Capacitive Touch Panel Self-Testing via Line Floating
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Solution Overview
Problem
Traditional methods for testing capacitive touch panels for short and open circuits are time-consuming, labor-intensive, and require expensive test fixtures, often leading to false positives and potential damage to the panels due to the need for physical probes to simulate finger touches.
Innovation Solution
A two-stage testing method that drives and floats drive and sense lines in specific patterns to detect shorts and opens without using external tools, allowing for faster, less error-prone, and cost-effective testing by analyzing signal changes on the sense lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional testing methods using physical probes are used, then the touch panel can be tested for short and open circuits, but the testing process becomes time-consuming, labor-intensive, and requires expensive test fixtures
Solution Approach 1:
The touch panel performs self-testing by internally driving drive lines and reading sense lines without requiring external test fixtures or probes. The controller within the touch panel executes test sequences that automatically detect shorts and opens in the matrix lines, eliminating the need for manual probe-based testing and significantly reducing testing time and labor requirements
Solution Approach 2:
The patent replaces the mechanical probe-based testing system with an electrical self-testing system. Instead of using physical probes to simulate finger touches and mechanically detect capacitance changes, the system uses electrical signals driven by the controller to test the electrical integrity of drive and sense lines, thereby eliminating expensive test fixtures and reducing testing complexity
2Reliability
If physical probes are used to simulate finger touches, then the touch panel can be tested, but the probes may cause false positives and potential damage to the panels
Solution Approach 1:
The touch panel performs self-testing by internally driving drive lines and reading sense lines without requiring external test fixtures or probes. The controller within the touch panel executes test sequences that automatically detect shorts and opens in the matrix lines, eliminating the need for manual probe-based testing and significantly reducing testing time and labor requirements
Solution Approach 2:
The patent replaces the mechanical probe-based testing system with an electrical self-testing system. Instead of using physical probes to simulate finger touches and mechanically detect capacitance changes, the system uses electrical signals driven by the controller to test the electrical integrity of drive and sense lines, thereby eliminating expensive test fixtures and reducing testing complexity
3Reliability
If a two-stage testing method is implemented, then the detection of shorts and opens is improved, but the test complexity increases
Solution Approach 1:
The testing process is segmented into two distinct stages: a first stage that tests drive lines by driving them sequentially while floating other drive lines, and a second stage that tests sense lines by driving all drive lines and alternating between enabling and floating sense lines. This segmentation allows systematic detection of shorts and opens in different line types, improving detection accuracy while keeping the test sequence organized and manageable through clear phase separation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables rapid detection of shorts and opens in capacitive touch panels within 50 milliseconds or less, reducing labor costs and minimizing panel damage, while eliminating the need for specialized test fixtures and probes.
Implementation Method 1
Capacitive touch panels are often used with touch screen devices. A capacitive touch panel generally includes an insulator, such as glass, coated with a transparent conductor, such as indium tin oxide (ITO). As the human body is also an electrical conductor, touching the surface of the panel results in a distortion of the panel's electrostatic field, measurable as a change in capacitance.
Data Source
AI summary
A capacitive touch panel is tested for the presence or absence of short and open circuits in drive and sense lines without the use of a tool that touches the surface of the panel. During a first stage of testing, drive lines of the touch panel are sequentially driven while the remaining drive lines are floated. Sense lines are read to indicate whether a driven drive line is shorted to an adjacent drive line, an open circuit, or coupled to a sense line that is an open circuit. During a second stage of testing, drive lines are driven while alternate sense lines are floated or enabled. The signals on the enabled sense lines are acquired to indicate whether the enabled sense lines are shorted to adjacent sense lines. This second stage can be repeated, switching the roles of the sense lines, to determine the locations of short and/or open circuits.