Fingerprint Sensor Package with Hardened Encapsulant
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Solution Overview
Problem
Fingerprint sensors are prone to surface damage due to direct contact, leading to a shortened lifespan, as the conventional package structure lacks adequate protection for the sensing area.
Innovation Solution
A package structure is developed with an encapsulant formed on a substrate, incorporating ceramic fillers to increase hardness and reduce surface roughness, and a bright layer is applied to enhance gloss and protect the sensing area from direct contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sensing area is exposed for direct finger contact, then the sensing function is accessible, but the sensing surface is easily damaged and lifetime is shortened
Solution Approach 1:
The patent introduces an encapsulant layer as an intermediary between the finger and the sensing surface. This encapsulant is formed by injecting molding compound that completely covers the sensing area, allowing optical signals to pass through while preventing direct contact and physical damage to the sensing elements below.
Solution Approach 2:
The encapsulant acts as a protective thin film/shell that covers the sensing area. It is transparent to allow optical signals to pass through for fingerprint sensing, while simultaneously providing mechanical protection against scratches and direct contact damage to the underlying sensing surface.
2Reliability
If the sensing area is completely covered by encapsulant, then the sensing surface is protected from damage, but the surface roughness increases
Solution Approach 1:
A release film is introduced as a mediator between the mold cavity and the molding compound. This release film has a smooth surface that transfers to the encapsulant during molding, reducing surface roughness. The release film is later removed, leaving the encapsulant with improved surface finish.
Solution Approach 2:
The patent changes the surface parameter of the mold cavity by adding a release film with specific surface properties. This modifies the surface roughness parameter of the resulting encapsulant, transforming it from a rough surface to a smoother surface that meets optical sensing requirements.
3Strength
If ceramic fillers are added to increase hardness, then the Mohs hardness increases, but the encapsulant composition becomes more complex
Solution Approach 1:
The patent creates a composite encapsulant material by combining polymer base material with ceramic fillers. This composite structure provides enhanced hardness and scratch resistance while maintaining the encapsulant's primary functions of protection and optical transparency for fingerprint sensing.
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 protects the sensing area from damage, prolongs the lifespan of the fingerprint sensor, and allows for a high-gloss, high-hardness, and colorful package structure.
Implementation Method 1
forming an encapsulant on the substrate to encapsulate the electronic element
Implementation Method 2
a release film is formed on an inner surface of the upper mold. As such, a molding process can be performed to form the encapsulant encapsulating the electronic element. The release film facilitates to reduce the surface roughness of the encapsulant
Implementation Method 3
The additive can be selected from ceramic fillers so as to increase the Mohs hardness of the encapsulant
Implementation Method 4
a bright layer is formed on the encapsulant. Therefore, the present invention obtains a high-gloss, high-hardness and colorful sensor package structure
Data Source
AI summary
A method for fabricating a package structure is provided, including the steps of: disposing and electrically connecting a sensing chip to a substrate; forming an encapsulant on the substrate to encapsulate the sensing chip; and forming a bright layer on the encapsulant to increase the gloss of the package structure. The encapsulant includes an additive to increase the Mohs hardness of the encapsulant. Further, the encapsulant with different additives presents different colors. Therefore, the invention obtains a high-gloss, high-hardness and colorful sensor package structure.