Pixel Circuit Layout for Display Defect Detection and Yield
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Solution Overview
Problem
Existing display devices face challenges in efficiently detecting defects during the production process, which affects yield and performance.
Innovation Solution
A pixel structure is designed with specific transistors and capacitors that allow for easy defect detection, including a first transistor controlling current flow, a second transistor connected to a data line, and a capacitor between nodes, along with additional transistors and capacitors for initialization and control signals, enabling efficient defect identification during a test process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a pixel structure is designed with multiple transistors and capacitors for easy defect detection, then manufacturing yield is improved, but device complexity increases
Solution Approach 1:
The pixel circuit is divided into multiple functional blocks with dedicated transistors (first transistor for current control, second transistor for data line connection, third transistor for reference power supply connection, fourth transistor for initialization power supply connection) and capacitors (first capacitor between first and second nodes, second capacitor between second node and third node). This segmentation allows independent testing of each component during manufacturing, improving defect detection capability while maintaining organized structure.
Solution Approach 2:
The connector is introduced as an intermediary element that electrically connects the first node to the second node, enabling test signal transmission between different circuit regions. This intermediary structure facilitates defect detection by providing a dedicated test path without disrupting the normal pixel operation, thus improving manufacturing yield without significantly increasing operational complexity.
2Difficulty of detecting and measuring
If a connector is added to connect first node to second node for defect detection, then ease of detecting defect is improved, but device complexity increases
Solution Approach 1:
The connector is extracted as a separate, dedicated component specifically for test purposes. It is configured to electrically connect the first node to the second node, creating an independent test path that can be activated during manufacturing without affecting the normal operational paths of the pixel circuit. This extraction approach simplifies defect detection by providing a dedicated test access point.
Solution Approach 2:
The connector serves multiple functions: during normal operation, it maintains the electrical connection between nodes for signal transmission, and during testing, it provides a dedicated path for defect detection. This multi-functionality allows the same structure to support both operational and testing requirements, improving defect detection capability without adding separate dedicated test structures.
3Reliability
If multiple transistors are used for controlling current and initialization, then reliability is improved, but use of energy increases
Solution Approach 1:
The third and fourth transistors are configured to connect the reference power supply and initialization power supply to appropriate nodes before normal pixel operation begins. This preliminary action ensures that all circuit elements are properly initialized and biased before data processing starts, improving reliability by preventing operational errors due to improper initialization. The transistors remain in a high-impedance state during normal operation, minimizing energy consumption.
Solution Approach 2:
The initialization transistors (third and fourth transistors) operate periodically to refresh and initialize the capacitor nodes, rather than continuously. This periodic action maintains reliable voltage levels and charge storage in the capacitors while minimizing energy consumption by keeping the transistors in a non-conducting state between initialization cycles. The periodic initialization ensures pixel reliability without continuous power expenditure.
Data Source
AI summary
A pixel includes: a light emitting element; a first transistor including a first electrode connected to a first power line, to which a voltage of the first power supply is supplied, where the first transistor controls, in response to a voltage of a first node connected to a gate electrode thereof, current flowing from the first power line to a second power line, to which a voltage of a second power supply is supplied, via the light emitting element; a second transistor connected between a data line and a second node, where the second transistor is turned on when a first scan signal is supplied thereto through a first scan line; a first capacitor connected between the first node and the second node; and a connector electrically connected between the first node to the second node.