Characteristics of nanosilver ink (UTDAg) microdroplets and lines on polyimide during inkjet printing at high stage velocity

Abstract

The performance of printed electronics strongly depends on printing techniques and printing resolution that enhance their electrical and mechanical properties. In this research paper, a Jetlab 4xl was used to control and dispense microdroplets of highly conductive nanosilver ink (UTDAg) on a polyimide substrate. The waveform effect on the droplet generation is characterized by measuring the size and the speed of the drops. The behavior of ejected drops on the substrate is studied by printing lines at different drop spacing and stage velocity. The jetting parameters that drive the piezoelectric actuator were properly determined and two waveforms (bipolar) were created to generate two different droplet characteristics in terms of speed and size. Then, printing on the fly using commands in a script file (called ‘in script’ hereafter) with burst mode (a single burst) was used to print lines with different droplet spacings of 50 μm, 60 μm, 70 μm, 80 μm, 90 μm and 100 μm and stage velocities of 20 mm s⁻¹, 30 mm s⁻¹, 40 mm s⁻¹, and 50 mm s⁻¹. The spreading behavior of the ejected droplets was investigated as well by printing lines with 250 μm spacing at the different stage velocities mentioned above. The physical characteristics of the printed lines were studied by optical microscopy and surface profilometry. Finally, the resistance of the printed line at 100 μm droplet spacing and 50 mm s⁻¹ stage velocity was measured at curing temperatures of 140 °C and 160 °C.