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BGA dropping off the board

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jo

#53632

BGA dropping off the board | 14 February, 2008

Anyone knows why BGA fell off sometimes from the board? I was running in a single sided only. I encountered a BGA falling off from the pcb pad. The pcb is ENIG and lead free process. The pads had no solder and didn't looks like having a black pad through visual inspection. I noticed that the solder paste had melt and merged onto the BGA balls but not on the pcb pads.

Any advice would be helpful.

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#53637

BGA dropping off the board | 14 February, 2008

How many fell off out of your entire lot? What was the soldering quality like on the ones that didn't fall off (xray, visual)? You need to determine if its a random problem or if even the ones that stayed on are barely on and go from there.

If the ones that stayed on are mechanically and electrically sound than you may have a board contamination issue (greasy fingers handling PCB), or maybe bad paste? When in the run of PCB's did you start seeing the bad ones? The last "x" out of 50 or was it mixed in the lot?

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aj

#53638

BGA dropping off the board | 14 February, 2008

There was hardly a dropped component or components under the BGA ? just a thought.

aj...

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#53639

BGA dropping off the board | 14 February, 2008

Questions are: * Do the BGA pads on the board take solder when you solder them by hand? * What is the temperature on the BGA pads during reflow? * What is the temperature on the other component pads during reflow?

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#53651

BGA dropping off the board | 14 February, 2008

That is bizarre. I would have to say that you need to do a test on the PCB to test solderability with an iron like mentioned before. If you don't find that the pads are contaminated or masked over lightly and the pads do take solder effortlessly, you got something special there. Are you sure there are no other close by locations that aren't showing some kind of wetting issue? If you are running lead-free and the solder got hot enough to melt and meld with the BGA balls leaving nothing on the pads whatsoever...the only explanation is the lands. IOs it possible the board house placed silk screen white dots on the BGA lands? I had a board house do this on all the pads on a board. You had to look hard at it to realize the pads were silked over.

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jo

#53655

BGA dropping off the board | 15 February, 2008

Thanks for the comments and advice. The rest of the components have good solderability except for the BGA that fell off. Our production is high mix low volume so the quantity was very small. I'll check the pcb lands next time I run. It could be a contamination like poor handling (grease), or silked pads. Maybe the old paste that we used (4days old)?

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#53676

BGA dropping off the board | 15 February, 2008

Creating a sound tin nickel intermetalic takes a bit more energy than other finishes (such as copper or tin). You can achieve wetting, but not have a viable intermetalic. You should cross section some intact boards from that process and see what the intermetalic looks like.

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#53678

BGA dropping off the board | 18 February, 2008

4 days seems a lot. You could be losing flux activation causing poor wetting on the enig. Check your suppliers data sheets for paste life. If it was contamination on the PCB, you'ld expect other components to solder badly as well. Try using a brand spanking new pot of paste on your next run.

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