TFT Fingerprint Sensor Circuit Layout for Lower Error and Thinner Buttons
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Solution Overview
Problem
Capacitive fingerprint sensors face challenges in reducing error rates and minimizing the non-display area due to the complexity of assembly and the overlap of fingerprint sensors with push buttons, leading to increased thickness and manufacturing costs.
Innovation Solution
A capacitive fingerprint recognition unit utilizing a thin-film transistor (TFT) sensor array with a gate driver, upper and lower switches, and a capacitance measurement circuit that changes the path of sensing signals to reduce error rates and improve sensitivity, integrated with a timing control unit to determine touch sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution sensor array and IC are formed together using a silicon wafer, then measurement precision is improved, but device complexity increases and non-display area increases
Solution Approach 1:
The patent merges the fingerprint sensor array and push button into a single integrated structure. The sensor array is formed directly on the front surface of the push button, eliminating the need for separate assembly of these components. This integration maintains high sensing resolution while reducing overall device complexity and non-display area.
Solution Approach 2:
The push button structure is designed to serve multiple functions: it acts as both a mechanical input device and a substrate for the fingerprint sensor array. This multi-functionality allows the system to achieve high measurement precision without requiring separate dedicated components, thereby reducing device complexity.
2Area of stationary object
If a push button and fingerprint sensor are formed to overlap with each other, then non-display area is reduced, but thickness increases
Solution Approach 1:
The patent transitions from a vertical stacking approach to a planar integration approach. The sensor array is formed on the front surface of the push button in a two-dimensional layout, allowing the fingerprint sensing area to be maximized without increasing the vertical thickness of the push button structure.
3Measurement precision
If a silicon wafer is used to integrally form sensor array and IC, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent segments the fingerprint sensing function from the IC processing function. The sensor array is formed using TFT technology on a separate substrate (push button), while the IC remains on the silicon wafer. This segmentation allows each component to be optimized and manufactured independently, reducing overall manufacturing cost while maintaining high sensing resolution.
Solution Approach 2:
The patent uses TFT-based sensor arrays that can be manufactured using existing LCD manufacturing processes. This approach copies the成熟 manufacturing techniques from the display industry, allowing for cost-effective production of high-resolution sensor arrays without requiring expensive custom silicon wafer fabrication for each sensor element.
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
The TFT sensor array-based solution reduces measurement error rates and allows for a more compact design by changing the signal path, enhancing fingerprint recognition accuracy and reducing the thickness of the fingerprint sensing area.
Implementation Method 1
The capacitance type fingerprint sensor uses a difference in the amount of electricity charged between a ridge and a valley in contact with the fingerprint sensor
Data Source
AI summary
A capacitive fingerprint recognition unit using a thin-film transistor (TFT) sensor array to sense a user's fingerprint in a capacitive manner, a capacitance measurement circuit of a fingerprint sensor, and a fingerprint recognition device having the capacitance measurement circuit are disclosed. A capacitive fingerprint recognition unit includes a thin-film transistor (TFT) sensor array, a gate driver, an upper switch and a lower switch. The TFT sensor array includes a plurality of gate lines, a plurality of sensing lines, a plurality of TFTs connected to the gate line and the sensing line, and a fingerprint recognition pattern connected to each of the TFTs. The gate driver sequentially supplies a gate signal to the gate line. The upper switch is connected to a first end of each of the sensing lines and the lower switch is connected to a second end of each of the sensing lines.