Hi Alan,
The only conformal coating I am aware of that has been shown a reliability
increase for solder joints is Parylene. Roger wild at IBM reported a 2 to
3-times increase in cyclic life in accelerated testing. At first it was
thought that the effect resulted form the exclusion of oxygen and/or corrosion
due to the Parylene encapsulation. However, that was found not to be the case
when additional tests exvluding oxygen and/or corrosion be other means proved
ineffective. Thus, despite the thin character of the Parylene layer,
mechanical support (surface compression?) seems to be mechanism.

Werner Engelmaier
Engelmaier Associates, L.C.
Electronic Packaging, Interconnection and Reliability Consulting
7 Jasmine Run
Ormond Beach, FL  32174  USA
Phone: 904-437-8747, Fax: 904-437-8737
E-mail: [log in to unmask]

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