OLED Test Line Routing to Prevent Signal Coupling
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Solution Overview
Problem
In OLED display devices using COF type driving ICs, signal coupling between test lines and output pads leads to distorted output signals, causing defects like vertical line defects due to overlapping test lines and output pads during the auto probe test process.
Innovation Solution
The display device is designed with test lines positioned in separate regions between adjacent output pads, and a switch is connected between each electrode pad and its corresponding connection line, which is turned off during signal output to prevent signal coupling, or a shield electrode is formed between the test lines and output pads to minimize electrical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If test lines are formed to extend from the side line for auto probe test process, then test functionality is enabled, but signal coupling occurs between test lines and output pads causing display defects
Solution Approach 1:
The harmful overlapping region between test lines and output pads is extracted and removed from the design. Test lines are routed to extend from the side line rather than from the top line, extracting them from the overlapping region with output pads. This spatial separation eliminates signal coupling while preserving test functionality.
Solution Approach 2:
The test lines are repositioned from extending along the top edge (one-dimensional arrangement) to extending from the side line (changing the dimensional approach). This dimensional change in routing strategy moves test lines out of the harmful overlapping region with output pads, preventing signal coupling.
2Reliability
If test lines extend inwardly from test pad to electrode pad, then signal transfer for testing is achieved, but overlapping with output pads causes vertical line defects
Solution Approach 1:
The substrate is functionally segmented into distinct regions: a test region where test lines extend from the side line, and a display region where output pads are located. This segmentation separates the test signal path from the display signal path, ensuring reliable signal transfer for testing while preventing interference that would cause display defects.
Solution Approach 2:
The side line acts as an intermediary structure that enables test line extension without direct interaction with output pads. By using the side line as the starting point for test lines rather than allowing them to extend from the top edge near output pads, the intermediary structure facilitates signal transfer while mediating against harmful coupling.
Data Source
AI summary
A display device includes a plurality of electrode pads which are arranged in a non-display region having a side line of a substrate; a circuit film which includes a plurality of output pads contacting the plurality of electrode pads and extending in a direction, and on which a driving IC is mounted; a plurality of test lines that extend in the direction from the side line; and a plurality of connection lines which connect the plurality of test lines to corresponding electrode pads, wherein each test line is located in a separate region between two output pads adjacent to both sides of each test line.