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What is the rootcause for BGA Lifted PAD after reflow

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MCR

#54803

What is the rootcause for BGA Lifted PAD after reflow | 20 May, 2008

Im qualifying a new PCB. I run 2 diff supplier. Supplier A has Zero failure. Supplier B has 4 failure all having Lifted PAD on Bga same location and same location pads that lifted. How can I prove that the PCB have problem? Input : Both run in same oven Both using same profile. Run in same shift

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#54805

What is the rootcause for BGA Lifted PAD after reflow | 20 May, 2008

Well something is different isn't it? * Paste * Part supplier * Board fabrication * Was the profile that you reference the measured temperature or the the settings keyed into the oven?

The cross sections seem to show less than expected ball collapse.

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MCR

#54807

What is the rootcause for BGA Lifted PAD after reflow | 20 May, 2008

> Well something is different isn't it? * Paste * > Part supplier * Board fabrication * Was the > profile that you reference the measured > temperature or the the settings keyed into the > oven? > > The cross sections seem to show less > than expected ball collapse.

everything are thesame except on the PCB (bord fabrication), reflow oven seeting or parameters, same profile, same solder paste,same printer parameters, I run the 2 diff pcb in same line.Bga that has having pad lifted is same supplier also. Only the PCb is different.Actually the one that got lifted pad is a new PCB supplier and this the first time I see this defect. By the way the BGA ball is a Non- eutectic using SAC305 ball thats why it doesnt collapse

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#54820

What is the rootcause for BGA Lifted PAD after reflow | 20 May, 2008

Sorry, we didn't do a good job of understanding your question. For more on delamination, look here: http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=54655

... but we're not so sure that this is a straight delamination issue, because: * One picture shows a delamination just below the BGA pads * Other picture shows the BGA sheared from the pads

So, something, probably heat, is ripping the board apart in the vacinity of this BGA. It appears that both of the two situations are seeing a tremenous amount of flexing, causing the seperation in same area, but producing slightly different results.

Compare the Tc and Td of the boards from the two suppliers.

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aj

#54827

What is the rootcause for BGA Lifted PAD after reflow | 21 May, 2008

Hi all,

We had similar problems a while back.

Boards would fail at test but if you applied pressure to the BGA they would pass.

Turned out that during the PTH assembly process the Operators were flexing the cards during the insertion of an Oupin Connector. ( the fit was tight , so they had to force them in).

We opended up the holes to allow easier insertion and made slight changes to the assembly process ,this fixed the problem.

Are there any connectors etc on close proximity to the BGA ? Is the BGA close to the edge of the board ?

It definitely looks like it is mechanical stress causing your tearing .

Can you let us know the process after Reflow ?

aj...

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MCR

#55025

What is the rootcause for BGA Lifted PAD after reflow | 9 June, 2008

Hi,

After reflow process we do Automatic inspection and after that direct to 5DX machine to check all the solder joints and we detected it at 5DX inspection. This card havent go to any testing.

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#55044

What is the rootcause for BGA Lifted PAD after reflow | 11 June, 2008

Out of curiosity, what is your top side peak temp @ reflow? Have you inspected the boards prior to SMT (at your 5DX machine?) Also, have you tried to run the board through reflow with out any parts or bga placed and inspected?

I how long are you in the oven for and what is your soak time/temp. What is your time above as well?

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#55072

What is the rootcause for BGA Lifted PAD after reflow | 16 June, 2008

Seen this with our old board house. The uncured board is causing your problem. Hard to catch, but looks like you have all your ducks in a row. We presented the exact same thing to our board house, and naturally they blamed our process, handling, and type of human we had at teh reflow oven. We then went to an outside consultant and had them audit our process and boards. They too found that it was all board related. This was a slam dunk and made the board house pay for our audit as well.

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