Micro-LED Pixel Array Structure for Repairable RDL Interconnection
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Solution Overview
Problem
The existing mass transfer and electrically connecting methods for micro-LEDs and micro-ICs in display pixel arrays are difficult to repair, as the redistribution layer (RDL) complicates the replacement of defective components, leading to high costs and potential uneven color or brightness issues due to binning challenges.
Innovation Solution
A light-emitting array structure comprising a substrate, light-emitting pixel units, signal wires, and an encapsulating layer, where each pixel unit includes a driver chip, flat layers, and redistribution layers, allowing for flip-chip bonding of light-emitting diodes and signal wires that are easily integrated and replaceable, with a reflective layer to enhance light emission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If mass transfer technique is used for bonding micro-LEDs via RDL, then micro-LEDs can be electrically connected to form display pixel array, but the structure becomes difficult to repair when defective components need replacement
Solution Approach 1:
The patent divides the display structure into separable modules: the RDL is separated from the substrate and made into an independent flexible layer, while micro-LEDs are mounted on separate carrier substrates. This segmentation allows the RDL to be detached and reattached when replacing defective micro-LEDs, enabling repair without destroying the original RDL structure.
Solution Approach 2:
The patent introduces a vertical stacking dimension by placing the RDL on a flexible substrate that can be bent and detached, rather than having it rigidly fixed to the display substrate. This dimensional flexibility allows the RDL to be temporarily removed for component replacement and then reconnected, solving the repairability issue.
2Ease of repair
If RDL is destroyed to replace defective micro-LED or micro-IC, then component replacement becomes possible, but the destroyed RDL must be recovered which is difficult and tremendously costly
Solution Approach 1:
The patent performs preliminary action by pre-attaching micro-LEDs to carrier substrates before mounting them on the display substrate. The RDL is also prepared in advance on a flexible substrate with connection structures that enable easy detachment and reattachment. This preliminary preparation eliminates the need to destroy and recover the RDL during repairs.
Solution Approach 2:
The patent enables recovery of the RDL by designing it as a separate flexible layer that can be detached and reused. Instead of destroying the RDL to access defective components, the system allows the RDL to be temporarily separated, the defective component replaced, and then the RDL reattached to the same or a new component.
3Productivity
If mass transfer technique is used for bonding micro-LEDs, then micro-LEDs can be arranged in array, but binning based on characteristics cannot be performed beforehand resulting in uneven color or brightness
Solution Approach 1:
The patent segments the micro-LED array into individual carrier substrates, each carrying a small number of micro-LEDs. This segmentation enables binning to be performed at the carrier substrate level before mass transfer, allowing selective assembly of carriers with matched characteristics onto the display substrate, thereby ensuring uniform color and brightness while maintaining mass transfer efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design simplifies the repair process, reduces costs, and ensures even brightness and color by allowing for easy replacement of defective components and integration of high-precision circuits, while improving light emission efficiency and preventing moisture damage.
Implementation Method 1
Each of the light-emitting pixel units comprises a driver chip, a first flat layer, a first redistribution layer, a second flat layer, a second redistribution layer, and a light-emitting diode
Implementation Method 2
the light-emitting array structure further comprises a reflective layer disposed on a top surface of each of the second flat layers
Data Source
AI summary
Disclosed is a light-emitting array structure having a substrate, a plurality of light-emitting pixel units, a plurality of first and second signal wires, and an encapsulating layer. The light-emitting pixel units are arranged in array on the substrate. Each light-emitting pixel unit includes a driving chip, a first flat layer, a first redistribution layer, a second flat layer, a second redistribution layer, and a light-emitting diode. Each first signal wire is electrically connected to a corresponding one of the first redistribution layers and extends in a first direction. The second signal wires extend in a level different from the first signal wires. Each second signal wire is electrically connected to a corresponding one of the second redistribution layers and extends in a second direction different from the first direction. The encapsulating layer covers the light-emitting pixel units, the first and second signal wires, and the substrate.