Fingerprint Module Mold Compound Layer Segmentation
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Solution Overview
Problem
Conventional fingerprint identification modules face challenges in accuracy due to increased thickness and uneven mold compound layer distribution, leading to inconsistent fiducial capacitance and potential misjudgment, as the molding process struggles to maintain uniform stress and flatness, affecting the distance between the fingerprint sensor and the finger.
Innovation Solution
A fingerprint identification module design featuring a substrate with electrical contacts, a fingerprint sensor die connected via wires, a covering adhesive layer, and a mold compound layer, where the fingerprint sensor die, adhesive layer, and cover plate are molded together, reducing overall thickness and maintaining consistent distance for enhanced sensing accuracy, and a manufacturing method involving wire-bonding, adhesive layer formation, and cutting to produce individual modules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a molding process is performed to form the mold compound layer to encapsulate the fingerprint sensor die, then the sensor die is protected and structurally stable, but the thickness of the mold compound layer increases the distance between the sensing surface and the finger, reducing sensing accuracy
Solution Approach 1:
The patent divides the mold compound layer into two distinct layers: a first mold compound layer with lower viscosity that penetrates into the wiring grooves to provide structural stability, and a second mold compound layer with higher viscosity that forms a thin, uniform covering layer. This segmentation allows each layer to perform its specific function optimally - the first layer provides mechanical support while the second layer maintains sensing accuracy by minimizing thickness.
2Reliability
If the molding process is performed to encapsulate the sensor die, then the sensor is protected, but the thickness of the mold compound layer is difficult to precisely control, resulting in uneven distribution and warpage
Solution Approach 1:
The patent applies different properties to different parts of the mold compound layer. The first mold compound layer has lower viscosity and is applied to penetrate into the wiring grooves and provide structural support, while the second mold compound layer has higher viscosity and is applied to form a thin, uniform protective covering. This local quality differentiation ensures that each region of the mold compound structure serves its intended function with appropriate thickness and properties.
3Reliability
If the mold compound layer is formed to encapsulate the sensor die and wires, then the components are protected and structurally stable, but the surface of the mold compound layer suffers from warpage, causing uneven adhesive layer thickness
Solution Approach 1:
The patent segments the mold compound application into two distinct steps: first applying a lower viscosity mold compound that penetrates and stabilizes the internal structure, then applying a higher viscosity mold compound that forms a flat, uniform external surface. This segmentation resolves the conflict between structural stability and surface flatness by assigning each function to a separate layer with optimized properties.
4Reliability
If the thickness of the mold compound layer is increased to provide adequate encapsulation, then the sensor die is better protected, but the distance between the finger and sensing surface increases, reducing sensing accuracy
Solution Approach 1:
The patent applies different thicknesses and viscosities to different regions and layers of the mold compound. The first mold compound layer penetrates into the wiring grooves to provide structural support where needed, while the second mold compound layer forms a thin, uniform covering that minimizes overall thickness. This local quality approach ensures adequate protection without compromising sensing accuracy.
Data Source
AI summary
A fingerprint identification module includes a substrate, a fingerprint sensor die, a covering adhesive layer, a cover plate and a mold compound layer. The fingerprint sensor die is attached on the substrate for sensing a fingerprint image. The covering adhesive layer is formed on a top surface of the fingerprint sensor die. The cover plate is attached on the covering adhesive layer. The mold compound layer is formed over the substrate. The fingerprint sensor die, the covering adhesive layer and the cover plate over the substrate are molded together through the mold compound layer, and the cover plate is exposed. The fingerprint identification module has small thickness and enhanced sensing accuracy.