Pixel Circuit Testing Element for TFT Accuracy
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Solution Overview
Problem
Current methods for testing thin-film transistors (TFTs) in LTPS AMOLED display panels are inefficient, often requiring the removal of organic and inorganic insulating layers, which is inaccurate and has a low success rate due to the difficulty in controlling corrosion and mechanical grinding to the micron level, and the use of focused ion beam (FIB) lapping results in fluctuating and insufficient testing accuracy.
Innovation Solution
A pixel circuit with integrated testing elements and terminals allows for testing of TFTs by applying control signals and acquiring output signals through specific terminals, enabling precise evaluation of TFT characteristics without the need to remove insulating layers, using a testing method that involves cutting off wiring to form a testing circuit and applying signals to determine TFT performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional testing methods (removal of insulating layers, FIB lapping) are used, then TFT testing can be performed, but testing accuracy is insufficient and success rate is low
Solution Approach 1:
The pixel circuit is segmented into functional sub-circuits (drive sub-circuit, reset sub-circuit, write sub-circuit, light emission control sub-circuit) with dedicated testing elements integrated into each segment. This segmentation allows independent testing of specific TFTs within the pixel circuit without affecting the entire circuit, thereby improving testing accuracy and success rate while maintaining circuit integrity.
Solution Approach 2:
Testing elements are introduced as intermediary components between the TFTs and the external testing environment. These testing elements (such as testing transistors and testing capacitors) act as mediators that enable electrical access to internal TFT parameters without requiring physical removal of insulating layers or destructive FIB lapping, thus achieving high-accuracy non-destructive testing.
2Difficulty of detecting and measuring
If insulating layers are removed for testing, then internal TFTs can be accessed, but the process is complex and has low success rate due to difficulty in controlling corrosion and grinding
Solution Approach 1:
The pixel circuit is designed to be self-testing through integrated testing elements that are part of the original circuit structure. The testing elements can activate and deactivate different circuit paths using control signals, allowing the circuit to test itself without external intervention or complex preparation processes such as layer removal, thereby simplifying the testing process while maintaining accessibility to internal TFTs.
Solution Approach 2:
The testing elements are designed with multi-functionality, serving both as functional components of the pixel circuit and as testing access points. For example, testing transistors can function as both switching elements in the circuit and as access transistors for testing adjacent TFTs, eliminating the need for separate testing structures and reducing overall device complexity.
Data Source
AI summary
The disclosure relates to a pixel circuit and a testing method of the pixel circuit. The pixel circuit comprises a light emitting element, a storage capacitor Cst, a drive sub-circuit, a reset sub-circuit, a write sub-circuit, a light emission control sub-circuit and a testing element, wherein a control terminal of the testing element is connected to s reset control signal line, a first terminal of the testing element is connected to a reset signal line, a second terminal of the testing element is connected to the drive sub-circuit, and the testing element is configured to test elements included in the pixel circuit.