Power Module Substrate Heat Sink Structure for Low Warping
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Solution Overview
Problem
Existing power-module substrates with heat-sinks suffer from warping due to differences in linear expansion coefficients between the substrate and the heat sink, leading to reliability issues during power cycles and hot-cold cycles.
Innovation Solution
The power-module substrate with heat-sink incorporates a heat sink formed from an aluminum-impregnated silicon carbide porous body, with a thicker metal layer than circuit layer, and a specific ratio of yield stress, thickness, and bonding area between the metal and circuit layers to minimize warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a heat sink made of aluminum or copper is used, then high thermal conductivity is achieved, but warping occurs due to large difference in coefficients of linear expansion from the power-module substrate
Solution Approach 1:
The heat sink is constructed as a composite material consisting of a silicon carbide porous body impregnated with aluminum or aluminum alloy. The silicon carbide matrix provides low thermal expansion coefficient matching the substrate, while the impregnated aluminum provides high thermal conductivity, thus simultaneously achieving both low warping and high heat dissipation performance
Solution Approach 2:
The invention changes the material parameters of the heat sink by using aluminum-impregnated silicon carbide instead of pure aluminum or copper. This material substitution fundamentally alters the coefficient of linear expansion to match the substrate while maintaining adequate thermal conductivity, resolving the contradiction between thermal performance and dimensional stability
2Ease of manufacture
If the power-module substrate is heated in mounting process or exposed in temperature change, then electronic parts are mounted, but warping occurs causing position dislocation or bonding reliability deterioration
Solution Approach 1:
The invention addresses thermal expansion mismatch by selecting aluminum-impregnated silicon carbide as the heat sink material. This material has a coefficient of linear expansion that closely matches the ceramic substrate, minimizing differential thermal expansion during heating and cooling cycles, thereby preventing warping-induced position dislocation and bonding failures
3Reliability
If the power-module substrate is warped repeatedly, then thermal-electric conductive grease flows out by pump-out phenomenon, but adhesiveness deteriorates and thermal resistance increases
Solution Approach 1:
By matching the thermal expansion coefficients of the heat sink and substrate through material selection (aluminum-impregnated silicon carbide), the invention eliminates repeated warping cycles that cause pump-out of thermal conductive grease. This maintains consistent contact between the heat sink and cooler, preserving both adhesiveness and thermal conductivity
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 reduces warping and enhances reliability against power cycles and hot-cold cycles by maintaining a stable bonding structure and preventing ceramic board cracking.
Implementation Method 1
The aluminum-impregnated silicon carbide porous body forming the heat sink has coefficient of linear expansion which is near to the ceramic board
Implementation Method 2
aluminum-impregnated silicon carbide porous body with low thermal expansion and high thermal conductivity
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Provided with a power-module substrate and a heat sink made of an aluminum-impregnated silicon carbide porous body formed by impregnating aluminum or the like in a porous body made of silicon carbide; where yield strength of a circuit layer is σ1 (MPa), a thickness of the circuit layer is t1 (mm), a bonding area of the circuit layer and a ceramic board is A1 (mm2), yield strength of a metal layer is σ2 (MPa), a thickness of the metal layer is t2 (mm), a bonding area of the metal layer and the ceramic board is A2 (mm2); the thickness t1 is formed to be between 0.1 mm and 3.0 mm (inclusive); the thickness t2 is formed to be between 0.15 mm and 5.0 mm (inclusive); the thickness t2 is formed larger than the thickness t1; and a ratio {(σ2 × t2 × A2) /(σ1 × t1 × A1)} is in a range between 1.5 and 15 (inclusive).