Aluminum-Copper Bonding via Controlled Si Phase
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Solution Overview
Problem
The formation of Kirkendall voids at the bonding interface between aluminum members with a high Si content and copper members during solid-phase diffusion bonding leads to increased heat resistance and deteriorated heat dissipation characteristics in power module substrates.
Innovation Solution
By controlling the Si concentration in the aluminum alloy between 1 mass% to 25 mass% and ensuring the Si phase at the bonding surface has an equivalent circle diameter of 1 µm to 8 µm, the method promotes fine Si phases, reducing Cu diffusion and suppressing Kirkendall void formation, while using electrical heating and pressure to facilitate solid-phase diffusion bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solid-phase diffusion bonding is performed between aluminum member with high Si content and copper member, then bonding strength is improved, but Kirkendall voids form at bonding interface causing heat resistance increase
Solution Approach 1:
The patent changes the physical state parameters of Si phase from coarse to fine dispersion, and controls the size parameter (equivalent circle diameter) to 1-8 µm. This parameter change in Si phase morphology prevents excessive Cu diffusion while maintaining bonding strength, thereby resolving the contradiction between bonding strength and heat dissipation characteristics.
2Reliability
If Ni plating film is formed on surface of circuit layer and metal layer, then bonding reliability is improved, but manufacturing complexity and cost increase due to masking process
Solution Approach 1:
The patent extracts and removes the Ni plating step and masking process from the manufacturing sequence. Instead of forming Ni plating film, the invention directly bonds aluminum member to copper member through solid-phase diffusion bonding with controlled Si phase, thereby eliminating the complex masking process while maintaining bonding reliability.
Solution Approach 2:
The patent introduces fine Si phase (1-8 µm equivalent circle diameter) as an intermediary layer between aluminum member and copper member. This Si phase mediator prevents excessive Cu diffusion and Kirkendall void formation, replacing the need for Ni plating film while simplifying the manufacturing process.
3Reliability
If Ag underlying layer is formed through plating to improve bondability, then bonding is improved, but manufacturing labor and cost increase
Solution Approach 1:
The patent removes the Ag underlying layer formation step from the manufacturing process. By directly using aluminum member with controlled fine Si phase (1-8 µm equivalent circle diameter) for solid-phase diffusion bonding, the invention eliminates the need for Ag plating, thereby improving manufacturing efficiency while maintaining bondability.
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 approach effectively suppresses Kirkendall voids, enhances bonding reliability, reduces heat resistance, and improves heat dissipation characteristics in power module substrates with complex structures, including those with flow passages.
Implementation Method 1
the aluminum member and the copper member are heated and pressurized to facilitate solid-phase diffusion bonding
Implementation Method 2
electrical heating and pressure to facilitate solid-phase diffusion bonding
Data Source
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AI summary
A method of manufacturing a bonded body is provided in which a copper member (13B) formed from copper or a copper alloy, and an aluminum member (31) formed from an aluminum alloy in which a Si concentration is set in a range of 1 mass% to 25 mass% are bonded to each other. In the aluminum member before the bonding, D90 of an equivalent circle diameter of a Si phase at a bonding surface with the copper member is set in a range of 1 µm to 8 µm, and the aluminum member and the copper member are subjected to solid-phase diffusion bonding.