Multilayer Coil Structure for Crack Diversion and Split Prevention
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Solution Overview
Problem
Conventional multi-layer coil components are prone to coil splitting when a crack is generated due to bending stresses in the substrate, as the crack tends to propagate parallel to the layers of the element body.
Innovation Solution
A multi-layer coil component design that includes a fragile portion in the layer through which the lead conductor penetrates, positioned closer to the external electrode than the coil, to divert the crack propagation away from the coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the element body has a multi-layer stacking structure with the coil provided inside, then the coil component achieves compact design and efficient space utilization, but bending stresses generated when the mounted substrate is bent cause cracks to propagate parallel to the layers, leading to coil splitting
Solution Approach 1:
The patent introduces fragile portions (through-holes) in advance within the magnetic layers at predetermined locations. These pre-positioned weak points are designed to intercept and arrest crack propagation before it reaches the coil, thereby preventing coil splitting while maintaining the compact multi-layer structure
Solution Approach 2:
The fragile portions act as intermediary elements between the external mounting surface and the coil. When cracks propagate from the mounting surface due to bending stresses, these fragile portions serve as crack arrestors that stop the crack progression, protecting the coil from damage while allowing the multi-layer compact design to be maintained
2Reliability
If the external electrodes continuously extend from the end surfaces to the mounting surface, then electrical connection is achieved, but the tip position of the external electrode becomes a stress concentration point where cracks are likely to initiate and propagate toward the coil
Solution Approach 1:
The fragile portions are positioned between the external electrodes and the coil to serve as crack arrestors. When cracks initiate from the external electrode tips due to stress concentration, these fragile portions intercept the crack propagation path, preventing cracks from reaching the coil while maintaining electrical connectivity
Data Source
AI summary
In the multi-layer coil component, the hole portion is provided in the vicinity of the side surface of the element body, and the distance from the tip position of the external electrode to the hole portion is shorter than the distance from the tip position of the external electrode to the coil. Therefore, when a crack is generated starting from the tip position of the external electrode on the mounting surface, the crack progress toward the hole portion located at a distance closer than the coil. Therefore, in the multi-layer coil component, splitting of the coil due to the crack can be prevented.