Fingerprint Sensor Cover Structure with Conductive Traces
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current fingerprint sensing modules for smart cards face challenges such as visible gaps between the sensor and the card body, reliability issues, and limitations in mass production due to the need for precise lamination, which affect both cosmetic and functional performance.
Innovation Solution
A fingerprint sensing module with a cover structure featuring conductive traces and insulating layers, where wire bonding is used to connect the sensor device to the cover structure from the backside, reducing the distance between the sensing array and the outer surface, and allowing for flexible integration and reduced footprint, including the use of wafer level fan-out technology and passive components for enhanced functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the fingerprint sensing module is soldered on an inlay and the card is laminated with the inlay as a center layer, then the fingerprint sensor can be integrated in a smart card, but a gap between the fingerprint sensing module and the card body is often visible creating reliability and cosmetic problems
Solution Approach 1:
The fingerprint sensor device is nested within a cover structure that has a cavity specifically designed to accommodate the sensor. The cover structure acts as a housing that encloses the sensor device, ensuring it is properly positioned and secured within the smart card assembly. This nesting approach eliminates gaps between the sensor and card body while maintaining a compact, integrated appearance.
Solution Approach 2:
The cover structure serves as an intermediary component between the fingerprint sensor device and the smart card body. It provides a mechanical interface that secures the sensor in place, fills void spaces, and ensures proper alignment. The cover structure with its cavity design acts as a mediator that resolves the gap issue by physically connecting the sensor to the card assembly in a reliable manner.
2Adaptability or versatility
If the fingerprint sensing module is integrated using lamination with a cavity, then the sensor can be exposed upon card lamination, but the process is typically only used for limited series and not suitable for mass production
Solution Approach 1:
The smart card assembly is segmented into distinct functional components: the smart card body, the cover structure with integrated cavity, and the fingerprint sensor device. The cover structure is pre-formed with the cavity and connection pads as an integrated unit, which can be manufactured independently and then assembled with the sensor and card body. This segmentation enables modular manufacturing suitable for mass production while maintaining the exposed sensor functionality.
Solution Approach 2:
The cover structure is prepared in advance with the cavity and connection pads already formed as part of its structure. This preliminary preparation of the cover structure allows for efficient assembly during mass production, as the sensor can be directly placed into the pre-formed cavity and connected to the pre-positioned connection pads without requiring complex post-assembly operations.
3Manufacturing precision
If wire bonding is used to connect the sensor device to the cover structure from the backside, then the distance between the sensing array and the outer surface is reduced, but the device complexity increases
Solution Approach 1:
The connection approach is moved to another dimension by implementing connection pads on the backside of the cover structure that align with connection pads on the sensor device. Wire bonds are routed through the backside of the cover structure, utilizing the z-dimension (thickness direction) rather than adding lateral complexity. This dimensional approach reduces the distance between the sensing array and outer surface while managing wire bonding complexity through spatial optimization.
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
There is provided a fingerprint sensing module (2) comprising a fingerprint sensor device (20) having a sensing array (21) arranged on a first side (22) of the device. The fingerprint sensor device also comprises connection pads (24) for connecting the fingerprint sensor device to external circuitry and a fingerprint sensor device cover structure (30), the cover structure having a first side (32) configured to be touched by a finger, and a second side (34) facing the sensing array, wherein the cover structure comprises conductive traces (35), arranged on the second side, for electrically connecting the fingerprint sensing module to external circuitry, and wherein a surface area of the cover structure is larger than a surface area of the sensor device. Moreover, the fingerprint sensor device comprises wire-bonds (40, 66) electrically connecting the connection pads of the fingerprint sensor device to the conductive traces of the cover structure.