Magnetic Isolator with Segmented Nanocrystalline Islands
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Magnetic isolators in NFC devices face challenges with eddy current losses due to metal surfaces, particularly when using nanocrystalline soft magnetic materials, as they can form continuous electrical paths and deform over time, leading to increased eddy current losses.
Innovation Solution
A magnetic isolator comprising a dielectric film with a layer of electrically-conductive soft magnetic material featuring substantially coplanar islands separated by a network of interconnected gaps, which are partially filled with a thermoset dielectric material to suppress eddy currents induced by external magnetic fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If nanocrystalline soft magnetic material is used to shield carrier wave from metal surface, then magnetic field shielding performance is improved, but eddy current losses increase due to continuous electrical paths
Solution Approach 1:
The continuous nanocrystalline soft magnetic material layer is segmented into discrete islands separated by gaps. This segmentation breaks the continuous electrical paths that cause eddy currents, while the islands remain sufficiently dense and distributed to maintain magnetic field shielding performance. The gaps act as electrical insulators that prevent eddy current formation.
Solution Approach 2:
The magnetic isolator exhibits different properties in different regions: the islands provide high permeability for magnetic field concentration and shielding, while the gaps provide electrical insulation to suppress eddy currents. This spatial variation in material properties allows simultaneous achievement of magnetic shielding and eddy current suppression.
2Loss of energy
If flaked or cracked ribbon is used to reduce eddy current loss, then eddy current suppression is improved, but contact points form between flakes due to deformation, increasing eddy current losses
Solution Approach 1:
The gaps between magnetic islands are pre-filled with dielectric material during manufacturing, creating permanent electrical insulation before the isolator is installed in the device. This preliminary action prevents future contact between islands even when the isolator undergoes deformation during handling or operation, maintaining reliable eddy current suppression.
Solution Approach 2:
Dielectric material is introduced as an intermediary substance between the magnetic islands. This intermediary maintains permanent separation between conductive islands, preventing direct electrical contact that would create eddy current paths, while still allowing the magnetic islands to function effectively for field shielding.
3Loss of energy
If ferrite or magnetic ceramics are used as magnetic isolator, then eddy current loss is reduced, but permeability is low requiring higher thickness for efficient isolation
Solution Approach 1:
The magnetic isolator uses a composite structure combining nanocrystalline soft magnetic material islands with dielectric material gaps. The nanocrystalline material provides high permeability (superior to ferrite) for efficient magnetic field shielding, while the dielectric gaps provide electrical insulation to suppress eddy currents. This composite approach achieves both high permeability and low eddy current loss in a thin layer.
Solution Approach 2:
The invention changes the material parameter from conventional ferrite/ceramic to nanocrystalline soft magnetic material, which has inherently higher permeability. This parameter change allows achieving the same magnetic shielding effect with reduced thickness, while the segmented structure with dielectric gaps simultaneously suppresses eddy currents.
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 configuration reduces eddy current losses and maintains the magnetic field integrity, enhancing the read range of NFC devices by preventing contact points between islands and minimizing deformation-induced losses.
Implementation Method 1
eddy current induced within the layer of soft magnetic material when in the presence of applied external magnetic field
Implementation Method 2
the interconnected gaps are at least partially filled with a thermoset dielectric material
Implementation Method 3
An ideal high permeability magnetic isolator will concentrate the field in its thickness without making any difference in the normal magnetic field at its surface
Implementation Method 4
amorphous FeCuNbSiB alloys (e.g., those marketed by VACUUMSCHMELZE GmbH & Co. KG, Hanau, Germany, under the VITROPERM trade designation) are designed to transform into nanocrystalline material when annealed above 550° C.
Data Source
AI summary
A magnetic isolator includes a dielectric film having a layer of electrically-conductive soft magnetic material bonded thereto. The layer of electrically-conductive soft magnetic material comprises substantially coplanar electrically-conductive soft magnetic islands separated one from another by a network of interconnected gaps. The interconnected gaps are at least partially filled with a thermoset dielectric material. The network of interconnected gaps at least partially suppresses electrical eddy current induced within the layer of soft magnetic material when in the presence of applied external magnetic field. An electronic device including the magnetic isolator and a method of making the magnetic isolator are also disclosed.