Chip-on-Film Wiring Layout to Prevent Display Pad Electro-Migration
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Solution Overview
Problem
Existing display devices face challenges in preventing electro-migration between wirings of a chip-on-film package, which can lead to insulation degradation and short-circuiting due to electric fields and moisture infiltration.
Innovation Solution
A display device design that includes a chip-on-film package with alternating voltage signals applied to first wirings and constant voltage signals applied to second wirings, with the first wirings being spaced apart from the display panel and the second wirings being adjacent to it, preventing the formation of electric fields between the wirings and thus reducing the risk of electro-migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wirings are placed close together in a chip-on-film package, then device area is reduced, but electro-migration occurs due to electric field formation and moisture infiltration
Solution Approach 1:
The patent applies equipotentiality by connecting both the first and second wirings to the same potential (ground or common voltage) through the first and second pads respectively. This eliminates potential difference between adjacent wirings, preventing electric field formation and thus preventing electro-migration even when wirings are placed close together. The insulation layer further maintains this equipotential condition by preventing moisture infiltration that could create conductive paths.
Solution Approach 2:
The patent introduces an insulation layer as an intermediary between the first and second wirings. This insulation layer acts as a mediator that prevents direct electrical interaction between the wirings, blocking moisture infiltration and preventing the formation of conductive paths that would lead to electro-migration. This allows wirings to be placed closer while maintaining insulation integrity.
2Productivity
If alternating voltage signals are applied to adjacent wirings, then signal transmission capability is improved, but electro-migration is induced due to electric field formation
Solution Approach 1:
The patent resolves this contradiction by making both wirings equipotential (connected to the same potential), which eliminates the electric field that would otherwise be formed by alternating voltage signals on adjacent wirings. This prevents electro-migration while still allowing both wirings to transmit signals effectively, as the signals are referenced to the same ground potential.
Solution Approach 2:
The patent converts the potentially harmful effect of alternating voltage signals into a beneficial configuration by referencing both wirings to the same ground potential. This creates a differential signaling scheme where the alternating signals can be transmitted with high capability while the common ground reference prevents electric field formation and electro-migration.
3Reliability
If wirings are spaced apart to prevent electro-migration, then insulation integrity is maintained, but device area increases
Solution Approach 1:
By making adjacent wirings equipotential (connected to the same potential), the patent eliminates the need for large spacing between wirings. The equipotential condition prevents electric field formation, allowing wirings to be placed close together without risking electro-migration, thus reducing device area while maintaining insulation integrity.
Solution Approach 2:
The insulation layer serves as an intermediary that enables close wiring spacing while maintaining insulation integrity. This thin insulating barrier prevents moisture infiltration and maintains electrical isolation between equipotential wirings, allowing compact layout without sacrificing reliability.
Data Source
AI summary
A display device may include a display panel including a substrate that includes a display area and a pad area adjacent to the display area, and a first pad and a second pad on the pad area of the substrate, and a chip-on-film package over the pad area of the substrate with the first pad and the second pad in between, the chip-on-film package including an insulation layer, a first wiring on an upper surface of the insulation layer and electrically connected to the first pad, and a second wiring on a lower surface of the insulation layer and electrically connected to the second pad. A first signal having alternating voltage levels may be applied to the first wiring, and a second signal having a constant voltage level may be applied to the second wiring.