Stabilization of the thermal decomposition process of self-reducible copper ion ink for direct printed conductive patterns

Abstract

In this study, a thermally triggered self-reducible copper ink is developed to print conductive patterns on flexible substrates. Inks containing only copper formate (CuF) and monoisopropanol amine (MIPA) generated large bubbles in the CuF decomposing process, and thus the surface morphologies of prepared thin films were largely disturbed. With the addition of octylamine (OA), the bubbling disturbance was relieved due to the lower surface tension and the film uniformity was greatly improved. A low resistivity of 2 Â 10 À7 U m (8.5% of bulk copper) can be reached by heating the ink at 140 C for 5 minutes under a nitrogen environment. XRD results showed the synthesized copper films were comprised of pure metallic copper crystalline. The copper films were composed of closely packed spherical grains of 50 to 500 nm in diameter. After the addition of 1 wt% polyvinylpyrrolidone (PVP) in the ink, the synthesized copper thin films showed great adhesion on glass substrates, and sustained the same conductivity after repeated tape tests.The ink can also be printed on flexible substrates, such as polyethylene terephthalate (PET) or polyimide (PI) thin films, to create highly-conductive tracks with a strong mechanical stability. Finally, various conductive patterns were printed on flexible substrates to show the great potential of this ink for various printed electronic applications. IntroductionThe recent advancements in printing technology have provided a new fabrication method for exible and light-weight electronic devices at low costs. To fabricate these so-called printed electronic devices, inks containing conductive materials are printed on plastic sheets to produce exible microelectronic circuits. As the most essential part in every circuit, electrically conductive interconnects from metal inks have been widely used in these printed devices. To reduce the manufacturing cost, copper has recently attracted wide attention for printed conductive features because of its low price, and high electric conductivity. The most commonly used copper inks are nanoparticle suspensions. 1-7 The printed patterns can yield a low resistivity down to 2.2 times of that for bulk copper 2 aer sintering at 200 C for an hour. However, most plastic substrates might melt or deform at this high temperature. Alternatively, electroless plating approach offers a low-temperature synthetic route for copper thin lm fabrication on plastic surfaces. 8-11Solutions containing active agents are rst printed with microcontact 12-14 or inkjet printing 15-20 methods to produce patterns on plastic substrates. Copper metal are then deposited selectively on the printed patterns in a subsequent electroless plating bath. 12,13,15,16,19 Although electroless plating methods can produce highly conductive copper thin lms on exible substrates at low temperatures, the method needs two processing steps and the plating uid might contaminate or modify the plastic surfaces other than the patterned area. Thus, copper inks that can directly print on selected area with l...

MODs vs. NPs: Vying for the Future of Printed Electronics

“…Huang et al synthesised a Cuf ink complexed with monoisopropanolamine. [81] Octylamine was added to the ink to improve surface tension and PVP was added as an adhesion promoter. Thermal sintering of the ink on glass at 140 8C for 5 min under N 2 resulted in films with 1 = 2.00 10 À7 W m. Following this in 2018, Xu et al aimed to optimise Cuf based inks by studying the effect of water concentration on shelf life and film resistivity (Figure 12).…”

“…Huang et al. synthesised a Cuf ink complexed with mono‐isopropanolamine [81] . Octylamine was added to the ink to improve surface tension and PVP was added as an adhesion promoter.…”

Filtration-induced production of conductive/robust Cu films on cellulose paper by low-temperature sintering in air

“…The transmitted-light microscopy images show that numerous holes are present in the Cu film on PI (electronic supplementary material, figure S4a), whereas fewer holes are present in the Cu film on cellulose paper (electronic supplementary material, figure S4b). The gas released from the decomposition of the MOD ink can reduce the quality of the produced Cu film [31]. As a result, many holes (caused by the gas release) are observed in the Cu films on PI substrates.…”

Sintering Copper Nanoparticles with Photonic Additive for Printed Conductive Patterns by Intense Pulsed Light

“…Thus, IPL with multiple pulses [20] is found to generate more uniform temperature distribution on nanoparticle thin films and results in more effective sintering without film damages. Besides nanoparticle inks, metal organic decomposition (MOD) inks [21,22,23,24,25] have also been proposed to produce conductive tracks. These inks containing metal salts can be easily converted into metal tracks via thermal or plasma post treatments.…”