it is very hard to find data or info in papers, I browsed IEEE & ScienceDirect and one book by Wong & Mai (Robust Design of Microelectronics Assemblies Against Mechanical Shock, Temperature and Moisture, see chapter 4, fig 4.30). I have found many papers but without details of the Tg region. Wong & Mai provide some data. E.g paper "Molecular dynamics approach to structure–property correlation in epoxy resins for

thermo-mechanical lifetime modeling" is very-very interesting but this is about epoxy only.

The assumption is that CME (or coeff of hygroscopic swelling CHS) and the saturated moisture saturation Csat are well behaved below and above Tg. But what actually happens in the Tg region? I assume that the CME and Csat will change in the Tg region, that is, both CME and Cat are functions of temperature.

I am asking because we experience (solder fatigue) problems due to an underfill of a FCBGA in warm-humid climates. The Tg of the underfill is but 70degC. I am trying to researching the impact of CME and Csat and if this can be modeled using FEM solid mechanics.

Can you hint at papers or puplications? Thank you.