Researchers from Korea's Kookmin University developed an integrated assembly technology, that can enable microLED devices to be precisely assembled at desired positions and in desired orientations.
The new technology integrates several manufacturing processes, including mass fluid assembly, chip orientation control, defective-pixel repair and mass transfer on a single alignment platform. The researchers term the technology "Dielectrophoretic Injection-Suction Printing", or DEP-ISP.
The researchers explain that the key to the technology is precisely controlling the dielectrophoretic forces and torque exerted on microLED chips by an electric field, as well as the fluidic forces generated during the injection and suction processes. This method reduces the consumption of the chip-containing solution, controls chip orientation using the DEP field, positions chips through subpixel grooves, and enables repair of misaligned chips.
Using dielectrophoretic forces, the team moves chips to their desired subpixel positions and uses rotational torque to control their orientation and distinguish their front and back sides. By combining dielectrophoretic forces with injection-suction printing, the process can selectively remove unnecessary or misplaced chips while retaining those that are correctly aligned.
In particular, correctly oriented chips are held in place by dielectrophoretic forces, while misoriented chips are removed by fluidic forces generated during the suction process, after which the vacant positions are refilled. This self-correcting repair process enables assembly, orientation control, defect removal and reassembly to be performed continuously within a single process.
