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BGA's shorting

kjwaskow

#17766

BGA's shorting | 3 October, 2001

We are getting solder blobs forming in open areas of the BGA, between the center array and outer array. THe ceter array balls are starved of solder, so they are presumably the source. The theory we hold is possible moisture causing the solder to move during reflow. Any ideas or advice is welcome! I can email pictures of the problem if you would like to see it.

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#17769

BGA's shorting | 3 October, 2001

Yes, moisture entrapment causes solder shorts 80% of the time. Cracks occur bottom side of the BGA. Use an acoustic microscope to find the cracks. So, what makes you think your BGA are blowing-off steam?

I posted a vid on SMTnet that showed the balls on a BGA bridging as a result of high thermal ramp rate.

Bridging on the out-side corners is often component or profile driven.

Your SUBJECT references bridging, but your discussion seems to saying solder balls. What's the story? What do mean when you say the center balls are "starved of solder"? Your e-mailed pix are probably worth a thousand words.

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Hussman

#17776

BGA's shorting | 4 October, 2001

Without seeing your X-ray, it sounds like your BGAs are out gassing. This casues the situation you described. Try baking some BGAs and run them along with ones not baked to see.

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#17790

BGA's shorting | 5 October, 2001

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