Electrical Sintering of Conductor Grids for Optoelectronic Devices

Metallic nanoparticle inks and pastes are recognized as an enabling technology for printing high-quality conductors on low-cost, flexible substrates. Conductor grids in optoelectronic devices are example applications, where low metal fill factor and high conductivity are desired. High conductivity is obtained through sintering of the nanoparticles, which is typically accomplished by heating the printed structure. However, sintering by oven curing is often problematic due to e.g. shrinking of the printing substrate and is generally considered an inconvenient process stage especially in the roll-to-roll (R2R) printing environment, where the required oven lengths may exceed tens of meters. As a solution to this technological drawback, the rapid electrical sintering (RES) method has recently been introduced. In this work, we demonstrate RES over a constantly moving substrate emulating a R2R printing environment. The sintering power is focused between sintering electrodes having a lateral spacing of less than 1 mm and a vertical working distance of 25 ?m from the ink layer on the substrate. Grid wiring inkjet printed on a temperature sensitive flexible substrate is efficiently sintered with a sintering power of 6.5 W across a 5 mm wide strip. We provide a power budget and relevant system tolerance limits when upscaling and applying the method in an industrial-scale R2R production line. The provided analysis applies to a number of large-area electronic applications utilizing narrow and highly conducting wiring such as organic light emitting diode (OLED) lighting panels, photovoltaics (PV), touch screens and backplane electrodes for displays.