Wafer-Level Capacitive Sensor Package for Mass-Produced Chip Cards
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Solution Overview
Problem
Existing chip cards with biometric sensors, such as fingerprint sensors, face challenges in achieving cost-effectiveness, reliability, and ease of assembly, particularly in mass production, and current assembly methods do not support contactless use.
Innovation Solution
A wafer-level package sensor device is developed using Fan-Out Wafer Level Packaging (FOWLP) to integrate a sensor controller chip with a sensor array formed by partially overlapping redistribution layers, allowing a capacitive sensor to be integrated into a chip card module through flip-chip connections, reducing costs and enabling mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If PCB substrate-based biometric fingerprint sensors are manufactured from PCB panels that are separated into pieces by punching, milling or cutting, then the sensors can be produced as individual modules, but the production process becomes complex and not suitable for mass production
Solution Approach 1:
The patent segments the sensor array from the controller chip, with the sensor array formed by overlapping RDL tracks on a substrate and the controller chip separately mounted. This segmentation allows each component to be optimized and manufactured independently, then assembled together, simplifying the overall production process while maintaining mass production capability
Solution Approach 2:
The patent transitions from traditional PCB panel manufacturing to a three-dimensional stacked architecture where the sensor array and controller chip are vertically integrated. This dimensional change enables wafer-level packaging and flip-chip connections, which are standard for mass production and eliminate the need for punching, milling, or cutting operations
2Ease of operation
If a T-shaped chip module is used for assembly, then the assembly process is simplified, but contactless use is not supported
Solution Approach 1:
The patent merges the sensor array, controller chip, and antenna into a single integrated wafer-level package. The antenna is formed on the same substrate as the sensor array, and both are electrically connected to the controller chip through RDL tracks. This integration enables contactless operation while maintaining a compact structure suitable for chip cards
3Reliability
If multiple components are electrically connected to form chip cards with biometric sensors, then functional requirements are met, but the structure becomes complex and costs increase
Solution Approach 1:
The controller chip serves multiple functions: it controls the sensor array, processes biometric data, and manages communication through the antenna. This multi-functionality reduces the number of separate components needed, simplifying the overall structure while maintaining functional reliability
Solution Approach 2:
The patent implements a nested structure where the sensor array is formed within the substrate, the controller chip is mounted on top, and both are interconnected through RDL tracks. The antenna is also integrated within the same package structure. This nesting approach consolidates multiple components into a compact, reliable unit
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 provides a cost-effective, reliable, and easily assembled biometric sensor suitable for chip cards, with reduced thickness and favorable manufacturing costs, supporting both contact-based and contactless operations.
Implementation Method 1
crossed tracks of the two topmost RDL layers can form a capacitive biometric sensor, such as a fingerprint sensor
Implementation Method 2
multiple contact surfaces connected to the controller, which are configured for electrical coupling to a chip card module carrier by means of a flip-chip connection
Data Source
AI summary
A wafer-level package sensor device including a capacitive sensor, a controller which is electrically conductively connected to the sensor, wherein the capacitive sensor is formed by partially overlapping redistribution layer tracks of the wafer-level package sensor device formed in different planes, and multiple contact surfaces connected to the controller, which are configured to electrically couple to a chip card module carrier using a flip-chip connection.