Surface Mount Inductor Terminal Plating to Prevent Solder Absorption
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Solution Overview
Problem
Conventional surface mount inductors experience reliability issues and deterioration in characteristics due to solder absorption and contact with the molded body, leading to unnecessary stress and degradation of Q values during mounting.
Innovation Solution
A surface mount inductor design featuring a molded body with a composite material and a metal plate structure where the external terminal has a plating layer on one side facing away from the molded body, preventing solder absorption and maintaining good solder wettability, while avoiding plating on the side facing the molded body to reduce stress and improve reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a plating layer is applied to the lead portion to improve solder wettability, then solder wettability is improved, but solder is absorbed between the molded body and the external terminal causing unnecessary load and reliability reduction
Solution Approach 1:
The plating layer is applied selectively only to the soldering surface of the external terminal, while the surface facing the molded body is left unplated. This local differentiation allows solder wettability to be improved at the soldering interface without causing solder absorption issues at the molded body interface.
2Ease of operation
If the lead is bent to form an external terminal, then the terminal structure is formed, but solder is absorbed between the molded body and the external terminal applying unnecessary load
Solution Approach 1:
The external terminal has different surface treatments at different locations: the surface facing the molded body is left unplated to prevent solder absorption, while the soldering surface has plating for good solder wettability. This local quality differentiation resolves the conflict between terminal structure formation and stress resistance.
3Productivity
If solder contacts the molded body, then mounting is completed, but the characteristics such as Q value deteriorate
Solution Approach 1:
The plating layer is extracted or removed from the surface of the external terminal that faces the molded body. This extraction prevents solder from being absorbed between the molded body and the terminal, thereby preventing Q value deterioration while still allowing the mounting process to proceed.
Data Source
AI summary
A surface mount inductor includes a molded body made of a composite material containing magnetic powder, and a metal plate including a first metal plate portion embedded in the molded body and a second metal plate portion extending from the first metal plate portion to an outside of the molded body. The second metal plate portion is extended from a side surface or mounting surface side of the molded body, is arranged along the molded body with a bent portion, and forms an external terminal arranged at least on the mounting surface side of the molded body. The external terminal includes a plating layer on a surface on an opposite side from a surface facing the molded body, and does not include a plating layer on the surface facing the molded body.