Common Mode Choke Coil with Differential Surface Roughness
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Solution Overview
Problem
Conventional common mode choke coils experience variations in impedance values due to the joining state of the magnetic core and plate, particularly warping during the sintering process, leading to inconsistent performance.
Innovation Solution
A common mode choke coil design with a magnetic core and flange parts, where the magnetic plate has joining parts with smaller surface roughness than the opposing parts, and trenches to reduce warping, along with an adhesive mixed with magnetic powder for improved joining strength and inductance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the magnetic core and magnetic plate are joined with an adhesive, then the assembly is formed, but variation in impedance value occurs due to joining state and warping during sintering
Solution Approach 1:
The magnetic plate is designed with different surface roughness at different locations: the joining parts have smaller surface roughness (Ra 0.1-1.0 μm) for precise adhesive bonding, while the opposing part has larger surface roughness (Ra 1.0-3.0 μm) to prevent warping. This local differentiation resolves the contradiction by optimizing each region for its specific function.
Solution Approach 2:
The surface roughness is controlled during the green sheet formation stage, before sintering and assembly. By pre-establishing the appropriate surface characteristics, the magnetic plate maintains dimensional stability during subsequent sintering and adhesive joining processes, preventing warping and impedance variation.
2Ease of manufacture
If sintered bodies are used for the magnetic core and magnetic plate, then the components are formed, but warping occurs during sintering causing impedance variation
Solution Approach 1:
The magnetic plate has non-uniform surface roughness: the opposing part has larger roughness (Ra 1.0-3.0 μm) that acts as a stress distribution mechanism during sintering, preventing warping, while the joining parts maintain smaller roughness for precise bonding. This local differentiation stabilizes the component composition during sintering.
3Ease of manufacture
If the magnetic plate has uniform surface roughness, then manufacturing is simplified, but warping occurs during sintering
Solution Approach 1:
The magnetic plate is designed with spatially varying surface roughness: the opposing part has larger roughness (Ra 1.0-3.0 μm) to prevent warping during sintering, while the joining parts have smaller roughness (Ra 0.1-1.0 μm) for precise adhesive bonding. This local differentiation simultaneously achieves warping control and manufacturing feasibility.
Solution Approach 2:
The surface roughness parameter is deliberately varied across different regions of the magnetic plate. By changing the roughness parameter from small (joining parts) to large (opposing part), the design achieves both dimensional stability during sintering and precise adhesive bonding capability.
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 configuration results in a choke coil with high impedance and minimal variation, reducing warping and maintaining stability in inductance values, even when the magnetic plate is slightly displaced.
Implementation Method 1
a magnetic plate joined to the pair of flange parts with an adhesive
Implementation Method 2
The magnetic core and the magnetic plate can be obtained by mixing a binding agent with ferrite powder, and pressing and sintering the mixture thereof
Data Source
AI summary
An object of the present disclosure is to provide a common mode choke coil with high impedance and small variation. A common mode choke coil includes magnetic core having winding core part and a pair of flange parts provided on opposite ends of winding core part, external electrodes formed on each of flange parts, a pair of windings wound on winding core part, with each of the ends being drawn out and joined to one of external electrodes, and magnetic plate joined to the pair of flange parts with adhesive. Magnetic plate has joining parts joined to flange parts and opposing part opposing winding core part, and surface roughness of joining parts is smaller than surface roughness of opposing part.