Split Lead Frame Magnetic Sensor Package
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Solution Overview
Problem
Existing integrated circuit packaging techniques for magnetic field sensors often face challenges in efficiently managing magnetic fields and reducing eddy currents, which can lead to interference and decreased sensor performance, particularly when using conductive lead frames and conventional die attach pads.
Innovation Solution
A split lead frame design is employed, where the semiconductor die is attached to non-contiguous die attach portions of multiple leads, and passive components like capacitors are integrated across these leads to reduce eddy currents and enhance magnetic field sensing, while a ferromagnetic element, such as a magnet, is strategically positioned to optimize magnetic field detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional conductive lead frame with contiguous die attach pad is used, then the manufacturing process is simple, but eddy currents are generated causing magnetic field errors and reduced sensor performance
Solution Approach 1:
The lead frame is divided into multiple separate leads (first lead, second lead, third lead, fourth lead) instead of using a single contiguous die attach pad. The semiconductor die is attached to non-contiguous die attach portions on these separate leads, which interrupts the path for eddy currents and reduces magnetic field errors while maintaining structural functionality.
Solution Approach 2:
Different regions of the lead frame are given different properties: the die attach portions are designed with specific geometries to minimize eddy currents, while connection portions maintain electrical connectivity. The separation of die attach functions across multiple leads creates local variations in electrical pathways that reduce overall eddy current effects.
2Measurement precision
If a split lead frame design is used to reduce eddy currents, then sensor performance is enhanced, but the manufacturing process becomes more complex
Solution Approach 1:
The lead frame structure is segmented into multiple discrete leads with separate die attach portions, which can be manufactured using standard lead frame fabrication techniques. The segmentation is designed to align with conventional manufacturing processes while achieving the goal of reducing eddy currents through interrupted electrical pathways.
3Object-affected harmful factors
If passive components are integrated across multiple leads, then EMC performance is improved and eddy currents are reduced, but the device complexity increases
Solution Approach 1:
Passive components are integrated directly onto the lead frame structure, merging multiple functions (electrical connection, magnetic shielding, and passive component integration) into a single package. This consolidation reduces the number of separate components and assembly steps while improving EMC performance through the inherent eddy current reduction of the split lead frame design.
Solution Approach 2:
The lead frame serves multiple functions simultaneously: it provides electrical connections through the leads, acts as a structural support for the semiconductor die, integrates passive components, and reduces electromagnetic interference through its segmented structure that minimizes eddy currents. This multi-functionality reduces overall device complexity despite the enhanced capabilities.
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 split lead frame design minimizes magnetic field errors, enhances sensor performance by reducing eddy currents, and allows for a more compact package with improved EMC performance, making it suitable for applications requiring precise magnetic field detection.
Implementation Method 1
a ferromagnetic element, such as a magnet, is strategically positioned to optimize magnetic field detection
Implementation Method 2
a magnetic field sensing element, or transducer, such as a Hall Effect element
Implementation Method 3
enhances sensor performance by reducing eddy currents
Data Source
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AI summary
A magnetic field sensor includes a lead frame having a plurality of leads, at least two of which have a connection portion and a die attach portion. A semiconductor die is attached to the die attach portion of the at least two leads and a separately formed ferromagnetic element, such as a magnet, is disposed adjacent to the lead frame.