Bottom-Side Fingerprint Sensor Layout for Thin Reliable Packaging
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Solution Overview
Problem
Conventional semiconductor packages and methods for forming sensor devices, such as fingerprint sensors, suffer from inadequate sensing accuracy, device reliability, manufacturability issues, and thickness that makes integration into other products difficult and costly.
Innovation Solution
A fingerprint sensor device architecture that includes a semiconductor die with a fingerprint sensing unit on one surface and a protective layer on the opposite surface, connected through conductive bumps, and a protective plate for sensing fingerprints, with a simplified manufacturing process involving flip chip configuration and encapsulating materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional semiconductor packages are used for fingerprint sensors, then manufacturing processes are established, but sensing accuracy is inadequate
Solution Approach 1:
The patent inverts the conventional package structure by placing the sensing surface on the bottom side of the die rather than the top side. This allows the sensing area to be fully exposed without being obscured by top-side electrodes or packaging components, thereby improving sensing accuracy while maintaining structural integrity and reliability
Solution Approach 2:
The patent repositions the sensing area from the traditional top surface to the bottom surface of the semiconductor die, utilizing the third dimension (vertical orientation) to resolve the conflict between sensing accuracy and device reliability. This dimensional reconfiguration allows optimal sensing performance without compromising structural stability
2Length of stationary object
If conventional package structures are used, then devices are structurally sound, but thickness is greater than necessary
Solution Approach 1:
The patent extracts and eliminates unnecessary intermediate packaging layers and structural components from the conventional design. By placing the sensing area on the bottom side, the design removes the need for certain protective layers and structural supports that would increase thickness, achieving a more compact form factor while maintaining manufacturability
Solution Approach 2:
The patent employs thin film structures and streamlined packaging that reduce overall device thickness. The bottom-side sensing configuration allows for thinner protective layers and more efficient use of vertical space, enabling integration into space-constrained applications without sacrificing manufacturing ease
3Area of stationary object
If top side electrodes are present, then electrical connections are established, but sensing area is reduced
Solution Approach 1:
By inverting the sensor orientation so the sensing area is on the bottom side, the patent eliminates the conflict between top-side electrodes and sensing area. The sensing surface is fully exposed on the bottom, maximizing sensing area, while electrical connections are established through the die substrate and packaging structure without interfering with the sensing region
Solution Approach 2:
The patent resolves the area-complexity tradeoff by transitioning to a bottom-side sensing architecture. This dimensional change allows sensing electrodes to be positioned on the bottom surface where they can cover the maximum area, while electrical connections are routed through alternative paths (substrate connections, side contacts) that do not compete for surface space
Data Source
AI summary
A fingerprint sensor device and a method of making a fingerprint sensor device. As non-limiting examples, various aspects of this disclosure provide various fingerprint sensor devices, and methods of manufacturing thereof, that comprise a sensing area on a bottom side of a die without top side electrodes that senses fingerprints from the top side, and/or that comprise a sensor die directly electrically connected to conductive elements of a plate through which fingerprints are sensed.