Laminated Inductor with Cr-Bound Oxide Films
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Solution Overview
Problem
Conventional laminated inductors with magnetic portions made of FeCrSi alloy face challenges in achieving high inductance characteristics due to the need for increased volume resistivity, which is compromised by the addition of glass, leading to reduced filling ratios and larger particle diameters that increase surface roughness and thickness, making it difficult to maintain both magnetic characteristics and insulation quality, especially in thinner designs.
Innovation Solution
A laminated inductor structure comprising multiple magnetic layers with small diameter magnetic alloy particles (average diameter of 4 μm or smaller) bound by oxide films, including Cr and Al, and a resin material, which allows for reduced thickness without compromising magnetic characteristics and insulation quality, by optimizing the arrangement and composition of the magnetic alloy particles and oxide films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass is added into magnetic alloy powder to increase volume resistivity, then insulation resistance is improved, but filling ratio is reduced and particle diameter must be increased which enlarges surface roughness and thickness
Solution Approach 1:
The patent changes the particle diameter parameter from conventional large sizes to 10 μm or smaller, which fundamentally alters the relationship between insulation resistance and thickness. Small particles provide larger surface area for oxide film formation, improving insulation without requiring glass addition, while also reducing the thickness needed to achieve the same insulation resistance level.
Solution Approach 2:
The patent creates a composite structure where magnetic alloy particles are bound by oxide films formed on their surfaces. This oxide film composite provides the insulation function traditionally achieved by adding glass, but without the negative effects of glass addition on filling ratio and particle size requirements.
2Reliability
If large diameter magnetic alloy particles are used to maintain magnetic permeability, then magnetic characteristics are improved, but surface roughness increases and thickness is enlarged
Solution Approach 1:
The patent inverts the conventional approach by using small particle diameter (10 μm or smaller) particles instead of large particles. The high magnetic permeability is achieved not through large particle size but through the dense packing and oxide film characteristics of small particles, which reduce surface roughness and overall thickness while maintaining magnetic performance.
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 enables a laminated inductor with reduced thickness while maintaining high magnetic and insulation qualities, achieving lower direct current resistance and improved quality factors, suitable for power devices handling large electric currents.
Implementation Method 1
a first oxide film binding the magnetic alloy particles together and containing a first component including one or both of Cr and Al
Implementation Method 2
magnetic alloy particles having an average particle diameter of 4 μm or smaller
Data Source
AI summary
One object is to provide a laminated inductor having a reduced thickness without reduction in the magnetic characteristic and the insulation quality. The laminated inductor includes a first magnetic layer, an internal conductor, second magnetic layers, third magnetic layers, and a pair of external electrodes. The first magnetic layer includes three or more magnetic alloy particles arranged in the thickness direction and an oxide film binding the magnetic alloy particles together and containing Cr. The three or more magnetic alloy particles have an average particle diameter of 4 μm or smaller. The internal conductor includes a plurality of conductive patterned portions electrically connected to each other via the first magnetic layer. The second magnetic layers are composed of magnetic alloy particles and disposed around the conductive patterned portions. The third magnetic layers are composed of magnetic alloy particles and disposed so as to be opposed to each other in thickness direction.