Magnetic Resin Wire Coil Core for Thermal Expansion Matching
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Solution Overview
Problem
Wire coil components with sintered cores or magnetic resin bodies face reliability issues due to thermal expansion mismatches with mount boards, leading to cracks and reduced performance over time, especially when polysiloxane binders are used.
Innovation Solution
A wire coil component with a shaped article made from a magnetic resin containing a binder resin and magnetic metal powder, having a thermal expansion coefficient of 12-16 ppm/K, and a coating resin that matches this range, along with terminal electrodes and an oxide coating for improved adhesion and stress distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sintered core is used for the wire coil component, then the component has good initial characteristics, but the difference in volume changes between the core and mount board causes stress and cracks, impairing reliability
Solution Approach 1:
The patent changes the thermal expansion parameter of the core material by transitioning from a sintered core to a magnetic resin body core. The magnetic resin body has a thermal expansion coefficient that can be controlled to match the mount board, reducing thermal stress and improving long-term reliability while maintaining initial characteristics
Solution Approach 2:
The patent uses a composite material structure where the magnetic resin body contains magnetic powder dispersed in a resin matrix. This composite structure allows the core to have both the magnetic properties needed for initial characteristics and the thermal expansion properties needed to match the mount board for long-term reliability
2Reliability
If a magnetic resin body with polysiloxane binder is used, then the difference in volume changes from the mount board is reduced, but the coating on the wire is damaged during compression or heating
Solution Approach 1:
The patent changes the chemical composition parameter of the binder resin from polysiloxane to epoxy-containing resin. This parameter change resolves the contradiction by providing a binder that does not damage the wire coating during processing while still achieving good thermal expansion matching with the mount board
Solution Approach 2:
The patent uses a binder resin (epoxy-containing resin) that provides sufficient functionality for the application without the harmful side effects of polysiloxane. The binder serves its purpose of holding the magnetic powder and providing thermal expansion matching without compromising the wire coating
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 configuration reduces the occurrence of cracks and enhances the reliability of the wire coil component by matching the thermal expansion of the core with the mount board, maintaining performance across temperature changes and improving adhesion to the mount board.
Implementation Method 1
The shaped article is formed from a magnetic resin containing a binder resin and a magnetic metal powder and has a thermal expansion coefficient of about 12 ppm/K or more and about 16 ppm/K or less (i.e., from about 12 ppm/K to about 16 ppm/K) from −55° C. to 150° C. This configuration limits the reliability degradations by virtue of the thermal expansion coefficient of the shaped article being close to that of the mount board onto which the wire coil component will be mounted.
Data Source
AI summary
A wire coil component includes a shaped article, a wire wound around the shaped article, and terminal electrodes to which the ends of the wire are connected. The shaped article is formed from a magnetic resin containing a binder resin and a magnetic metal powder and has a thermal expansion coefficient of about 12 ppm/K or more and about 16 ppm/K or less (i.e., from about 12 ppm/K to about 16 ppm/K) from −55° C. to 150° C.