Fingerprint Sensor Planar Layer Fills Rugged Conductive Microstructure
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Solution Overview
Problem
Fingerprint identification devices face noise issues due to the rugged microstructure of the conductive layer, which creates a gap between the finger and the conductive layer, leading to increased noise during fingerprint recognition.
Innovation Solution
A fingerprint identification device is designed with a substrate, a piezoelectric layer, a conductive layer, and a planar layer, where the planar layer fills into the rugged microstructure of the conductive layer, and is manufactured by forming a piezoelectric material, a conductive material with a rugged surface, and a planar material that adheres and is thermally pressed to fill the microstructure, reducing noise and preventing scratches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive layer is formed with standard manufacturing processes, then the conductive layer provides necessary electrical conductivity, but the conductive layer develops a rugged microstructure on its surface
Solution Approach 1:
A planarization layer is introduced as an intermediary between the conductive layer and the finger. This planarization layer has a planar upper surface that contacts the finger and fills into the rugged microstructure of the conductive layer, thereby eliminating the gap caused by the rugged surface while maintaining the electrical conductivity function of the conductive layer.
2Ease of manufacture
If the conductive layer has a rugged microstructure, then the manufacturing process is simplified, but a gap exists between the finger and the conductive layer during fingerprint identification
Solution Approach 1:
The device structure is segmented into distinct functional layers: the conductive layer maintains its rugged microstructure for ease of manufacture, while a separate planarization layer provides the required surface flatness. This segmentation allows each layer to optimize its own characteristics without compromising the other.
3Device complexity
If the rugged microstructure is left exposed, then the device structure remains simple, but noise increases during fingerprint recognition
Solution Approach 1:
The planarization layer serves as a mediator that eliminates the harmful effect of the rugged microstructure by filling into its valleys and providing a smooth upper surface. This reduces the gap between the finger and conductive layer, thereby reducing noise during fingerprint recognition while adding only one additional layer to the device structure.
4Productivity
If the conductive layer is exposed, then manufacturing steps are reduced, but the conductive layer is susceptible to scratches and oxidation
Solution Approach 1:
The planarization layer is formed in advance to cover and protect the conductive layer before the device is put into service. This preliminary protective action prevents scratches and oxidation of the conductive layer, enhancing its durability and reliability without adding complex post-manufacturing protection steps.
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 solution reduces noise and prevents the conductive layer from being scratched or oxidized, improving the accuracy of fingerprint recognition while maintaining optimal dicing performance and signal intensity.
Implementation Method 1
thermal-pressing the high acoustic impedance material
Implementation Method 2
a piezoelectric layer, a conductive layer disposed on the piezoelectric layer
Data Source
AI summary
A fingerprint identification device includes a substrate, a piezoelectric layer, a conductive layer, and a planar layer. The piezoelectric layer is disposed on the substrate. The conductive layer is disposed on the piezoelectric layer, and the conductive layer has a rugged microstructure on an upper surface of the conductive layer. The planar layer is disposed on the conductive layer, and a bottom of the planar layer fills the rugged microstructure of the conductive layer.