Characterization of Silver Inkjet Overlap-printing through Cohesion and Adhesion

Abstract

-We introduce an understanding of silver (Ag) inkjet overlap-printing characteristics from the viewpoints of cohesion between ink droplets and adhesion between an ink droplet and a surface. The printing characteristics were closely monitored by changing the surface energy to elucidate the effect of adhesion and cohesion on printing instability, such as droplet merging and line bulging. The surface energy of the substrate was changed through the hydrophilization of a hydrophobic fluorocarbon-coated surface. The surface energy and ink wettability of the prepared surfaces were characterized using sessile drop contact angle analysis, and printing instability was observed using an optical microscope after drop-on-demand inkjet printing with a 50% overlap in diameter of deposited singlet patterns. We found that the surface energy is not an appropriate indicator based on the experimental results of Ag ink printing on a hydrofluoric-treated silicon surface. The analytical approach using adhesion and cohesion was helpful in understanding the instability of the inkjet overlap-printing, as adhesion and cohesion represent the direct interfacial relationship between the Ag inks used and the substrate.

Characterization of Inkjet-Printed Silver Patterns for Application to Printed Circuit Board (PCB)

“…The printing system was composed of a print-head, a motorized X-Y stage with positioning accuracy of 2 ㎛, a heatable working table, and an alignment system. Before printing the patterns, we first optimized the droplets ejected from the nozzle by controlling the voltage and waveform of the piezo actuator drive to ensure stable single droplet deposition during all the experiments [10]. We used Ag ink (Advanced Nano Products Co., Korea) in which ~20 nm Ag nano-particles were dispersed in a triethylene glycol monomethyl ether (TGME) solution with a viscosity of 12.8 cP, a vapor pressure of 0.001 kPa at 20 o C, and a surface tension of 35.9 mN/m, respectively.…”

High-resolution CPW fabricated by silver inkjet printing on selectively treated substrate

“…Various factors can affect the shape and surface profile of the printed structure, such as viscosity of the ink, surface energy of the substrate, sintering temperature and duration, and temperature of the substrate during the printing process. More detailed analysis about the effect of these factors on the shape of the structure is shown in our previous research [6,7,16,17]. The thickness of the CPW is optically measured using a 3-D non-contact surface profilometer (Surf, Nanofocus AG, Germany).…”

“…The size of a dot made by a single droplet is mostly governed by the nozzle diameter, viscosity of the ink, and the substrate condition [5]. Previous research on the influence of the substrate condition on dot size reveals that the minimum feature size decreases by reducing the surface energy of the substrate [6,7]. In other words, highresolution printing can be realized on a hydrophobic substrate.…”

Evaluation of Standard Electrical Bonding Strategies for the Hybrid Integration of Inkjet-Printed Electronics

“…Two layers of ink were printed on each sample using a PIXDRO LP50 (Meyer Burger Technology AG, Thun, Netherlands) system with a Spectra SE-128 AA 128 (Fujifilm Dimatix Inc., Santa Clara, CA, USA) 30 pL print head at a resolution of 600 × 600 dpi. Before printing the second layer the first had to sufficiently dry to obtain a homogenous surface and avoid spreading of ink (which depends on the cohesive forces of the ink and the adhesive forces between the ink and the substrate) [56,57]. To promote the evaporation of solvents and hence accelerate the drying process, the substrate table was heated to 57 • C. Subsequently, the samples were sintered in order to achieve formation of a compact, homogeneous layer.…”