Coil Component Core Geometry to Prevent Reflow Cracking
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Solution Overview
Problem
Magnetic base bodies in coil components can crack due to rapid temperature changes during the reflow process, leading to a reduction in inductance.
Innovation Solution
A coil component design with a magnetic base body that has a core region with an area ratio of 32% or larger to the sum of the core region and winding portion areas, and where the peripheral edge of the core region is curved or circular, reducing the likelihood of cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the magnetic base body is manufactured by binding metal magnetic particles together with a resin binder, then the magnetic base body can be formed with a closed magnetic path, but the magnetic base body contains voids and absorbs water, leading to cracking during reflow process
Solution Approach 1:
The patent changes the geometric parameters of the core region, specifically setting the area ratio of the core region to the total area (core region + winding portion) to be 32% or larger, and designing the peripheral edge with curved lines rather than angles. This parameter optimization reduces stress concentration during thermal expansion in the reflow process, preventing cracking while maintaining the closed magnetic path structure.
Solution Approach 2:
The patent applies curvature by designing the peripheral edge of the core region with curved lines instead of straight angles. This curvature distributes stress more evenly during thermal expansion, reducing the likelihood of crack initiation at sharp corners while preserving the functional magnetic path.
2Ease of manufacture
If the magnetic base body contains water absorbed by the resin binder, then the manufacturing process is simplified, but the magnetic base body expands rapidly during reflow process causing cracking
Solution Approach 1:
The patent optimizes the geometric parameters of the magnetic base body, specifically the core region area ratio (32% or larger) and the curved peripheral edge design. These parameter changes reduce stress concentration during thermal expansion caused by water evaporation, thereby preventing cracking while maintaining the ease of manufacturing through the existing binder-based process.
3Ease of manufacture
If cracks occur in the magnetic base body during reflow process, then the manufacturing is simple, but the inductance of the coil component is reduced
Solution Approach 1:
The patent changes the geometric parameters of the magnetic base body, setting the core region area ratio to 32% or larger and designing the peripheral edge with curved lines. These parameter changes prevent crack formation during reflow while maintaining manufacturing simplicity, thereby ensuring inductance stability without complicating the manufacturing process.
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
The design effectively inhibits the reduction of inductance due to cracking in the magnetic base body, maintaining a stable inductance property even under thermal stress.
Implementation Method 1
When the coil component including the magnetic base body is mounted on a substrate by the reflow process, the magnetic base body containing water expands its volume due to a rapid temperature change.
Data Source
AI summary
A coil component according to one aspect of the present invention includes: a magnetic base body containing a plurality of metal magnetic particles and a binder binding the plurality of metal magnetic particles together; and a coil conductor provided in the magnetic base body and including a winding portion wound around a coil axis, wherein as viewed from a direction of the coil axis, the magnetic base body includes a core region enclosed by the winding portion, and a ratio of an area of the core region to a sum of an area of the winding portion and the area of the core region is 32% or larger.