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detecting BGA micro cracks

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#61067

detecting BGA micro cracks | 8 February, 2010

Looking for methods for detecting BGA microcracks without cross sectioning.

Currently evaluating a new package and will be putting together a thermal stress eval. We would like to perform intermediate inspections for cracks. Once all cycles are done we will cross section to confirm intermediate findings.

I am looking at X-ray and ultrasound as methods. Does anyone have any advice on these or other methods and equipment?

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#61071

detecting BGA micro cracks | 8 February, 2010

We believe that neither xray nor SAM will provide satisfactory results and that sectioning throughout the process will provide conclusive information.

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#61074

detecting BGA micro cracks | 8 February, 2010

Dave,

I agree totally, but dye-and-pry should also be part of the evaluation.

Glenn Robertson Process Sciences Inc

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#61075

detecting BGA micro cracks | 8 February, 2010

Thanks Dave and Glenn,

I have setteled on Dye for the destuctive checks, and was thinking about impedence testing at intervals during ESS. Based on the research I have been doing the last several days, this seems like a method that should identify most cracks.

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#61076

detecting BGA micro cracks | 8 February, 2010

Woody: Consider using test BGA with no chip in, but daisy chains that you can monitor. After soldering, run environmental tests and follow with electrical tests to determine if the product concept is good enough.

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#61079

detecting BGA micro cracks | 8 February, 2010

Woody,

Daisy chain packages are definitely needed, but if you can get packages with a dummy chip inside these will provide a more accurate simulation of working components. If possible, continuous monitoring of resistance during the test will be very useful in detecting transient opens.

Glenn

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#61094

detecting BGA micro cracks | 10 February, 2010

Daisy chained parts and impedence testing were my original reccomendation. Unfourtuantely I can not get the resources for this testing.

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#61101

detecting BGA micro cracks | 11 February, 2010

It's OK to have the daisychain done in the interposer rather than the die (and a lot cheaper) but in thermal cycling the parts MUST have representative die. That's where a large part of the CTE mismatch comes from to cause fatigue damage. Thermal cycling results on parts without die won't be meaningful.

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