Power Module Substrate Corner Roughness for Brazed Joint Reliability
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Solution Overview
Problem
Conventional power module substrates face low joint reliability due to thermal stress concentration at corner parts, which is exacerbated by reduced brazing material spread, leading to potential cracks and reduced insulation.
Innovation Solution
The power module substrate features metal plates with increased surface roughness at corner parts compared to plane parts, allowing the brazing material to spread more onto the insulating substrate, thereby dispersing thermal stress and enhancing joint reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If metal plates are manufactured by punching to have lateral surfaces perpendicular to insulating substrate, then space between metal plates is reduced, but thermal stress concentrates at corner parts leading to low joint reliability
Solution Approach 1:
The patent applies local quality by creating different surface roughness characteristics at different locations on the metal plate. Specifically, the corner parts are designed with larger surface roughness compared to plane parts, allowing localized control of brazing material behavior where thermal stress concentrates most, while maintaining smooth surfaces elsewhere for optimal brazing coverage.
Solution Approach 2:
The patent changes the surface roughness parameter of the metal plate at corner parts to resolve the contradiction. By increasing surface roughness at corner parts, the brazing material is restrained from climbing up and is forced to spread more onto the insulating substrate, thereby dispersing thermal stress and improving joint reliability while maintaining the compact perpendicular configuration.
2Volume of moving object
If brazing material spread is reduced to minimize space, then module size decreases, but thermal stress concentration causes cracks and reduces insulation
Solution Approach 1:
The patent uses local quality by differentiating surface characteristics between corner parts and plane parts. The corner parts have enhanced surface roughness to control brazing material flow and dispersal, directly addressing thermal stress concentration zones, while plane parts maintain standard characteristics for compact overall dimensions.
Solution Approach 2:
The patent converts the harmful effect of thermal stress concentration at corner parts into a beneficial outcome. By increasing surface roughness at these specific locations, the brazing material is guided to spread more at the corner parts, transforming the stress concentration zone into a stress-dispersing region that enhances joint reliability and insulation.
3Reliability
If surface roughness is increased at corner parts, then brazing material spreads more onto insulating substrate, but manufacturing complexity increases
Solution Approach 1:
The patent applies local quality by implementing surface roughness modification only at corner parts rather than uniformly across the entire metal plate. This localized approach achieves the desired brazing material control and thermal stress dispersion while minimizing additional manufacturing complexity compared to comprehensive surface treatment.
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 improves the joint reliability of metal plates and insulating substrates by effectively dispersing thermal stress, reducing the likelihood of cracks and maintaining high insulation integrity.
Implementation Method 1
metal plates 2 joined to main surfaces (upper and lower surfaces) of the insulating substrate 1 with brazing materials 3 in between
Implementation Method 2
corner part(s) 2a farthest from the center of the metal plate 2 in plan view, where thermal stress tends to concentrate
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A power module substrate 10 is provided with: an insulating substrate 1; and a metal sheet 2 that is joined to the insulating substrate 1 via a brazing material 3, wherein regarding the surface roughness, in the thickness direction, of the lateral surface of the metal sheet 2, the surface roughness of a corner 2a farthest from the center of the metal sheet 2 is larger than the surface roughness of plane parts 2b, which bound the corner, in at least a plan view. Also provided is a power module 100 which is formed by mounting an electronic component 40 on this power module substrate 10.