Dear Technetters!

I am sending these links because lately I performed cross sections with very
similar results on a flip chip BGA which failed at our customer's site.

As stated by our customer, by applying force on the component, the
electrical results seemed to change, and the first supposition was that the
solder joints between the BGA and the circuit had failed. X-ray results can
not show cracks, but the re-reflow was not successful, and in the meantime a
second identical component failed.

I was given the first one for analysis and checked it by x-ray, separately,
so that I had a much better image of the inner solder bumps. I found that
the bumps had random voids.

I started a very time consuming cross section of the bumps under the die and
reached a region with voids under UBM and even melted bumps. The damaged
bumps were random, and on the same row there were perfectly good ones. 

Question:

Has anybody encountered such a problem?

 <http://www.jedec.org/download/search/JEP154.pdf>
http://www.jedec.org/download/search/JEP154.pdf


https://nscnt12.nsc.gov.tw/APPLYFORM/WRITINGS/L120452153/pb1-36.pdf


http://www.imec.be/ngfcs/13_Labie_EM_public.pdf




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