Coil Component With Fe-Based Magnetic Powder for Low AC Resistance
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Solution Overview
Problem
Magnetic resonance circuits require coil components that maintain low effective AC resistance (Rac) even at large amplitude currents to prevent heating, as existing components experience increased Rac and decreased Q factor with higher current amplitudes.
Innovation Solution
A coil component with an Fe-based magnetic powder and binding agent, having a magnetic permeability of 5 or more and volume resistivity of 1.0×10^7 Ω·cm or more, along with a coil conductor, where the Fe-based magnetic powder has an average particle size (D50) of 5 μm or smaller, and optionally includes an insulator film with inorganic oxide and water-soluble polymer, and a terminal electrode with specific metals for improved adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional magnetic cores are used in magnetic resonance circuits with large amplitude currents, then the circuit can operate at resonant frequency, but the effective AC resistance increases and Q factor decreases causing heating
Solution Approach 1:
The patent applies parameter changes by optimizing the particle size of Fe-based magnetic powder to 5 μm or smaller (specifically 2 μm or smaller in preferred embodiments) and controlling volume resistivity to 1.0×10^7 Ω·cm or more (preferably 10^10 Ω·cm or more). These parameter optimizations reduce eddy current losses and maintain low effective AC resistance even when large amplitude currents of about 1 Arms or larger are passed through the coil component.
Solution Approach 2:
The patent employs composite materials by combining Fe-based magnetic powder with specific binding agents (cyclic siloxane or branched siloxane) to create a magnetic core that achieves both high magnetic permeability (5 or more) and high volume resistivity. This composite structure reduces eddy current losses while maintaining magnetic performance, thereby keeping effective AC resistance low under large current conditions.
2Power
If larger amplitude current is passed to increase power output, then magnetic resonance circuit performance improves, but heating occurs due to increased effective AC resistance
Solution Approach 1:
By changing the particle size parameter to 5 μm or smaller and volume resistivity to 1.0×10^7 Ω·cm or more, the patent reduces effective AC resistance, allowing large amplitude currents to be passed without excessive heating, thus enabling high power output while controlling temperature rise.
3Loss of energy
If Fe-based magnetic powder with smaller particle size is used, then effective AC resistance is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies a particle size of 5 μm or smaller (preferably 2 μm or smaller) which balances the reduction of effective AC resistance with manufacturability. This parameter range is sufficiently small to reduce eddy current losses while remaining achievable through conventional powder metallurgy processes.
Solution Approach 2:
The patent applies local quality by using Fe-based magnetic powder with specific surface properties and insulator films on particle surfaces. This localized treatment of powder particles reduces eddy current paths at the particle level while maintaining bulk magnetic properties, achieving low effective AC resistance without requiring extremely tight control over all manufacturing parameters.
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 effectively keeps Rac low and Q factor high even at large amplitude currents, reducing the rate of increase in Rac and maintaining performance, making it suitable for magnetic resonance circuits in wireless power transmission.
Implementation Method 1
the Fe-based magnetic powder having a volume resistivity of 1.0×10^7 Ω·cm or more... possible to keep the Rac low even when a large amplitude current is passed
Implementation Method 2
a magnetic core that contains an Fe-based magnetic powder and a binding agent and that has a magnetic permeability of 5 or more
Data Source
AI summary
A coil component including: a magnetic core that contains an Fe-based magnetic powder and a binding agent, the Fe-based magnetic powder having an insulator film and having a volume resistivity of 107 Ω·cm or more; and a coil conductor. The average particle size D50 of the Fe-based magnetic powder is 5 μm or smaller and the magnetic permeability of the magnetic core is 5 or more.