The remarkable price increases in particular US stocks, most notably GameStop, made the news last week as the power of retail investors to move markets became clear. On Monday, February 1, the BBC reported that silver prices increased by around 10% as retail investors turned their attention to commodities, reaching a 5-month high of almost $950/kg.
While silver has many uses, such as mirrors and jewellery, conductive ink is a significant application with a market estimated by IDTechEx at around $2.3billion annually. By far the most common use for silver ink is in the conductive fingers and busbars onto solar panels, making silver ink an essential component in the adoption of renewable energy sources. Additionally, silver ink is used across the entire range of printed electronics technologies, such as printed pressure sensors and wearable skin patches.
The most established and widely used category of conductive ink is based on micron-scale silver flakes, with various polymeric binders added to adjust the rheology. Silver makes up at least 80% of the cost of flake-based inks, meaning that ink prices are very sensitive to price variations of the raw material. As recent events show, these prices can be influenced by speculative activity as well as fundamental changes to the underlying supply and industrial demand.
If silver metal prices continue to rise, it could lead to changes in the composition of conductive ink markets. The most obvious is an acceleration in the transition from silver to copper, with the latter metal currently over 100x cheaper at around $8/kg. This price differential means that, replacing silver with copper, has long been highly desirable. However, it has proved extremely challenging since copper is far more reactive than silver and oxidises relatively quickly in air to insulating copper oxide (illustrated by green copper roofs and statues).
A range of technical approaches have been tried to avoid oxidation when printing with copper rather than silver inks. These include making copper nanoparticles with a silver shell and printing the copper under an inert atmosphere. However, these strategies saw little success as they increased the cost of the printing process while reducing durability. Recent promising approaches, which are beginning to gain commercial traction, involve incorporating additives into copper nanoparticle-based inks that are believed to act as a reducing agent during sintering.
An additional, more subtle transition induced by rising silver prices could be a greater replacement of flake-based conductive inks by nanoparticle-based and particle-free alternatives. Both of these alternatives typically have higher conductivity than flake-based inks, up to 80% of the conductivity of bulk silver in some cases. As might be expected, these inks are more expensive per volume due to the additional manufacturing complexity. However, since raw silver makes up a small proportion of the total cost for these alternative conductive ink formulations, they will become increasingly good value on a per-unit conductivity basis and thus potentially see greater uptake at the expense of flake-based inks.
Extensive discussion of the conductive ink market, tracked by IDTechEx over many years, including details of all the players and applications, along with granular forecasts across 30 categories, can be found in the IDTechEx report “Conductive Inks 2020-2030: Forecasts, Technologies, Players”.