Capacitive Input Device Short Circuit Detection via Test Electrode
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Solution Overview
Problem
Existing electrostatic capacitance-type input devices face challenges in reliably detecting short circuits in electrodes without requiring large-scale test devices, as the difference in capacitance between normal and short-circuited electrodes is small, making it difficult to identify short circuits.
Innovation Solution
Incorporating a test electrode and test wiring connected through an insulating film on the substrate, which measures capacitance values between the test wiring and signal wirings to determine if an electrode is short-circuited by identifying capacitance values equal to or less than a set value, allowing for reliable detection of short circuits without needing a large-scale test device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sensor electrode is brought to be in proximity to a plurality of electrodes one after another by a SCARA robot to test for short circuits, then short circuit detection capability is improved, but device complexity and scale increase significantly
Solution Approach 1:
The patent extracts the test electrode functionality from the main electrode structure by providing a separate test electrode that faces the other-side end portions of the first and second electrodes through an insulating film. This allows dedicated short circuit detection without requiring external robotic equipment, thereby reducing test device complexity while maintaining detection capability.
Solution Approach 2:
The test electrode serves multiple functions: it detects short circuits in both the first electrodes extending in the X direction and the second electrodes extending in the Y direction. By facing the other-side end portions of both electrode types through the insulating film, a single test electrode structure achieves universal testing capability for the entire electrode array.
2Ease of operation
If capacitance coupling is present between electrodes to enable position detection, then input detection functionality is improved, but the ability to identify short circuits deteriorates due to small capacitance differences
Solution Approach 1:
The insulating film acts as an intermediary between the test electrode and the signal wirings/ electrodes. It allows capacitance measurement to detect short circuits while maintaining the necessary electrical isolation to prevent false readings, thus enabling accurate short circuit identification without disrupting normal position detection functionality.
Solution Approach 2:
The patent applies different functional qualities to different regions: the signal wirings maintain capacitance coupling for position detection, while the test electrode region uses the insulating film to create a measurement interface specifically optimized for short circuit detection. This local differentiation allows both functions to operate effectively without interfering with each other.
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
This configuration enables reliable detection of short circuits in electrostatic capacitance-type input devices, even when capacitance is already present, without hindering position detection and without requiring a large-scale test device, ensuring the electrodes' reliability.
Implementation Method 1
measuring a capacitance value between the test wiring and a plurality of signal wirings
Data Source
AI summary
An electrostatic capacitance-type input device includes: a plurality of first electrodes, which detect an input position, extending in a first direction in an input area on a substrate; a plurality of second electrodes, which detect an input POSITION, extending in a second direction intersecting with the first direction in the input area; a plurality of signal wirings that extend from one-side end portions of the first electrodes and one-side end portions of the second electrodes on the substrate; a test electrode that faces the other-side end portions of at least one of the first electrodes and the second electrodes through an insulating film on the substrate; and a test wiring that is electrically connected to the test electrode.