Capacitive Touch Sensor on Curved Surfaces Using Segmented PCB Stem
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Solution Overview
Problem
Capacitive touch sensors on rigid or semi-rigid printed circuit boards face challenges when accommodating curved surfaces, as they require flexible PCBs to maintain proper alignment without causing stress on solder joints, which increases costs.
Innovation Solution
A capacitive touch sensor design featuring a flat printed circuit board with a stem that can be flexed to align with a curved outer surface, allowing the sensor to detect capacitance changes without stressing solder joints, using a stem that is integral with the printed circuit board and offset from its base plane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible PCB is used to accommodate a curved outer surface, then the capacitive touch sensor can maintain proper alignment with the curved surface, but the manufacturing cost increases
Solution Approach 1:
The PCB is divided into two distinct parts: a flat base portion that remains rigid and provides stable mounting for electronic components, and a stem portion that is flexible and can be bent to align with the curved outer surface. This segmentation allows each part to fulfill its specific function optimally while avoiding the need for an entirely flexible PCB, thus reducing manufacturing costs.
Solution Approach 2:
Different portions of the PCB have different mechanical properties tailored to their specific functions. The base portion is made rigid to provide stable electrical connections and component mounting, while the stem portion is made flexible to accommodate the curved surface alignment. This local differentiation of material properties resolves the contradiction between adaptability and manufacturing cost.
2Adaptability or versatility
If the printed circuit board is flexed to match the curved surface, then the capacitive touch sensor aligns with the curved surface, but stress is applied to solder joints of components on the PCB
Solution Approach 1:
By segmenting the PCB into a rigid base portion and a flexible stem portion, the design ensures that only the stem portion undergoes flexing to align with the curved surface. The rigid base portion remains stationary and free from stress, thereby protecting the solder joints of components mounted on it from damage while still achieving the necessary alignment.
Solution Approach 2:
The flexible alignment function is extracted from the entire PCB and confined to only the stem portion. This extraction allows the majority of the PCB (the base portion) to remain rigid and stress-free, maintaining solder joint integrity while the isolated flexible stem provides the necessary curvature adaptation.
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 the use of capacitive touch sensors on curved surfaces without stressing solder joints, reducing costs associated with flexible PCBs while maintaining effective capacitance detection.
Implementation Method 1
capacitive touch sensors that utilize a user's body capacitance to operate. In particular, capacitive touch sensors can detect a change in capacitance when the user touches the control panel
Data Source
AI summary
A user interface includes a curved outer surface, a generally flat printed circuit board defining a base plane, and a capacitive touch sensor connected to the generally flat printed circuit board and offset from the base plane. The capacitive touch sensor is substantially aligned with the curved outer surface. The user interface may be provided on an appliance.