Pixel Pad Structure With Series-Parallel LEDs for Defect Tolerance
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Solution Overview
Problem
Display devices using light emitting elements face issues with defects such as short circuits and disconnections, which can lead to entire pixels failing to emit light due to the connection relationships of the light emitting elements.
Innovation Solution
The display device incorporates light emitting elements connected in series and parallel configurations, with a specific structure including a substrate, insulating layers, contact electrodes, and a pad unit to ensure robustness against defects, allowing other elements to continue emitting light even if some experience short circuits or disconnections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If light emitting elements are connected in series, then the pixel can emit light with sufficient brightness, but if a short circuit or disconnection occurs in any element, the entire pixel fails to emit light
Solution Approach 1:
The pixel is divided into multiple light emitting elements (first, second, third, and fourth light emitting elements) that are arranged in a segmented configuration. This segmentation allows the pixel to be divided into functional units that can operate independently or in combination, enabling the pixel to maintain light emission even when some elements fail.
Solution Approach 2:
The patent implements a dynamic connection configuration where light emitting elements can be connected in series, parallel, or a combination of both, depending on operational conditions. This dynamic flexibility allows the system to adapt to defects by reconfiguring connections to maintain overall functionality and light emission.
2Reliability
If light emitting elements are connected in parallel, then the pixel maintains functionality even if some elements fail, but the overall brightness and luminance may be insufficient
Solution Approach 1:
The patent merges series and parallel connection configurations into a hybrid arrangement where multiple light emitting elements are connected both in series and in parallel. This combination allows the system to achieve sufficient brightness through series connections while maintaining reliability through parallel paths, resolving the contradiction between luminance and defect tolerance.
Solution Approach 2:
The electrical connection structure uses a composite configuration of conductive pathways, combining series and parallel connection topologies within the same pixel. This composite connection architecture enables the system to exhibit both high brightness characteristics (from series connections) and high reliability (from parallel redundancy).
3Reliability
If multiple insulating layers and contact electrodes are added to enable series-parallel connections, then defect robustness is improved, but the device structure becomes more complex
Solution Approach 1:
The second insulating layer serves multiple functions: it provides electrical insulation between different conductive elements, defines connection pathways for series and parallel configurations, and structurally supports the contact electrodes. This multi-functionality reduces the need for additional specialized components, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent employs a nested layer structure where the first insulating layer is positioned beneath the light emitting elements, the second insulating layer is positioned above specific portions of the first layer, and contact electrodes are embedded within or on top of these insulating layers. This nested arrangement integrates multiple functional layers in a compact configuration, minimizing structural complexity while achieving the desired series-parallel connectivity.
Data Source
AI summary
A display device includes a substrate including a display area and a non-display area, a pixel located in the display area, a pad unit on one side of the non-display area, and a driver connected to the pixel. The pixel includes a first insulating layer, a first light emitting element on the first insulating layer, a second insulating layer on the first light emitting element and exposing one end portion and another end portion of the first light emitting element, a first contact electrode on the second insulating layer and connected to the one end portion of the first light emitting element, and a second contact electrode on the second insulating layer and connected to the other end portion of the first light emitting element. The pad unit includes a pad metal layer, a first pad insulating layer, a second pad insulating layer, and a pad electrode.