Multilayer Coil Component Electrodes for Low Resistance and Stress Relief
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Solution Overview
Problem
The challenge is to design coil components with external electrodes that minimize DC resistance and are resistant to stress, particularly when these electrodes are provided on only one face of a coil component, as this configuration can lead to stress-related issues during mounting on a substrate.
Innovation Solution
A coil component with a magnetic base body, a conductor, and external electrodes comprising multiple layers: a first electrode layer with a high metal filling rate, a second electrode layer with a lower metal filling rate, and a third electrode layer covering both, where the second electrode layer has a smaller dimension perpendicular to the substrate, reducing stress and DC resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If each external electrode is provided on only one face of the coil component, then the size of the coil component is reduced, but stress generated in or around the external electrodes becomes a serious problem
Solution Approach 1:
The external electrodes extend from the first face through to the second face of the magnetic base body, utilizing the thickness dimension of the component. This through-electrode configuration allows the electrodes to span the entire height of the component, distributing mechanical stress along the vertical dimension rather than concentrating it at a single face, thereby reducing stress while maintaining compact size.
Solution Approach 2:
The external electrodes are constructed as multi-layer composite structures with different metal materials having different physical properties. The first electrode layer contains a first metal material, the second electrode layer contains a second metal material, and the third electrode layer contains a third metal material. These layers have different thermal expansion coefficients and mechanical properties, allowing the composite structure to accommodate thermal and mechanical stress more effectively than a single-material electrode.
2Reliability
If the external electrodes are made with sufficient thickness to ensure low DC resistance, then DC resistance is reduced, but the stress problem in single-face electrode configuration is exacerbated
Solution Approach 1:
The multi-layer electrode structure uses different metal materials with different properties to simultaneously achieve low DC resistance and stress resistance. The first metal material provides primary conductivity, while the second and third metal materials with different thermal and mechanical properties reduce stress concentration and accommodate thermal expansion, allowing sufficient electrode thickness without exacerbating stress problems.
Solution Approach 2:
By extending electrodes through the entire thickness of the magnetic base body from first face to second face, the stress is distributed along the vertical dimension. This allows the electrodes to have sufficient cross-sectional area for low DC resistance while the through-length provides stress relief pathways, decoupling the thickness requirement for conductivity from the stress concentration problem.
3Stress or pressure
If the external electrodes are made with sufficient thickness to cope with stress, then stress resistance is improved, but DC resistance increases
Solution Approach 1:
The multi-layer structure with different metal materials allows optimization of each layer's function. The first electrode layer can be designed with high conductivity material for low DC resistance, while the second and third layers with different mechanical properties provide stress resistance. This composite approach achieves both low DC resistance and stress resistance without requiring uniform thickness increase throughout the entire electrode structure.
Data Source
AI summary
A coil component includes a base body formed of metal magnetic particles; a conductor provided inside and/or on the base body; and an external electrode electrically connected to the conductor. The external electrode includes first, second, and third electrode layers. The first electrode layer contains a metal material and is provided in a first predetermined area of a first face of the base body. The second electrode layer is provided in a second predetermined area of a second face and contains a metal material at a metal filling rate lower than that of the first electrode layer. The third electrode layer covers the first electrode layer and the second electrode layer and extends over the first predetermined area of the first face and the second predetermined area of the second face of the base body.