AlSiC Power Semiconductor Module Thermal Stress Management
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Solution Overview
Problem
Power semiconductor modules face thermal stress failures due to mismatched coefficients of thermal expansion (CTE) between materials, limiting their operating temperature and preventing the reduction of heat sinks and cooling systems in size and weight, especially in weight-sensitive applications like aircraft.
Innovation Solution
A power semiconductor module design using AlSiC for the conductive circuit layer and baseplate, with CTE values less than 8.0×10−6/°C and density less than 4 g/cm3, to minimize thermal stresses and enable operation from -65° C to 250° C, allowing for reduced heat sinks and cooling systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If traditional materials (copper, aluminum) are used for conductive circuit layer and baseplate, then electrical conductivity is improved, but thermal stress failures occur due to CTE mismatch with insulating substrate
Solution Approach 1:
The patent uses AlSiC (aluminum silicon carbide) composite material for both the conductive circuit layer and baseplate. This composite material combines aluminum's electrical conductivity with silicon carbide's low CTE (coefficient of thermal expansion), achieving CTE matching with AlN insulating substrate while maintaining good electrical conductivity. The composite structure resolves the contradiction between electrical conductivity and thermal stress resistance.
Solution Approach 2:
The patent changes the CTE parameter of the conductive material from traditional copper (17×10^-6/°C) or aluminum (25×10^-6/°C) to AlSiC with CTE less than 8.0×10^-6/°C, specifically matching the AlN substrate's CTE of 4.3×10^-6/°C. This parameter change eliminates thermal stress failures while maintaining electrical functionality.
2Temperature
If SiC-based power semiconductors are used, then operating temperature capability is improved to 250°C, but thermal stress failures still occur due to CTE mismatch with copper/aluminum components
Solution Approach 1:
The patent employs AlSiC composite material throughout the module structure (conductive circuit layer, baseplate, and heat sink) to match the CTE of SiC power semiconductors and AlN insulating substrate. This ensures thermal stress resistance across the entire temperature range from -65°C to 250°C, enabling SiC devices to operate at their full temperature capability without failure.
Solution Approach 2:
The patent applies CTE-matched AlSiC material specifically at critical interfaces where thermal stress occurs most severely - between the SiC power devices and AlN substrate, and between these layers and the conductive circuit layer/baseplate. This localized application of special material properties prevents failure at stress concentration points while maintaining overall module performance.
3Weight of stationary object
If heat sink size and weight are reduced to take advantage of SiC properties, then weight is improved, but thermal stress failures occur due to insufficient thermal management
Solution Approach 1:
The patent uses AlSiC for the baseplate and heat sink components, which provides both low weight (density less than 4 g/cm³) and CTE matching with SiC devices and AlN substrate. This allows significant reduction in heat sink size and weight compared to traditional copper or aluminum designs while maintaining thermal stress resistance through proper material matching.
Solution Approach 2:
The patent changes the material parameters of the heat sink from traditional heavy metals to AlSiC composite, achieving density less than 4 g/cm³ and CTE less than 8.0×10^-6/°C. This parameter change enables weight reduction while preventing thermal stress failures through CTE matching with the AlN insulating substrate and SiC power devices.
4Reliability
If various configurations with closer CTE values are used, then thermal stress resistance is improved, but weight reduction is insufficient for weight-sensitive applications
Solution Approach 1:
The patent uses AlSiC composite material that simultaneously achieves CTE matching (less than 8.0×10^-6/°C, close to AlN's 4.3×10^-6/°C) and low density (less than 4 g/cm³). This composite material provides both thermal stress resistance and significant weight reduction, making it ideal for weight-sensitive applications like aircraft where traditional materials fail to provide both properties.
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
The design achieves a lightweight power semiconductor module with reduced thermal stresses and efficient heat dissipation, enabling operation over a wide temperature range while minimizing weight and size of heat sinks and cooling systems, suitable for aircraft applications.
Implementation Method 1
conducting heat generated by the power conversion from the power semiconductor devices first through a conductive circuit layer, then through an insulating substrate, to a baseplate
Implementation Method 2
The baseplate and the conductive circuit layer are formed of a material with a coefficient of thermal expansion less than about 8.0×10−6/° C.
Data Source
AI summary
A method of converting power using a power semiconductor module includes conducting power to power semiconductor devices; converting the conducted power with the power semiconductor devices; conducting heat generated by the power conversion from the power semiconductor devices first through a conductive circuit layer, then through an insulating substrate, to a baseplate; and removing the heat from the baseplate. The conductive circuit layer and the baseplate are formed of a material with a coefficient of thermal expansion less than about 8.0×10=6/° C. and a density less than about 4 g/cm3.