Power Module Substrate Heat Sink Design
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Solution Overview
Problem
The existing power-module substrates with heat-sinks face issues due to thermal expansion differences between the substrate and heat sink, leading to warping, reduced bonding reliability, and increased thermal resistance, which affects the reliability and performance under power and thermal cycles.
Innovation Solution
A power-module substrate design with a copper or copper alloy circuit layer on one surface of a ceramic board, an aluminum layer bonded on the metal layer, and a copper layer bonded on the aluminum layer, using an aluminum-impregnated silicon carbide porous body heat sink, with diffusion layers of intermetallic compounds to absorb thermal stress and reduce warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat sink is formed from aluminum or copper, then high thermal conductivity is achieved, but the power-module substrate warps due to large difference in linear thermal expansion
Solution Approach 1:
The heat sink is formed from a composite material consisting of an aluminum-impregnated silicon carbide porous body. This composite structure combines aluminum (providing thermal conductivity) with silicon carbide (providing low thermal expansion), thereby achieving both high thermal conductivity and reduced warping through the synergistic properties of the composite material.
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 parameter change modifies both the thermal conductivity and the coefficient of linear thermal expansion, optimizing the balance between thermal performance and dimensional stability to reduce warping.
2Stability of the object's composition
If the heat sink is formed from aluminum-impregnated silicon carbide porous body, then warping is reduced, but bonding reliability deteriorates due to insufficient adhesion
Solution Approach 1:
A diffusion layer is introduced as an intermediary between the aluminum-impregnated silicon carbide porous body and the metal layer. This diffusion layer, containing intermetallic compounds of aluminum and copper, serves as a bonding bridge that enhances adhesion and bonding reliability while allowing the underlying composite structure to maintain its low-warpage properties.
Solution Approach 2:
The invention applies local quality by creating a diffusion layer with specific intermetallic compound composition at the bonding interface. This localized region has enhanced bonding properties compared to the bulk material, providing strong adhesion where needed (at the interface) while maintaining the overall low thermal expansion characteristics of the aluminum-silicon carbide composite.
3Adaptability or versatility
If the power-module substrate is repeatedly bent, then thermal expansion differences are accommodated, but cracks arise in the ceramic board
Solution Approach 1:
The invention utilizes thermal expansion principles by selecting materials with matched coefficients of thermal expansion. The aluminum-impregnated silicon carbide porous body has a coefficient of linear thermal expansion close to that of the ceramic board, reducing differential thermal expansion stresses during repeated heating and cooling cycles, thereby preventing crack formation in the ceramic board.
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 bonding reliability, reduces warping, and maintains thermal performance by effectively managing thermal expansion differences, improving the substrate's reliability under power and thermal cycles.
Implementation Method 1
the heat sink is formed from an aluminum-impregnated silicon carbide porous body having low thermal expansion and high thermal conductivity instead of aluminum or copper
Implementation Method 2
between the metal layer and the aluminum layer, between the aluminum layer and the copper layer, and between the copper layer and the aluminum-impregnated silicon carbide porous body, diffusion layers having intermetallic compounds of aluminum and copper are formed
Implementation Method 3
a heat sink bonded on the copper layer and formed from an aluminum-impregnated silicon carbide porous body in which aluminum or an aluminum alloy is impregnated to a porous body made of silicon carbide
Implementation Method 4
The heat sink formed from aluminum or copper has a large difference in linear thermal expansion with respect to the power-module substrate
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention is provided with: a power-module substrate, which is constructed by disposing a metal layer and a circuit layer comprising copper or the like on both surfaces of a ceramic board; an aluminum layer; a copper layer; and a heat sink comprising an aluminum-impregnated silicon carbide porous body, wherein diffusion layers having an intermetallic compound of aluminum and copper are formed between the metal layer and the aluminum layer, between the aluminum layer and the copper layer, and between the copper layer and the aluminum-impregnated silicon carbide porous body, also wherein the circuit layer has a thickness t1 of 0.1-3.0 mm, the meta layer has a thickness t2 of 0.1-3.0 mm, a thickness t3 is not more than 3.0 mm, a thickness t4 is between 0.1 mm and 5.0 mm, and the ratio [(σ1 × t1 × A1) / {(σ2 × t2 × A2) + (σ3 × t3 × A3) + (σ4 × t4 × A4)}] falls within the range of 0.06-0.70.