Capacitance Sensor Array for Non-Contact Conductive Pattern Imaging
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Solution Overview
Problem
Conventional capacitance detection methods for conductive patterns on circuit boards face challenges such as damage from sensor terminals, limited spatial resolution, and difficulty in detecting defects like breaks and short-circuits, especially in complex pattern geometries, due to reliance on direct contact and low sensitivity.
Innovation Solution
A capacitance detection area sensor with a two-dimensional array of sensor elements that uses capacitive coupling to detect changes in capacitance without direct contact, incorporating a sensor electrode, storage element, and reset element, along with a differential signal processing system to generate images of conductive patterns, enabling high-sensitivity and high-resolution defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct contact sensing terminals are used to detect conductive patterns, then the sensing signal can be reliably detected, but the conductive patterns may be damaged
Solution Approach 1:
The patent introduces a capacitance sensor that detects conductive patterns through capacitive coupling without direct physical contact. The sensor electrode faces the conductive pattern with a gap, using the conductive pattern itself as a counter electrode. This intermediary capacitive coupling mechanism allows sensing signal detection while eliminating mechanical contact that could damage the conductive patterns.
2Measurement precision
If conventional contact-based sensors are used, then the sensing signal can be detected, but the spatial resolution is limited
Solution Approach 1:
The patent divides the sensor into multiple pixel units arranged in a two-dimensional array, where each pixel contains a sensor electrode and associated circuitry. This segmentation allows parallel detection across the entire conductive pattern area, significantly improving spatial resolution and enabling precise localization of defects while maintaining manageable device complexity through modular architecture.
3Object-affected harmful factors
If non-contact capacitance sensing is used, then damage to patterns is reduced, but thermal noise from reset transistors increases
Solution Approach 1:
The patent employs periodic reset operations where the reset transistor is turned on briefly to discharge parasitic capacitance, then turned off for the actual measurement period. By controlling the timing and duration of reset operations, the system eliminates thermal noise accumulation while maintaining the non-contact sensing advantage. The measurement is performed during the stable period after reset, ensuring high detection precision.
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 approach allows for precise detection of defects in complex conductive patterns with improved spatial resolution and reduced risk of damage, enabling faster and more accurate identification of defects in conductive patterns, including those with branched or looped configurations.
Implementation Method 1
a sensor electrode capacitively coupled to this counter electrode, the potential of the sensor electrode, which changes through the capacitive coupling as the voltage level of the counter electrode is changed from the ground level to a certain voltage level, is measured to achieve the detection
Data Source
AI summary
A capacitance detection area sensor includes capacitance sensor elements arranged in a two-dimensional array, is shaped into an appropriate shape, and capacitively coupled to an external electrode. To the external electrode, a sensing signal having a potential difference is supplied. The first and second sensor output signals are acquired from a capacitance sensor element capacitively coupled to the external electrode, at the timing of the sensing signal being a first signal and being a second signal, respectively. A differential signal is generated from a difference between the acquired first and second sensor output signals, and an image indicating the shape of the external electrode is generated based on the level of the differential signal, in different colors or different tones.