Raised Capacitive Touch Sensor for Liquid-Resistant Keyboards
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Solution Overview
Problem
Capacitive touch sensors in mechanical keyboards are prone to failure due to liquid ingress and reduced sensitivity and accuracy due to the presence of keycaps, which obstruct the sensing surface.
Innovation Solution
A capacitive touch sensor with a trace carrier and connecting structure that positions the sensing surface above the keycaps, using Laser Direct Structuring to form electrically conductive traces, allowing for mutual capacitance sensing and easy liquid removal, while providing tactile feedback and improved sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitive sensing surface is placed beneath a mechanical tactile keyboard, then tactile feedback and key input accuracy are improved, but liquid ingress prevents operation and reduces reliability
Solution Approach 1:
The sensing surface is extracted from beneath the keyboard and positioned above the keycaps on a raised platform, removing it from the harmful environment where liquid can accumulate and preventing liquid ingress while maintaining tactile feedback functionality
Solution Approach 2:
The sensing surface is moved to a different spatial dimension (above the keycaps rather than beneath them), creating a raised platform that elevates the sensing area away from liquid-prone zones while preserving the mechanical keyboard structure below
2Measurement precision
If keycaps are present on the keyboard, then tactile feedback is provided, but the touch sensitive surface is separated from the user reducing sensitivity and accuracy
Solution Approach 1:
The sensing surface is repositioned to a higher dimension above the keycaps, eliminating the separation distance that reduces sensitivity while allowing keycaps to remain in place for tactile feedback
Solution Approach 2:
A raised platform structure serves as an intermediary element that positions the sensing surface above the keycaps, allowing both the sensing surface and keycaps to coexist without interfering with each other's functionality
3Ease of manufacture
If a raised sensing surface is implemented, then liquid removal is facilitated and sensitivity is improved, but device complexity increases
Solution Approach 1:
The sensing surface is elevated to a raised platform above the keyboard plane, creating a natural drainage path for liquid removal while maintaining relatively simple structural implementation
Solution Approach 2:
The raised platform structure serves multiple functions simultaneously: it elevates the sensing surface for better sensitivity, creates liquid drainage paths, and provides structural support, thereby reducing overall device complexity despite the elevated design
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 enhances sensitivity and accuracy by keeping the sensing surface clear of liquids and providing tactile feedback, allowing for effective touch detection even in adverse conditions.
Implementation Method 1
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
using Laser Direct Structuring to form electrically conductive traces
Data Source
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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.