Eliminating TFT backplanes in microLED displays using ultra precise deposition (UPD) printed interconnects

Developing microLED processes compatible with the production of fine pitch displays of TV size is one of the main challenges to exceed their limitation to small screens such as found on microLED based smartwatches. The EU funded project “Building Active matrix MicroLED displays By Additive Manufacturing” (BAMBAM) develops unique manufacturing technologies for realizing fine pitch displays based on active microLED pixels which can be mass transferred. One of the key technologies is printing of electrical and optical structures with an Ultra Precise Deposition (UPD) technique. This paper presents first results of UPD printed Ag wires realizing the interconnections between pixel driver ICs and microLEDs. Therefore, the influence of different substrate types, such as Glass, PCB and flex PCB, on the printing processes were evaluated. Additionally, a sidewall insulation process by insulator printing was developed to enable Ag ink wire printing on chips with non-insulated sidewalls. The BAMBAM technology developments shall enable a renewal of the European display industry by removing the need for thin film transistor arrays for addressing large size, fine pitch microLED displays.