Frank Louwet discusses how nanosilver conductive inks will replace today’s flake ink solutions.
Agfa has developed a nanosilver conductive ink which allows users to cut material costs and drive miniaturisation in many key applications (RFID and smart cards, NFC for communication between devices but also remote control devices for small equipment). Besides outperforming silver flake inks, it as also proves to be an effective replacement for indium tin oxide (ITO) in displays.
The main advantage of nanosilver inks is its high conductivity, ad it can be expected that this new ink will replace silver flake inks in many applications soon. With the new inks it is possible to design a target resistance with a far thinner layer (1-2µ versus 10-20µ, obviously using a finer printing mesh) or reduce the dimensions of the printed traces, or a combination of both. The coverage [= conductive area per kilogram of ink] of the nanosilver ink is much higher than with traditional flake inks: 60-80 m2/kg, compared to 15-20m2/kg. As a bonus, it is possible to print much finer lines and spaces, supporting the ongoing trend for miniaturisation. Recently, printed circuits were designed and printed featuring 150µ lines and spaces. This was not possible with standard inks.
One of the spurs for developing the new nanosilver conductive ink aimed at improving Agfa’s existing products based on conductive polymer, which is used to form a transparent antistatic layer for the manufacturing of LCD displays. Beyond this specific application, nano conductive silver ink also finds its way into flexible transparent electrode applications, to replace the incumbent technology based on ITO (indium tin oxide). ITO is not the ideal solution as it has limitations in conductivity when applied on polymer (film) substrates; on one hand because it is very brittle, but also because it must be annealed at high temperature during manufacturing. The new ink has been used to produce a conductive grid for displays that is so fine that it is practically invisible yet deliveres increased overall conductivity. Research has predicted that by finding niches like a replacement for ITO, demand for new copper- and silver-conductive inks can reach up to 22% of the total conductive ink market by 2018.
Replacing ITO in displays has been identified as an interesting application for conductive inks, amongst many other opportunities. Companies active in the membrane keyboard market, which are now looking to deploy their expertise in new markets like printed electronics, show high interest too, especially when conductive inks are a major part of the bills of materials cost and there is a clear advantage in reducing the amount of ink needed. Electronic product code (EPC) companies have also considered the use of the new inks as a means to integrate RFID antennas into products.
To apply the nanosilver inks on a substrate a screen printing technique was developed combined with a sintering process at 130°C or more, all very comparable with solutions for applying silver flake inks. Alternatives using inkjet or flexo techniques are currently under investigation aiming at a wider choice for the integrators.
With the new ink, Agfa has moved beyond the laboratory stage and prepares for large-scale supply in 2014.
Meanwhile Agfa is cooperating with various systems integrators. They value the nanosilver ink mainly for its peerless electrical performance in small printed circuits.