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May 22, 2006
Failure at the ENIG finish on the BGA substrate
On May 7, B.G. asked a question about BGA joint failures on ENIG finished boards. We have a similar problem, but the failure is at the ENIG finish on the BGA substrate. The part is an Alterra Stratix package, and we see the issue in at least 3 different applications. The failure happens in downstream assembly operations, sometime after the board-level boundary scan testing. Is this a common problem?
J.K.
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Ask the Experts Comments
May 25, 2006
We are dealing with a similar issue at this time. Most BGAs are electrolytic nickel/immersion gold, but sometimes you have an ENIG finish, which can be susceptible to black pad. Where are the failure points? Do you see mud-cracking?
You could also be simply overloading the package, as SnNi intermetallics are weaker than SnCu. Have you measured the board level strain during manufacturing in that general vicinity?
Dr. Craig D. Hillman, CEO & Managing Partner
DfR Solutions
chillman@dfrsolutions.com
 Dr. Hillman's specialties include best practices in Design for Reliability, strategies for transitioning to Pb-free, supplier qualification (commodity and engineered products), passive component technology and printed board failure mechanisms. Dr. Hillman has over 30 publications and has presented on a wide variety of reliability issues to over 150 companies and organizations.
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