Top Emission OLED Signal Pad Corrosion Protection
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Solution Overview
Problem
Top emission type organic light emitting display devices face issues with signal pad corrosion and additional process requirements for preventing corrosion and connecting to external driving circuits, which affect the aperture ratio and manufacturing efficiency.
Innovation Solution
The solution involves a top emission type organic light emitting display device with a substrate having an active area and a pad area, featuring a thin film transistor (TFT), an organic emission layer, auxiliary electrodes, and a signal pad covered by a pad electrode to prevent corrosion, along with a method of manufacturing that minimizes additional processes by forming exposed areas simultaneously and using multi-layer electrodes to enhance corrosion resistance and connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the top of the signal pad is exposed to connect to external driving circuit, then connectivity is achieved, but corrosion resistance deteriorates
Solution Approach 1:
The signal pad structure is segmented into multiple layers: a lower signal pad layer formed during TFT fabrication, and an upper pad electrode layer formed subsequently. This segmentation allows the lower layer to provide connectivity while the upper layer provides corrosion protection, resolving the contradiction between exposed connectivity and corrosion resistance.
Solution Approach 2:
The lower signal pad layer is formed in advance during the TFT fabrication process before the upper pad electrode layer is added. This preliminary action ensures that the corrosion-resistant layer is already in place to protect the signal pad during subsequent manufacturing steps and device operation.
2Reliability
If a separate metal layer is formed to prevent signal pad corrosion, then corrosion resistance improves, but manufacturing process complexity increases
Solution Approach 1:
The upper pad electrode layer is merged with the anode electrode and auxiliary electrode formation process. By using the same patterning and deposition steps to create both the protective pad electrode and the functional electrodes, the corrosion protection function is added without requiring separate manufacturing processes.
Solution Approach 2:
The upper pad electrode layer serves multiple functions: it protects the signal pad from corrosion, provides electrical connectivity to external circuits, and acts as an anode electrode for the OLED structure. This multi-functionality eliminates the need for dedicated corrosion protection layers.
3Ease of operation
If etching process is performed before forming anode electrode pattern, then signal pad exposure is achieved, but etchant damage to signal pad occurs
Solution Approach 1:
The upper pad electrode layer is formed as a preliminary protective layer before the etching process that forms the anode electrode pattern. This preliminary action creates a barrier that prevents etchant from contacting and damaging the signal pad while still allowing the etching process to proceed for pattern formation.
Solution Approach 2:
The upper pad electrode layer acts as a cushioning protective layer that absorbs or prevents the harmful effects of the etchant during the patterning process. This beforehand protection ensures that the signal pad remains undamaged while achieving the necessary exposure for connectivity.
Data Source
AI summary
A method of manufacturing an organic light emitting display device, the method includes forming a thin film transistor (TFT) in an active area of a substrate and forming a signal pad and a first pad electrode, connected to the signal pad, in a pad area of the substrate, forming a passivation layer on the TFT and the first pad electrode, forming a planarization layer on the passivation layer, removing a certain region of the passivation layer to simultaneously form an area, through which the TFT is exposed to the outside, and an area through which the first pad electrode is exposed to the outside, forming a first anode electrode connected to the TFT, a first auxiliary electrode spaced apart from the first anode electrode, and a second pad electrode that is connected to the first pad electrode and covers the exposed first pad electrode; and forming a second anode electrode, covering a top and a side surface of the first anode electrode, and a second auxiliary electrode covering a top and a side surface of the first auxiliary electrode.