Display Pad Metal Stack for Wire Defect Reduction
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Solution Overview
Problem
Display devices face reliability issues due to wire defects in the non-display area and pixel defects in the display area, which existing technologies have not effectively addressed.
Innovation Solution
The implementation of a display device design that includes a substrate with a metal pattern in the pad portion, comprising layers of titanium and aluminum, connected to a printed circuit board or data driver, with specific thickness ranges and etching processes to minimize defects, and a connection electrode structure to enhance electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional single-layer metal structure is used in the pad portion, then the manufacturing process is simple, but wire defects occur frequently leading to poor reliability
Solution Approach 1:
The metal layer in the pad portion is segmented into multiple sub-layers (first sub-metal layer, second sub-metal layer, third sub-metal layer) with different materials and functions. This segmentation allows each layer to perform specific functions: the first layer provides adhesion, the second layer provides conductivity, and the third layer provides protection, thereby improving reliability without requiring additional mask processes.
Solution Approach 2:
The patent employs composite material structure by combining different metal materials in the pad portion. The first sub-metal layer uses a first metal material, the second sub-metal layer uses a second metal material, and the third sub-metal layer uses a third metal material. This composite structure leverages the advantages of each material to achieve both high reliability and defect prevention.
2Reliability
If the second metal layer is made thin to reduce defects, then wire defects are reduced, but electrical connection stability deteriorates
Solution Approach 1:
The patent uses composite material structure where the second sub-metal layer (with second metal material) is positioned between the first and third sub-metal layers. This allows the second layer to be thin for defect prevention while the first and third layers provide structural support and stability, ensuring both defect reduction and connection stability are achieved simultaneously.
Solution Approach 2:
The first and third sub-metal layers act as cushioning layers that protect the thin second sub-metal layer. The first layer provides adhesion to the underlying structure, while the third layer provides protection from environmental factors. This beforehand cushioning allows the second layer to be thin without compromising overall connection stability.
3Reliability
If additional mask processes are added to improve pad portion reliability, then wire defects are reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The patent merges the formation of multiple metal layers with the existing manufacturing process flow. The first, second, and third sub-metal layers are formed in sequence using standard deposition techniques that are already part of the display device manufacturing process, eliminating the need for additional mask processes while achieving improved pad portion reliability.
Solution Approach 2:
The multi-layer metal structure in the pad portion serves multiple functions simultaneously: adhesion, conductivity, protection, and defect prevention. This multi-functionality allows the structure to improve reliability without requiring separate dedicated processes, as the same layers perform multiple roles in the manufacturing and operation of the display device.
Data Source
AI summary
A display device includes: a substrate including a display area and a non-display area; a transistor and a light emitting element, which are disposed on the display area; a pad portion disposed in the non-display area, where the pad portion includes a first metal pattern; and a printed circuit board or a data driver, which is connected with the pad portion. The transistor includes a semiconductor layer disposed on the substrate and a source electrode or a drain electrode which is electrically connected with the semiconductor layer. The source electrode or the drain electrode includes a first layer including a first metal, a second layer including a second metal, and a third layer including the first metal, where the first metal pattern includes the first metal, and is connected with the printed circuit board or the data driver.