Ink-jet fabrication of electronic components

Nanosized metallic particles dispersed in a polymeric matrix have been used conventionally as a paste or ink to print electrically active patterns on different substrates. The potential of ink-jet printing in this field is clearly important but the challenge to date has been how to achieve prints of low volume resistivity from the very low viscosity ink required for ink-jet printing. In this study, ink-jet printing techniques were used to directly deposit metallic conductive patterns to produce wiring boards, antennas, electrodes and so forth. In these methods, aqueous solutions of metal salt and reducing agent were ink-jet printed consecutively onto the substrate, where an immediate chemical reduction transformed the metal cations into very fine metallic particles. The best performing reducing agent for ink-jet metal deposition was found to be ascorbic acid at neutral pH. Using this chemistry, nanosized silver patterns, composed of particles in the size range 10-200 nm, were successfully formed using a standard office ink-jet thermal-head printer. Deposited layers of silver with high electrical conductance up to 1.89 x 10(5) S m(-1) and sheet resistance up to 0.5 Omega/square were printed whilst higher conductivities might be expected using more appropriate devices.