Screen Printed Vias for a Flexible Energy Harvesting and Storage Module

This case study evaluates a highly flexible screen printed through-hole-via using silver microparticle inks for applications in energy harvesting and storage modules. The printed vias fabrication and reliability are evaluated by means of a double sided screen-printing method and repetitive (cyclic) bending tests. Vias, in 125 μm thick PET, were laser cut (50, 100, 150, and 200 μm nominal diameter) then filled, and simultaneously connected to adjacent vias, by screen printing. To investigate the use of the printed via in a monolithic energy module, the vias were used for the fabrication of a flexible printed supercapacitor (aqueous electrolyte and carbon electrode). The results indicate that the lower viscosity silver ink (DuPont 5064H) does not fill the via as effectively as the higher viscosity ink (Asahi LS411AW), and only the sidewall of the vias are coated as the via size increases (≥ 150 μm diameter). Conversely, the Asahi silver paste fills the via more thoroughly and exhibited a 100 % yield (1010 vias; 100 μm nominal via diameter) with the 2-step direct screen-printing method. The bending test showed no signs of via specific breakdown after 30 000 cycles. The results indicate that this via filling process is likely compatible with roll-to-roll screen printing to enable multi-layered printed electronics devices.