Surface Mount Inductor Resin Coating Insulation
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Solution Overview
Problem
Surface mount inductors face challenges in ensuring sufficient withstand voltage due to the use of metal magnetic powders with poor insulating properties in their molded bodies.
Innovation Solution
A surface mount inductor design featuring a coil with winding and extension portions embedded in a molded body containing metal magnetic powder, where a resin coating is applied excluding terminal regions, and the outer terminals are positioned such that their width is between 55% and 95% of the width between ridges, ensuring proper insulation and connection strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a molded body containing metal magnetic powder is used, then the inductor can be manufactured with good magnetic properties, but the insulating property is poor resulting in insufficient withstand voltage
Solution Approach 1:
The invention divides the molded body surface into different functional regions: insulating regions covered with resin coating and conductive regions (outer terminals) exposed for electrical connection. This segmentation allows the insulating property to be enhanced in appropriate areas while maintaining electrical connectivity where needed, resolving the contradiction between magnetic functionality and insulation performance.
Solution Approach 2:
The resin coating is selectively applied to specific regions of the molded body surface (excluding regions with outer terminals), creating local differences in insulating properties. This local quality approach ensures high insulation where required while preserving electrical connection capability at terminal areas, directly addressing the withstand voltage issue caused by the inherently poor insulating property of metal magnetic powder.
2Strength
If the outer terminal width is increased to improve connection strength, then the electrical connection is enhanced, but the insulating distance is reduced lowering withstand voltage
Solution Approach 1:
The invention optimizes the width parameter of outer terminals to a specific range (0.5mm to 1.5mm) and controls the spacing between terminals (1.0mm to 2.0mm). These parameter changes balance the competing requirements: sufficient terminal width for strong electrical connection while maintaining adequate insulation distance for high withstand voltage, thus resolving the contradiction between connection strength and insulating performance.
Data Source
AI summary
A surface mount inductor includes a coil including a winding portion and extension portions that extend from the outer circumference of the winding portion, a molded body which contains a metal magnetic powder and in which the coil is embedded, and outer terminals. The molded body is a rectangular parallelepiped. Each end portion in the longitudinal direction of the principal surface has an outer terminal connected to the extension portion. A resin coating is formed on the molded body except regions in which the outer terminals are provided, and W1 is less than W0, where the width between ridges opposite to each other in a lateral direction of the principal surface is denoted as W0 and the width of each outer terminal in the lateral direction is denoted as W1, and neither end in the width direction of each outer terminal is in contact with the ridges.