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Why does my solder joints look so wrinkled?

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Why does my solder joints look so wrinkled? | 11 October, 2005

Hi folks, I had posted this earlier but I think there was some confusion on where the wrinkled joints were. The picture is the side view of a BGA soldered onto the PCB. I was able to take this picture becuase the BGA was at the edge of the board. I received a couple of response/comments about solder bumping the BGA itself (I was not making the BGA, I am soldering the BGA onto the board). I appricated those comments but didn't really address my concern.

The picture is at

Does anybody have any ideas what caused these and any potential reliability problems with the wrinkled solder joints?

Solder joints on non-BGA parts look just fine.

Thank you in advance for any advice, suggestion, or cause


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Why does my solder joints look so wrinkled? | 12 October, 2005

Hly, The solder ball in your picture looks just like the countless BGA solder joints that I�ve produced over the past 8+ years. We've had a good number of these joints X-rayed, cross-sectioned, and thermally stressed. Some say that the stretched look is from the warping of the component during processing. To the best of my knowledge, we have never received a returned part for a bad BGA solder joint. But, You might want to run some of your own tests to ensure your safe. At least send a sample out to a quality lab that can cross-section it for you.

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Why does my solder joints look so wrinkled? | 12 October, 2005

Most likely happening during the cooling phase. I also produce many of these joints with no reliability, DOA, or field failures to date (thousands upon thousands). Contact your paste supplier and they will give you the technical stuff on what you are seeing.

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Why does my solder joints look so wrinkled? | 20 October, 2005

during the soldering process on larger BGAs the corners can bend up or down due the large copper heatsink on top expanding quicker than the material the bga is made out of, in the worst cases this can lead to to the balls lifting out of the paste and giving open circuits (either at the corners or in the center of the bga), as the solder starts to solidify the bga is cooling and streching the joints.

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