Modelling electrical conductivity of anisotropic chemical adhesives [for flat panel interconnections]

This paper addresses the electrical resistance of anisotropic chemical adhesives used for connecting flexible driver circuits onto liquid crystal display glass. This work is a part of the FLEXIL European project devoted to "fine pitch (54 micrometers) interconnects on flexible printed circuits". The frame of the matter developed in this report deals with modeling the electrical behavior of anisotropic conductive adhesive film made of glue filled by small spherical metal particles needed for flat panels interconnections. A theoretical modeling of the electrical behavior has been developed in the frame of a resistive transmission line analysis. This theoretical study has been completed by the computation of electrical resistance of a stand alone spherical particle stressed between two conductive plates. This has been applied to estimate the number of really connected particles into the conductive glue of interconnections between copper leads of a flexible tape and the ITO traces drawn on the glass of a liquid crystal display. This number of conductive particles is directly related to the quality of anisotropic chemical adhesive bonding process. In summary, this report addresses the electrical performances of the anisotropic chemical adhesive technology in the frame of its LCD display assembly application that gives the way of an analysis which is not obviously limited to the mentioned displays.