Experimental and Numerical Investigations for Deposited Nanosilver Tracks on Polyimide Films

摘要

Experimental measurements and numerical computations have been performed to study the nanosilver solution ejected from a drop-on-demand piezoelectric inkjet printhead and the characteristics of the deposited nanosilver tracks on the PI substrates. The inkjet printing system for ejecting the nanosilver solution and observing the droplets' evolutions in flight and equilibrium results on the PI substrate consists of a commercial inkjet printhead incorporated with a signal generator, two CCD cameras, a moving stage and a hot plate. The continuity, Navier-Stokes and volume-of-fluid equations will be adopted to govern the inkjet droplet's evolution and deposition. Besides, the PI films will be processed with O_2 plasma treatment for 2 and 4 minutes and the conductive tracks will be sintered at 200°C for one hour and 100°C for half an hour respectively. The optical microscopic images, line widths and resistances of the deposited nanosilver tracks for different treated surfaces, print times and various inter-dot spacings (20 μm to 50 μm) will be investigated. It is found that the sheet resistances of the deposited nanosilver films can be reduced below 0.4 Ohm/sq for triple prints at 100°C for half an hour. The nanosilver track with a resistance of 1.44 Ω per centimeter and a reduced line width of 680 μm can be attained with only one print and the inter-dot spacing of 20 μm on the PI substrate treated with 2 minutes O_2 plasma. In addition, the deposited nanosilver track with a line width of 30 μm can be predicted numerically by deposition a 36 μm droplet on the gap with a pitch of 30 μm between the hydrophobic heterostructures fabricated on the PI substrates.