I have posted the pictures in the Technet photo site:
http://ipc-technet.groupsite.com/gallery/12585

Doug Pauls



Leif Laerum <[log in to unmask]>
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07/07/2010 05:11 PM
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[TN] Underfill as a Remedy for Electro Migration?






Technetters,

We have identified electromigration as the root cause of some field
failures we have been seeing. During the troubleshooting we came across
the following NASA paper. All of the details of this paper fits our
situation perfectly. We use the same package as described.

http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/40854/1/08-23.pdf

The executive summary is that the silver in the epoxy used to attach as
die attach migrated to create a short. The migration was triggered by
humidity.

The paper suggests using underfill or conformal coating to remedy the
problem. Currently we do not use either in our process. I have some
questions regarding these:

- What are the pros and cons using either of these for this particular
purpose? IMO underfill seems the best solution for us.
- Does anyone have any experience as to whether this is a good solution? I
am not quite understanding the "chemistry" here.
- Does anyone have a recommendation as to what type of underfill would
work well for this application?

Thank you for your input.



--
Leif Erik Laerum



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