Coil Built-in Multilayer Substrate Parasitic Inductance Reduction
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Solution Overview
Problem
Existing DC-DC converter modules face challenges in reducing size and achieving high efficiency due to the need for smaller coil openings and the generation of parasitic inductance from interlayer connection conductors that penetrate through magnetic bodies.
Innovation Solution
A coil built-in multilayer substrate with a magnetic field interrupting portion, either as a gap or an insulating material with lower permeability, is integrated inside the spiral coil conductor pattern to increase coil opening size and reduce parasitic inductance by interrupting the magnetic field generated along the lateral surface of interlayer connection conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If interlayer connection conductors are formed outside the coil, then the coil opening size is reduced, but parasitic inductance is generated and module size reduction becomes difficult
Solution Approach 1:
The interlayer connection conductors are nested inside the coil conductor pattern, with the conductors positioned within the spiral structure. This allows the connection conductors to be enclosed by the coil windings, increasing the effective opening size while the magnetic field interrupting portion prevents parasitic inductance generation by breaking the magnetic flux path around the connection conductors.
Solution Approach 2:
A magnetic field interrupting portion is introduced as an intermediary element between the interlayer connection conductors and the surrounding magnetic field. This interrupting portion, formed by gaps or low-permeability materials, mediates the magnetic field interaction by preventing circular magnetic flux generation around the connection conductors, thereby eliminating parasitic inductance while allowing the conductors to be positioned inside the coil.
2Reliability
If interlayer connection conductors penetrate through magnetic body, then connection is achieved, but parasitic inductance component is generated
Solution Approach 1:
The magnetic field interrupting portion serves as an intermediary that selectively interacts with the magnetic field generated by the interlayer connection conductors. By positioning this interrupting portion at strategic locations around the conductors, the magnetic flux path is broken, preventing the formation of parasitic inductance loops while maintaining the electrical connection function of the conductors through the magnetic layer.
Solution Approach 2:
The magnetic field interrupting portion is locally applied only in regions where interlayer connection conductors are present, rather than uniformly across the entire magnetic layer. This localized approach maintains magnetic continuity in areas without connection conductors, preserving inductance performance, while specifically addressing the parasitic inductance problem only where connection conductors penetrate the magnetic body.
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 allows for increased coil opening size while minimizing parasitic inductance, enabling the creation of compact, high-efficiency power supply modules with improved switching IC characteristics.
Implementation Method 1
A magnetic field interrupting portion is defined by a gap in contact with the interlayer connection conductor and extending along a direction in which the interlayer connection conductor extends, or is made of an insulating material disposed in contact with the interlayer connection conductor, extending along the direction in which the interlayer connection conductor extends, and having a lower permeability than that of the magnetic layer
Data Source
AI summary
A coil built-in multilayer substrate includes a multilayer substrate, a coil, interlayer connection conductors, and gaps. The multilayer substrate includes a magnetic layer, a component-mounting land conductor provided on a first principal surface, and a terminal conductor provided on a second principal surface. The coil is provided in the magnetic layer and includes an axis extending in a direction perpendicular or substantially perpendicular to the first and second principal surfaces. The interlayer connection conductors are provided in the magnetic layer in a region inside the spiral coil. Gaps penetrate lateral surfaces of the interlayer connection conductors.