Laminated Ferromagnetic Alloy Core for Micro-Inductors
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Solution Overview
Problem
High-frequency micro-fabricated inductors and transformers face increased power losses due to the skin effect, which is exacerbated by the need for thinner magnetic films that reduce the cross-sectional area and inductance, while maintaining sufficient magnetic material volume is challenging.
Innovation Solution
The method involves sequential electro-deposition and chemical mechanical polishing (CMP) steps over a patterned thick photoresist film to form a laminated ferromagnetic alloy core with multiple contiguous thin laminations separated by dielectric material, reducing eddy current losses without the need for new photoresist deposition for each lamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If thinner magnetic films are plated to reduce skin effect power loss, then power loss is reduced, but the cross-sectional area of the magnetic core is reduced, which linearly reduces the inductance
Solution Approach 1:
The magnetic core is divided into multiple thin lamination layers (e.g., 4-10 layers) stacked together. Each layer is separated by an insulating layer, creating a segmented structure that reduces eddy current losses while maintaining sufficient total cross-sectional area for inductance. The segmentation allows the magnetic path to be constructed from multiple thin films rather than a single thick film.
Solution Approach 2:
The patent transitions from a single-layer magnetic film to a multi-layer stacked structure, adding the vertical dimension (stacking direction) to the magnetic core construction. This allows the horizontal cross-sectional area to be maintained while the vertical thickness is distributed across multiple thin layers, reducing skin effect losses.
2Volume of moving object
If multiple thin magnetic films are plated to maintain sufficient magnetic material volume, then inductance is preserved, but eddy current losses increase at high frequency
Solution Approach 1:
The magnetic core is divided into multiple thin lamination layers (e.g., 4-10 layers) stacked together. Each layer is separated by an insulating layer, creating a segmented structure that reduces eddy current losses while maintaining sufficient total cross-sectional area for inductance. The segmentation allows the magnetic path to be constructed from multiple thin films rather than a single thick film.
Solution Approach 2:
The patent creates a composite magnetic core structure consisting of multiple magnetic alloy layers (such as nickel-iron or cobalt-iron alloys) alternated with thin insulating layers. This composite structure combines the magnetic properties needed for inductance with the electrical insulation needed to reduce eddy current losses.
3Volume of moving object
If thick photoresist is used to provide high volume of magnetic material, then magnetic material volume is maintained, but the process complexity increases due to multiple electro-deposition and CMP steps
Solution Approach 1:
A thick photoresist layer is deposited and patterned first, creating deep cavities that will contain the magnetic material. This preliminary action establishes the magnetic core volume and shape before the magnetic material is deposited, allowing subsequent electro-deposition steps to fill the predetermined cavities efficiently.
Solution Approach 2:
The magnetic core is divided into multiple thin lamination layers (e.g., 4-10 layers) stacked together. Each layer is separated by an insulating layer, creating a segmented structure that reduces eddy current losses while maintaining sufficient total cross-sectional area for inductance. The segmentation allows the magnetic path to be constructed from multiple thin films rather than a single thick film.
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 approach maintains sufficient magnetic material volume while reducing eddy current losses at high frequencies, preserving the inductance of micro-fabricated inductors and transformers by effectively managing the magnetic core's thickness and area.
Implementation Method 1
sequential electro-deposition, planarization and insulator deposition steps are performed over a patterned thick photoresist film to form a laminated ferromagnetic alloy core
Implementation Method 2
sequential electro-deposition, planarization and insulator deposition steps
Data Source
AI summary
A plurality of sequential electro-deposition, planarization and insulator deposition steps are performed over a patterned thick photoresist film to form a laminated ferromagnetic alloy core for micro-fabricated inductors and transformers. The use of a plurality of contiguous thin laminations within deep patterns on non-removable photoresist film provides sufficient volume of magnetic film in, for example, high frequency applications, and reduces eddy current loss at high frequency.