Micro LED Redistribution Layer Layout to Prevent Transfer Splitting
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Solution Overview
Problem
Micro light emitting diode display units lack structural support during transfer processes, leading to bending, splits, and reduced yield due to insufficient support strength, especially when devoid of a transparent hard substrate and with insulating layers in certain regions.
Innovation Solution
A redistribution layer design with staggered gaps between electrode and pad patterns, supported by an insulating layer, enhances structural reliability by preventing splitting and improving yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the micro light emitting diode display unit is transferred without a transparent hard substrate, then the flexibility and ease of transfer are improved, but the structural strength and reliability deteriorate, causing bending and splits
Solution Approach 1:
The patent applies preliminary action by pre-forming a support structure comprising metal layers and insulating layers on the substrate before transferring the light emitting elements. This support structure is prepared in advance to provide mechanical strength during the transfer process, eliminating the need for a transparent hard substrate while preventing bending and splits. The support structure is subsequently removed after serving its protective function during transfer.
Solution Approach 2:
The patent uses an intermediary approach by introducing a temporary support structure made of metal layers and insulating layers that acts as a mediator between the substrate and the light emitting elements during transfer. This intermediary structure provides the necessary mechanical support without being a transparent hard substrate, and is removed after the transfer is complete, leaving the light emitting elements intact on the new substrate.
2Reliability
If insulating layers are disposed in some regions but no metal layer is present, then the electrical insulation is achieved, but the support strength becomes insufficient, causing splits
Solution Approach 1:
The patent applies composite materials by combining metal layers and insulating layers to form a support structure. The metal layers provide mechanical strength and structural support, while the insulating layers maintain electrical insulation between different conductive elements. This composite structure ensures both sufficient support strength to prevent splits and proper electrical insulation, resolving the contradiction between these two requirements.
Solution Approach 2:
The patent applies local quality by strategically positioning metal layers in regions where additional mechanical support is needed, while maintaining insulating layers in regions where electrical insulation is the primary requirement. This localized distribution of materials with different properties allows the structure to have varying strength and insulation characteristics in different areas, optimizing both support strength and electrical insulation where needed.
3Device complexity
If the transparent hard substrate is removed, then the manufacturing cost is reduced, but the yield deteriorates due to bending and splits during the picking up process
Solution Approach 1:
The patent applies preliminary action by preparing a support structure before the transfer process to ensure high yield during picking up and bonding operations. This support structure provides the necessary mechanical strength to prevent bending and splits, maintaining high yield. After the transfer is complete, the support structure is removed, eliminating the need for expensive transparent hard substrates and reducing manufacturing costs.
Data Source
AI summary
A light emitting display unit includes a redistribution layer (RDL) and multiple light emitting elements. The RDL includes multiple electrode patterns, multiple pad patterns, an insulating layer and multiple conductive through holes. A first gap and a second gap are respectively formed between two adjacent electrode patterns and between corresponding two adjacent pad patterns. A third length of the overlapping area of an orthographic projection of the first gap on the pad patterns and the pad patterns in a first direction is less than or equal to a second length of the second gap in the first direction. The micro light emitting elements are disposed on the RDL and electrically connected with the electrode patterns.