Coil Component Core Region Layout for Reflow Crack Resistance
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Solution Overview
Problem
Magnetic base bodies in coil components are prone to cracking due to water absorption and rapid temperature changes during the reflow process, leading to reduced inductance.
Innovation Solution
A coil component design featuring a magnetic base body with a core region and winding portion ratio of 32% or larger, where the core region has a circular shape and no angles, inhibiting cracking by distributing compressive stress evenly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the magnetic base body contains water absorbed by the resin binder, then the manufacturing process is simple, but the magnetic base body expands during reflow process causing cracking
Solution Approach 1:
The patent changes the physical-chemical parameters of the binder resin by specifying gel fraction (5-60%), hydroxyl value (15-50 mg KOH/g), and acid value (3-20 mg KOH/g). These parameter changes modify the resin's water absorption characteristics and curing behavior, allowing the magnetic base body to withstand reflow processing without cracking while maintaining manufacturing simplicity.
Solution Approach 2:
The patent creates a composite material system combining metal magnetic particles with specifically formulated binder resin containing hydroxyl groups. This composite structure allows the resin to form strong bonds with metal particles while controlling water absorption through the hydroxyl value parameter, preventing cracking during thermal cycling.
2Reliability
If multiple types of metal magnetic particles with different average particle diameters are used, then the filling factor increases and magnetic permeability improves, but the manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by using metal magnetic particles with different average particle diameters in different regions or combinations within the magnetic base body. This allows optimization of packing density and magnetic permeability in specific areas while maintaining overall manufacturing feasibility through controlled resin content and curing parameters.
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 prevents inductance reduction by minimizing cracking in the magnetic base body, maintaining inductance stability during thermal expansion and contraction.
Implementation Method 1
the resin serving as the binder absorbs water. Therefore, the magnetic base body contains water absorbed therein
Implementation Method 2
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.