Surface-Mount Inductor Symmetrical Coil Winding Axis
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Solution Overview
Problem
Conventional surface-mount inductors face issues with thermal and mechanical stresses, asymmetrical coil shapes, and contact resistance due to welded metal pieces and orthogonal winding axes, which complicate manufacturing and affect electrical characteristics.
Innovation Solution
A surface-mount inductor with a symmetrical coil wound using a rectangular wire sealed with resin and filler, where the winding axis is parallel to the mounting face, and lead ends are used as external terminals, reducing mechanical and thermal stresses and eliminating contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If coil ends are welded to metal pieces, then external terminals are formed, but thermal and mechanical stresses occur at contact portions and contact resistance arises
Solution Approach 1:
The patent merges the coil lead wire and external terminal into a single continuous structure. The coil is wound with a wire whose both ends serve simultaneously as the coil winding and the external terminal, eliminating the separate welding connection between coil ends and metal pieces. This integration removes the contact interface that causes contact resistance and thermal/mechanical stress.
2Ease of manufacture
If winding axis is orthogonal to wide surface of rectangular wire, then coil is formed, but inner and outer diameters are exposed to mechanical stress during winding
Solution Approach 1:
The patent deliberately adopts an asymmetrical winding configuration where the winding axis is parallel to the wide surface of the rectangular wire rather than orthogonal. This asymmetric orientation changes the stress distribution during winding, preventing concentrated mechanical stress on the inner and outer diameters while still forming a functional coil structure.
3Ease of manufacture
If one lead end goes from bottom side to bottom and other lead end goes from upper side to bottom, then coil is formed, but asymmetrical shape requires polarity marking
Solution Approach 1:
The patent intentionally creates a symmetrical coil structure where both lead ends emerge from the same side (bottom side) rather than different sides. This symmetrical configuration makes the inductor electrically identical from either terminal perspective, eliminating the need for polarity marking and reducing device complexity.
Data Source
AI summary
A surface-mount inductor having a molded body which includes a coil formed by winding a rectangular wire and sealed by sealant having resin and filler, a surface of the molded body being a mounting face, the coil includes: first rolls wound in two-roll arrangement along the winding axis, the ends of the wire being placed at the outermost turn; and second rolls wound in positions adjacent to the first rolls and oppositely shifted along the winding axis, the inner diameter being equal to or larger than the outer diameter of the first rolls, the ends of the wire are brought out from the outermost turn of the second rolls as lead ends which are sealed in a manner that the winding axis is parallel with the mounting face and the lead ends are partially exposed at the mounting face, as well as a method for manufacturing the same.