Multilayer Coil Component Structure to Prevent Cracking and Ferrite Erosion
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Solution Overview
Problem
The existing common mode noise filters face issues with base body cracking due to stress from substrate deflection and degradation of magnetic portions during sintering, primarily caused by the erosion of Si components in the non-magnetic layer.
Innovation Solution
A coil component with a multilayer structure comprising ferrite layers and a glass layer, where the outermost ferrite layers have specific Zn and Ni compositions to enhance strength and maintain sinterability, preventing erosion from Si components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the outermost layer is made of dielectric glass to provide insulation, then electrical insulation is improved, but base body strength deteriorates and cracking occurs due to stress
Solution Approach 1:
The patent uses a composite structure where a ferrite layer is formed on the outer surface of the glass layer. The glass layer provides electrical insulation while the ferrite layer provides mechanical strength and stress resistance. This composite material approach allows both electrical insulation and structural strength to coexist without compromising either property.
2Ease of manufacture
If Si component is added to the non-magnetic layer for sinterability, then sintering process is improved, but erosion of magnetic portions occurs during sintering
Solution Approach 1:
The patent introduces a non-magnetic layer containing Si component as an intermediary barrier between the glass layer and the magnetic layers. This non-magnetic layer acts as a protective buffer that facilitates sintering while preventing direct contact and erosion between the Si component and magnetic portions, thus resolving the contradiction between sinterability and magnetic layer integrity.
Solution Approach 2:
The patent segments the base body into distinct functional layers: a glass layer for insulation, a non-magnetic layer with Si component for sinterability, and magnetic layers for electromagnetic function. This segmentation allows each layer to perform its specific function without interfering negatively with other layers, particularly preventing Si-induced erosion of magnetic portions.
3Strength
If Zn content is increased in ferrite material to improve strength, then base body strength is improved, but sinterability deteriorates
Solution Approach 1:
The patent applies local quality by having different ferrite compositions in different layers. The ferrite layer formed on the outer surface of the glass layer has high Zn content (X/(X+Y) > 0.73) to provide strength and erosion resistance, while the internal magnetic layers have lower Zn content (X/(X+Y) ≤ 0.73) to maintain good sinterability. This spatial variation in composition allows both strength and sinterability requirements to be satisfied simultaneously.
Data Source
AI summary
A coil component includes a base body including a multilayer body in which a first ferrite layer, a second ferrite layer, a glass layer, a third ferrite layer, and a fourth ferrite layer are stacked in this order; a coil inside the glass layer; and an outer electrode on an outer surface of the base body and electrically connected to the coil. A ferrite material that constitutes the first, second, third and fourth ferrite layers contains X (X≥0) mol % of Zn in terms of ZnO and Y (Y≥0) mol % of Ni in terms of NiO, and X+Y>0, when the amounts of Fe, Zn, Cu, and Ni are respectively expressed in terms of Fe2O3, ZnO, CuO, and NiO, and the total amount of Fe2O3, ZnO, CuO, and NiO is 100 mol %.