Power Module Base Plate Geometry for Warpage-Free Heat Dissipation
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Solution Overview
Problem
The existing power modules face issues with heat radiation efficiency due to differences in thermal expansion coefficients between ceramic insulating substrates and metal base plates, leading to warpage and inadequate contact with heat radiation components, which affects the heat radiation properties.
Innovation Solution
A power module design featuring a base plate with a convex heat radiation surface and metal layers on both sides of the ceramic insulating substrate, where the thermal expansion coefficients of the base plate and ceramic substrate are matched to minimize warpage and ensure close contact with heat radiation components, using materials like AIN, Si3N4, Al2O3, Cu, Al, and alloys to achieve optimal thermal conductivity and expansion compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a ceramic insulating substrate with low linear thermal expansion coefficient is soldered to a metal base plate with high linear thermal expansion coefficient, then the thermal conductivity is improved, but the heat radiation surface becomes warped with concave shape
Solution Approach 1:
The patent applies parameter changes by carefully selecting and matching the linear thermal expansion coefficient of the base plate material to be close to that of the ceramic insulating substrate. This parameter matching prevents differential thermal expansion during temperature changes, thereby avoiding warpage of the heat radiation surface while maintaining good thermal conductivity through the base plate.
Solution Approach 2:
The patent employs composite materials by using a base plate made from metal matrix composite materials that combine metals (such as aluminum or copper) with ceramic particles (such as SiC, Al2O3, or AlN). These composite materials provide both high thermal conductivity and linear thermal expansion coefficient matching with the ceramic insulating substrate, thus resolving the contradiction between thermal performance and dimensional stability.
2Ease of manufacture
If the base plate and ceramic insulating substrate have different thermal expansion coefficients, then the bonding process is simplified, but stress is generated at bonding and during packaging causing surface warpage
Solution Approach 1:
The patent changes the material parameters by selecting base plate materials with linear thermal expansion coefficients specifically matched to the ceramic insulating substrate. This parameter matching eliminates differential thermal expansion stress during bonding and packaging processes, ensuring surface flatness and bonding reliability without complicating the manufacturing process.
Solution Approach 2:
The patent converts the potential harmful effect of thermal expansion differences into a benefit by deliberately selecting base plate materials whose thermal expansion characteristics closely match those of the ceramic insulating substrate. This transformation eliminates stress-related problems and surface warpage, turning a potential manufacturing challenge into a design advantage.
3Ease of manufacture
If a flat base plate is used, then the manufacturing is simpler, but the heat radiation surface warps with concave shape due to thermal expansion difference
Solution Approach 1:
The patent maintains manufacturing simplicity by using flat base plates while resolving the warpage issue through parameter changes in material selection. By choosing base plate materials with linear thermal expansion coefficients matched to the ceramic insulating substrate, the patent eliminates differential thermal expansion effects, allowing flat base plates to maintain flat heat radiation surfaces even after bonding and thermal cycling.
Solution Approach 2:
The patent uses metal matrix composite materials for the base plate that combine the benefits of simple flat geometry with tailored thermal expansion properties. These composite materials enable the base plate to remain flat during manufacturing while simultaneously matching the thermal expansion characteristics of the ceramic insulating substrate to prevent warpage during operation.
4Ease of manufacture
If the heat radiation surface is not flat, then the bonding to ceramic substrate is easier, but air gaps are generated when heat radiation component is attached deteriorating heat radiation property
Solution Approach 1:
The patent applies parameter changes by matching the linear thermal expansion coefficients of the base plate and ceramic insulating substrate. This ensures that the heat radiation surface remains flat after bonding and during thermal cycling, eliminating air gaps between the heat radiation component and the base plate, thereby maximizing heat radiation efficiency while maintaining ease of bonding.
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 radiation properties by ensuring a flat and convex surface contact, reducing heat resistance and preventing air gaps, thereby maintaining efficient heat transfer and preventing semiconductor element damage.
Implementation Method 1
a linear thermal expansion coefficient α1 (× 10 -6 /K) of a base plate is close to a linear thermal expansion coefficient α2 of a ceramic insulating substrate
Implementation Method 2
a Cu, Al or Al-SiC base plate with excellent thermal conductivity
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A power module 1 comprises a base plate 2, a ceramic insulating substrate 4 bonded on the base plate 2, and a semiconductor element 6 bonded on the ceramic insulating substrate 4, wherein a surface 2b of the base plate 2 on a side opposite to the ceramic insulating substrate 4 has a warp 2c with a convex shape, and a linear thermal expansion coefficient α1 (× 10-6/K) of the base plate 2 and a linear thermal expansion coefficient α2 (× 10-6/K) of the ceramic insulating substrate 4 when a temperature decreases in the range of 25°C to 150°C satisfy the following Expression (1). α1−α2α1+α2/2×100≤10