Capacitive Touch Sensor Layout for Moisture-Resistant Key Input
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Solution Overview
Problem
Capacitive touch sensors in mechanical keyboards lack tactile feedback and are sensitive to moisture, making them less accurate and prone to operational issues with liquid exposure.
Innovation Solution
A capacitive touch sensor design featuring a trace carrier with conductive traces formed using Laser Direct Structuring, positioned beneath the keycaps to create a raised sensing surface that is electrically connected to a capacitive sensing circuit, allowing for improved tactile feedback and resistance to moisture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive sensing surface is placed beneath a mechanical tactile keyboard to provide both touch input and key input, then tactile feedback and key input accuracy are improved, but the device becomes sensitive to liquid and moisture, preventing operation when liquid is spilled
Solution Approach 1:
The patent introduces keycaps as an intermediary layer between the user's finger and the capacitive sensing surface. The keycaps are made of electrically insulating material that allows capacitive coupling while protecting the sensing surface from direct liquid exposure. This mediator enables tactile feedback transmission while isolating the sensitive electronic components from harmful liquids and moisture.
2Adaptability or versatility
If a capacitive sensing surface is placed beneath a mechanical tactile keyboard, then touch input functionality is added, but the keycaps separate the touch sensitive surface from the user, reducing sensitivity and accuracy of touch detection
Solution Approach 1:
The patent optimizes the electrical properties of the keycap material to achieve optimal capacitive coupling. By carefully selecting materials with appropriate dielectric constants and thicknesses, the system maintains high touch detection accuracy despite the keycap barrier. The parameters of the keycap (material composition, thickness, surface properties) are specifically engineered to maximize capacitive signal transmission while maintaining mechanical functionality.
3Adaptability or versatility
If a capacitive sensing surface is placed beneath a mechanical tactile keyboard, then combined touch and key input is achieved, but the keycaps prevent easy removal of liquid from the surface
Solution Approach 1:
The keycaps serve as a removable intermediary that protects the capacitive sensing surface from liquid accumulation. Their insulating properties allow them to be easily wiped clean, and their design facilitates rapid liquid removal through the keycap structure, preventing liquid from reaching the sensitive sensing surface beneath.
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
The solution provides enhanced sensitivity and accuracy by keeping the sensing surface above any liquid, allowing easy cleaning and offering tactile feedback, thus improving user interaction in wet conditions.
Implementation Method 1
Each trace forms a sensing pattern on the sensing surface... and a capacitive sensing circuit operable to electrically couple to the traces at the connecting surface of the trace carrier, sense a capacitance change when a touch takes place
Implementation Method 2
conductive traces formed using Laser Direct Structuring
Data Source
AI summary
The present disclosure provides a capacitive touch sensor for an electronic device. The touch sensor has a trace carrier having a sensing surface, a connecting surface, and a number of electrically conductive traces on the trace carrier. The traces form a sensing pattern on the sensing surface and pass from the sensing surface to the connecting surface. The sensor also includes a capacitive sensing circuit operable to electrically couple to the traces at the connecting surface of the trace carrier, and to sense a capacitance change. A touch position on the sensing surface is determined dependent upon the sensed capacitance change.