TFT Panel Test Layout for Low-Precision Bonding Pad Inspection
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Solution Overview
Problem
The existing test methods for TFT panels in X-ray flat panel detectors require high precision and costly test devices, resulting in a low test success rate and increased production capacity costs due to the small pitch and high number of bonding pads.
Innovation Solution
A TFT panel with a reduced number of drive and test pads integrated into a TFT test area, allowing for m+n low-precision tests instead of m×n high-precision tests, which reduces the requirements for test devices and jigs and lowers material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin film probe is bonded to each bonding pad for testing, then complete electrical connection and testing can be achieved, but the requirements for test device precision and test jig precision become extremely high due to the large number of bonding pads with small pitch
Solution Approach 1:
The patent segments the testing process by dividing the m×n bonding pads into m groups, where each group shares a common drive pad. Instead of testing each bonding pad individually, the system tests groups of bonding pads simultaneously through shared drive and test pads, reducing the number of probe connections from m×n to m+n
Solution Approach 2:
The drive pads and test pads serve multiple functions: drive pads both drive TFT devices and serve as test connection points, while test pads both read test signals and provide group-level testing capability. This multi-functionality reduces the total number of pads needed from m×n bonding pads to m+n pads
2Reliability
If a thin film probe is bonded to each bonding pad, then electrical connection is established, but the test success rate becomes low due to high precision requirements and cleanliness requirements
Solution Approach 1:
The patent segments the large number of bonding pads into groups that share common drive and test pads. This segmentation reduces the number of individual probe bonding operations from m×n to m+n, thereby reducing the cumulative probability of bonding failures and improving overall test success rate
Solution Approach 2:
The patent uses millimeter-level drive pads and test pads instead of precise thin film probes for each bonding pad. These larger, coarser pads are easier to bond with and tolerate more variation in bonding precision, effectively replacing high-precision bonding requirements with lower-precision alternatives
3Measurement precision
If thin film probes are used for testing each bonding pad, then complete testing coverage is achieved, but material costs of test devices become high
Solution Approach 1:
The patent merges multiple bonding pad testing functions into shared drive pads and test pads. Instead of requiring m×n individual probe connections, the system uses m drive pads and n test pads that serve multiple bonding pads each, significantly reducing the quantity of test device materials required
Solution Approach 2:
Each drive pad serves multiple bonding pads within its group, and each test pad reads from multiple bonding pads. This universal functionality reduces the total number of test device components from m×n to m+n, directly reducing material costs
4Reliability
If testing is performed on all m×n bonding pads individually, then complete testing is achieved, but production capacity costs increase due to low test success rate
Solution Approach 1:
The patent segments the testing into m group-level tests instead of m×n individual bonding pad tests. This segmentation maintains testing completeness by systematically testing all bonding pads through their respective groups, while reducing the total number of test operations and improving productivity
Solution Approach 2:
The drive pads and test pads are pre-configured in the TFT panel structure before final assembly. This preliminary configuration of test access points enables efficient group-level testing without requiring individual probe bonding to each bonding pad, reducing rework and improving production capacity
Data Source
AI summary
A thin-film transistor (TFT) panel and a test method are disclosed. The TFT panel includes: m×n bonding pads, where m and n are both natural numbers greater than or equal to 1, and the m×n bonding pads are arranged correspondingly to and electrically connected to TFT units in a TFT active area; a TFT test area including m drive pads, n test pads, and m×n TFT devices, where the m×n TFT devices are divided into n groups, each of which includes m TFT devices. the m TFT devices in each group corresponding to and are electrically connected to the m drive pads and m bonding pads respectively, and the m TFT devices in each group are electrically connected to a same test pad of the n test pads. The m×n bonding pads that were originally bonded by pressure once are tested in m sessions.