Isolated Power Converter Package With PCB Thermal Path
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Solution Overview
Problem
Thermal impedance limits the maximum isolated power transfer capability in isolated power converter packages with transformer stacks, as there is no direct thermal path for heat dissipation from the laminate substrate's coil to the system heatsink, such as a printed circuit board (PCB).
Innovation Solution
Incorporating a downset pad and feature in the leadframe that connects the transformer stack's supports directly to an exposed metal pad on the PCB, providing a thermal path through thermal vias for enhanced cooling, utilizing a thermally conductive attach material with a thermal conductivity of at least 1 W/m·K to reduce thermal impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer stack with embedded coils in laminate substrate is used for isolation, then galvanic isolation and voltage transformation are achieved, but thermal impedance increases and heat dissipation capability deteriorates
Solution Approach 1:
The patent introduces a third-dimensional thermal management solution by adding a thermal via structure that extends vertically from the laminate substrate through the transformer stack to the heatsink. This vertical thermal path operates in a different dimension than the planar electrical isolation layers, allowing heat dissipation without compromising galvanic isolation in the horizontal plane.
Solution Approach 2:
The patent introduces thermal vias as intermediary elements that mediate between the heat-generating coil windings in the laminate substrate and the external heatsink. These vias act as thermal conductors that bridge the thermal gap, enabling efficient heat transfer while maintaining the electrical isolation provided by the laminate structure.
2Temperature
If direct thermal path is added from coil to heatsink, then heat dissipation improves, but device complexity increases
Solution Approach 1:
The patent merges the thermal management function with the existing structural components by integrating thermal vias into the laminate substrate construction process. The thermal path is combined with the electrical isolation layers and support structures, creating a multi-functional component that provides both electrical isolation and thermal conduction without adding separate complex cooling systems.
Solution Approach 2:
The laminate substrate structure is designed to serve multiple functions simultaneously: providing galvanic isolation through dielectric layers, supporting coil windings, and conducting heat through integrated thermal vias. This multi-functionality reduces overall device complexity by eliminating the need for separate thermal management components.
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 thermal resistance by approximately 16% and allows for higher power operation by facilitating effective heat dissipation from the transformer stack to the PCB, enhancing cooling efficiency.
Implementation Method 1
utilizing a thermally conductive attach material with a thermal conductivity of at least 1 W/m·K to reduce thermal impedance
Implementation Method 2
providing a thermal path through thermal vias for enhanced cooling
Data Source
AI summary
An isolated power converter package includes a leadframe including a first and second die pad, first and second supports connected to first leads, second leads, at least one downset pad, and at least one downset feature between the supports and downset pad. A first semiconductor die is on the first die pad and a second semiconductor die is on the second die pad. The transformer stack includes a top and bottom side magnetic sheet on respective sides of a laminate substrate including an embedded coil that has coil contacts. Edges of the laminate substrate are on the supports. Bond wires are between the first die bond pads and the second leads, between the second die bond pads and the second leads, between the first die bond pads and coil contacts, and between the second die bond pads and the coil contacts. The downset pad is exposed from a mold compound.