Capacitive Touch Keys with Shielding for Thin Electronic Cards
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Solution Overview
Problem
Conventional electronic cards with integrated control means and multiple components face challenges in reducing thickness while maintaining reliability and functionality, particularly in adhering to ISO standards for bank cards, due to the difficulty in integrating components like batteries, display devices, and actuatable switches without compromising thickness or reliability.
Innovation Solution
The electronic card incorporates capacitive keys with a conductive shielding screen on one side, remote from the keys, which reduces the card's thickness and allows for efficient detection of finger or pen contact, enabling reliable operation while minimizing component size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional control means (push buttons with dome portions) are used, then the card can perform basic control functions, but the thickness cannot be reduced significantly
Solution Approach 1:
The patent replaces mechanical push buttons with capacitive touch keys that detect contact through electrical field changes. This eliminates the need for physical dome portions and mechanical switching elements, enabling thin-card design while maintaining control functionality through capacitive sensing
Solution Approach 2:
The patent changes the detection parameter from mechanical displacement (push button depression) to electrical capacitance change. By detecting capacitance variations when a finger approaches or contacts the key, the system achieves operation without mechanical movement, enabling thickness reduction while preserving control reliability
2Length of moving object
If multiple electronic components (battery, display, integrated circuit, control means) are integrated in conventional arrangements, then the card is functional, but the thickness exceeds the required low thickness
Solution Approach 1:
The patent merges the control means directly into the card structure by integrating capacitive keys with the circuit board and insulating material layers. This consolidation eliminates separate mechanical switch assemblies and dome structures, reducing overall component count and enabling thin-profile design
Solution Approach 2:
The patent transitions from three-dimensional mechanical components (push buttons with dome portions) to two-dimensional planar capacitive structures. By detecting contact through changes in the electrical field above the key surface rather than requiring mechanical depression, the design achieves thickness reduction while maintaining functionality
3Reliability
If capacitive keys are used without a conductive shielding screen, then the card structure is simpler, but the detection reliability of finger or pen contact is insufficient
Solution Approach 1:
The patent introduces a conductive shielding screen as an intermediary element between the capacitive key electrodes and the external environment. This screen enhances the electrical field interaction with the user's finger or pen, improving detection reliability by mediating the capacitive coupling while maintaining a relatively simple overall structure
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 design allows for a significant reduction in card thickness to less than 2 mm, enhancing reliability and functionality by optimizing the placement and detection of capacitive keys, thus addressing the limitations of existing technologies.
Implementation Method 1
control means in the form of capacitive keys... the integrated circuit only to detect the presence of a finger or of a pen in contact on the contact surface opposite at least one of the touch keys
Implementation Method 2
a conductive shielding screen disposed on one side of the electrodes of the capacitive keys which is opposite the contact surface
Data Source
AI summary
The electronic card comprises at least one integrated circuit disposed on a printed circuit board, connection means to an electrical supply source connected to the printed circuit board in order to supply said integrated circuit, and control means which can be actuated manually and are connected to the integrated circuit. The integrated circuit is provided for processing signals generated by the control means. Said integrated circuit, the control means at least a part of connection means to and the supply source are enclosed in at least one layer of insulating material forming said card. The control means are formed by an assembly of electrodes in order to define a touch screen with capacitive keys which can each be activated by means of a finger (D) of a user or a pen placed on one contact surface of the card opposite at least one touch key for introduction of data or a command. A conductive shielding screen is provided on one side of the electrodes of the capacitive keys which is opposite the contact surface.