Simultaneous Investigation of Conductive and Mechanical Properties of Individual, Silver Coated Polymer Particles

Isotropic conductive adhesives (ICAs) represent an environmentally friendly alternative to lead based soldering in electrical interconnects of solar modules. By replacing the solid silver flakes of conventional ICAs with silver coated, micron sized polymer spheres, the amount of silver required to obtain conductive pathways throughout the adhesive can be significantly decreased. The similar mechanical properties of the polymer cores and the surrounding polymer matrix of the adhesive will also reduce the effect of the mechanical mismatch between silver and polymer. The mechanical properties of the individual particles are thus an important factor in the functionality of the ICA. At NTNU Nanomechanical Lab, there is much expertise on the investigation of mechanical, thermal and conductive properties of materials by both experimental methods and computational modelling. We have previously developed a nanoindentation-based flat punch method for investigating the properties of individual, micron sized polymer particles. In this presentation, we will show a further development of this method, where we attach a four-probe measurement setup to the nanoindenter tip and a conductive substrate. This allows for simultaneous investigation of the conductive and mechanical behavior of the metal coated polymer spheres during compression, yielding valuable insight for optimizing the ICA.