Contact resistance of anisotropically conductive interconnection

Anisotropically conductive adhesives (ACA) are becoming more and more popular in electronic device high density interconnections. The main application areas for ACA are in the attachment of flip chip on glass (COG), flip chip on flex (COF) and TCP (tape carrier package)-flex on displays. The understanding of the conduction mechanisms for anisotropically conductive adhesives is of vital importance when choosing the right adhesive for a specific application. In the conductivity model, a formula has been created that can be used to estimate how the degree of deformation of the particles affects the resistance, especially in the case of soft metal-coated polymer particles. Since the particle resistance is only a part of the total contact resistance, the model has to take into account the interface resistances between the different materials. Using this model, it is possible to calculate an estimate of the total contact resistance. Some comparisons are made with real measurements to verify the model.