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BGA dropping off underside of board

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#51370

BGA dropping off underside of board | 13 August, 2007

I am building a double sided SMT board. On the first side I have a 405 ball BGA. When we build and run the second side through our reflow oven on about 25% of the boards run the 405 ball BGA on the underside of the board has fallen off. About 80% of the balls remain attached to the board, the device body has come away from the balls. Our reflow oven is running at peak 222 deg C for 60 sec (SnPb product). We have built this product on 2 previous occasions using the same process with no issues. My question is should this happen? and what would be the likely cause. We are of the oppinion that we have defective parts but unsurprisingly the supplier is blaming our process. Any advice would be helpful.

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#51376

BGA dropping off underside of board | 13 August, 2007

Your theory is reasonable about a component issue. You need to investigate the solderability of the pads on the BGA interposer.

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#51377

BGA dropping off underside of board | 13 August, 2007

Good morning,

Does BGA pin configuration allow to add one glue dot? Is you PCBA populated with BGAs from both sides?

BR, Pavel

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#51378

BGA dropping off underside of board | 13 August, 2007

Might want to check to see if the weight of your part has increased. If it has increased, you may not have enough surface tension to hold the part on the board.

I am assuming you already checked that the component isn't getting hit by something in your over? (I.e. Center board support wire, plastic zone dividers, etc)

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#51381

BGA dropping off underside of board | 13 August, 2007

Would I be correct in assuming that the solder used to attach the BGA ball to the device body should have a higher liquidous point that the solder used to attach the device to the board. If the peak reflow temp for SnPb is around 225 deg should the ball attach solder liquidous be greatyer than this?

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#51392

BGA dropping off underside of board | 13 August, 2007

The solder used to attach the BGA ball to the BGA interposer would have a liquidous point dependent on the type of solder used by the device fabricator. If this is a lead free device [altho we don't think so], the solder used by the fabricator would have a higher liquidous that your SnPb solder.

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#51536

BGA dropping off underside of board | 24 August, 2007

Did you check your board finishing? If you are using ENIG finishing on your board you may have a Black Pad issue which causes BGA falling apart from the board

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