Abstract
The field of printed electronics is rapidly evolving, producing low cost applications with enhanced performances with transparent, stretchable properties and higher reliability. Due to the versatility of printed electronics, industry can consider the implementation of electronics in a way which was never possible before. However, a post-processing step to achieve conductive structures—known as sintering—limits the production ease and speed of printed electronics. This study addresses the issues related to fast sintering without scarifying important properties such as conductivity and surface roughness. A drop-on-demand inkjet printer is employed to deposit silver nanoparticle-based inks. The post-processing time of these inks is reduced by replacing the conventional oven sintering procedure with the state-of-the-art method, named near-infrared sintering. By doing so, the post-processing time shortens from 30–60 min to 6–8 s. Furthermore, the maximum substrate temperature during sintering is reduced from 200 °C to 120 °C. Based on the results of this study, one can conclude that near-infrared sintering is a ready-to-industrialize post-processing method for the production of printed electronics, capable of sintering inks at high speed, low temperature and with low complexity. Furthermore, it becomes clear that ink optimization plays an important role in processing inkjet printable inks, especially after being near-infrared sintered.
Highlights
Over the last decade, drop on demand (DoD) inkjet printing has become a widely used technique to print thin conductive silver patterns for various applications including: Radio-frequency identification (RFID) tags, temperature and humidity sensors, flexible circuits, heaters, strain sensors, capacitive sensors, on many types of substrates like glass, plastics, paper and textiles [1,2,3,4]
Since inkjet printing requires only software modifications in contrast to hardware modifications for screen printing, slot die printing, gravure printing and offset printing [6,7,8,9], it creates a great improvement in patterning flexibility
Inkjet printing can be performed with different types of inks
Summary
Drop on demand (DoD) inkjet printing has become a widely used technique to print thin conductive silver patterns for various applications including: Radio-frequency identification (RFID) tags, temperature and humidity sensors, flexible circuits, heaters, strain sensors, capacitive sensors, on many types of substrates like glass, plastics, paper and textiles [1,2,3,4]. Depending on the ink composition, this method requires high temperatures of 140 to 400 ◦C for 10 to 60 min to achieve a conductive printed silver layer [10,15,16,17] These high temperatures and long curing times make it impossible to sinter silver patterns on heat-sensitive substrates without causing thermal degradation [18]. This sintering method results in very smooth surfaces (Ra: 10–20 nm) with a low sheet resistance, ranging between 0.04 and 0.13 Ω/ for commercially available JS-B40G silver nanoparticle ink, bought from Novacentrix (Austin, TX, USA), as one of the inks studied in this paper [10]. Ninannoomvaatetriivales 2w02a0y, 1t0o, 8m92onitor the moment the structure becomes conductive, based on the emissiv3itoyf o14f the printed layer, is applied and compared to standard four-probe sheet resistance measurements
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