Moisture Effects on the Creep of Thermosetting IC Packaging Polymers

We have investigated the behaviour of moisture absorption in various humidity environments at constant temperature of two types of epoxy novolac polymers. In addition, we examined the effects of moisture on the viscoelastic properties. The water absorption is carried out in an adjustable thermal and humidity chamber at different temperature and humidity. The diffusion coefficients at different conditions were obtained through early stage moisture absorption tests. The moisture absorption was revealed to be of the Fickian type of diffusion for both types of samples and to shift the creep compliance to the left of that of a dried sample, as an effect of plasticization. The relationship between loga
_H
and the equilibrium water content is analogically described by the WLF-type equation on the time-temperature superposition. The time-moisture superposition was confirmed to hold at various equilibrium moisture contents at constant temperature. The more moisture in the sample, the more plasticization will happen for the epoxy