부산대학교 도서관

Epoxy resin has been widely used in electronic devices because of the excellent electrical properties for insulators. Cracking on the interface of epoxy resin is one problem in curing process, and hence many investigations on the cause have been experimentally done. A few reports that deal with this problem by numerical methods appear in the literature, because a relation laying among the reaction rate, temperature, the stress, and the strain is too complex to be express numerically. The finite element analysis with a coupled matrix of the relation is the most suitable to solve the relation. The relation determined with numerical analysis is useful for designing electronic devices, although many parameters are necessary to accomplish the analysis. Because stress relaxation reduces the internal stress, also material constitutive law has great influence on the internal stress but the stress relaxation has been not taken into account in the previous work. To deal with the stress relaxation of epoxy resin, complex modulus was determined with dynamic mechanical analyzer. The complex modulus was converted to relaxation modulus in order to deal with the stress relaxation in the finite element analysis. The relaxation modulus was expressed in Prony series. Influence of stress relaxation on internal stress of epoxy resin was estimated with the determined relaxation modulus. Stress relaxation reduced the internal stress. Maximum equivalent stress with the stress relaxation was one-fiftieth that without the stress relaxation. Experimental results gave good agreement with ones in numerical analysis without mean normal stress relaxation when the epoxy resin was put between metal parts. It indicates that the mean normal stress relaxation of epoxy resin is negligible between metal parts.