Electrical through-hole and planar interconnect generation in roll-to-roll LED lighting manufacturing using industrial inkjet printheads

Despite the availability of many high-volume and low-cost manufacturing processes for LED-based lighting applications, relying mainly on fixed patterns such as LED-backlights and RGB-pixelated displays, novel applications, such as “mood lighting” or interior wall displays call for more complicated and shaped LED arrangements. The presented work is based of a novel roll-to-roll (R2R) process to adaptively and cost-efficiently generate LED arrangements on RMPD ® substrates. Inkjet printing of planar and though-hole electrical interconnections is of high importance to the process, as it provides a fully digital way of interconnecting devices electrically, accounting for the actual position of the component and spatially provide different ink film thicknesses. Xaar’s industrial inkjet printheads are used to dispense defined volumes of 50 pL of a silver nanoparticle ink in order to provide high reliability and good positioning accuracy while main-taining low satellite drop densities. Specific printing strategies are investigated at a print speed of 0.1 m/s to allow for a reliable electrical connection in case of up to 50 μm deep via connections to the buried component. Due to the low glass-transition nature of the underlying substrates, low sintering tempera-tures are required to preserve the mechanical properties of the substrate. Low temperature oven sintering yielding sufficient conductivity to drive a current of 40 mA will be discussed.