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Wrinkles on soldered BGA ball joints

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HLy

#36899

Wrinkles on soldered BGA ball joints | 29 September, 2005

Hi, I noticed that the solder joints on my BGAs end up with a lot of wrinkles after reflow. See picture at: http://pstr-r02.ygpweb.aol.com/data/pictures/02/01A/17/DD/E3/9E/n8BhepQLFDs6GMSwaRNxPCTWR5NdpUJZ0300.jpg

Does anybody have any ideas what causes this 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

HLy

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#36909

Wrinkles on soldered BGA ball joints | 30 September, 2005

Alternate explanations are: * Your reflow profile needs to be tweeked. * Bumps under a die look different than elsewhere on the package.

Severe creases may indicate a problem, but creases of only a 0.001 to 0.002" deep should not pose any difficulties. Reflowing the PCB will subsequently eliminate these wrinkles.

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Kris

#37012

Wrinkles on soldered BGA ball joints | 7 October, 2005

the direction in which the solders cool in a BGA are also different than the rest of the boards as the joints " hidden" to ambient.

Refer to an analogus phenomenon in the cookson application note. http://www.cooksonsemi.com/pdfs/How%20&%20Why%20Bumps%20Wrinkle_2002.pdf

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