Fingerprint Sensor Lead Frame Isolation for Stable Package Separation
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Solution Overview
Problem
The existing fingerprint chip packaging structure is prone to deformation and electrical short-circuiting due to its design, leading to instability and difficulty in testing and separation of individual packages, especially for large-sized chips.
Innovation Solution
A fingerprint-sensor chip package design featuring a lead frame with a base island and connecting rib, where the connecting rib is disconnected from the chip using bonding wires, allowing for a plastic packaging part to enclose the chip and lead frame, and the connecting rib is partially or completely etched to prevent electrical short-circuits, enabling stable adhesion and efficient separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a connecting rib connects all components of the lead frame to achieve physical connection, then structural stability is improved, but electrical short-circuiting occurs between components
Solution Approach 1:
The connecting rib is segmented into multiple isolated sections through etching, creating electrical insulation barriers between adjacent components while maintaining physical structural integrity. This segmentation allows the rib to provide mechanical support without causing electrical short-circuits between chips and connecting fingers.
Solution Approach 2:
The etched connecting rib acts as an intermediary structure that provides mechanical connection and support while the etched portions serve as electrical insulators. This intermediary approach allows simultaneous achievement of structural stability and electrical isolation.
2Area of stationary object
If connecting ribs are made long to support large-sized package body, then coverage area is improved, but deformation occurs causing base island to lean
Solution Approach 1:
The long connecting rib is divided into multiple shorter segments through etching, reducing the span length of each segment and thereby minimizing deformation and bending. This segmentation maintains support coverage for large package bodies while preventing base island leaning.
Solution Approach 2:
The connecting rib structure is optimized locally by creating etched sections at strategic positions, providing enhanced support where needed while reducing material in areas where electrical isolation is required. This local quality improvement prevents deformation in critical support areas.
3Reliability
If connecting rib is made of metal for electrical connection, then electrical conductivity is improved, but cutting difficulty increases compared to plastic elements
Solution Approach 1:
The mechanical cutting process is replaced with a chemical etching process to create the isolated sections in the metal connecting rib. This substitution allows precise electrical isolation while avoiding the difficulties of mechanically cutting metal, maintaining electrical conductivity where needed.
4Stability of the object's composition
If all components are connected by connecting rib, then physical connection is achieved, but test in strips cannot be performed due to electrical short-circuit
Solution Approach 1:
The connecting rib is segmented into electrically isolated sections, allowing adjacent packages on a strip to be electrically independent while maintaining physical structural connection. This enables test in strips to be performed without electrical short-circuits between adjacent packages.
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
This design enhances production stability, reduces cutting difficulty, and allows for effective testing of fingerprint chip packages in strips by ensuring complete electrical disconnection between components, improving the efficiency of package separation and adhesion.
Implementation Method 1
the chip is electrically connected to the at least one connecting finger on at least one side of the connecting rib that is not fixedly connected to the base island by connecting fingers by a bonding wire
Implementation Method 2
an adhesive tape is adhered to the bottom surface of the lead frame panel so that the die attach pad may be held in position
Data Source
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AI summary
A fingerprint chip package and method for processing same, relating to a field of biometric identification. The fingerprint chip package includes: a lead frame (1), a chip (2), and a plastic packaging part enclosing the lead frame (1) and the chip (2); the lead frame (1) comprises a base island (13), a connecting rib (11), and a golden finger (12); the base island (13) is used for bearing the chip (2); the connecting rib (11) is used for supporting the lead frame (1) and connecting the base island (13) via the golden finger (12); and the golden finger (12) is used for fixing the base island (13) and electrically connecting with the chip (2)