Wave energy-assisted fluidic self-assembly of LED chips for display applications

Micro-light-emitting diode (micro-LED) displays have excellent image characteristics, particularly in terms of contrast ratio, response to electric field, and color expressions. However, these are expensive due to the price of the LED chips. This can be overcome by reducing the size of the LED chip, but the efficiency will decrease as a result. Moreover, the rapid and accurate arrangement of a few million chips with a size of ∼50 µm to form pixels on the substrate is a challenging task. In this study, fluidic self-assembly process was introduced. The self-assembly design and implementation were limited to building a micro-scale system. With geometric constraints, external forces may influence the outcome of a self-assembled product. In this case, wave energy was used as the external force to manipulate the LED chips on the substrate. Target-generated waveforms in the fluid were used to control the movement of the LED chips. The arrays of the LED chips were arranged on a fine metal mask, i.e. transfer cartridge. The chips were then transferred to a circuit-printed glass plate by face-to-face pressing under high temperature and high pressure. It was found that the wave energy-assisted self-assembly is applicable and beneficial to LED module fabrication.