Antioxidant high-conductivity copper paste for low-cost flexible printed electronics

Abstract

The flexible printed electronics (e.g., wearable devices, roll-up displays, heating circuits, radio frequency identification (RFID) tags) calls for high-conductivity and low-cost materials, particularly for copper pastes. It is still a big challenge to develop reliable copper pastes for both antioxidant and high-conductivity flexible printed films and lines. In this work, an antioxidant copper paste was achieved using copper microflakes with surface passivation by formate ions and thiols, with high conductivity of 13400 S cm−1 (the same order of magnitude of silver pastes, 1.8–2.5 × 104 S cm−1). The universal applications of as-prepared copper paste in flexible printed electronics (e.g., electromagnetic interference (EMI) shielding films, anti-fog films, and RFID tags) via screen printing and curing at 170 °C under ambient atmosphere were demonstrated. The as-printed electronics showed high performance in flexibility, stability, and reliability. This work shows the great potential of anti-oxidation copper pastes in low-cost flexible printed electronics for commercial usage.

Durable Oxidation-Resistance of Copper via Light-Powered Bidentate Binding of Carbon Dioxide Anion Radicals

“…Even though these efforts have contributed to the development of unprecedented corrosion-resistant surfaces, the fabrication procedure is energy-intensive since the required high-temperature treatment or electrochemical protocol consumes a large amount of heat or electricity. In addition, the methods are extremely powerful to produce antioxidant nanoparticles, collectors, and electronics but show the inadequate capability to enhance the oxidation-resistance of massive Cu-based materials that have already been used. Therefore, there is an urgent need to develop more easily scalable, cost-effective, and efficient antioxidation methods.…”

“…4,5 The conventional method for antioxidant Cu involves alloying with chromium or nickel, which is environmentally unfriendly and can cause a pronounced degradation in service; that is, Cu alloys lose 60−90% electrical conductivity. 6,7 Coating methods mostly use small organic inhibitors such as azole-based compounds, 8 diols, 9 and amino acids 10 to form a protective film through chemical or/and physical adsorption processes. Nevertheless, the durable antioxidation efficiency is often attenuated by film depletion due to the susceptibility to a wide array of corrosive chemicals and the weak electrostatic and/or van der Waals interactions.…”

“…Copper (Cu) has long been an essential industrial metal and continues to contribute to global initiatives such as grid energy storage and electric vehicles, because of its excellent malleability, ductility, and thermal and electricity conductivity. , Over the past decades, the annual global consumption of Cu has dramatically increased, up to an amount of around 25 million metric tons in 2021 . However, the ubiquitous corrosion induced by, for example, atmospheric oxygen/pollutants and electrolytes poses grand operational, economic, and safety challenges in power wiring, electronic circuits, wind turbines, engines, and pipelines. , The conventional method for antioxidant Cu involves alloying with chromium or nickel, which is environmentally unfriendly and can cause a pronounced degradation in service; that is, Cu alloys lose 60–90% electrical conductivity. , Coating methods mostly use small organic inhibitors such as azole-based compounds, diols, and amino acids to form a protective film through chemical or/and physical adsorption processes. Nevertheless, the durable antioxidation efficiency is often attenuated by film depletion due to the susceptibility to a wide array of corrosive chemicals and the weak electrostatic and/or van der Waals interactions. , …”

Copper inks for printed electronics: a review

“…225,228 However, the disadvantages are the high roughness of the deposited film and the low resolution. It is usually used to prepare passive devices, such as electrodes or antenna, 98,112,114,121,127,229 as shown in Fig. 6d.…”

“…The most mainstream method is to produce a dense passivation layer consisting of metal salts on the outermost surface by reacting an organic corrosion inhibitor with the copper. 112,268,269 The passivation layer keeps O molecules from the environment and the electrochemical process of the doped material in the passivation layer can give the passivation layer resistance to acids and alkali. The commonly used corrosion inhibitors are azole nitrogen, amines and some self-assembled organic short chains.…”