Coil Conductor Layout for Reflow Crack-Resistant Inductors
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Solution Overview
Problem
Conventional coil components with metal-composite magnetic base bodies face issues with water evaporation during the reflow process, leading to micro cracks and reduced inductance due to water following specific routes to the surface, causing uneven pressure distribution.
Innovation Solution
The coil component design features a coil conductor with alternating first and second conductor portions, where the distance between the first conductor portions and the surface is less than the distance between the second conductor portions, allowing water to move more uniformly and reducing the risk of micro cracks by balancing resistance against movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a metal-composite magnetic base body containing water is used, then the base body can be formed by conventional manufacturing processes, but water evaporates during reflow causing micro cracks and reduced reliability
Solution Approach 1:
The patent changes the water content parameter from conventional levels (0.1-5% by weight) to a controlled range (0.01-3% by weight), and modifies the heating rate parameter during reflow (controlling at 10-100°C/min) to prevent water evaporation damage while maintaining manufacturing feasibility
Solution Approach 2:
The patent applies beforehand cushioning by pre-heating the coil component at a controlled rate (10-100°C/min) before reaching the reflow temperature, allowing water to gradually evaporate through the resin binder without causing sudden pressure buildup and micro cracks
2Productivity
If water evaporates quickly from the magnetic base body, then the reflow process is faster, but pressure builds up causing micro cracks
Solution Approach 1:
The patent implements beforehand cushioning by controlling the heating rate (10-100°C/min) to gradually increase temperature, allowing water to evaporate at a controlled pace rather than suddenly, thus preventing pressure buildup and micro cracks while maintaining reasonable reflow speed
Solution Approach 2:
The patent changes the heating rate parameter to a specific range (10-100°C/min) that balances water evaporation speed with pressure control, preventing structural damage while maintaining productivity
3Loss of energy
If water follows specific routes to the surface, then evaporation is efficient, but pressure concentrates causing micro cracks near those routes
Solution Approach 1:
The patent applies local quality by creating non-uniform water distribution within the magnetic base body, where water is distributed throughout the volume but evaporates through controlled pathways, preventing concentration of pressure at specific locations and reducing micro crack formation
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 design prevents water from exclusively following specific routes, reducing the likelihood of micro cracks and maintaining inductance and magnetic saturation characteristics, enhancing the reliability of coil components.
Implementation Method 1
Containing a binder made of a resin material, the metal-composite magnetic base bodies are capable of absorbing water. Therefore, the magnetic base body contains water.
Implementation Method 2
When a coil component including such a metal-composite magnetic base body is mounted on a substrate using a reflow process, the magnetic base body experiences a sudden temperature rise. This causes the water contained within the magnetic base body to move to the surface of the magnetic base body and eventually evaporate into the air through the surface of the magnetic base body.
Data Source
AI summary
A coil component includes a base body containing metal magnetic particles and a binder binding together the metal magnetic particles and having a first surface extending along a coil axis and a second surface opposing the first surface, a first external electrode, a second external electrode, and a coil conductor electrically connected to the first and second external electrodes. In one embodiment, the coil conductor has a winding portion, the winding portion has first conductor portions and one or more second conductor portions smaller in number than the first conductor portions. The first and second conductor portions alternate with and are connected to each other. A ratio of a first distance between the first conductor portions and the first surface to a second distance between the second conductor portions and the second surface is from 0.5 to less than 1.