Coil Component Core Fatigue Prevention via Mold Releasing Agent Gap
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Solution Overview
Problem
The coil components used in small-sized electronic devices face reliability issues due to differences in thermal expansion rates between the resin with magnetic powder and the drum-shaped core, leading to stress fatigue and potential breakage of the core over temperature changes.
Innovation Solution
A method involving the application of a mold releasing agent to create a gap between the flange portions, followed by winding and coating with a thermosetting resin and magnetic powder, which is then thermally cured to manage thermal expansion and contraction without applying stress to the flange portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resin with magnetic powder is applied to coat the winding around the drum-shaped core, then the coil component can be used in DC/DC converters of portable electronic devices, but the core may be fatigued and broken due to different thermal expansion rates between the resin and the core
Solution Approach 1:
The invention introduces a gap between the flange portions of the drum-shaped core, dividing the continuous contact interface into separate regions. This segmentation allows the resin with magnetic powder to expand and contract independently without transmitting thermal stress to the flange portions, thereby preventing core fatigue and breakage while maintaining the functional integrity of the coil component
Solution Approach 2:
The gap acts as an intermediary element between the resin with magnetic powder and the flange portions. By introducing this intermediate space, the invention decouples the thermal expansion/contraction movements of the resin from the flange portions, allowing the resin to undergo volume changes without directly stressing the core structure, thus resolving the thermal stress fatigue problem
2Ease of manufacture
If the resin with magnetic powder is applied directly to the flange portions, then the manufacturing process is simple, but the flange portions are fatigued to be broken due to thermal expansion and contraction
Solution Approach 1:
The invention segments the coating application area by introducing a gap between the flange portions. The resin with magnetic powder is applied only to specific regions (excluding the gap area), which simplifies the manufacturing process compared to complex stress-management structures, while simultaneously protecting the flange portions from thermal fatigue by preventing direct contact in the gap region
3Reliability
If a gap is formed by applying a mold releasing agent between the flange portions and the resin with magnetic powder, then the core is protected from breakage during temperature changes, but the gap may affect the magnetic path
Solution Approach 1:
The invention converts the potentially harmful gap in the magnetic path into a beneficial feature. By strategically positioning the gap between the flange portions, the invention allows the magnetic field to effectively pass through the resin with magnetic powder and the winding, while the gap simultaneously provides stress relief during thermal cycles. The magnetic path integrity is maintained because the gap is filled with magnetically permeable material or the gap dimensions are controlled to minimize magnetic reluctance
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 solution provides a highly reliable coil component that withstands temperature changes without core breakage, as demonstrated by increased cycle durability in temperature shock tests, and maintains inductance properties with minimal impact from the gap in the magnetic path.
Implementation Method 1
since the thermal expansion rate of the resin with magnetic powder, which coats the winding, and that of the drum-shaped core are different from each other, the resin with magnetic powder expands to serve to extend the space between the upper and lower flanges when the temperature is high
Implementation Method 2
applying a resin with magnetic powder formed of a thermosetting resin to a space on an outer periphery of the winding interposed between the pair of flange portions, and thermally curing the resin with magnetic powder
Data Source
AI summary
A coil component, in which a space on an outer periphery of a winding interposed between a pair of flange portion is coated with a resin with magnetic powder, has a problem of long-term reliability that a thermosetting resin expands and contracts due to change in a temperature and the flange portions are fatigued to be broken. An object of the present invention is to provide the coil component of which core is hardly broken even when the resin with magnetic powder expands and contracts and a method of manufacturing the same. In order to solve the above-described problem, the method of manufacturing the coil component according to one embodiment of the present invention is a method of manufacturing a coil component including a drum-shaped core including a winding core portion and a pair of flange portions provided on both ends in an axial direction of the winding core portion, and a winding wound around the winding core portion, including applying a mold releasing agent for providing a gap on at least one of opposed surfaces of the pair of flange portions, winding the winding around the winding core portion, applying a resin with magnetic powder formed of a thermosetting resin to a space on an outer periphery of the winding interposed between the pair of flange portions, and thermally curing the resin with magnetic powder.