Touch Screen Display Pad Connection Layer Reliability
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Solution Overview
Problem
In touch screen-integrated display devices, the thick passivation layer causes disconnection or cracking of the pad connection layer due to its steep slope, leading to deteriorated image quality, especially in high-temperature and high-humidity environments.
Innovation Solution
The passivation layer is removed from signal supply pads and control signal lines, reducing the step height between line pads and signal supply pads, and a pad connection layer is formed through contact holes to connect them, thereby reducing contact resistance and suppressing damage to the pad connection layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick passivation layer is formed on the display panel, then protection and insulation are improved, but the pad connection layer may be disconnected or cracked due to the steep slope
Solution Approach 1:
The passivation layer is segmented by forming a first opening that exposes the signal supply pad, separating the thick passivation layer into regions with and without the layer. This allows the pad connection layer to be formed on a relatively flat surface in the opening region, avoiding disconnection or cracking while maintaining protection in other areas.
Solution Approach 2:
The passivation layer is removed locally at the signal supply pad area to create a region with different properties (no passivation layer) compared to the rest of the panel (thick passivation layer). This local modification reduces the step height specifically where the pad connection layer is formed, preventing damage while preserving the protective function elsewhere.
2Reliability
If a thick passivation layer is formed, then insulation is improved, but contact resistance between signal supply pad and line pad increases
Solution Approach 1:
The passivation layer is segmented to create a first opening that exposes the signal supply pad. This allows the pad connection layer to directly contact the signal supply pad without having to traverse through the thick passivation layer, significantly reducing contact resistance while maintaining insulation in other areas.
Solution Approach 2:
The first opening acts as an intermediary structure that facilitates direct electrical contact between the pad connection layer and the signal supply pad. By removing the passivation layer barrier in this specific location, the opening serves as a mediator that reduces contact resistance without compromising the overall insulation provided by the passivation layer elsewhere.
3Device complexity
If control signal lines are formed on the passivation layer, then integration is improved, but the pad connection layer is damaged due to the steep slope of the passivation layer
Solution Approach 1:
The passivation layer is segmented to create a first opening that exposes the signal supply pad and provides a flat surface for forming the pad connection layer. This segmentation allows control signal lines to be integrated on the passivation layer in other areas while preventing pad connection layer damage in the opening region where the steep slope would otherwise cause problems.
Solution Approach 2:
The passivation layer is locally removed at the signal supply pad area to create a flat surface suitable for pad connection layer formation, while maintaining the passivation layer in other areas for integration of control signal lines. This local quality change allows both integration and structural integrity to coexist.
Data Source
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AI summary
There is provided a touch screen-integrated display device. The touch screen-integrated display device includes: a substrate including an active area including a plurality of subpixels and a non-active area; a gate line and a data line to define one subpixel; a thin-film transistor disposed in subpixel; a first electrode electrically connected to a source electrode of the thin-film transistor; and a second electrode disposed to be overlapped with the first electrode with a protective layer interposed therebetween, and further includes a pad connection layer configured to connect the line pad and the signal supply pad in the non-active area. Thus, it is possible to reduce a contact resistance between the signal supply pad and the line pad and also possible to suppress damage to the pad connection layer.