Fingerprint Detection Circuit Adhesion and Optical Filtering
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Solution Overview
Problem
Current fingerprint identification devices with under-screen type fingerprint identification face challenges such as a wide bezel in electronic devices due to the external placement of fingerprint recognition capabilities, and the adhesive used to fix the detection circuit can be prone to fractures when the flexible base film is bent, affecting the accuracy and reliability of fingerprint identification.
Innovation Solution
A fingerprint identification device is designed with a base film, a detection circuit, and an adhesive layer where the detection circuit is adhered to the base film via the adhesive layer, which has a flexible and adhesive surface to improve fixation, and a refractive index matching film is added between the base film and the adhesive layer to filter out stray light, enhancing the accuracy and reliability of fingerprint recognition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive layer is used to fix detection circuit onto base film, then fixation strength is improved, but adhesive fractures occur when flexible base film is bent
Solution Approach 1:
The adhesive layer is divided into multiple segments or patterns rather than being continuous, which allows the adhesive structure to flex and deform without fracturing when the base film is bent, while still maintaining sufficient fixation strength at key attachment points
Solution Approach 2:
The adhesive layer is designed as a thin film structure with appropriate thickness and material properties that enable it to accommodate the flexibility of the base film during bending operations, preventing fracture while maintaining adhesion
2Measurement precision
If refractive index matching film is added between base film and adhesive layer, then stray light is filtered out and fingerprint recognition accuracy is improved, but device structure becomes more complex
Solution Approach 1:
The refractive index matching film performs multiple functions simultaneously: it matches refractive indices to reduce stray light, provides additional adhesive bonding surface area, and maintains structural integrity. This multi-functionality justifies the added layer by delivering multiple benefits rather than a single function
Solution Approach 2:
The refractive index matching film changes the optical parameter (refractive index) of the interface between base film and adhesive layer, transforming the optical properties to eliminate stray light reflections and improve fingerprint recognition accuracy
3Area of stationary object
If detection circuit is adhered onto base film with adhesive layer, then fixation area is increased, but adhesive fractures when base film is bent
Solution Approach 1:
The adhesive layer is segmented into multiple smaller adhesive regions rather than a single continuous layer, allowing each segment to independently accommodate bending stresses while collectively providing extensive contact area for secure fixation
Solution Approach 2:
The adhesive layer is designed with dynamic properties that allow it to deform and flex during bending operations, maintaining its bonding function across a large area without fracturing, by accommodating the dynamic mechanical stresses through appropriate material selection and structural design
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 improves the fixation and accuracy of the detection circuit, reducing the likelihood of adhesive fractures and enhancing the quality of fingerprint images by increasing the contact area and using the refractive index matching film to filter out stray light, thus improving the overall fingerprint identification process.
Implementation Method 1
a refractive index matching film is added between the base film and the adhesive layer to filter out stray light
Implementation Method 2
the refractive index matching film has a first refractive index; the adhesive layer has a second refractive index; and the first refractive index is larger than the second refractive index
Data Source
AI summary
A fingerprint identification device and manufacturing method thereof, and electronic device are disclosed. The fingerprint identification device includes a base film, a detection circuit, and an adhesive layer. The detection circuit is provided at a first side of the base film; the adhesive layer is provided on the first side of the base film, and is provided between the base film and the detection circuit, so as to adhere the detection circuit onto the base film.