Fingerprint Chip Packaging Polymer Encapsulation
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Solution Overview
Problem
Conventional fingerprint identification devices require high sensitivity for the fingerprint identification chip, which complicates manufacturing and limits their application due to the need for a thick glass substrate for protection, making it difficult to accurately detect capacitance differences between finger ridges and valleys.
Innovation Solution
A packaging structure for the fingerprint identification chip that uses a plastic encapsulation layer made of polymer, which reduces the distance between the chip and the surface, allowing direct contact with the finger and providing protection while reducing the sensitivity requirements of the chip, and includes a substrate with solder pads and a protecting ring for electrical isolation and static protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick glass substrate is used to protect the fingerprint identification chip, then the chip is protected from damage, but the distance from the sensing chip to the surface increases, making it difficult to accurately detect capacitance differences
Solution Approach 1:
The patent changes the material parameter from glass to polymer encapsulation layer, and controls the thickness parameter to be within 100 micrometers, which maintains protection while reducing the distance to the sensing chip surface, enabling accurate capacitance detection
Solution Approach 2:
The patent uses a thin polymer encapsulation layer instead of a thick glass substrate, creating a flexible thin film structure that provides protection while maintaining close proximity to the sensing chip for accurate fingerprint detection
2Measurement precision
If the distance from the sensing chip to the surface is reduced to improve detection accuracy, then capacitance differences can be detected more accurately, but the sensing chip becomes more vulnerable to damage
Solution Approach 1:
The patent optimizes the thickness parameter of the polymer encapsulation layer to be within 100 micrometers, achieving a balance between close proximity for accurate detection and sufficient thickness for protection
Solution Approach 2:
The patent uses a composite structure with polymer encapsulation layer, glass substrate, and protecting ring together to provide comprehensive protection while maintaining close sensing distance
3Length of stationary object
If a polymer encapsulation layer is used instead of glass substrate, then the distance to the sensing chip is reduced and detection is improved, but the material hardness and durability may be compromised
Solution Approach 1:
The patent combines polymer encapsulation layer with glass substrate and protecting ring to create a composite structure that provides both the close proximity needed for detection and the hardness/durability of glass and metal components
Solution Approach 2:
The patent applies different materials with different properties to different locations: polymer for the encapsulation layer needing flexibility and thinness, glass for the substrate needing hardness, and metal for the protecting ring needing strength
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 the sensitivity requirements of the fingerprint identification chip, enabling wider application and improving the accuracy and cost-effectiveness of fingerprint detection by using a polymer encapsulation layer that is durable and flexible, allowing for easier detection of fingerprints while maintaining high hardness and electrical isolation.
Implementation Method 1
The plastic encapsulation layer is arranged on the substrate surface and the first surface of the sensing chip, where the plastic encapsulation layer is made of a polymer, the plastic encapsulation layer surrounds the wire and the sensing chip
Implementation Method 2
There is one or more capacitive plates in the fingerprint identification chip 101. As there are a convex ridge and a concave valley on epidermis or beneath the epidermis of a user finger, when the user finger 103 contacts the surface of the glass substrate 102, a distance from the ridge to the fingerprint identification chip 101 is different from a distance from the valley to the fingerprint identification chip 101. So capacitance between the ridge of the user finger 103 and the capacitive plate is different from capacitance between the valley of the user finger 103 and the capacitive plat.
Data Source
AI summary
A packaging structure and a packaging method for a fingerprint identification chip are provided. The packaging structure includes a substrate, a sensing chip, a wire and a plastic encapsulation layer. The substrate is provided with a first solder pad layer. The sensing chip has a first surface and a second surface opposite to the first surface, the first surface comprises a sensing area and a peripheral area surrounding the sensing area, and the surface of the sensing chip in the peripheral area is provided with a second solder pad layer. Two ends of the wire are electrically connected to the first solder pad layer and the second solder pad layer respectively. The plastic encapsulation layer is made of a polymer, the plastic encapsulation layer surrounds the wire and the sensing chip.