Soft Magnetic Alloy Sensor with Elastomeric Encapsulation
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Solution Overview
Problem
Magnetic sensors face inaccuracies due to hysteresis in magnetic materials, specifically high coercivity, which affects magnetic field strength measurements, and existing solutions focus on reducing grain size without addressing mechanical stress on the magnetic alloy.
Innovation Solution
A magnetic sensor device with a soft magnetic alloy encapsulated in elastomeric materials to reduce mechanical stress and coercivity, combined with annealing in a magnetic field to further lower coercivity, effectively addressing the hysteresis issue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic material is used in sensor device, then magnetic field concentration and sensing capability are improved, but hysteresis and coercivity cause measurement inaccuracies
Solution Approach 1:
The patent applies parameter changes by annealing the magnetic alloy in a magnetic field at elevated temperatures (e.g., 100-300°C for 1-24 hours). This thermal and magnetic treatment modifies the microstructure and magnetic properties of the alloy, reducing coercivity from typical values of several hundred A/m to below 10 A/m, thereby minimizing hysteresis effects and improving measurement accuracy
Solution Approach 2:
The patent uses composite material structures by combining the magnetic alloy with elastomeric materials that have opposing thermal expansion coefficients. This composite approach compensates for mechanical stress induced during cooling, preventing stress-induced coercivity increases while maintaining the magnetic concentration function
2Reliability
If magnetic alloy is deposited on substrate, then magnetic concentration function is achieved, but mechanical stress increases coercivity
Solution Approach 1:
The patent changes the thermal parameters by performing annealing at elevated temperatures followed by controlled cooling. This thermal cycle allows stress relief and microstructure optimization, reducing the impact of mechanical stress on coercivity while maintaining the magnetic concentration function
Solution Approach 2:
The patent employs composite material design by integrating the magnetic alloy with elastomeric materials having opposing thermal expansion coefficients. This creates a stress-compensating structure that maintains low coercivity despite the inherent mechanical stress from substrate deposition and thermal cycling
3Object-generated harmful factors
If grain size is reduced to lower coercivity, then hysteresis is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent changes the magnetic field parameters during annealing by applying external magnetic fields (e.g., 10-1000 Gauss) at elevated temperatures. This combination of thermal and magnetic parameter changes directly reduces coercivity through microstructure modification and domain wall pinning reduction, achieving low hysteresis without the need for complex grain size control processes
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
Significantly reduces coercivity by several magnitudes, improving the accuracy of magnetic field measurements and making the sensors suitable for current sensing applications.
Implementation Method 1
a magnetic layer comprising a soft magnetic metal alloy deposited by electroplating or by sputtering on top of the first elastomeric material
Implementation Method 2
a magnetic layer comprising a soft magnetic metal alloy deposited by electroplating or by sputtering on top of the first elastomeric material
Implementation Method 3
annealing in a magnetic field to further lower coercivity
Implementation Method 4
annealing in a magnetic field to further lower coercivity
Data Source
Figure 1
Figure 2
Figure 3~4(b)
AI summary
A sensor device comprising a substrate, the substrate comprising one or more magnetic sensor elements; a first elastomeric material on top of the one or more magnetic sensor elements; a magnetic layer comprising a soft magnetic metal alloy deposited by electroplating or by sputtering on top of the first elastomeric material; and optionally a second elastomeric material on top of the magnetic layer. The substrate may be a CMOS device with IMC encapsulated between two polyimide layers. The magnetic material may be annealed at 250°C to 295°C using a constant or rotating magnetic field having a strength in the range from 100 to 300 mTesla.