Fingerprint Sensor Shading Layer Moisture and ESD Protection
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Solution Overview
Problem
Existing fingerprint sensing devices face issues with moisture absorption leading to corrosion and abnormal operation, and lack anti-electrostatic discharge (ESD) protection due to their design without metal frames and single circuit boards.
Innovation Solution
The fingerprint sensing device incorporates a substrate with a sensing area, operation area, and peripheral area, featuring a planarization layer with trenches, an insulating layer, and a shading layer connected to signal lines to prevent moisture absorption and provide anti-ESD protection, using organic and inorganic materials with metal and transparent oxide layers for effective moisture blocking and static discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If organic materials are stacked to provide sufficient thickness for microlens focusing effects and light collimation, then clear fingerprint images can be obtained, but moisture absorption ability increases leading to corrosion of conductive wires and abnormal operation
Solution Approach 1:
The device is divided into distinct functional areas: a sensing area for fingerprint capture, an operation area for circuit operations, and a peripheral area for signal processing. This segmentation allows the organic planarization layer to be confined to specific regions where it is needed for optical functions, while other areas can be protected from moisture through separate protective structures.
Solution Approach 2:
A shading layer is introduced as an intermediary component between the organic planarization layer and the conductive signal lines. This shading layer acts as a protective barrier that prevents moisture absorbed by the organic material from reaching and corroding the conductive wires, thereby resolving the contradiction between maintaining optical performance and ensuring device reliability.
2Device complexity
If a single circuit board design is used without metal frames, then device complexity is reduced, but anti-ESD capability is lost
Solution Approach 1:
The shading layer is designed to serve dual functions: it provides ESD protection by being connected to signal lines (including grounded lines) and simultaneously performs its optical function of shading. This merging of protective and functional components adds anti-ESD capability without significantly increasing device complexity, as the same structural element fulfills multiple roles.
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 effectively prevents moisture impact on the operation element and achieves anti-ESD functionality, ensuring reliable operation and improved fingerprint recognition quality.
Implementation Method 1
the first insulating layer is located on the first planarization layer and in the first trench... the first insulating layer includes an inorganic material
Implementation Method 2
a first shading layer located on the first insulating layer and connected to the first signal line through the first opening
Data Source
AI summary
A fingerprint sensing device has a sensing area, an operation area, and a peripheral area, and the operation area is disposed between the sensing area and the peripheral area. The fingerprint sensing device includes a substrate, a sensing element located at the sensing area, an operation element located at the operation area, a first signal line located at the peripheral area, a first planarization layer, a first insulating layer, and a first shading layer. The first planarization layer is located on the substrate and has a first trench, and the first trench overlaps the first signal line. The first insulating layer is located on the first planarization layer and in the first trench, and the first insulating layer has a first opening located in the first trench. The first shading layer is located on the first insulating layer and connected to the first signal line through the first opening.