Power Module Thermal Interface With Cavity Gel And FR4 Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current thermal interface materials for power modules, such as those used in wide band gap devices, lack conformability, thermal conductivity, electric isolation, and cost-effectiveness, particularly in managing heat extraction from multi-functional PCBs where heat needs to be removed at specific locations like below power semiconductor dies.
Innovation Solution
A power module design featuring a heat sink with a substrate and a thermal interface comprising a highly conductive gel material and FR4 pre-preg sheets, where the gel provides conformability and thermal conductivity, and the FR4 sheets ensure electric isolation and low cost, with additional FR4 sheets acting as spacers to maintain distance and allow gas flow, assembled using standard PCB processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal interface materials (FR4 pre-preg, polymide, thermal grease) are used, then electric isolation is provided, but thermal conductivity is insufficient
Solution Approach 1:
The thermal interface is divided into multiple layers with different functions: a first FR4 pre-preg layer provides electric isolation, while a second FR4 pre-preg layer with cavity provides both isolation and thermal management. This segmentation allows each layer to optimize for its specific function while working together as a system.
Solution Approach 2:
The invention uses composite construction by combining multiple FR4 pre-preg layers with different configurations (one with cavity, one without) to create a thermal interface that achieves both electrical isolation and improved thermal conductivity, overcoming the limitations of single-material solutions.
2Ease of operation
If high conformability materials are used to compensate PCB irregularities, then contact quality improves, but thermal conductivity decreases
Solution Approach 1:
The interface structure is segmented into multiple layers where the first FR4 pre-preg layer provides conformability to compensate for PCB irregularities, while the second FR4 pre-preg layer with cavity provides enhanced thermal management. This allows each layer to specialize in one function.
Solution Approach 2:
The second FR4 pre-preg layer features a cavity structure that concentrates thermal management resources locally beneath the power die, providing high thermal conductivity where needed most while maintaining overall interface conformability through the multi-layer construction.
3Temperature
If thermal interface materials are designed for homogeneous high thermal conduction across entire surface, then cooling efficiency improves, but cost increases
Solution Approach 1:
The second FR4 pre-preg layer incorporates a cavity structure that concentrates thermal management capabilities specifically beneath the power die where heat generation is highest, rather than providing uniform thermal conduction across the entire surface. This localized approach reduces material costs while maintaining cooling efficiency.
Solution Approach 2:
The thermal interface is segmented into functional zones: the first FR4 pre-preg layer provides general isolation and conformability, while the second FR4 pre-preg layer with cavity provides targeted thermal management beneath the power die. This segmentation allows cost-effective thermal management focused on the critical heat-generating area.
4Reliability
If thick isolating pads are used to ensure electric isolation, then safety improves, but thermal conductivity and conformability deteriorate
Solution Approach 1:
Electric isolation is segmented across multiple thin FR4 pre-preg layers rather than relying on a single thick isolating pad. The first layer provides isolation, while the second layer with cavity provides both additional isolation and enhanced thermal management, achieving both goals simultaneously.
Solution Approach 2:
The invention uses composite construction with multiple FR4 pre-preg layers of optimized thickness, replacing the conventional single thick isolating pad. This composite approach maintains sufficient electric isolation while improving thermal conductivity and conformability through the combined properties of the layered 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 configuration enhances thermal conductivity and isolation while maintaining low costs, effectively addressing the limitations of existing thermal interface materials by providing efficient heat dissipation and electrical safety for power modules.
Implementation Method 1
the first material having a thermal conductivity that is higher than the thermal conductivity of the second material, the second material having a first cavity below the power die and the first material is in the first cavity of the second material. Thus, the power die is cooled through a highly conductive thermal path involving the first material.
Implementation Method 2
a high conformability to compensate the large irregularities of the PCB and for bending effects due to unequal pressure application and thermo-mechanical strain
Implementation Method 3
an electric isolation between heat-sink and the PCB for security reasons
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The present invention concerns a power module comprising a heat sink, a substrate on which a power die is attached, the power module further comprises a first and a second material between the substrate and the heat sink, the first material having a thermal conductivity that is higher than the thermal conductivity of the second material, the second material having a first cavity below the power die and the first material is in the first cavity of the second material.