Surface Mount Inductor Layout for Lower DC Resistance
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Solution Overview
Problem
Existing surface mount inductors experience an increase in direct current resistance due to long current flow paths between feeder end portions and mount boards, and the deformation required to expose feeder end portions perpendicular to the mount surface compromises conformance quality.
Innovation Solution
A surface mount inductor design where the coil axis is parallel to the mount surface, allowing feeder end portions to be exposed without deformation, with external terminals formed only on the non-pressed surface to reduce direct current resistance and enhance withstanding voltage and ESD resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the feeder end portions are exposed from the side surfaces of the compact, then the inductor can be mounted on the mount surface, but the current flow path becomes long and direct current resistance increases
Solution Approach 1:
The patent inverts the conventional orientation by exposing feeder end portions from the mount surface instead of from the side surfaces. This reversal of the exposure location shortens the current flow path through the external terminal, directly reducing DC resistance while maintaining mounting capability.
2Object-affected harmful factors
If the feeder end portions are exposed from the mount surface, then the current flow path is shortened, but the coil must be deformed considerably which compromises conformance quality
Solution Approach 1:
The patent employs asymmetric design by orienting the coil axis parallel to the mount surface rather than perpendicular to it. This asymmetric orientation allows feeder end portions to be exposed from the mount surface without requiring considerable deformation of the coil, thus maintaining conformance quality while shortening the current flow path.
3Volume of moving object
If external terminals are formed on the pressed surface, then the inductor structure is compact, but the withstanding voltage and ESD resistance are reduced
Solution Approach 1:
The patent applies local quality differentiation by forming external terminals only on the non-pressed surface of the compact. This localized placement on the non-pressed surface (which has different mechanical and electrical properties) enhances withstanding voltage and ESD resistance compared to forming terminals on the pressed surface, while maintaining compact overall dimensions.
Data Source
AI summary
A surface mount inductor includes a coil including a wound portion and a feeder end portion drawn out from the wound portion, a compact that contains a magnetic powder and that encapsulates the coil, and an external terminal disposed on the compact and connected to the coil. The compact has surfaces including two pressed surfaces, opposing each other in a direction of an axis of the wound portion and formed by being pressed in the direction of the axis, and a non-pressed surface, adjacent to the two surfaces and not pressed. The coil is disposed so that the axis of the wound portion is parallel to a mount surface of the compact. The mount surface is included in the non-pressed surface, the feeder end portion is exposed from the mount surface, and the external terminal is formed on only the non-pressed surface and connected to the feeder end portion.