Power Module Buffer Plate Thermal Stress Management
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power modules with direct cooling types face issues with heat dissipation due to differences in coefficient of linear expansion between semiconductor elements and coolers, leading to cracks and insufficient heat conductivity, and existing solutions do not adequately address the joining strength and heat conductivity of the joining layer.
Innovation Solution
A power module configuration that includes a buffer plate with a higher coefficient of linear expansion than the semiconductor element and lower than the insulated circuit board, and a joining material divided into multiple portions to facilitate binder discharge, enhancing joining strength and heat conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a buffer layer is provided between the ceramic substrate and the metal bottom plate to avoid cracks caused by thermal expansion differences, then the reliability of the joining layer is improved, but the heat conductivity in the joining layer becomes insufficient
Solution Approach 1:
A buffer layer made of sintered silver is introduced as an intermediary component between the ceramic substrate and the metal bottom plate. This buffer layer serves dual functions: it acts as a stress buffer to prevent cracks due to thermal expansion differences, and it provides adequate heat conductivity through its high thermal conductivity material properties
Solution Approach 2:
The joining layer structure is modified by changing the material parameters and thickness of the buffer layer. The buffer layer is designed with specific thickness and material composition to optimize the balance between mechanical stress buffering and thermal conductivity, ensuring both reliability and heat dissipation performance
2Loss of energy
If a stress buffer plate is provided directly below the semiconductor element to diffuse heat, then the heat dissipation performance is improved, but the joining strength becomes weak due to binder remaining in the joining material
Solution Approach 1:
The joining material is divided into multiple separate portions rather than applied as a continuous layer. This segmentation creates gaps between adjacent joining material portions, providing escape paths for binder vapor during heating. The segmented structure allows binder to be discharged through the gaps, preventing binder accumulation that would weaken the joining layer while maintaining adequate joining strength
3Strength
If the joining material is heated to join the ceramic substrate and buffer layer, then the joining strength is improved, but the binder remains in the joining material causing weak subsequent joining strength and insufficient heat conductivity
Solution Approach 1:
The harmful binder component is extracted or removed from the joining material system by providing escape paths through the segmented structure. During heating, the binder vapor is able to escape through the gaps between joining material portions, effectively removing the harmful substance that would otherwise remain trapped and degrade the joining layer's electrical and thermal 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 configuration effectively alleviates thermal stress, suppresses crack formation, and improves heat dissipation performance by reducing heat resistance and increasing the reliability of the joining layer.
Implementation Method 1
Fatigues and crack formation caused by the difference in coefficient of linear expansion between the ceramic substrate and the metal bottom plate are avoided by plastic deformation of the buffer layer
Implementation Method 2
the heat conductivity in the joining layer becomes insufficient
Data Source
AI summary
A power module includes an insulated circuit board, a semiconductor element, a first buffer plate, and first and second joining materials. The semiconductor element is disposed on a side of one main surface of the insulated circuit board. The first buffer plate is disposed between the insulated circuit board and the semiconductor element. The first joining material is divided into a plurality of portions in a plan view. The first buffer plate is higher in coefficient of linear expansion than the semiconductor element and lower in coefficient of linear expansion than the insulated circuit board. The first buffer plate is lower in Young's modulus than the semiconductor element.