COG LCD Testing Transistors Uniform Etching
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Solution Overview
Problem
The COG type LCD device experiences block dim effects during inspection due to non-uniform etching of testing thin film transistors caused by loading effects from bump pads, leading to inaccurate defect detection and increased manufacturing costs.
Innovation Solution
The COG type LCD device is designed with testing lines and pads arranged to maintain a constant interval between first testing thin film transistors, and additional testing pads are included to detect disconnections in data link lines, allowing for accurate defect detection before attaching the driving IC, thereby preventing block dim effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If testing thin film transistors are formed in the driving IC region with bump pads, then defect detection capability is improved, but non-uniform etching occurs due to loading effects causing block dim effects
Solution Approach 1:
The patent extracts the testing thin film transistors from the driving IC region and relocates them to the non-display area. This separation removes the harmful loading effects from bump pads that caused non-uniform etching, while still preserving the defect detection function through the testing lines and pads in the non-display area.
Solution Approach 2:
The patent segments the substrate into distinct functional areas: the display area with pixel electrodes, the non-display area with testing structures, and the driving IC region. This spatial segmentation allows testing thin film transistors to be formed in the non-display area away from bump pads, eliminating loading effects while maintaining inspection capability.
2Reliability
If additional testing pads are added to detect data link line disconnections, then inspection completeness is improved, but device complexity increases
Solution Approach 1:
The patent designs the testing thin film transistors and testing lines to serve multiple functions: they can detect defects in pixel electrodes, gate lines, and data lines, and additionally detect disconnections in data link lines through the fourth data testing pad. This multi-functionality achieves comprehensive inspection without proportionally increasing device complexity.
Data Source
AI summary
A COG type LCD device includes a first substrate including a display area and first, second, third and fourth non-display areas, gate and data lines in the display area on the first substrate and defining pixel regions, switching thin film transistor at each crossing portion of the gate and data lines and connected to the gate and data lines, a pixel electrode in each pixel region and connected to the thin film transistor, first testing thin film transistors in the second non-display area connected to the data lines and spaced apart from each other with a constant interval therebetween, first, second and third data testing lines connected to one ends of the data lines through the first testing thin film transistors, first, second and third data testing pads connected to the first, second and third data testing lines, respectively, data link lines in the first non-display area and connected to another ends of the data lines, second testing thin film transistors in the first non-display area and connected to the data link lines, gate link lines connected to the gate lines, third testing thin film transistors connected to the gate link lines, gate testing lines connected to the gate lines through the third testing thin film transistors, gate testing pads connected to the gate testing lines, a common testing line and a common pad in the non-display area, a second substrate spaced apart from the first substrate, a color filter layer and a common electrode sequentially formed on the second substrate, wherein the common electrode is connected to the common testing line, and a liquid crystal layer between the first and second substrates, wherein a driving IC is attached in the first non-display area.