Power Module Substrate with Aluminum-Copper Metal Layer
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Solution Overview
Problem
Existing power module substrates with heat sinks face issues such as thermal strain-induced cracking of insulating substrates due to thermal expansion differences, inadequate heat dissipation due to lower thermal conductivity materials, and reduced durability under power cycle loads, particularly with copper and aluminum sheets.
Innovation Solution
A power module substrate configuration with a copper or copper alloy circuit layer and an aluminum or aluminum alloy metal layer, where the thickness ratio of the metal layer to the circuit layer is optimized (t2/t1 ≥ 2.5) to alleviate thermal strain, and additional elements like Si, Cu, Ag, Zn, Mg, Ge, Ca, Ga, and Li are used in solid solution at the bonding interface to enhance bonding strength and deformation resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a copper sheet is disposed between the aluminum heat sink and the insulating substrate, then thermal strain is partially alleviated, but the insulating substrate is still prone to cracking during thermal cycle loading
Solution Approach 1:
The patent employs a composite structure consisting of an aluminum alloy sheet (first metal sheet) bonded to the insulating substrate, with a copper or copper alloy sheet (second metal sheet) bonded to the aluminum alloy sheet. This composite metal layer structure combines the advantages of both materials: the aluminum alloy provides thermal expansion compatibility with the insulating substrate, while the copper layer provides superior thermal conductivity for heat dissipation. The specific configuration with the aluminum alloy sheet directly bonded to the insulating substrate and the copper sheet bonded to the aluminum alloy sheet creates an effective composite material system that simultaneously addresses both thermal strain management and heat dissipation requirements.
2Reliability
If an organic heat-resistant adhesive is used to bond the heat sink, then thermal strain is moderated, but thermal resistance increases and heat dissipation efficiency decreases
Solution Approach 1:
The patent removes the organic heat-resistant adhesive layer from the bonding interface between the metal layers and the heat sink. Instead, it uses direct metal-to-metal bonding through brazing or diffusion bonding processes, which eliminate the thermal resistance introduced by organic adhesives. The aluminum alloy sheet and copper sheet are directly bonded to each other and to the heat sink without intermediate organic layers, thereby extracting the harmful thermal resistance element while maintaining structural integrity through proper bonding process selection.
3Reliability
If an aluminum sheet is used as the circuit layer, then thermal strain is reduced, but thermal conductivity decreases and heat dissipation becomes inferior
Solution Approach 1:
The patent applies local quality differentiation by using different metal materials in different functional zones. The aluminum alloy sheet (first metal sheet) is positioned where thermal expansion compatibility with the insulating substrate is critical, while the copper or copper alloy sheet (second metal sheet) is positioned where high thermal conductivity is most important for heat dissipation. This spatial differentiation of material properties allows each layer to perform its primary function optimally without compromising the other.
4Strength
If the metal layer thickness is increased to alleviate thermal strain, then substrate cracking is suppressed, but thermal resistance in the metal layer increases
Solution Approach 1:
The patent uses a composite metal layer structure where a relatively thicker aluminum alloy sheet (first metal sheet) is bonded to a copper or copper alloy sheet (second metal sheet). The aluminum alloy layer provides sufficient thickness for thermal strain accommodation and substrate cracking suppression, while the copper layer provides a low thermal resistance pathway for heat conduction. This composite configuration allows the system to achieve both mechanical reliability through adequate thickness and thermal performance through high-conductivity material placement.
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 effectively suppresses cracking of the insulating substrate during thermal cycles, enhances heat dissipation, and improves durability under power cycle loading, ensuring reliable heat management and substrate integrity.
Implementation Method 1
additional elements like Si, Cu, Ag, Zn, Mg, Ge, Ca, Ga, and Li are used in solid solution at the bonding interface to enhance bonding strength and deformation resistance
Implementation Method 2
an aluminum or an aluminum alloy metal layer... enhances heat dissipation
Implementation Method 3
thermal strain caused by the difference in the coefficients of thermal expansion of the heat sink and the insulating substrate
Data Source
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AI summary
A power module substrate (10) including an insulating substrate (11), a circuit layer (12) formed on one surface of the insulating substrate (11), and a metal layer (13) formed on the other surface of the insulating substrate (11), wherein the circuit layer (12) is composed of copper or a copper alloy, one surface of this circuit layer (12) functions as an installation surface on which an electronic component (3) is installed, the metal layer (13) is formed by bonding an aluminum sheet composed of aluminum or an aluminum alloy, a thickness t1 of the circuit layer (12) is within a range of 0.1 mm ≤ t1 ≤ 0.6 mm, a thickness t2 of the metal layer (13) is within a range of 0.5 mm ≤ t2 ≤ 6 mm, and the relationship between the thickness t1 of the circuit layer (12) and the thickness t2 of the metal layer (13) satisfies t1 < t2.