Conduction mechanisms in anisotropic conducting adhesive assembly

This paper explores both experimentally and through analytical and computational models, the mechanisms of conduction in flip-chip interconnections made using anisotropic conducting adhesives. A large number of assemblies have been constructed with geometries in the range of 200–500 m, and wide variations in their joint resistance were observed to occur both within the same assembly and between assemblies under the same experimental conditions. In order to attempt to explain the origin of these unsatisfactory connections, a series of experiments to measure the linearity of the contact resistance of both high and low resistance joints was made. The results from these measurements show that the large number of low resistance joints are ohmic, while most of the joints of relatively high resistance show resistive heating. In addition to the linearity measurements, computational models of metallic conduction in solid and polymer cored particles have been constructed to help understand the mechanism of conduction. These models, which are based on the finite element (FE) method, represent typical conductor particles trapped between appropriate substrate and component metallization. The results from the models show that the contact area required to explain the high resistances is small and that the likelihood of obtaining a high resistance through such a small area of metal-to-metal contact is small, thus, giving a strong indication of the presence of high resistivity films at the contact surfaces of the joints.