Sealed Magnetic Sensor With Inclined Pinned Layer for Stable Output

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Solution Overview

Problem

Magnetic sensors with sealed magnetoresistive effect elements are susceptible to output fluctuations due to external stress, which affects the precision of detected electric current values, particularly in applications requiring stable and precise detection.

Innovation Solution

The magnetic sensor design incorporates a magnetoresistive effect element with a pinned layer whose magnetization direction is inclined relative to the sealed part's shape, using a quadrilateral configuration to mitigate stress sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a magnetoresistive effect element with a pinned layer and free layer is used to detect external magnetic fields, then the sensor can measure changes in resistance value corresponding to external magnetic field strength, but the output fluctuates when external stress is applied due to inverse magnetostrictive effects changing the free layer magnetization direction

Engineering Contradiction:

Improvedetection precisionVSAvoidoutput stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies asymmetry by configuring the magnetization direction of the pinned layer at a specific angle (e.g., 45 degrees) relative to the stress direction, rather than parallel or perpendicular. This asymmetric orientation ensures that stress-induced magnetization changes in the free layer do not directly translate to resistance changes, thereby suppressing output fluctuations while maintaining detection precision

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the magnetization direction parameter of the pinned layer from conventional orientations (parallel or perpendicular to stress) to an inclined orientation. This parameter change optimizes the sensor's response characteristics, making the resistance change less sensitive to stress-induced magnetization deviations while preserving sensitivity to external magnetic fields

Inventive Principle:

Principle #35Parameter changes

2Power

If TMR-type magnetoresistive effect elements are used to achieve high MR ratio and superior output properties, then the sensor output is greatly enhanced, but the sensor becomes more sensitive to external stress applied on the magnetic sensor chip

Engineering Contradiction:

Improveoutput propertiesVSAvoidstress sensitivity

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent uses asymmetry by setting the pinned layer magnetization direction at an inclined angle relative to the stress axis. This asymmetric configuration decouples the stress sensitivity from the output signal while preserving the high MR ratio characteristics of TMR elements, thereby maintaining superior output properties while reducing stress sensitivity

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by creating different functional orientations within the magnetoresistive effect element: the pinned layer is oriented at an inclined angle to resist stress effects, while the free layer maintains its ability to respond to external magnetic fields. This localized differentiation of functional qualities allows simultaneous achievement of high output and low stress sensitivity

Inventive Principle:

Principle #3Local quality

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 effectively suppresses output fluctuations caused by external stress, enhancing the stability and precision of magnetic sensor readings.

Implementation Method 1

Magnetoresistive effect elements (MR elements) such as giant magnetoresistive effect elements (GMR elements), tunnel magnetoresistive effect elements (TMR elements), anisotropic magnetoresistive effect elements (AMR elements) and the like have been applied in the field of magnetic sensors

Methodology Applied

Scientific EffectMagnetoresistive effect: Magnetoresistance

Implementation Method 2

When an external magnetic field is not applied on the magnetoresistive effect element, the magnetization of the free layer is oriented in a fixed direction by a bias magnet

Methodology Applied

Scientific EffectMagnetism: Magnetism

Implementation Method 3

When the stress is received, the magnetization direction of the free layer may change due to an inverse magnetostrictive effect

Methodology Applied

Scientific EffectInverse magnetostrictive effect: Magnetostriction

Data Source

PatentUS20250334653A1Magnetic sensor

Publication Date: 2025.10.30 TDK CORP

AI summary

A magnetic sensor includes a magnetic sensor chip that includes a magnetoresistive effect element and a sealed part. The magnetoresistive effect element includes a free layer and a pinned layer. The sealed part has a first surface and a second surface, which is opposite the first surface. The shape of the sealed part in the plan view from the first surface side is substantially quadrilateral. The substantially quadrilateral shape has a first side and a second side, which are substantially parallel to each other. In the plan view, from the first surface side of the sealed part, the magnetization direction of the pinned layer, in a state in which the external magnetic field is not applied on the magnetoresistive effect element, is inclined with respect to an approximately straight line found through the least squares method using a plurality of points arbitrarily set on the first side.