Dynamic cure and diffusion monitoring in thin encapsulant films

The response of a microdielectric sensor to cure in a thin epoxy film is investigated. The multifrequency loss-factor data are reduced to a single ion-viscosity response curve, representative of the change in ion mobility during the cure reaction. The dynamic dielectric data are compared to Tg as a function of time for several partially cured samples. The dielectric response is shown to be extremely sensitive to the entire cure process. A similar epoxy film is exposed to alternately wet and dry environments while the dielectric response is monitored. The diffusion coefficient of water in the cured resin is estimated through the dynamic change in permittivity using a simple Fickian model and the results are shown to be in good agreement with literature values. Changes in dielectric properties of a photoresistor during ultraviolet exposure are presented.<>