Vision-Guided Electrical Test Alignment for Roll-to-Roll Web Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In roll-to-roll electrical testing, the alignment of test probes with test pads is unreliable due to distortion in fiducial marks, leading to inaccurate placement and potential false failure detection, especially in miniaturized devices with tight spacing and flexible substrates prone to web tension or slippage.
Innovation Solution
A vision-guided electrical testing system that combines a digital imaging system for capturing images of test pads and fiducial marks with a fiducial sensing system to determine spatial relationships, allowing for precise alignment and contact of test probes with test pads, even with variable placement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional alignment methods are used for test probes, then the system is simple and easy to operate, but the alignment accuracy with test pads deteriorates due to fiducial mark distortion
Solution Approach 1:
The system performs preliminary capture of fiducial mark positions using a digital imaging system before the actual electrical testing. This preliminary action allows the controller to calculate alignment compensation values in advance, which are then applied to adjust test probe positions, ensuring accurate alignment despite fiducial mark distortion
Solution Approach 2:
A controller acts as an intermediary between the digital imaging system and the electrical test fixture. The controller receives image data, calculates spatial relationships, determines alignment compensation values, and translates these into positional adjustments for the test probes, bridging the gap between vision guidance and physical testing
2Measurement precision
If vision-guided alignment is implemented, then alignment accuracy improves, but the device complexity increases due to additional imaging and sensing systems
Solution Approach 1:
The digital imaging system serves multiple functions: capturing fiducial mark positions, determining test pad locations through spatial relationship analysis, and providing data for alignment compensation calculations. This multi-functionality reduces the need for separate dedicated components for each function
Solution Approach 2:
The system uses the existing fiducial marks on the substrate to guide its own alignment process. The fiducial marks serve as self-reference points that the digital imaging system detects and the controller uses to automatically calculate and apply alignment compensation, eliminating the need for external manual alignment procedures
3Reliability
If fiducial marks are used for alignment, then the alignment process is simplified, but reliability deteriorates due to web tension and slippage causing mark distortion
Solution Approach 1:
The digital imaging system continuously monitors the actual positions of fiducial marks and test pads, providing feedback to the controller. The controller calculates alignment compensation values based on detected deviations and applies these corrections to test probe positions, creating a closed-loop system that compensates for fiducial mark distortion caused by web tension and slippage
Solution Approach 2:
The system dynamically changes the positional parameters of the test probes based on detected fiducial mark positions. By calculating spatial relationships and generating alignment compensation values, the system adjusts test probe coordinates in real-time to account for distortions in the fiducial marks, maintaining accurate alignment despite substrate deformation
Data Source
AI summary
An electrical testing system is adapted to perform electrical tests on devices fabricated on successive frames of a web of substrate, each frame including a plurality of fiducial marks. A digital imaging system captures a digital image of a frame, which is analyzed to determine spatial relationships between positions of a set of test pads and positions of the fiducial marks. The frame is advanced to an electrical test fixture which includes a set of test probes adapted to make electrical contact with the test pads. A fiducial sensing system including a plurality of fiducial sensors determines positions of the fiducial marks. The position of the electrical test fixture is adjusted responsive to the determined spatial relationships and the determined fiducial mark positions so that the test probes are aligned with corresponding test pads, and an electrical test of the device is performed.