Conductivity Model for Metal-coated Polymer Particles used in Anisotropically Conductive Adhesives

摘要

The increasing demand for fine pitch interconnections has growth the interest for anisotropically conductive adhesives as an alternative for solder joints in high density applications. The understanding of the conduction mechanisms behind anisotropically conductive adhesives (ACA) has a vital importance when choosing the right adhesive for the application. In the conductivity model, a formula has been created that can be used to estimate how the degree of deformation of the particles effects to the resistance. This model can be used especially in the case of soft metal-coated polymer particles. Comparisons between soft metal-coated polymer particles and hard metal particles have been made. Since particle resistance is only a part of the total contact resistance, the model must also take into account the interface resistances between the different materials. With this model it is possible to calculate an estimate of the total contact resistance. Some comparisons to the real measurements was done with gold and ITO surfaces, using gold-coated polymer particles and gold bumped chips. For gold surfaces, the measurements showed a good correlation to the model. In the case of the ITO surface, the interface resistances seems to be the major part of the total resistance.