Pad Electrode Structure Corrosion Protection
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Solution Overview
Problem
Display devices face issues with corrosion on pad electrode structures due to organic or inorganic insulating layers, leading to electrical disconnection and contact defects with external devices.
Innovation Solution
The design minimizes the step difference on the pad electrode structure by spacing insulating layers apart from the signal, connection, and pad electrodes, allowing direct contact and covering the electrodes with a cover electrode to prevent corrosion, while maintaining electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If organic or inorganic insulating layers are used to cover metal layers to prevent corrosion, then corrosion protection is improved, but step difference increases causing electrical disconnection
Solution Approach 1:
A planarization layer is introduced as an intermediary between the insulating layers and the pad electrode structure. This planarization layer fills the step differences created by the insulating layers, providing a flat surface that enables proper electrical connection while allowing the insulating layers to remain in place for corrosion protection.
Solution Approach 2:
The solution addresses the step difference problem by adding a vertical dimension through the planarization layer. Instead of trying to reduce the height of insulating layers, the planarization layer compensates for the height difference by filling the space, transforming the three-dimensional step problem into a fillable volume problem.
2Manufacturing precision
If insulating layers are placed close to pad electrodes to reduce step difference, then electrical connection is improved, but corrosion protection is reduced
Solution Approach 1:
The protective function is segmented between two distinct components: insulating layers that provide chemical corrosion protection (even when distant from electrodes), and planarization layers that provide physical flatness for electrical connection. This segmentation allows each component to optimize its specific function without compromise.
Solution Approach 2:
The planarization layer acts as a mediator that decouples the relationship between insulating layer position and electrical connection quality. It allows insulating layers to be positioned optimally for corrosion protection while independently providing the necessary flat surface for electrical connections.
3Manufacturing precision
If step difference is reduced for better contact, then electrical connectivity is improved, but corrosion protection capability is weakened
Solution Approach 1:
The planarization layer serves as a mediator that separates the functions of corrosion protection and contact optimization. It allows the structure to have large step differences (good for corrosion protection with thick insulating layers) while providing a flat contact surface (good for electrical connection) through its filling function.
Solution Approach 2:
The solution changes the physical state and properties of the planarization layer material to fill the step differences. By selecting materials with appropriate viscosity, curing characteristics, and shrinkage properties, the planarization layer transforms the irregular stepped surface into a flat plane, optimizing both protection and connection parameters simultaneously.
Data Source
AI summary
A display device includes a substrate including a display area and a pad area, a pixel structure disposed on the display area, a pixel insulating layer disposed on the pad area and having a first opening, and a pad electrode structure including a signal electrode disposed in the first opening, a connection electrode disposed on the signal electrode, and a pad electrode disposed on the connection electrode. An upper surface and a side surface of the signal electrode come into direct-contact with a lower surface of the connection electrode. An upper surface and a side surface of the connection electrode come into direct-contact with a lower surface of the pad electrode.