I just picked up a copy of IPC-D-279 (July 1996) and noted two references to
moisture absorption that I need clarification on. On page 73, section E-1.5,
the second sentence reads "This phenomenon (delamination/package cracking)
normally occurs at ~220C. In extremely susceptible components, the threshold
temperature is expected to be lower than ~220C." On page 130 "IPC-TM-650"
section 4.2 paragraph 2., 220C is identified as the reference temperature
beyond which the moisture rating achieved by this test is not applicable.

1) What moisture rating would be considered "extremely susceptible"?
2) How does this rating correlate to the JEDEC A112-A rating that is
displayed on
    the packaging of moisture sensitive components? Is it the same?
3) If a plastic component has a rating lower than this (i.e.. less
sensitive) and the
    package temperature never exceeds 220C, is moisture absorption
irrelevant?

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