Wiring Structure for TFT Array Substrate Film Floating
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Solution Overview
Problem
The fringe field switching (FFS) mode TFT array substrates for liquid crystal display devices face issues with film floating of insulating films on transparent conductive films, leading to reduced yield and reliability, and poor electrical connectivity between transparent conductive films and metal films, particularly when ITO is used on Al-based metal layers.
Innovation Solution
A wiring structure is designed with a first insulating film, a conductive film, and a transparent conductive film where the transparent conductive film covers at least one end surface of the conductive film, and the angle at the corner part where it contacts the insulating film is greater than 90 degrees but less than 270 degrees or has an arc shape, preventing stress concentration and ensuring electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the transparent conductive film is arranged on the metal film pattern with no insulating film interposed therebetween to reduce the number of photoengraving steps, then the number of manufacturing steps is reduced, but the area of the transparent conductive film pattern increases, which increases the frequency of film floating occurrence
Solution Approach 1:
The patent applies local quality by providing insulating films at specific locations (under the transparent conductive film in contact regions and at corner parts) rather than uniformly across the entire structure. This localized insulation approach prevents film floating at critical areas while maintaining the reduced manufacturing step structure, thus resolving the contradiction between productivity improvement and reliability maintenance.
2Device complexity
If the transparent conductive film makes direct contact with the lower insulating film to simplify the structure, then the structure is simplified, but stress concentration occurs at corner parts, causing film floating and reducing yield and reliability
Solution Approach 1:
The patent introduces insulating films at specific critical locations (corner parts and contact regions) rather than uniformly throughout the structure. This localized approach maintains structural simplicity while preventing stress concentration-induced film floating, thus resolving the contradiction between device complexity and reliability.
3Ease of manufacture
If ITO transparent conductive film is disposed on Al-based metal film to achieve electrical connectivity, then the wiring structure is formed, but poor electrical connectivity occurs due to incompatible conductivity between the materials
Solution Approach 1:
The patent employs composite material structures by combining ITO transparent conductive film with Al-based metal films in specific configurations. The insulating films are strategically positioned to manage the interface between these materials, enabling both structural formation and acceptable electrical connectivity despite material incompatibility, thus resolving the contradiction between ease of manufacture and electrical connectivity reliability.
Data Source
AI summary
In a wiring conversion part which connects a lower conductive film to a first conductive film each functioning as a wiring, a first transparent conductive film is formed into a pattern in which it covers an end surface of the first conductive film, and an angle formed at a corner part in a portion of the first transparent conductive film making contact with a lower first insulating film (outside a width of the first conductive film) is larger than 90 degrees and smaller than 270 degrees or the corner part has an arc shape. A second transparent conductive film is connected to the lower conductive film and the first transparent conductive film, and the first transparent conductive film is connected to the first conductive film, so that the lower conductive film and the first conductive film are electrically connected to each other.