Effect of curing conditions on the interconnect properties of isotropic conductive adhesives composed of an epoxy-based binder

This paper investigates variations in the electrical properties of a typical isotropic conductive adhesive (ICA) with an epoxy-based binder that are caused by differences in the curing conditions. In-situ monitoring of the various processes that were used to cure the ICA revealed that electrical conduction in ICA specimens depends on both the high-temperature curing conditions and the cooling conditions to temperatures below the glass transition temperature (T_g). The internal stress induced by shrinkage of the binder is considered to influence the electrical resistance of the ICA. The electrical resistivity of the cured ICA specimens after cooling to ambient temperature decreased with increasing degree of conversion, tending towards a convergence value that decreased with increasing curing temperature. The electrical resistivity of the specimens was also varied significantly by the subsequent annealing process. However, the electrical resistivity achieved after annealing at temperatures above the curing temperatures clearly depended on the particular curing temperature that was used. The characteristics of the polymer structure in the adhesive binder are considered to be different, depending on the curing temperature, and this affects the electrical properties of the ICA; i.e., the characteristics of the polymer structure obtained during the curing process affect the electrical resistance of the ICA, even after subsequent annealing processes