Coil Device Terminal Segmentation for Solder Adhesion
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Solution Overview
Problem
Conventional surface mounting type coil devices face challenges with insufficient solder adhesion and bonding strength, particularly when reducing size and height, leading to potential disconnection and reduced product life.
Innovation Solution
The coil device incorporates a core with a winding and flange part, a coil wound on the core, an electrode film with a wire connecting part, and a metal terminal bonded to a terminal fitting part on the electrode film, allowing for separate soldering and improved bonding strength, with the metal terminal being fixed using solder or conductive adhesive, enhancing reliability and preventing disconnection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermocompression is applied to the metal terminal to bond the wire, then the wire connection is secure, but solder adhesion becomes difficult and bonding strength is insufficient
Solution Approach 1:
The patent divides the metal terminal into functionally distinct regions: a first surface for wire bonding (thermocompression) and a second surface for solder mounting. This segmentation allows each surface to be optimized for its specific function without interference, resolving the contradiction between wire bonding strength and solder adhesion.
Solution Approach 2:
The metal terminal exhibits different surface properties at different locations: the first surface is optimized for thermocompression bonding with appropriate roughness and composition, while the second surface is optimized for solder adhesion with suitable wettability and composition. This local quality differentiation enables both functions to perform optimally simultaneously.
2Volume of moving object
If the coil device size and height are reduced, then miniaturization is achieved, but the bonding area of the solder is insufficient and bonding strength reduces
Solution Approach 1:
The patent utilizes the vertical dimension by creating a protruding structure where the metal terminal extends beyond the coil assembly. This allows the solder bonding area to be positioned at a different height level, effectively increasing the available bonding area without increasing the planar footprint of the device.
Solution Approach 2:
The metal terminal is segmented into distinct functional zones with the second surface specifically dedicated to solder mounting. This separate bonding surface provides adequate solder area even in miniaturized devices, as it is spatially separated from the wire bonding region and can be optimized independently.
3Device complexity
If the wire edge is bonded directly to the metal terminal, then the structure is simple, but the mounting area is limited and reliability is reduced
Solution Approach 1:
The electrode film serves as an intermediary layer between the wire edge and the metal terminal. This intermediate layer provides a dedicated wire bonding surface (first surface) that is optimally positioned and configured, while also providing a separate second surface for solder mounting, thereby enhancing reliability without significantly increasing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the bonding strength and reliability of the coil device, preventing disconnection and extending product life, even when size and height are reduced, as demonstrated by improved performance in heat cycle tests.
Implementation Method 1
The wire edge may be electrically bonded and fixed to the wire connecting part of the electrode film by such as thermocompression
Implementation Method 2
the metal terminal may be suitably bonded to the electrode film at the terminal fitting part of the electrode film apart from the wire connecting part, by solder or a conductive adhesive
Data Source
AI summary
Provided is coil device 1 including: core 10 including winding core part 12 and flange parts 14a, 14a provided on both edges of winding core part 12, and coil part 30 including wires 31, 32 wound on winding core part 12. Electrode film 40, having wire connecting part 41 where wire edges 31a, 31b, 32a, 32b are connected, and formed on a surface of the flange parts 14a, 14a. Metal terminal 50 is connected to a terminal fitting part 42 formed on a surface of electrode film 40 at a place different from the wire connecting part. According to the invention, a coil device having a high reliability for bonding at mounting part can be provided.