Fingerprint Sensor Packaging via Rear Redistribution Layer
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Solution Overview
Problem
Conventional wire bonding packaging processes in fingerprint recognition chips create an arc height that prevents human fingers from contacting the recognition sensor area, potentially damaging bonded wires.
Innovation Solution
A chip packaging module where a first chip with a pad on its front surface is connected to a second chip on its rear surface using a redistribution layer, allowing direct contact with the fingerprint recognition sensor area and reducing communication distance between chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wire bonding packaging process is used, then interconnection between circuits is achieved, but arc height is created that prevents human finger contact with sensor area
Solution Approach 1:
The patent moves the bonding pads from the front surface (2D plane) to the rear surface of the chip, utilizing the third dimension (depth/thickness) to resolve the conflict. This allows the sensor area on the front surface to remain flat and accessible for finger contact, while wire bonding connections are established on the rear surface where arc height does not interfere with user interaction.
2Reliability
If wire bonding is performed on front surface, then circuit interconnection is achieved, but bonded wire may be damaged due to lack of protection
Solution Approach 1:
The patent introduces the rear surface of the chip as an intermediary location for wire bonding operations. This mediator surface allows the bonding wires to be connected and protected from damage, while simultaneously enabling the front sensor surface to remain fully accessible for fingerprint recognition without any bonding wires in the way.
3Speed
If multiple chips are stacked for interconnection, then communication distance is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent combines multiple functional chips (fingerprint sensor chip and control chip) into a single stacked package structure. The first chip contains the sensor array and is positioned on the front surface, while the second chip containing control circuits is positioned on the rear surface, with redistribution layers providing interconnections between them. This merging achieves short communication distances while maintaining manageable manufacturing complexity through standardized packaging processes.
Data Source
AI summary
The present disclosure discloses a chip packaging module, including: a first chip, where a first pad is disposed on a side neighboring to a front surface of the first chip; at least a second chip, where at least one second chip is disposed on a rear side of the first chip, each second chip has a second pad, and wherein the first pad of the first chip is connected to the second pad of the second chip via a redistribution layer. According to the chip packaging module in the present disclosure, a second chip is disposed on a rear side of a first chip, and a first pad is connected to a second pad via a redistribution layer. By means of a redistribution technology on surfaces of multiple chips, a lead of a pad on a front surface of a fingerprint recognition chip is masterly winded to the back for interconnection, so that an induction area on the front surface of the chip can fully contact with a human body. In addition, the multi-chip redistribution technology can also greatly narrow down an interconnection distance between chips, which improves efficiency of communication between chips.