Wire-Wound Inductor With Chromium Oxidized Core
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Solution Overview
Problem
There is a need for wire-wound inductors that offer improved inductor characteristics while supporting high-density mounting and low-height mounting on circuit boards, particularly for smaller, thinner electronic devices.
Innovation Solution
A wire-wound inductor design featuring a core member with a pillar-shaped core and flange parts, a coil conductive wire wound around the core, and an insulation member made of magnetic powder-containing resin, where the core is composed of soft magnetic alloy grains with an oxidized layer containing chromium, providing enhanced magnetic properties and reduced dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the inductor size is reduced for high-density mounting, then mounting density is improved, but inductor characteristics deteriorate
Solution Approach 1:
The patent employs a composite core structure combining ferrite material with specific magnetic powder compositions to achieve high magnetic permeability and saturation flux density in a compact form. The insulation member also uses composite resin material containing magnetic powder, creating a multi-material system that maintains inductor performance while reducing overall size for high-density mounting
Solution Approach 2:
The patent optimizes key parameters including chromium content (2-15% by weight) in the soft magnetic alloy, oxidized layer thickness (5-50 nm), and core dimensions (3-5 mm length/width, 1.5 mm or less height) to achieve the desired balance between compact size and inductor characteristics. The magnetic permeation ratio is controlled at 10 or more while saturated magnetic flux density is maintained at 1.2 T or more
2Length of stationary object
If the inductor height is reduced for low-height mounting, then mounting height is improved, but magnetic properties deteriorate
Solution Approach 1:
The patent applies different material compositions and structures to different parts of the inductor: the core uses soft magnetic alloy grains with oxidized layers for high magnetic permeability, while the insulation member uses resin with magnetic powder for localized magnetic support. This localized optimization allows reduced height while maintaining overall magnetic performance
Solution Approach 2:
The patent compensates for reduced height by optimizing the planar dimensions and internal magnetic flux distribution. The pillar-shaped core with flange parts creates specific magnetic flux paths that maintain effective magnetic properties despite the constrained height dimension, effectively redistributing magnetic functionality across available dimensions
3Reliability
If chromium content in soft magnetic alloy is increased, then oxidized layer quality is improved, but manufacturing cost increases
Solution Approach 1:
The patent establishes an optimal chromium content range of 2-15% by weight in the soft magnetic alloy, balancing oxidized layer quality with manufacturing cost. This parameter optimization ensures sufficient chromium for forming protective and magnetic oxidized layers while avoiding excessive chromium addition that would unnecessarily increase material cost
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 design achieves high inductance values and direct-current bias capabilities while minimizing size and height, enabling effective high-density and low-height mounting on circuit boards, thus contributing to the size reduction and functional enhancement of electronic devices.
Implementation Method 1
each soft magnetic alloy grain has an oxidized layer of the soft magnetic alloy grain on its surface, the oxidized layer contains more chromium than does the soft magnetic alloy grain, and grains are bonded together via their oxidized layers
Implementation Method 2
a coil conductive wire wound around the core of the core member
Data Source
AI summary
A small wire-wound inductor has a drum-shaped core member constituted by an assembly of soft magnetic alloy grains, a coil conductive wire wound around the core member, a pair of terminal electrodes connected to the terminals of the coil conductive wire, and an outer sheath member covering the wound coil conductive wire and constituted by a magnetic powder-containing resin having a specified magnetic permeation ratio, wherein the soft magnetic alloy grains are fixedly bonded together via oxidized layers, and the core member contains 2 to 15 percent by weight of chromium (Cr).