Base Plate Stress Profiling for Uniform Heat Sink Contact
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Solution Overview
Problem
The deformation of base plates due to mismatched coefficients of thermal expansion (CTE) during the assembly of power semiconductor modules leads to non-uniform connection layers, resulting in poor heat conduction and unwanted cavities or voids between the base plate and heat sink, which negatively affect heat dissipation.
Innovation Solution
The base plate is designed with locally deformed or stressed areas to differ from surrounding areas, increasing yield strength and stiffness, thereby reducing deflections and ensuring better contact with the heat sink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base plate is made from a uniform metallic material without local modifications, then the manufacturing process is simple, but the base plate deforms during assembly due to CTE mismatch, leading to non-uniform connection layers and poor heat conduction
Solution Approach 1:
The base plate incorporates local quality variations through differently alloyed metal regions. The first region contains a higher proportion of elements from the third group of the periodic table (e.g., Al, Si) compared to the second region, creating distinct mechanical and thermal properties in different areas. This allows the base plate to have enhanced stiffness and reduced deflection in critical areas while maintaining overall structural integrity and heat conduction performance.
Solution Approach 2:
The invention changes the chemical composition parameters of the metallic material to control deflection behavior. By adjusting the proportions of metal groups (first group: Cu, Ag, Au; second group: Ni, Pd, Pt; third group: Al, Si, Ga), the patent modifies the CTE and mechanical properties of specific regions. The first region has a higher third-group element content (≥6 wt% Al or ≥4 wt% Si) compared to the second region, creating parameter variations that reduce overall deflection during assembly.
2Reliability
If the connection layer thickness is increased to fill gaps caused by base plate deflection, then cavities and voids are reduced, but heat conduction deteriorates due to the poor thermal properties of the connection layer material
Solution Approach 1:
The base plate is designed with predetermined compositional variations before assembly. The first region, with its higher third-group element content, is pre-configured to exhibit greater stiffness and reduced deflection during the assembly process. This preliminary structural optimization ensures that the connection layer maintains more uniform thickness throughout, minimizing the formation of cavities and voids without requiring excessive connection layer material that would impede heat conduction.
3Ease of manufacture
If the base plate material is kept uniform throughout, then manufacturing is easier, but local deflections occur during assembly due to differential thermal expansion, creating cavities under substrates
Solution Approach 1:
The base plate incorporates local quality variations through differently alloyed metal regions. The first region contains a higher proportion of elements from the third group of the periodic table (e.g., Al, Si) compared to the second region, creating distinct mechanical and thermal properties in different areas. This allows the base plate to have enhanced stiffness and reduced deflection in critical areas while maintaining overall structural integrity and heat conduction performance.
Solution Approach 2:
The invention changes the chemical composition parameters of the metallic material to control deflection behavior. By adjusting the proportions of metal groups (first group: Cu, Ag, Au; second group: Ni, Pd, Pt; third group: Al, Si, Ga), the patent modifies the CTE and mechanical properties of specific regions. The first region has a higher third-group element content (≥6 wt% Al or ≥4 wt% Si) compared to the second region, creating parameter variations that reduce overall deflection during assembly.
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 design enhances heat dissipation by minimizing cavities and voids, improving thermal coupling and overall performance of the semiconductor module.
Implementation Method 1
the at least one substrate, the connection layer (e.g., solder layer), and the base plate usually have different CTEs (coefficients of thermal expansion). When heating, and subsequently cooling the different components during the assembly process, the difference between the CTEs of the different materials (e.g., copper, ceramic, solder) leads to a deformation of the base plate
Implementation Method 2
forming at least one first area in the layer of metallic material, wherein forming the at least one first area either comprises locally deforming the layer of metallic material, or locally inducing stress into the layer of metallic material
Data Source
AI summary
A method comprises producing a base plate, wherein producing the base plate comprises forming a layer of a metallic material, and forming at least one first area in the layer of metallic material, wherein forming the at least one first area either comprises locally deforming the layer of metallic material, or locally inducing stress into the layer of metallic material, or both such that a deflection or a local stress or both in the at least one first area differs from a deflection or a local stress or both of those areas of the metallic layer surrounding the at least one first area.