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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.

Experts Comments

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?

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Dr. Craig D. Hillman
CEO & Managing Partner
DfR Solutions
Dr. Hillman's specialties include best practices in Design for Reliability, strategies for transitioning to Pb-free, supplier qualification, passive component technology and printed board failure mechanisms.
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