유연 Printed Electronics 적용을 위한 형상제어 은 나노재료의 제조 및 전기적 특성평가

Abstract

Conductive pastes are one of the most important materials for the formation of conductive path and interconnect in electronic devices. Recently, with increasing the demand to flexible electronics, it is necessary to the development of the conductive paste that can be presented a high conductivity and dense microstructure at low sintering temperature. Silver are used extensively for making electrical contact in silicon solar cells, hybrid circuits and semiconducting devices owing to their excellent electrical conductivity and high resistance to oxidation. Most previous works on silver conductive pastes for flexible electronics have focused spherical nanoparticles to decrease the sintering temperature to below the glass temperature of polymeric substrate. However, in case of the paste based on nanoparticles, it is difficult to prepare the paste contained a number of conductive media because of low tap density and the creation of pores cannot be avoided after sintering at low temperature. One of the solutions is that the paste was prepared using conductive nanoparticles with flat surface coverage that can be easily stacked. Among the various shapes of fillers, plate type is probably formed perfect conductive pathways under the lower loading level of the filler than sphere fillers and good adhesive strength. The plate type has a good stacking and mechanical property, however, has a poor sinterability with lower reactivity compared to spherical nanoparticles. In order to develop the sinterability of plate type, spherical nanoparticles which could be easily achieved to sinter between particles at low temperature were mixed with nanoplate. In composites with both silver plate and spherical nanoparticles as conductive fillers, if mixed particles are sintered together, the number of contact points between fillers will reduce and this will lead to lower contact resistance. By using as conductive fillers, the sinterability can be maintained by nano-sized materials and the empty space can be minimized through improved stack density. In this study, we synthesized platelet silver nanoparticles by solvothermal process. Silver conductive paste was prepared by mixing with silver nanoplates and spherical particles in ethanol. It was printed on a glass substrate and then annealed in air atmosphere at 200 and 300 oC for 1hr. The printed patterns were analyzed by various methods. The resistivity was investigated as a function of the weight ratio of the mixed composites and annealing temperature.