Ag Nanoparticle Inks: Achieving Ever Higher Conductivity at Lower Curing Time and Temperature

Silver nanoparticle inks improve every year. These improvements are often incremental, but very important. One ever-present direction of development is towards inks which offer ever higher conductivity levels at a low curing temperature and a short curing time. This a critical figure of merit because it opens more substrate choices, saves time, and lowers energy consumption costs.

Here, we highlight the progress by Agfa, who offers both solvent and water based, as well as screen and inkjet printed (IJ) Ag nanoparticle (NP) inks. The first slide below shows the progress in curing time and temperature of a solvent-based IJ printable Ag NP inks. The left picture is the zoomed up version of the right picture. The compares the properties of two different solvent based IJ Ag NP inks: SPS201 and SPS210 sintered at different temperatures (110C, 130C, and 150C).

For a given sintering temperature, we can see that SPS210 reaches a lower resistivity level at a shorter time compared to SPS201, clearly demonstrating this incremental but important advancement of the Ag NP ink technology. As seen in the following slide, the SP2010 Ag NP IJ ink can achieve 3mOhm/sqr/mill when sintered at just 130C for 10min. These are excellent results.

IJP Ag NP inks are beginning to find suitable applications. In the last slide, you can see printed Ag NP lines as narrow (70um) metallization line on a thin film photovoltaic technology (note: screen printed lines on Si PV are now 34um). Next to it, you can see a transparent heater application.

Here, the application is a photochromic laminate for motor sport visors. The visor can change optical transmission to maintain good visibility in different outdoor light levels. One limitation of the photochromic laminate is that it can change its transparency state only slows. This can be a challenge when the driver enters, for example, a tunnel, transitioning from intense sun light into darkness quickly. To overcome this limitation, the laminate can be heated to accelerate the transition. To this end, a CNT or ITO solution is deployed. The result are ok however homogeneous heating can still take too long (40s or longer).

To overcome this limitation, a metal mesh with linewidth of 70um and pitch of 2mm is inkjet printed using Ag NP inks (SPS211). As seen in the slide below, it reduces resistance to 11ohm, and achieves uniform heating in just 20s, which meets requirements.