Display Pad Wiring Layout for Reduced Step Difference
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Solution Overview
Problem
Display devices face challenges in minimizing the step difference in pad areas where multiple layers are stacked, leading to potential connectivity issues and manufacturing defects due to uneven surfaces.
Innovation Solution
The design incorporates a specific arrangement of electrodes and wirings in the pad area, including first and second pads with different width portions and contact holes, and connection wirings that overlap each other, to reduce the step difference and ensure smooth connection with flexible films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple layers are stacked in the pad area to achieve complex electrical connections, then the electrical connectivity is improved, but the step difference increases causing uneven surfaces
Solution Approach 1:
The patent transitions from a two-dimensional planar arrangement to a three-dimensional stacked structure by adding vertical layers (pad base layer, pad upper layer, connection wirings at different levels). This dimensional change enables complex electrical connections while managing step differences through careful layer design and overlapping arrangements that distribute height variations.
Solution Approach 2:
The patent implements nested structures where connection wirings are embedded within insulating layers, and pad structures are nested with multiple sub-layers (pad base layer, pad upper layer). The connection wirings overlap each other in a nested fashion across different levels, with insulating layers sandwiched between them, creating a compact multi-layer nested architecture that reduces overall step difference.
2Manufacturing precision
If connection wirings overlap each other in the pad area to reduce step difference, then surface uniformity is improved, but the device complexity increases
Solution Approach 1:
The patent merges multiple functions into the overlapping connection wiring structure. The same overlapping wirings simultaneously achieve electrical connection, surface planarization, and mechanical support functions. Insulating layers are merged with the wiring structure, forming an integrated multi-layer system that reduces overall complexity despite the multi-layer arrangement.
Solution Approach 2:
The overlapping connection wiring structure serves multiple purposes: providing electrical connectivity between pads, reducing step difference for surface uniformity, and serving as a structural framework. The pad structures also perform dual functions of electrical connection and mechanical support, reducing the need for separate structural elements.
3Reliability
If pad structures include multiple layers with contact holes to ensure smooth connections, then connection reliability is improved, but the manufacturing precision required increases
Solution Approach 1:
The patent performs preliminary actions by pre-forming the pad base layer and pad upper layer with integrated contact holes before final wiring assembly. The overlapping connection wirings are designed to align with pre-established contact hole patterns, allowing for tolerance accumulation to be managed in favor of alignment rather than against it.
Solution Approach 2:
Insulating layers serve as intermediaries between overlapping connection wirings and between wirings and pads. These intermediary layers provide mechanical support, electrical isolation, and alignment references that facilitate precise positioning of contact holes and wirings, reducing the overall manufacturing precision requirements through built-in alignment features.
Data Source
AI summary
A display device includes first and second electrodes, light-emitting elements on the first and second electrodes, data lines extending from a pad area to a display area, connection wirings spaced apart from the data lines and extending from the pad area to a non-display area on respective sides of the display area, first pads overlapping the data lines in the pad area, and second pads overlapping the connection wirings, wherein the connection wirings include a first connection wiring overlapping a second pad, a second connection wiring not overlapping the second pad and overlapping the first connection wiring in the non-display area, and a third connection wiring overlapping the first connection wiring and electrically connected to the second pad, wherein the first and third connection wirings overlap each other in the pad area, and the first, second, and third connection wirings overlap each other in the non-display area.