Cu-Al Bonded Heat Sink Structure for Thermal Cycle Reliability
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Solution Overview
Problem
The bonding of aluminum and copper members through solid-phase diffusion results in a relatively hard intermetallic compound layer, leading to increased heat resistance and decreased bonding rate under hot-cold cycle loads due to the presence of phases like η2, ζ2, and δ phases in the bonding interface.
Innovation Solution
A bonded body configuration where the aluminum alloy member has a Mg concentration between 0.4 and 7.0 mass% and a Si concentration less than 1 mass%, with a Cu-Al-Mg layer between θ and γ2 intermetallic compound layers, suppressing the growth of hard phases and enhancing bonding strength by using a magnesium oxide film with a crystalline granular structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solid-phase diffusion bonding is used to bond aluminum and copper members, then bonding strength is improved, but heat resistance increases and bonding rate decreases under hot-cold cycle loads due to hard intermetallic compound phases
Solution Approach 1:
The patent changes the chemical composition parameters of the aluminum alloy, specifically controlling Mg concentration at 0.4-7.0 mass% and Si concentration at less than 1 mass%. This parameter modification transforms the intermetallic compound phase structure in the bonding interface, suppressing the formation of hard phases (η2, ζ2, δ) while promoting softer phases (θ, γ2), thereby resolving the contradiction between bonding strength and heat resistance under thermal cycling
Solution Approach 2:
The patent creates a composite intermetallic compound layer structure consisting of multiple phases (θ phase, γ2 phase, and Cu-Al-Mg layer) rather than a single-phase structure. This composite phase structure combines the advantages of different phases: θ and γ2 phases provide bonding strength while the Cu-Al-Mg layer suppresses crack propagation, achieving both high bonding strength and reliability under hot-cold cycles
2Strength
If solid-phase diffusion bonding is used to bond aluminum and copper members, then bonding strength is improved, but bonding rate decreases under hot-cold cycle loads
Solution Approach 1:
By modifying the aluminum alloy composition (Mg: 0.4-7.0 mass%, Si: <1 mass%), the patent changes the phase transformation characteristics during bonding. This enables faster formation of a stable, crack-resistant intermetallic compound layer structure, thereby improving bonding rate under hot-cold cycle conditions while maintaining bonding strength
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 the generation of cracks in the compound layer during hot-cold cycles, maintaining high bonding rates and low heat resistance, thereby improving the reliability and efficiency of the bonding process.
Implementation Method 1
the aluminum alloy member and the copper member are bonded to each other through solid-phase diffusion
Implementation Method 2
heat transferred from the semiconductor element toward the insulated circuit board side is diffused to the outside through the heat sink
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An aluminum alloy member (31) is made of an aluminum alloy having a Mg concentration set in a range of 0.4 mass% or more and 7.0 mass% or less and a Si concentration set to less than 1 mass%, the aluminum alloy member (31) and a copper member (13B) are bonded to each other through solid-phase diffusion, and a compound layer (40) made up of a first intermetallic compound layer (41) that is disposed on the aluminum alloy member (31) side and made of a θ phase of an intermetallic compound of Cu and Al, a second intermetallic compound layer (42) that is disposed on the copper member (13B) side and made of a γ2 phase of an intermetallic compound of Cu and Al, and a Cu-Al-Mg layer (43) provided between the first intermetallic compound layer (41) and the second intermetallic compound layer (42) is provided in a bonding interface between the aluminum alloy member (31) and the copper member (13B).