Magnetic Field Sensor With Recessed Chip For 100 μm Magnet Distance
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Solution Overview
Problem
Existing magnetic field sensors face limitations in achieving very small distances between the sensor magnet and the sensor chip due to structural constraints, such as passivation layers and tribological layers, which affect sensitivity, reliability, and susceptibility to electrostatic discharge (ESD).
Innovation Solution
A magnetic field sensor design featuring a recessed sensor chip on a flat sensor carrier with a tribological protective layer, allowing the sensor magnet to be guided closely underneath, and a manufacturing method involving a recessed connection area and passivation to achieve ultra-thin substrate carriers with minimal distances of 100 μm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a passivation layer is applied to protect the sensor chip, then mechanical protection and reliability are improved, but the distance to the sensor magnet increases and sensitivity deteriorates
Solution Approach 1:
The sensor chip is rotated by 90 degrees relative to the sensor magnet movement direction, changing the spatial orientation from the conventional configuration. This dimensional change allows the magnetoresistive measurement surface to face the sensor magnet while the passivation layer protects the top surface, resolving the contradiction between protection and sensitivity.
2Ease of operation
If a tribological sliding layer is applied to reduce friction, then ease of operation is improved, but electrostatic discharge susceptibility increases
Solution Approach 1:
The harmful tribological sliding layer that causes ESD is completely removed from the design. Instead, a groove is introduced to guide the sensor magnet, eliminating the need for a sliding layer and thereby eliminating the ESD risk while still providing ease of operation through guided movement.
3Ease of manufacture
If the sensor chip is mounted flush with the substrate surface, then manufacturing simplicity is improved, but the distance to the sensor magnet cannot be reduced below 200 μm
Solution Approach 1:
The sensor chip is rotated 90 degrees and positioned with its measurement surface facing the sensor magnet, rather than being mounted flush with the substrate surface. This dimensional reorientation allows the chip to extend beyond the substrate edge, reducing the distance to the sensor magnet to approximately 100 μm while maintaining manufacturing feasibility.
4Reliability
If bond wires with loop heights are used for electrical connection, then electrical connectivity is achieved, but minimum technological heights cannot be undercut
Solution Approach 1:
The sensor chip is rotated and positioned vertically relative to the substrate, extending beyond the substrate edge. This reorientation allows the magnetoresistive measurement surface to be closer to the sensor magnet while the bond wires connect to bond pads on the substrate surface, effectively bypassing the height constraint imposed by conventional bond wire loop structures.
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 enables extremely small distances between the sensor magnet and chip, enhancing sensitivity and longevity while reducing ESD risks, allowing for high-precision magnetic field measurements with improved mechanical protection.
Implementation Method 1
a magnetoresistive sensor chip (12) and a planar sensor carrier (14)
Data Source
Figure 1a~2
Figure 3a~4
Figure 5a~5b
AI summary
The invention relates to a magnetic field sensor (10, 30, 40, 50) for measuring a variable magnetic field, in particular for a motion sensor or position sensor. The magnetic field sensor (10, 30, 40, 50) comprises a magnetoresistive sensor chip (12) and a planar sensor carrier (14), which carries the sensor chip (12) and has a top side (44), from which the sensor chip (12) can be electrically contacted. The top side of the sensor carrier (14) has a cavity (16) or recess (18), in which the sensor chip (12) is arranged. According to the invention, the sensor chip (12) can be electrically contacted from the top side (44) and the sensor chip (12) senses a magnetic field to be measured via a bottom side of the sensor carrier (14). The invention further relates to a production method for producing a magnetic field sensor (10, 30, 40, 50) as described above and to a measuring method.