Fingerprint Sensor Electrode Matrix with 1-to-N Switch Circuits
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Solution Overview
Problem
The capacitance type fingerprint identification technology faces challenges with low accuracy due to weak sensing signals and strong noise signals, which are exacerbated by the need to maintain a distance between sensing electrodes and the finger, leading to increased costs and reduced product tolerance and lifetime.
Innovation Solution
A high-efficiency fingerprint identification device is developed using a matrix of sensing electrodes and 1-to-N switch circuits, with control lines and signal selection switch circuits to dynamically select electrodes as sensing regions, creating deflection focusing and convergence stabilizing regions to enhance signal gathering and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensing electrodes are integrated with sensing circuits into an integrated circuit chip and protected by a sealant, then the chip is protected from damage, but the sensing distance is reduced to tens of micrometers which seriously influences accuracy
Solution Approach 1:
A protection glass is introduced as an intermediary component between the integrated circuit chip and the finger. The protection glass is positioned above the chip with a specific distance relationship, allowing the sensing electrodes to be closer to the finger while maintaining chip protection. The glass acts as a mediator that enables both protection and improved sensing accuracy simultaneously.
2Measurement precision
If the sensing electrodes are positioned closer to the finger to improve accuracy, then sensing sensitivity and accuracy improve, but the chip becomes vulnerable to damage and packaging complexity increases
Solution Approach 1:
The protection glass serves as a protective intermediary that allows the chip to be positioned closer to the finger for improved accuracy while the glass itself absorbs the mechanical stress and protection requirements, shielding the vulnerable integrated circuit chip from direct contact and damage.
3Measurement precision
If a sapphire film with high dielectric constant is used to replace the sealant, then sensing performance improves, but the cost increases significantly
Solution Approach 1:
The patent replaces the expensive sapphire film with a protection glass that has appropriate dielectric properties but is significantly cheaper to manufacture. The glass provides sufficient electrical insulation and mechanical protection without the high cost associated with sapphire, making the overall device more economically viable while maintaining acceptable sensing performance.
4Adaptability or versatility
If an opening is formed on the protection glass to embed the fingerprint identification chip, then the chip can be integrated, but the package manufacturing complexity and material cost increase
Solution Approach 1:
The protection glass is designed with a segmented structure featuring a recessed region that accommodates the fingerprint identification chip. This segmentation allows the chip to be embedded within the glass structure rather than requiring complex opening formation and embedding processes, simplifying the overall packaging manufacturing while achieving effective chip integration.
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 configuration improves sensing sensitivity, stability, and accuracy, increases the sensing distance, and reduces costs by enhancing the signal-to-noise ratio.
Implementation Method 1
configure the sensing electrodes surrounding the sensing region to be a corresponding deflection focusing region, and configure the sensing electrodes surrounding the deflection focusing region to be a corresponding convergence stabilizing region, thereby gathering and pulling up the electric flux lines from the sensing electrodes
Data Source
AI summary
A high-efficiency fingerprint identification device includes an electrode substrate, plural 1-to-N switch circuits formed on the electrode substrate, plural sensing electrodes and plural wires. Each 1-to-N switch circuit has one first end, N second ends and m control ends. The m control ends control connection between the N second ends and the first end. Each sensing electrode corresponds to a nearby 1-to-N switch circuit. The wires are divided into sensing and driving lines and control lines. The sensing electrodes in each column correspond to a sensing and driving line. The sensing and driving line is connected to one of the N second ends of the 1-to-N switch circuits in the column. The sensing electrodes in each row correspond to m control lines. Each control line is connected to ones of the m control ends of the 1-to-N switch circuits in the row.