A New Chemorheological Analysis of Highly Filled Thermosets Used in Integrated Circuit Packaging PETER J. HALLEY Department of Chemical Engineering, The University of Queensland, Brisbane QLD 4072, Australia Received 6 March 1996; accepted 24 June 1996 ABSTRACT: Chemorheology ( and thus process modeling ) of highly ﬁlled thermosets used in integrated circuit ( IC ) packaging has been complicated by their highly ﬁlled nature, fast kinetics of curing, and viscoelastic nature. This article summarizes a more thorough chemorheological analysis of a typical IC packaging thermoset material, in- cluding novel isothermal and nonisothermal multiwave parallel-plate chemorheology. This new chemorheological analysis may be used to optimize existing and design new IC packaging processes.  1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 95–106, 1997 Key words: Chemorheology; thermosets; chemoviscosity; gelation; epoxy INTRODUCTION allel-plate rheometry to characterize the chemor- heology of highly ﬁlled thermoset IC packaging material and used these data to produce realistic Traditionally design, operation, and optimization of integrated circuit (IC) packaging has been un- ﬂow simulations. However, it is noted that mea- surements are made using individual dynamic dertaken by empirical trial and error methods, due to the complexity of the ﬂow and gelation be- shear rate tests, which may be inﬂuenced by sam- ple-to-sample variation. Also, the correlation be- havior ( chemorheology ) of the highly ﬁlled ther- moset encapsulants. However, these trial-and-er- tween dynamic viscosity and steady shear viscos- ity is assumed to follow the modiﬁed Cox–Merz ror methods inevitably lead to high design and raw material costs. Clearly, a more scientiﬁc rule 3 but it has not been checked. Peters et al. 4 also investigated nonisothermal dynamic paral- model of the IC packaging process that incorpo- rates an understanding of the complex chemor- lel-plate rheometry to describe the chemorheology of highly ﬁlled thermoset IC packaging materials, heology of these materials is required. Highly ﬁlled thermoset materials ( typically ep- but required ﬂow visualization measurements to reﬁne chemorheological data for model develop- oxy-molding compounds ) are used in IC packag- ing due to their low cost ( high silica loading ) , high ment. Once again, the potential sample-to-sample variability and dynamic-steady viscosity assump- thermal conductivity and low thermal expansion, which enables good integration with other chip tions were present. Pahl and Hesenkamp 5 inves- tigated isothermal parallel-plate rheometry to components. However, these materials show highly complex chemorheological ( chemoviscosity characterize the chemorheology of moderately ﬁlled epoxy-molding compounds for use in the and gelation ) behavior due to their highly ﬁlled nature, fast kinetics of curing, and viscoelastic development of a chemorheological model and compared this model with nonisothermal data. nature. Recent work on the rheology of highly ﬁlled thermosets is scarce; however, Nguyen 1,2 in- However, data were obtained from dynamic rate sweeps, which are prone to unwanted effects of vestigated the use of nonisothermal dynamic par- cure due to the experimental time required at each frequency. Interestingly, Pahl and Hesen- Contract grant sponsors: Moldﬂow; The University of kamp showed that the original Cox–Merz rule 6 Queensland  1997 John Wiley & Sons, Inc. CCC 0021-8995/97 / 010095-12 applies. Previous work by Halley et al. 7 showed 95 8e90 ll10 / 8e7C$$ll10 02-07-97 10:31:24 polaal W: Poly Applied