Aluminum-Copper Bonding Interface with Ti and Al-Ti-Si Layers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power module substrates face issues with bonding reliability due to oxidation of Ni plating films, poor bonding properties of silver oxide paste, and the formation of hard layers at bonding interfaces, leading to cracks and reduced reliability when aluminum members and metal members like copper, nickel, or silver are bonded.
Innovation Solution
A bonding body with a Ti layer and Al-Ti-Si layers, where the Ti layer is disposed at the metal member side and the Al-Ti-Si layer is between the Ti layer and the aluminum member, suppressing diffusion and preventing the formation of hard layers, thereby enhancing bonding reliability across the aluminum and metal member interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ni plating film is formed on aluminum member surfaces by electroless plating, then bonding between aluminum and other metals is improved, but oxidation of Ni plating film occurs during processing, reducing bonding reliability
Solution Approach 1:
A Ti layer is introduced as an intermediary between the Al layer and the Cu layer, preventing direct contact and oxidation of the Ni plating film. The Ti layer acts as a protective barrier during processing, eliminating the harmful oxidation effect while maintaining bonding functionality.
Solution Approach 2:
The bonding structure uses a composite material system consisting of Al layer, Ti layer, and Cu layer. This composite structure combines the advantages of each material: Al for bonding to semiconductor devices, Ti for oxidation resistance and interface stability, and Cu for electrical conductivity and bonding to heat sinks.
2Ease of manufacture
If Al layer and Cu layer are bonded directly or with simple Ti interlayer, then bonding process is simple, but hard layers form at bonding interface under heat cycles, causing cracks and reducing reliability
Solution Approach 1:
The Si concentration in the Al layer is controlled within a specific range (0.01-3.0 mass%), which changes the bonding interface parameters to prevent excessive diffusion and hard layer formation. This parameter optimization maintains bonding simplicity while ensuring reliability under heat cycles.
Solution Approach 2:
The Ti layer serves as a mediator that controls diffusion between Al and Cu layers. It prevents direct formation of hard Al-Cu intermetallic compounds while allowing sufficient bonding, thus preventing cracks under heat cycling conditions.
3Object-affected harmful factors
If oxidation coating film of Al is formed on circuit layer and metal layer surfaces, then natural protection is provided, but solder material cannot bond to the surfaces
Solution Approach 1:
The Ti layer acts as an intermediary that prevents oxidation of the Al layer surface while maintaining bonding capability. It provides a surface that is both protected from oxidation and compatible with solder material bonding, eliminating the need for masking treatments.
Solution Approach 2:
The composite structure of Al layer with controlled Si content and Ti interlayer creates a surface that combines oxidation resistance with solder wettability, eliminating the trade-off between protection and bonding capability.
4Reliability
If masking treatment is performed before Ni plating to avoid electric corrosion, then bonding reliability is improved, but production process complexity and cost increase
Solution Approach 1:
The Ti layer serves as a permanent intermediary that eliminates the need for temporary masking treatments. It provides continuous protection against electric corrosion without requiring additional process steps, thereby reducing production complexity while maintaining reliability.
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
The solution effectively prevents cracks and improves bonding reliability between aluminum and metal members, ensuring reliable bonding even under heat cycles, and reduces production costs by simplifying the bonding process.
Implementation Method 1
the Al-Ti-Si layer being disposed between the Ti layer and the aluminum member and containing Si which is solid-solubilized into Al3Ti
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A bonding body includes: an aluminum member composed of aluminum; and a metal member composed of any one of copper, nickel, and silver, wherein the aluminum member and the metal member are bonded together. In a bonding interface between the aluminum member and the metal member, a Ti layer (15) and an Al-Ti-Si layer (16) are formed, the Ti layer (15) being disposed at the metal member side in the bonding interface, and the Al-Ti-Si layer (16) being disposed between the Ti layer (15) and the aluminum member and containing Si which is solid-solubilized into Al3Ti. The Al-Ti-Si layer (16) includes: a first Al-Ti-Si layer (16A) formed at the Ti layer (15) side; and a second Al-Ti-Si layer (16B) formed at the aluminum member side and a Si concentration of which is lower than a Si concentration of the first Al-Ti-Si layer (16A).