Exposed Core Package Design for Power Converter Thermal Management
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Solution Overview
Problem
Traditional encapsulated power converter assemblies face issues with thermal resistance, mechanical stress, and manufacturing inefficiencies due to the over-molding of inductive components, which can lead to blistering, void formation, and increased core losses.
Innovation Solution
The proposed solution involves an exposed core package design where the magnetic core surfaces are left unencapsulated, with large radii bends and gaps in the core structure to reduce flux concentration and eddy current losses, and a molding process that allows the core to be positioned relative to the PCB with controlled clearance, ensuring proper encapsulation without covering the core surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the magnetic core is fully encapsulated with molding compound, then mechanical protection and insulation are improved, but thermal performance deteriorates due to increased thermal resistance
Solution Approach 1:
The patent applies local quality by selectively encapsulating only certain portions of the magnetic core while leaving other portions exposed. Specifically, the molding compound covers the PCB assembly and portions of the core for mechanical protection and insulation, while exposing the top surface of the core for direct thermal management. This localized approach allows different regions of the same component to have different levels of encapsulation based on their specific functional requirements.
2Reliability
If the magnetic core is fully encapsulated, then insulation is improved, but core losses increase due to flux concentration and eddy currents
Solution Approach 1:
The patent implements local quality by creating distinct encapsulation zones around the magnetic core. The molding compound provides insulation where needed (around the PCB and side surfaces of the core) while deliberately leaving the top flux path surface exposed. This selective insulation approach maintains electrical isolation between conductive components while preserving the magnetic flux path integrity, thereby reducing eddy current losses and flux concentration effects.
Solution Approach 2:
The patent applies segmentation by dividing the core into different functional zones: encapsulated portions for mechanical support and insulation, and exposed portions for optimal magnetic flux path. The core is structurally segmented to allow different surfaces to serve different purposes, with the top surface remaining exposed to minimize magnetic losses while other surfaces are encapsulated for protection.
3Productivity
If the core surface is exposed, then thermal performance and manufacturing efficiency are improved, but mechanical stress protection is worsened
Solution Approach 1:
The patent applies local quality by providing mechanical protection through encapsulation at locations where stress protection is needed (around the PCB assembly and lateral surfaces of the core) while leaving the top surface exposed for thermal and manufacturing benefits. The molding compound acts as a mechanical buffer in regions subject to stress during assembly and operation, while the exposed core surface maintains thermal performance without requiring additional protective coatings.
4Loss of energy
If large radii bends are added to the core structure, then eddy current losses are reduced, but device complexity increases
Solution Approach 1:
The patent applies the spheroidality principle by incorporating large radii bends in the magnetic core geometry instead of sharp corners. The core features rounded internal corners and curved flux paths with radii of curvature substantially greater than the skin depth at the operating frequency. This curvature design smooths the magnetic flux distribution, reduces eddy current formation, and minimizes flux concentration effects while maintaining a relatively simple overall core structure.
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 design enhances thermal performance, reduces core losses, and improves manufacturing efficiency by eliminating the need for costly pre-baking and buffer coatings, while maintaining mechanical integrity and insulation.
Implementation Method 1
a core structure for directing a magnetic field along a flux path, the core structure having a core surface
Implementation Method 2
Encapsulation in this manner may aid in conducting heat out of the over-molded components
Data Source
AI summary
An encapsulated electronic device includes a magnetically permeable core structure which is exposed within and coplanar with a flat top surface of the device. A bottom surface of the core may be exposed within the bottom surface of the device. The bottom core surface may be recessed beneath, coplanar with, or protruding from the bottom surface of the device. Alternatively the bottom surface may be encapsulated within the device. A method for manufacturing the exposed core package includes positioning a first component relative to a second component before encapsulating the device. An improved planar magnetic core structure includes internal bevels having a radius greater than or equal to 15% and preferably 25%, 35%, or as much as 50% of the core thickness to reduce concentration of the magnetic field around the internal corners.