Stepped Terminal Electrode for Coil Component Soldering
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Solution Overview
Problem
The existing surface-mount type coil components face issues with solder wettability and mounting failures due to the formation of a wide alloy layer between the wire and the terminal electrode, which inhibits the formation of a solder fillet and makes it difficult to cut and remove the wire after thermocompression bonding.
Innovation Solution
The coil component features a terminal electrode with a stepped surface, where the terminal portion is thermocompression-bonded only onto the upper stage surface, preventing a wide alloy layer formation and allowing easy wire removal, while the lower stage surface is not alloyed to enhance solder wettability and prevent solder fillet inhibition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the leading end section of the wire is aligned to the end portion of the terminal surface, then thermocompression bonding is achieved, but the alloy layer is formed over a wide area and plating thickness is reduced, inhibiting solder fillet formation
Solution Approach 1:
The terminal surface is divided into two distinct areas: a first terminal surface extending in the wire extending direction for thermocompression bonding, and a second terminal surface in the width direction for soldering. This segmentation allows easy thermocompression bonding alignment while preventing alloy layer intrusion into the soldering area, ensuring precise solder fillet formation.
2Reliability
If the wire is thermocompression-bonded at a position inward from the end portion of the terminal surface, then alloy layer formation is reduced, but the wire passes the terminal surface and requires removal, which becomes difficult if the plating film melts
Solution Approach 1:
The terminal electrode provides a dedicated first terminal surface for wire bonding and a separate second terminal surface for soldering. This segmentation allows the wire to be bonded without passing over the soldering area, making wire removal easy while preserving plating film integrity for soldering.
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 ensures reliable and easy wire removal and enhances solder wettability on the terminal surface, improving the electrical and mechanical connection reliability of the coil component during surface mounting.
Implementation Method 1
the wire end terminal electrode are connected in such that a leading end section of the wire is thermocompression-bonded on the terminal electrode. When the wire is thermocompression-bonded on the terminal electrode, a material (Cu) of the wire and a plating film (Ni and Sn) on a surface of the terminal electrode react with each other to form an alloy layer.
Implementation Method 2
The first surface has a stepped surface including an upper stage surface and a lower stage surface. The first terminal portion has a stepped shape including an upper stage portion formed on the upper stage surface and a lower stage portion formed on the lower stage surface. The upper stage portion has a first terminal surface contacting the terminal section of the coil. The lower stage portion has a second terminal surface positioned on an extension line of the terminal portion and not contacting the terminal section of the coil.
Data Source
AI summary
A coil component is provided with a coil, a base supporting the coil having a first surface parallel to an extending direction of the terminal section of the coil, and a terminal electrode having a first terminal portion printed on the first surface of the base. The first surface has a stepped surface including an upper stage surface and a lower stage surface. The first terminal portion has a stepped shape including an upper stage portion formed on the upper stage surface and a lower stage portion formed on the lower stage surface. The upper stage portion has a first terminal surface contacting the terminal section of the coil. The lower stage portion has a second terminal surface positioned on an extension line of the terminal section of the coil and not contacting the terminal section of the coil.