Manufacture of microelectronic circuitry by drop-on-demand dispensing of nano-particle liquid suspensions

An emerging selective metallization process utilizes Drop-On-Demand (DOD) inkjet printing, and recent developments in nano-particle fluid suspensions to fabricate fine-line circuit interconnects. The suspensions consist of silver or gold particulates of 1-10 nm in size that are homogeneously suspended in an organic carrier solvent. A pine-electric droplet generator driven by a bipolar voltage signal is used to dispense 50-70 mum diameter droplets traveling at 1-3 m/s before impacting a compliant substrate. The deposit/substrate composite is subsequently processed at 300 degreesC for 15 minutes to allow for evaporation of the solvent carrier and sintering of the nano-particles, thereby yielding a finished circuit product. Test vehicles created using this technique exhibited features as fine as 120-200 mum wide and 1-3 mum thick. The circuitry performed well during environmental conditioning studies. However, repeatability of the results showed sensitivity to the generation of steady, satellite-free droplets. In an effort to generate droplets consistently, it is essential to develop a strong fundamental understanding of the correlation between device excitation parameters and fluid properties, and resolve the microrheological behavior of the conductive ink as it flows through the droplet generator.