Multilayer Coil Stress Relief via Complexing Agent Interface Treatment
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Solution Overview
Problem
Multilayer coil components face issues with internal stress due to thermal expansion coefficient differences between ferrite and conductor layers, leading to variations in impedance and reliability concerns, particularly in small-sized products where voids are difficult to form without thinning conductors or reducing adhesion of external electrodes.
Innovation Solution
A multilayer coil component with a helical coil in a ferrite element, where internal conductors are surrounded by ferrite with no voids at interfaces, and a complexing agent solution is used to isolate these interfaces, maintaining conductor thickness and reducing stress through a segregation coefficient of Cu at 5% or less, and a pore area fraction of 6% to 20% in side gap portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voids are formed between ferrite layers and internal conductor layers to reduce stress, then reliability is improved, but manufacturing complexity increases and direct-current resistance increases
Solution Approach 1:
The patent extracts the harmful voids from the interface between ferrite and internal conductors by using a complexing agent solution that dissolves Cu segregation, thereby eliminating the need for additional stress-relief structures while maintaining interface integrity and reducing manufacturing complexity
Solution Approach 2:
The patent changes the chemical parameter of the interface by controlling Cu segregation through complexing agent treatment, transforming the interface from a Cu-rich segregated state to a homogeneous state, which reduces stress without requiring void formation
2Stress or pressure
If internal conductors are thinned to form voids, then stress influence is reduced, but direct-current resistance increases
Solution Approach 1:
The patent converts the harmful Cu segregation at the interface into a beneficial homogeneous distribution by using complexing agent solution, which reduces stress influence without thinning the conductors, thereby maintaining low direct-current resistance
Solution Approach 2:
The patent changes the compositional parameter at the interface by dissolving Cu segregation through complexing agent treatment, achieving stress reduction while preserving conductor thickness and electrical conductivity
3Stress or pressure
If adhesion of external electrodes is reduced to form voids, then stress influence is reduced, but reliability deteriorates
Solution Approach 1:
The patent extracts Cu segregation from the interface using complexing agent solution, eliminating the need for void formation and preserving strong adhesion between external electrodes and ferrite, thereby maintaining high reliability
Solution Approach 2:
The patent changes the interface composition by removing Cu segregation through complexing agent treatment, achieving stress reduction while maintaining optimal adhesion parameters for high reliability
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 approach alleviates stress issues without forming voids, ensuring high reliability, low direct-current resistance, and preventing conductor breakage, while maintaining conductor thickness and adhesion, achieving stable impedance and inductance.
Implementation Method 1
a complexing agent solution is used to isolate these interfaces, maintaining conductor thickness and reducing stress through a segregation coefficient of Cu at 5% or less
Data Source
AI summary
A multilayer coil component is provided to have high reliability and in which internal stress arising from the difference in firing shrinkage behavior and/or thermal expansion coefficient between ferrite layers and internal conductor layers is alleviated without forming conventional voids between the ferrite layers and the internal conductor layers. A method of manufacturing a multilayer coil includes a step of isolating interfaces between internal conductors and surrounding ferrite by allowing a complexing agent solution to reach interfaces between the internal conductors and the surrounding ferrite through side gap portions from side surfaces of a ferrite element including a helical coil. The complexing agent solution contains at least one selected from the group consisting of an aminocarboxylic acid, a salt of the aminocarboxylic acid, an oxycarboxylic acid, a salt of the oxycarboxylic acid, an amine, phosphoric acid, a salt of phosphoric acid, and a lactone compound.