RESUMO
Two types of conductive microcapsules with a median size of less than 5 µm are proposed, and their high potential as a key functional material for self-restorable conductive pastes for applications in printed electronic circuits is verified. A well-dispersed suspension of carbon nanoparticles in toluene is prepared as the core material of the microcapsules. The restoration capabilities of the microcapsules for the physical structure and electrical conductivity of silver-based electronic circuit lines are compared. In the assessment of the microcapsule restoration efficiency, the two conductive microcapsules exhibit distinct capabilities for the restoration of damages caused by different mechanical fracturing. That is, the smaller microcapsule is more effective than the larger one to restore circuit lines from a tensile test, whereas the opposite result is obtained from a scratching test, demonstrating the significance of microcapsule size for the restoration of dissimilar fractures that may occur in various applications.
RESUMO
Silver nanopowders (nano-Ag) have extremely high surface energy and are generally difficult to have an effective dispersant for their dispersion stabilization. This study proposes two brush copolymers that show a strong preference for adsorption on the nano-Ag surface via their backbone, while their side chains extend into the dispersion solvent for particle stabilization. After adding only 5 wt % (based on the mass of nano-Ag) of the proposed dispersants, the nano-Ag particles can be stably suspended without settling for at least 2 months. Besides, 5 wt % of these dispersants can well stabilize at least 40 wt % nano-Ag dispersed in di(ethylene glycol) ethyl ether, which is a common solvent for conductive inks and pastes. For applications, a thin film cast using the dispersed nano-Ag shows greatly improved surface flatness as compared to that made without the dispersant, and a low electrical resistivity of 2 × 10-5 Ω cm is obtained after the film is annealed at 170 °C for 20 min.