Tiled Display Pad Electrode Inspection for Micro-LED Bonding
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Solution Overview
Problem
The increase in pixel count in large display devices leads to higher defect rates and decreased productivity and reliability, particularly due to damage of pad electrodes during bonding of inorganic light emitting diodes.
Innovation Solution
A display device design that includes inspection transistors or resistors overlapping pad electrodes to detect damage, using flip chip type micro light emitting diodes and connection members for tiled display devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the number of pixels is increased to achieve large display size, then the display area is improved, but the defect rate increases and reliability decreases
Solution Approach 1:
The patent divides the large display device into multiple smaller sub-display regions, each with its own independent pixel array and control circuits. This segmentation allows each module to be manufactured and tested separately with lower defect rates, then assembled into a large-scale display system, thereby maintaining reliability while achieving large display area.
Solution Approach 2:
The patent introduces inspection transistors as intermediary elements between the pad electrodes and the pixel circuits. These inspection transistors serve as mediators to detect bonding defects without affecting the normal operation of display pixels, enabling quality control in large-scale displays while maintaining the segmented structure.
2Ease of manufacture
If inorganic light emitting diodes are bonded to display panel, then the light emitting function is achieved, but pad electrode damage occurs due to bonding pressure
Solution Approach 1:
The patent implements inspection transistors that can detect pad electrode bonding status before the display device is fully assembled and shipped. This preliminary inspection allows defective bonds to be identified and addressed early in the manufacturing process, preventing reliability issues from reaching the customer while maintaining ease of manufacture through standardized bonding procedures.
Solution Approach 2:
The inspection transistors provide feedback signals that indicate whether pad electrodes have been properly bonded to the light emitting diodes. This feedback mechanism allows manufacturers to monitor bonding quality in real-time and adjust bonding parameters or replace defective components, ensuring pad electrode integrity while maintaining manufacturing efficiency.
3Reliability
If inspection transistors are added to detect pad electrode damage, then reliability inspection is improved, but device complexity increases
Solution Approach 1:
The patent places inspection transistors only at specific critical locations where pad electrode bonding occurs, rather than uniformly across the entire display panel. This localized approach provides necessary reliability inspection capability at bonding interfaces while minimizing the increase in overall device complexity by avoiding redundant inspection elements in non-critical areas.
Solution Approach 2:
The inspection transistors are designed to serve multiple functions: they can detect bonding defects, serve as part of the pixel driving circuitry during normal operation, and potentially function as additional switching elements for display control. This multi-functionality reduces the net increase in device complexity while maintaining reliable inspection capability.
Data Source
AI summary
A display device includes a plurality of sub-pixels, wherein a sub-pixel of the plurality of sub-pixels includes: a first pad electrode and a second pad electrode on the substrate and spaced from each other in a plan view; a light emitting device on the first pad electrode and the second pad electrode; and a first inspection transistor overlapping the first pad electrode in a thickness direction of the substrate, wherein the first inspection transistor overlaps the light emitting device in the thickness direction of the substrate.