Pushing Yields in Micro-LED Display Manufacturing

(Summary) A micro-LED display device that can meet high-resolution requirements and has a high micro-LED product yield for manufacturing. The device has a circuit substrate with micro-LED units on one side and a metal conductive layer on the other. The conductive layer contacts the epitaxial layer of the micro-LEDs and has light conversion regions. A light conversion layer in some regions converts emitted light. Light-shielding structures on the epitaxial layer cover some areas. The metal layer is thicker than the epitaxial layer.

(Summary) Display device using micro-LEDs with a method to selectively separate defective micro-LED chips before assembly on the display substrate. It involves arranging micro-LEDs in different types of assembly grooves on the substrate. Micro-LEDs from the chamber are moved magnetically into the grooves. The grooves and electrodes are designed to exert different dielectrophoresis forces on normal versus defective micro-LEDs. This allows only the defective chips to be recovered while the good ones remain in place.

(Summary) Manufacturing process for an ultra-high-resolution Micro-LED micro-display screen with a simple process and few pixel defects. The process includes: providing an LED epitaxial wafer; forming isolation columns on the wafer to divide it into chip regions; placing conductive solders in the chip regions; performing a first CMP process to remove the conductive solders outside the chip regions; forming electrodes and LED light-emitting structures on the wafer; performing a second CMP process to remove upper parts of the electrodes and LED structures outside the chip regions; and removing the isolation columns to separate the chips. The process enables producing micro-displays with ultra-high pixel density and resolution suitable for AR/VR headsets.

(Summary) A method for manufacturing micro-LED display panels that simplifies the mass transfer of millions of micro-LEDs by bonding them directly to a backplane substrate through a conductive layer on the LED surface. The method starts with growing the LED epitaxial layers on a base substrate that can then be peeled off by laser lift-off. The peeled LEDs are then bonded to a backplane using a conductive layer. This eliminates the need for separate transfer steps and improves yield compared to conventional methods.

(Summary) A micro-LED display panel design allows for repairing defective pixels to improve panel yield. The driving backplane of the micro-LED display is designed with multiple spatially independent electrode pairs. The LED chips are soldered to any of the electrode pairs. If a chip in a pixel is defective, it can be desoldered and resoldered to a different electrode pair. This allows the repair of individual pixels instead of scrapping the whole panel when a single pixel is bad.

(Summary) Micro LED display module manufacturing method that improves yield by allowing replacement of defective LEDs before final assembly. The method involves pressurizing the LEDs on the substrate before curing the adhesive layer, to electrically connect them and check their operation. Defective LEDs are identified and replaced with alternatives.

(Summary) A micro LED display repair method that can increase repair yield compared to conventional methods. The repair method involves using two soldering layers in each pixel area of the display. A first soldering layer is used to bond the primary micro LED to the circuit layer. If the primary micro LED is found to be faulty, the second soldering layer is used to bond a secondary micro LED in its place. The key aspect that increases repair yield is that the first soldering layer is larger and covers the full circuit surface, while the second soldering layer is smaller and only partially covers the secondary micro LED. This allows easier alignment and bonding when replacing a faulty micro LED.

(Summary) Micro-LED with improved light extraction efficiency and manufacturing yields by shaping the LED geometry to minimize losses of side-emitted light. The micro-LED has a reflective layer surrounding a tilted side surface to redirect and extract light emitted from the sidewall. This improves total light extraction compared to conventional vertical sidewall micro-LEDs. The tilted sidewall also allows more LEDs to be grown on a substrate. The micro-LED has a vertical sidewall on one side and a tilted sidewall on the other.

(Summary) Mass transfer method and apparatus for Micro LED manufacturing. The method involves designing differently shaped Micro LED chips of different colors and matching shaped transfer cavities on a vibrating transfer mold surface. When dumped and vibrated together, each color's uniquely shaped LED chips fall into corresponding cavities. This allows mass transfer of multiple colors at once, improving efficiency exponentially while ensuring high yield.

(Summary) Micro LED display module with densely packed micro LEDs on a multilayer circuit board with minimal pads. This allows high-resolution displays with reduced thickness, improved yield and simplified bonding compared to individual LED encapsulation. The circuit board has top and bottom layers with pads matching orthographic projections of the micro LEDs. Internal layers between them provide routing. A flat insulating layer covers the LEDs. The pads connect to drive the LEDs which are arranged in a matrix.