Thanks, Inge, I will try to do it.
I was thinking also about the design of the boards, like stress factors 
after soldering.I can not eliminate those- we are just assembling a wide 
variety of boards and we don't always know what happes after assembly.
I was thinking also about the residual stresses in the BGA-like warping.Each 
failure has its own footprint, which I recognize. The question is, what 
others are doing usually when they have to repair a BGA site- what is their 
experience in reliability and cost?
IPC speaks only about replacing.Is there someone who is doing additional 
reflow on the old component as a repair method? Is it considered reliable?
Gaby
----- Original Message ----- 
From: "Ingemar Hernefjord" <[log in to unmask]>
To: "'TechNet E-Mail Forum'" <[log in to unmask]>; "'Gabriela Bogdan'" 
<[log in to unmask]>
Sent: Friday, October 28, 2005 12:41 PM
Subject: SV: [TN] BGA failure and assembly repair


> 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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>
> 

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