Integrated Fingerprint Sensor Through Glass Overlay
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Solution Overview
Problem
Current fingerprint sensors integrated into smartphones face reliability issues due to exposure to environmental factors and the degradation of measurement signals caused by protective cover glasses, leading to performance degradation and increased production costs.
Innovation Solution
A fingerprint sensor is integrated into the glass surface of touch-screen devices, with probes extending through the glass overlay and connected to conductor leads on the backside, allowing for capacitive or resistive measurements while being protected from the environment, and utilizing a redistribution layer to decouple the signal processing unit from the sensing area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sensor surface is directly exposed to the environment for finger contact, then ease of operation is improved, but reliability deteriorates due to exposure to humidity, wear, corrosion, and chemical substances
Solution Approach 1:
The patent introduces a transparent cover glass as an intermediary element between the finger and the sensor surface. This cover glass allows capacitive coupling for fingerprint sensing while protecting the underlying sensor circuits from environmental damage. The sensor is positioned beneath the cover glass at a controlled distance, enabling measurement through the glass without direct exposure to harmful factors.
2Reliability
If thick dielectric layers are added to protect the sensor, then reliability is improved, but measurement precision deteriorates due to signal degradation
Solution Approach 1:
The patent optimizes the thickness and material properties of the dielectric layer between the sensor surface and the cover glass. By carefully controlling the distance (kept minimal) and selecting appropriate dielectric materials, the system achieves adequate protection while maintaining capacitive coupling strength for accurate fingerprint measurement. The dielectric layer parameters are tuned to balance protection and signal quality.
3Reliability
If additional metal and dielectric layers are added for protection, then reliability is improved, but manufacturing complexity and production costs increase
Solution Approach 1:
The patent integrates the fingerprint sensor directly into the touch screen assembly, merging multiple functions into a unified structure. The sensor is positioned within the touch screen's existing layer structure, utilizing the cover glass as both a protective element and a functional component. This integration eliminates the need for separate protective housings and reduces overall manufacturing complexity.
4Reliability
If the sensor is positioned under thick protective cover glass, then reliability is improved, but measurement precision deteriorates severely
Solution Approach 1:
The patent严格控制 the distance between the sensor surface and the cover glass, keeping it minimal to maintain adequate capacitive coupling. The sensor is positioned immediately beneath the cover glass rather than at greater depths, ensuring that the measurement signal remains strong enough for accurate fingerprint recognition while still benefiting from the protective coverage.
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 solution enhances the durability and reliability of fingerprint sensors, maintains signal quality, and reduces production costs by integrating the sensor within the glass surface of smartphones, addressing the limitations of existing technologies.
Implementation Method 1
allowing for capacitive or resistive measurements
Implementation Method 2
allowing for capacitive or resistive measurements
Data Source
Figure 1~2
Figure 3a~3d
Figure 4a~4b
AI summary
The invention relates to a fingerprint sensor and fingerprint sensor system especially for integration in a device having an overlay made of an insulating material, the fingerprint sensor system comprising a plurality of sensing elements positioned on a first side of the overlay; a plurality of probes positioned in a predetermined pattern defining a fingerprint sensing area on a second side of the overlay, the plurality of probes extending from the first side of the overlay at least partially through the overlay; a plurality of conductor leads on the first side of the overlay interconnecting the plurality of probes with the plurality of sensing elements; a plurality of amplifiers connected to the plurality of sensing elements, the number of amplifiers being less than the number of sensing elements; and an activation circuit connected to the plurality of sensing elements, the activation circuit being adapted to output at least one activation signal.