Common Mode Filter Coil Layout for Lower Inter-Wire Capacitance
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Solution Overview
Problem
Inter-wire capacitance between adjacent coil patterns in common mode filters with stacked conductor layers affects high-frequency characteristics.
Innovation Solution
The design incorporates non-overlap sections in the outermost and innermost turns of the coil patterns, reducing inter-wire capacitance by ensuring these turns do not overlap, and optionally using dummy patterns to facilitate coil pattern formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If coil patterns are stacked closely to improve filter compactness, then device size is reduced, but inter-wire capacitance increases degrading high-frequency characteristics
Solution Approach 1:
The outermost and innermost turns of adjacent coil patterns are segmented into non-overlapping sections, creating intentional gaps that reduce inter-wire capacitance. This segmentation allows the filter to maintain compact stacking while preventing harmful capacitive coupling at critical terminal regions.
Solution Approach 2:
The non-overlap sections are applied locally only to the outermost and innermost turns where terminal electrodes connect, rather than throughout the entire coil pattern. This localized approach reduces inter-wire capacitance at critical points while maintaining overlapping structure in intermediate turns for compactness and inductance.
2Reliability
If non-overlap sections are added to reduce inter-wire capacitance, then high-frequency characteristics improve, but coil pattern complexity increases
Solution Approach 1:
The non-overlap sections create an asymmetric pattern where the outermost and innermost turns differ from intermediate turns. This asymmetric design is simple to implement using standard PCB trace routing or etching processes, adding minimal complexity while effectively reducing inter-wire capacitance at terminal regions.
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 enhances high-frequency characteristics by minimizing insertion loss and improving coupling between coil patterns, thereby optimizing the common mode filter's performance.
Implementation Method 1
inter-wire capacitance between adjacent coil patterns has influence on high-frequency characteristics
Data Source
AI summary
Disclosed herein is a common mode filter that includes: a plurality of conductor layers stacked with an insulating layer interposed therebetween, the plurality of conductor layers including at least first and second conductor layers; and first, second, third, and fourth terminal electrodes. The first conductor layer has a spiral-shaped first coil pattern having an outer peripheral end connected to the first terminal electrode and an inner peripheral end connected to the third terminal electrode. The second conductor layer has a spiral-shaped second coil pattern having an outer peripheral end connected to the second terminal electrode and an inner peripheral end connected to the fourth terminal electrode. The outermost turn of the first coil pattern has a first non-overlap section that is wound at least by ¼ turn without overlapping the outermost turn of the second coil pattern.