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ABSTRACT:The DEBGA-MHHPA epoxy system has found increasing applications in microelectronics packaging for which the ability to understand and model the cure kinetics mechanism accurately is crucial. The present article reports on the work done to elucidate accurate knowledge of the gel point by rheological methods. To determine the gel point using the GЈ-GЉ crossover method was found not to be accurate, and the gel point obtained by this method was found to be frequency-dependent. Using the point where tg␦ was found independent of the frequency can accurately define the gel point at different temperatures. At the gel point determined by this method, GЈ and GЉ were found to follow the same power law, demonstrating the accuracy of the method in determining the gel point. The scaling exponent obtained was 0.75-0.79. The activation energy for the cure reaction of the system was determined to be 75.1 kJ/mol by the obtained gel times at different temperatures. The steady-shear rheology test was also used to observe the viscosity change at the gel point.

The DGEBA–MHHPA epoxy system has found increasing applications in microelectronics packaging, making crucial the ability to understand and model the cure kinetics mechanism accurately. The present article reports on work done to elucidate an appropriate model, modified from the empirical DiBenedetto's equation, to relate the glass‐transition temperature (Tg) to the degree of conversion for a DGEBA–MHHPA epoxy system. This model employs the ratio of segmental mobility for crosslinked and uncrosslinked polymers, λ, to fit the model curve to the data obtained. A higher ratio value was shown to indicate a more consistent rate of increase of Tg in relation to the degree of conversion, while a lower value indicated that the rate of Tg increase was disproportionately higher at higher degrees of conversion. The best fit value of λ determined by regression analysis for the DGEBA–MHHPA epoxy system was 0.64, which appeared to be higher than for those previously obtained for other epoxy systems, which ranged from 0.43–0.58. The highest Tg value obtained experimentally, Tg max, was 146°C, which is significantly below the derived theoretical maximum Tg∞ value of 170. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 511–516, 2000