism)
Lately we have performed several destructive tests in order to  see the
nature of the failures which could not be repaired by reflow, and found:
through hole cracks or corrosion in plugged holes
pad lifting and conductor cracks
solder joint cracks
All these were not detected by X-ray.
Could you suggest the best procedure?

Gaby

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