Analysis of the Constriction Resistance in an ACF Bond

Abstract

The standard model for electrical resistance of an anisotropic conducting film (ACF) bond has been analyzed for the case that includes both constriction resistance and a film resistance between the conducting particle and the bond pad. The electrical circuit for the bond resistance is divided into its different geometric regions for analysis. Evidence is give against the prevailing practice of equating the apparent physical area of contact between the conducting particle and the bond pad to the real area of electrical contact. A calculation evaluates the resistance of an ACF bond versus electrical current. This analysis shows that the constriction resistance for the ACF bond can be determined from the slope of the resistance versus current squared plot. Previous calculations for separable contact that extract the constriction resistance from the resistance versus current relationship have been carried out only for conductors that obey the Wiedemann-Franz law. Calculations in this work have extended the results to materials used in ACF bonds. Finally, it is argued that higher than expected contact resistance in anisotropic conducting adhesive bonds is likely due to a high resistivity temperature independent film resistance