Characterization of the time‐temperature‐viscosity behavior of curing B‐staged epoxy resin

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Abstract
The work described herein was initiated in order to generate resin characterization data that could describe a B‐staged epoxy material via the viscosity‐time‐temperature interactions that are inherently related to the nature of thermoset processing. The technique of chemorheology is explored as a means of characterizing the viscosity‐time‐temperature behavior of the B‐staged epoxy resins. The resins studied are typical of those available as glass‐impregnated prepreg bonding sheets used to manufacture multilayer printed wiring boards. The B‐staged resins were characterized isothermally at various curing temperatures. Their isothermal behavior was correlated via an empirical viscosity expression in the form of a dual Arrhenius model. Experiments were then conducted in a nonisothermal temperature mode, measuring viscosity as a function of both time and temperature. The viscosity model was taken into the nonisothermal temperature mode by introducing a time‐temperature integral. Good correlations between measured and predicted dynamic viscosity profiles are presented. Deviations are explained in terms of resin chemistry. The generalizations of behavior are discused. Calculations are presented which allow the comparison of the various B‐staged resins in terms of their viscosity behavior under the influence of an actual lamination thermal profile.

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