Characterization of Moisture Diffusion into Polymeric Thin Film

摘要

The moisture within polymeric material typically used in electronic devices causes popcorn failures due to the vapor pressure in addition to the thermal stress. The knowledge of characteristics of moisture diffusion into the material is essential in the optimal material development and reliability assessment. The clarified procedures for measuring moisture sorption properties in a thin film form of semicrystalline polyethylene terephthalate (PET) using thermo-gravimetry and differential permeation are studied. The effective diffusivity of moisture into the material obtained from both the moisture transmission through the material and the solubility of moisture is proposed as a reliable method than the direct half time approximation over various water activities and temperatures. The parameterized isothermal desorption process according to Arrhenius equation investigates the possible effect of moisture on the polymer matrix as a form of bound water with polarity. The activation energy of diffusivity and solubility required for moisture diffusion into the material is discussed together with the required energy for evaporation of water.