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October 2004

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Subject:
From:
Werner Engelmaier <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Mon, 18 Oct 2004 16:49:29 EDT
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Hi Tom,
As you recognized, this is bad quality, and thus not subject to any modeling 
or prediction capability.
1)Develop or identify some sort of standard physical test (shear or tensile) 
to measure the as-shipped or as-received strength of the ball-to-package 
joint, probably room temperature, maybe at an elevated temperature.
We are way ahead of you on this; take alook at: 
IPC/JEDEC-9702 “Monotonic Bend Test Method for Surface Mount Solder 
Attachments” and upcoming
IPC-9703 “Shock Test Methods and Qualification Requirements for Surface Mount 
Solder Attachments;” these standards address the issues of "brittle" failure 
and waek metallizations. IPC-9701 “Performance Test Methods and Qualification 
Requirements for Surface Mount Solder Attachments” deals with the reliability 
expectations of good solder joints on the various components.
2)Start gathering a data base, linking mean and variability to material and 
process.
Unfortunately, that may not be particularly helpful, since these kind of 
'defective' attachment metallizations are 'defective' on a sporadic basis without 
much in terms of 'predictors,' and when they occur they are typically 
catastrophic.
3)Start relating this relative ball-to-package strength data to maverick 
failures at the interface, in t-cycle testing.
See 2)
4)Depending on results, and if these failures persist in mil/aero 
applications, consider adding a suitable qualification and lot-acceptance test and 
criteria to incoming BGAs.
See 1)

Regards,
Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL 32174 USA
Phone: 386-437-8747, Fax: 386-437-8737, Cell: 386-316-5904
E-mail: [log in to unmask], Website: www.engelmaier.com

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