Lead Frame Pad Layout to Attenuate Eddy Currents in Hall Sensors
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Solution Overview
Problem
Existing methods for attenuating eddy current effects in lead frames have limited effectiveness in reducing the reversed magnetic field, leading to weakened detection sensitivity and accuracy of Hall effect sensors.
Innovation Solution
A pad structure comprising first and second pad components disposed on adjacent sides of a chip placement region, electrically connected to surround the region, with one end of the first pad component extending for a preset length and the pad optionally featuring stress relief holes, integrated structure, and arc-shaped corners to reduce eddy current loops and stress accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a U-shaped trench is formed at the pad to interrupt the connection, then eddy current loops are partially prevented, but the reversed magnetic field is only weakly reduced
Solution Approach 1:
The pad is divided into multiple isolated pad components (first pad component and second pad component) that are electrically connected through a narrow connection portion. This segmentation breaks the continuous metal path into discrete segments, effectively interrupting eddy current loops while maintaining electrical connectivity for sensor operation.
Solution Approach 2:
The pad components are strategically positioned to surround the chip placement region on adjacent sides, creating localized electromagnetic shielding exactly where the Hall sensor operates. This localized arrangement optimizes the reduction of reversed magnetic field impact on detection accuracy.
2Object-generated harmful factors
If the pad area is reduced to break eddy current loops, then reversed magnetic field is weakened, but the contact area with package body decreases
Solution Approach 1:
Instead of reducing pad area in two dimensions, the solution extends pad components along adjacent sides in a dimensional arrangement that surrounds the chip placement region. This maintains sufficient contact area with the package body while breaking eddy current loops through the segmented structure and narrow connections.
3Object-generated harmful factors
If pad components are extended to surround the chip placement region, then eddy current loops are reduced, but structural stress increases
Solution Approach 1:
The pad structure is segmented into multiple pad components connected by narrow portions, which act as stress relief zones. This segmentation allows the pad to accommodate thermal expansion and mechanical stress without generating excessive force that could cause delamination.
Solution Approach 2:
The narrow connection portions between pad components serve as intermediary elements that flexibly accommodate stress. These narrow portions deform more easily under stress, protecting the overall structure from excessive force while maintaining electrical connectivity.
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 proposed pad structure reduces closed eddy current loops, enhancing sensor detection sensitivity and accuracy while increasing contact area with the package body to reduce stress and delamination, thereby improving structural stability.
Implementation Method 1
due to the eddy current loops in the large metal of the lead frame pad, a reversed magnetic field is generated
Implementation Method 2
The Hall effect is widely used in contactless sensing fields such as current detection
Data Source
AI summary
Disclosed in this disclosure are a pad, lead frame, and sensor packaging structure for attenuating an eddy current effect, which are applied to the field of semiconductor preparation. The pad includes a first pad component and a second pad component, where the first pad component and the second pad component are disposed on two adjacent sides of a chip placement region; and the first pad component and the second pad component are electrically connected, such that the first pad component and the second pad component surround the chip placement region on the two adjacent sides. In this disclosure, by means of arranging the pad along two adjacent sides of a chip, the formation of closed eddy current loops in a metal frame can be further reduced, thereby weakening the impact of a reversed magnetic field, and thus improving the detection sensitivity and accuracy of a sensor.