Corrosion Resistant Test Lines for Thin-Film Displays
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Solution Overview
Problem
The trimming process of electronic device substrates to remove peripheral test structures can expose test lines to corrosive conditions, leading to moisture intrusion and potential circuit faults and damage.
Innovation Solution
Forming test lines with multiple parallel fingers shorted together and using multiple conductive thin-film layers resistant to corrosion, such as semiconductor materials, to prevent moisture intrusion and corrosion along the exposed edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If substrate edges are trimmed to remove test pads, then display size is reduced and manufacturing efficiency is improved, but test lines are exposed to corrosive conditions causing moisture intrusion and circuit faults
Solution Approach 1:
The test line structure is modified locally at the substrate edge to include multiple parallel conductive layers and corrosion-resistant materials specifically at the exposed edge portions, while the rest of the test line maintains its original single-layer structure. This localized enhancement protects against moisture intrusion without affecting the overall manufacturing process or display performance.
Solution Approach 2:
The test line is constructed using composite material structure with multiple conductive layers (such as aluminum, copper, or other corrosion-resistant materials) stacked and shorted together at the edge portions. This composite structure provides both electrical conductivity and enhanced resistance to corrosion from moisture exposure during and after the trimming process.
2Reliability
If test lines are formed with multiple parallel fingers shorted together, then resistance to moisture intrusion is improved, but device complexity increases
Solution Approach 1:
The multi-finger parallel structure is implemented only at specific locations where the test line intersects with the substrate cut line or is most exposed to moisture, rather than throughout the entire test line length. This localized application reduces structural complexity while maintaining corrosion resistance where it is most needed.
Solution Approach 2:
Multiple parallel conductive fingers are shorted together and merged into a single composite conductive structure at the edge portions. This merging approach provides enhanced corrosion resistance through the combined protective effect of multiple layers while presenting a unified structure that simplifies the overall design and manufacturing process.
Data Source
AI summary
A display may have an array of pixels formed from thin-film transistor circuitry. The thin-film transistor circuitry may include thin-film layers of dielectric, semiconductor, and metal on a dielectric substrate. Test structures may be formed around the periphery of the substrate to facilitate testing of the thin-film circuitry during manufacturing. The test structures may include test pads that are coupled to the thin-film circuitry by test lines extending from the thin-film circuitry. Following testing, the outermost portions of the display and the test pads on these display portions may be removed by cutting the substrate along a substrate cut line. The test lines may be formed from parallel lines that are shorted together, semiconductor layers, multiple layers of conductive material, and other structures that resist corrosion along the cut line.