CONDUCTION MECHANISMS IN ANISOTROPIC CONDUCTING ADHESIVE ASSEMBLY

This paper explores both experimentally and through analytical and com putational models, the mechanisms of conduction in flip-chip interconn ections made using anisotropic conducting adhesives. A large number of assemblies have been constructed with geometries in the range of 200- 500 mu m, and wide variations in their joint resistance were observed to occur both within the same assembly and between assemblies under th e same experimental conditions, In order to attempt to explain the ori gin of these unsatisfactory connections, a series of experiments to me asure the linearity of the contact resistance of both high and low res istance joints was made, The results from these measurements show that the large number of low resistance joints are ohmic, while most of th e joints of relatively high resistance show resistive heating. In addi tion to the linearity measurements, computational models of metallic c onduction in solid and polymer cored particles have been constructed t o 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 metalliz ation, The results from the models show that the contact area required to explain the high resistances is small and that the likelihood of o btaining 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 mms at the contact surfaces of the joints.