| Fabrication of microelectronic devices using screen printing of conductive composites is a widely adopted inexpensive technique. Thermoplastic, screen printable, UV-curable electrically conductive ink compositions were developed using combinations of monofunctional acrylate monomers, dissolved PMMA resin and combinations of silver-based conductive particles. Selection of monofunctional acrylate monomers yielded a binder system that retained its thermoplastic character even after UV polymerization. It was possible to develop a completely solventless UV curable system when silver flakes and glass beads coated with silver were used as the conductive fillers. Formulations with enhanced electrical conductivity were prepared using combinations of silver flakes and silver nanoparticles. Curing of these formulations was achieved by either dual curing or by a thermal curing process and a VOC-exempt solvent was used to achieve optimum printing consistency.Rheology of an ink formulation is an important variable which influences the screen printing process. Therefore, the rheology of the ink formulations was studied in detail under both static and dynamic conditions. Evaluation of screen printing parameters to achieve optimum screen printing conditions was done by screen printing experiment under variable operating conditions.An alternative route to prepare conductive composites excluding the heavy metals as fillers is to use carbon-based conductive materials. Therefore exfoliated graphite plates were used as the electrically conductive filler. Binder formulations were based on a cycloaliphatic epoxy resin and polyalcohol compounds and were hardened by cationic UV curing technique. Electrical conductivity was achieved at a very low concentration of filler. |
