Smart Card Fingerprint Sensor Module With Homogeneous Polymer Protection
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Solution Overview
Problem
Smart card biometric sensors are prone to damage from environmental factors like humidity, sweat, and mechanical abrasion, which affects their longevity and functionality, while existing protective measures can compromise fingerprint detection or aesthetics.
Innovation Solution
A biometric sensor module with a dielectric substrate featuring a homogeneous polymer material on the external face, providing mechanical and chemical resistance without disrupting biometric measurements, and using a single material for both protection and electrical connections, allowing for aesthetic integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is added to cover the detection area, then resistance to environmental factors (humidity, sweat, abrasion) is improved, but the detection accuracy and aesthetics are compromised
Solution Approach 1:
The patent applies the homogeneity principle by using a uniform dielectric material (such as polyimide or polyester) for the entire substrate including the detection zone. This homogeneous material provides protective properties throughout while maintaining capacitive coupling for fingerprint detection, eliminating the need for separate protective layers that would interfere with measurement accuracy.
Solution Approach 2:
The substrate material serves multiple functions simultaneously: it provides mechanical support, electrical insulation, environmental protection, and maintains capacitive coupling for fingerprint detection. This multi-functionality resolves the contradiction by making the protective substrate itself capable of both protection and detection support without requiring additional layers.
2Reliability
If multiple layers are used to protect the sensor, then durability is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the protective function and the substrate function into a single integrated dielectric substrate. Instead of using separate protective layers over the sensor, the substrate itself is made from durable dielectric material that provides both structural support and environmental protection, thereby reducing device complexity while maintaining durability.
Solution Approach 2:
The patent employs composite material structures where the dielectric substrate is integrated with the sensor element in a unified construction. This composite approach allows the substrate to provide mechanical strength and environmental resistance while maintaining electrical properties necessary for sensor operation, achieving durability without requiring multiple discrete protective layers.
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
Enhances the durability and reliability of biometric sensors on smart cards by protecting sensitive elements from environmental damage while maintaining detection accuracy and adding aesthetic value without additional protective layers.
Implementation Method 1
The homogeneous polymer material is mechanically resistant (for example to abrasion from a finger repeatedly placed on the detection zone)
Implementation Method 2
The homogeneous polymer material is also chemically resistant (for example to acidic or basic sweat, but also to solvents such as fuel oil, ethanol, or other solvents mentioned in the ISO10373-1 standard)
Implementation Method 3
a dielectric substrate comprising an external face and an internal face... tracks and connection pads made from a sheet of electrically conductive material resting on the internal face of the substrate
Implementation Method 4
detection element formed by a set of sensitive elements (for example capacitive)
Data Source
Figure 1~2b
Figure 2c~3
AI summary
A method for manufacturing a biometric sensor module (4) for a smart card, comprising steps in which a dielectric substrate having a front face and a back face is provided, and a biometric sensor (300) for fingerprint detection is attached to the back face, a detection area covered by the sensor (300) on the back face being positioned opposite a detection zone (108) configured for a finger to be placed upon it. At least on the surface of this detection zone (108), the dielectric substrate comprises a bare, homogeneous polymer material.