Micro LED Pixel Transfer Mapping to Prevent Display Mura
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Solution Overview
Problem
The process of transferring ultra-small light emitting devices, such as mini LEDs and micro LEDs, is inefficient due to the presence of defective products and variations in electrical and optical characteristics across the wafer, leading to time-consuming individual transfer and potential mura in displayed images.
Innovation Solution
A method involving the singularization of unit pixels on a temporary substrate, measurement of their electrical and optical characteristics, and selective transfer to a carrier substrate in predetermined areas, ensuring uniform distribution and preventing mura.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If individual transfer of light emitting devices is performed using pick-and-place, then defective products can be removed, but the process time becomes excessively long
Solution Approach 1:
The transfer process is segmented into two stages: first, collective transfer of multiple light emitting devices in a group from the wafer to the carrier substrate; second, individual transfer of only the defective devices from the carrier substrate to the circuit board. This segmentation allows most devices to be transferred efficiently in bulk while enabling selective removal of defects.
Solution Approach 2:
The carrier substrate serves as an intermediate stage where light emitting devices are temporarily placed before final mounting. This preliminary action allows for post-transfer inspection and selective removal of defective devices, separating the transfer efficiency requirement from the defect removal requirement.
2Ease of manufacture
If light emitting devices are transferred maintaining relative locational relationship, then transfer process is simplified, but mura occurs in displayed image due to luminance variations
Solution Approach 1:
The method measures electrical and optical characteristics of each light emitting device individually and transfers devices to specific locations on the carrier substrate based on their measured quality. High-luminance devices are placed in regions requiring higher brightness, while low-luminance devices are placed in regions requiring lower brightness, achieving local matching of device characteristics to display requirements.
Solution Approach 2:
The transfer process uses measured parameters (electrical and optical characteristics) to determine the destination location of each device. By changing the transfer destination based on measured parameters rather than maintaining fixed relative positions, the system achieves uniform luminance distribution across the display.
Data Source
AI summary
A transferring method for a light emitting device for a display includes manufacturing a wafer having unit pixels, cutting the wafer on a temporary substrate to singularize the unit pixels, measuring electrical or optical characteristics of the singularized unit pixels, and transferring unit pixels selected according to the electrical or optical characteristics to a carrier substrate. The selected unit pixels are transferred to the carrier substrate in a unit of a predetermined area encompassing a plurality of unit pixels.