Two Novel Methods in the Electrical Characterization of Single Metal-Coated Polymer Spheres
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In the phasing out of lead-based solders used in electronics interconnections, electrical conductive adhesives (ECA) prove to be a promising alternative. Recently, Metal-coated Polymer Spheres (MPS) have begun to replace traditional silver flakes as conductive fillers in the adhesive. The conductive mechanisms of such micron-sized particles are not too well understood. Previous efforts comprise resistivity measurements of numerous particles already embedded in the adhesive or methods relying on computer simulations together with physical measurements. In this project, a technique known as the van der Pauw method is used to electrically characterize individual particles. Additionally, an analytical method using 4-point measurements on spherical thin films is developed. Using micron-sized MPS as test samples, the two methods are implemented in practice. The results from the two methods are consistent and offer new approaches in the electrical characterization of single MPS, a scientific area which, until recently, has been little explored.