Coil Terminal Structure for Low-Resistance Electrode Bonding
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Solution Overview
Problem
As wires become thinner and coil devices smaller, the contact area between the exposed portion and the electrode decreases, leading to increased contact resistance and reduced electrical reliability, bonding strength, and fixing strength between the electrode and the mounting board.
Innovation Solution
The coil device incorporates a lead portion with a terminal portion that includes an embedded portion and an exposed portion with a bent portion, extending along the electrode formation surface, which increases the contact area and surface area, thereby reducing contact resistance and enhancing bonding and fixing strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the coil device is made smaller with thinner wires, then the size of the coil device is reduced, but the contact area between the exposed portion and the electrode decreases
Solution Approach 1:
The exposed portion is configured to extend in a direction substantially perpendicular to the wire axis, creating a planar structure that increases contact area without increasing the overall volume of the coil device. This dimensional transformation allows the terminal portion to achieve larger electrode contact area while maintaining compact coil dimensions.
Solution Approach 2:
The exposed portion includes a bent portion that curves the wire path, allowing the terminal to wrap around or contact the electrode over a larger surface area. This curvature enables increased bonding interface between the exposed portion and electrode without proportionally increasing the linear dimensions of the component.
2Reliability
If the contact area between the exposed portion and the electrode is increased, then the contact resistance is reduced, but the structure becomes more complex
Solution Approach 1:
The exposed portion serves multiple functions simultaneously: it provides electrical connection to the electrode, ensures mechanical bonding strength, and maintains compact overall dimensions. This multi-functionality achieves improved electrical reliability without proportionally increasing structural complexity, as the same geometric configuration addresses multiple requirements.
3Strength
If the exposed portion is extended to increase contact area, then the bonding strength between exposed portion and electrode is improved, but the length of the lead portion increases
Solution Approach 1:
The terminal portion is designed with localized geometric features (bent portion and perpendicular extension) specifically at the electrode contact region, while the rest of the lead portion maintains its original compact configuration. This localized modification increases bonding strength at the critical interface without significantly increasing the overall length of the lead portion.
Data Source
AI summary
A coil device includes a core, a coil, and an electrode. The coil includes a winding portion disposed inside the core and a lead portion leading from the winding portion. The electrode is formed on an electrode formation surface of the core. The lead portion includes a terminal portion extending to the electrode formation surface. The terminal portion includes an embedded portion embedded inside the core and an exposed portion exposed from the electrode formation surface and connected to the electrode. The exposed portion includes a bent portion.