SiC Power Module Ceramic Frame Stress Suppression
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Solution Overview
Problem
Silicon Carbide (SiC) power devices bonded on metallic substrates, such as DBC substrates, experience degradation or rupture during heat cycle tests due to significant differences in coefficients of thermal expansion (CTE), leading to reliability issues in power modules.
Innovation Solution
A power module design incorporating a ceramic frame that encloses the semiconductor devices and a resin layer to mitigate stress caused by CTE differences between the metallic pattern and the semiconductor devices, thereby reducing shear stress and preventing degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If semiconductor devices are bonded on metallic substrates, then electrical performance is improved, but reliability deteriorates due to CTE mismatch causing bonded portion degradation
Solution Approach 1:
A ceramic frame member is introduced as an intermediary component between the metallic substrate and semiconductor devices. This frame member has a coefficient of thermal expansion that is lower than the metallic substrate but higher than the semiconductor devices, creating a gradient that reduces the overall CTE mismatch stress. The frame acts as a stress buffer that protects the bonded portions from degradation during thermal cycling.
Solution Approach 2:
The patent employs a composite structure combining metallic substrate, ceramic frame member, and semiconductor devices. This composite approach allows each material to contribute its optimal properties: the metallic substrate provides electrical conductivity and mechanical strength, the ceramic frame provides thermal stability with intermediate CTE, and the semiconductor devices provide functional performance. The composite structure effectively manages thermal expansion differences.
2Productivity
If power modules are miniaturized using thin type designs, then productivity is improved, but manufacturing precision deteriorates due to fabrication difficulties
Solution Approach 1:
The ceramic frame member is formed on the metallic substrate before the semiconductor devices are mounted. This preliminary formation of the frame structure provides a pre-established mechanical framework that guides subsequent bonding operations. The frame's presence during the bonding process helps maintain precise alignment and positioning, ensuring high bonding precision even in miniaturized module designs.
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 ceramic frame effectively suppresses shear stress and degradation at the bonded portion, enhancing the reliability and durability of the power module, even under conditions of large CTE differences, and allows for miniaturization and cost reduction in module fabrication.
Implementation Method 1
the frame member suppresses a stress according to a difference between a coefficient of thermal expansion of the metallic pattern and a coefficient of thermal expansion of the power devices
Data Source
AI summary
The power module includes: a first metallic pattern; a plurality of power devices bonded on the first metallic pattern, each of the plurality of the power devices has a thickness thinner than a thickness of the metallic pattern; a frame member disposed so as to collectively enclose a predetermined number of the power devices on the first metallic pattern; a second metallic pattern disposed outside the frame member; and a resin layer configured to seal the plurality of the power devices and the first and second metallic patterns so as to include the frame member, wherein the frame member suppresses a stress according to a difference between a coefficient of thermal expansion of the metallic pattern and a coefficient of thermal expansion of the power devices. There is provided the power module easy to be fabricated, capable of suppressing the degradation of the bonded portion and improving reliability.