Magnetic Multilayer Sheet for Low Core Loss POL Converters
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Solution Overview
Problem
Conventional magnetic core materials for power inductors in medium to high power Point-of-Load (POL) converters face challenges in achieving low core loss density, high saturation magnetization, large permeability, and integration compatibility, especially at frequencies above 1 MHz, due to issues such as eddy current losses, manufacturing costs, and compatibility with semiconductor devices.
Innovation Solution
A dual-level magnetic laminate with a multilayer structure comprising thin isolated magnetic sublayers separated by insulating layers, where each sublayer is less than one micron thick, and the total magnetic thickness is greater than 5 microns, providing a high magnetic fraction and relative permeability above 20, suitable for use in POL converters and other power electronics applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional amorphous and nanocrystalline ribbons are used, then magnetic properties are maintained, but core loss increases due to thickness and low resistivity
Solution Approach 1:
The magnetic core is divided into multiple thin magnetic layers (each less than one micron thick) separated by insulating layers. This segmentation reduces eddy current paths within each magnetic layer while the insulating layers provide additional electrical isolation between layers, significantly reducing core loss at high frequencies
Solution Approach 2:
The patent creates a composite structure combining thin magnetic layers with insulating layers. The magnetic layers provide the necessary magnetic properties while the insulating layers (such as oxide, nitride, or carbide layers) provide electrical isolation, creating a composite material that achieves low core loss without complex manufacturing processes
2Adaptability or versatility
If bulk power ferrites are used, then high frequency performance is achieved, but integration with semiconductor devices is difficult due to size and susceptibility to fracture
Solution Approach 1:
The ferrite material is segmented into thin layers that are less susceptible to fracture. The insulating layers between magnetic layers provide stress relief and prevent crack propagation, making the overall structure more robust and suitable for integration with semiconductor devices while maintaining high frequency performance
Solution Approach 2:
The patent uses thin film technology to create magnetic layers that are flexible and adaptable to various substrate shapes and sizes. These thin magnetic films can be deposited on flexible substrates or conformal surfaces, enabling better integration with semiconductor devices compared to rigid bulk ferrites
3Loss of energy
If magnetic films are made thinner to reduce eddy current losses, then core loss decreases, but manufacturing complexity increases due to vacuum melting and chemical etching processes
Solution Approach 1:
The insulating layers are formed in-situ during the magnetic layer deposition process, eliminating the need for separate chemical etching or vacuum melting steps. The insulating material is deposited concurrently with or between magnetic layers using standard sputtering or evaporation techniques, simplifying the manufacturing process while achieving the necessary thin layer structure for low eddy current loss
4Power
If total magnetic thickness is increased to meet power application requirements, then power handling capability improves, but eddy current losses increase
Solution Approach 1:
The total magnetic thickness is segmented into multiple thin magnetic layers separated by insulating layers. This allows the overall magnetic core to have sufficient thickness for power handling while each individual magnetic layer remains thin enough to minimize eddy current losses. The insulating layers interrupt eddy current paths between layers, enabling the structure to scale in thickness without proportionally increasing losses
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
The solution achieves lower core loss, higher permeability, and flexibility, enabling compatibility with printed circuit board integration while meeting the thickness requirements for medium to high power applications, thus addressing the limitations of existing materials.
Implementation Method 1
Conventional amorphous and nanocrystalline ribbons are too lossy in the MHz range due to their thickness (generally around about 18 μm) and their low resistivity, both of which can promote eddy current losses
Implementation Method 2
Each of the isolated magnetic sublayers comprises at least one of a single magnetic metal element, a magnetic alloy, or a magnetic nano-granular film
Data Source
AI summary
A multilayer magnetic sheet is described which comprises a plurality of stacked magnetic component layers separated by first electrically insulating layers. Each of the plurality of magnetic component layers comprises a plurality of isolated magnetic sublayers having a magnetic layer thickness of less than one micron. The multilayer magnetic sheet has a magnetic fraction between about 5% and about 80%; a total magnetic thickness of greater than or equal to 5 microns; and a relative composite permeability of greater than about 20.