Copper-Titanium-Aluminum Joint Interface for Thermal Cycle Reliability
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Solution Overview
Problem
The increasing heat generation density in power semiconductor, LED, and thermoelectric elements on insulating circuit substrates leads to peeling at the bonded interface of copper and titanium layers under thermal cycles, compromising reliability.
Innovation Solution
A copper/titanium/aluminum bonded body is developed where the copper and aluminum members are bonded via a titanium layer, with an intermetallic compound forming at the interface, and the maximum length of unformed intermetallic compound regions is limited to 20 μm or less, ensuring sufficient interdiffusion and improved bonding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aluminum layer and a copper layer are bonded via a titanium layer in insulating circuit substrates, then conductivity and heat radiation are improved, but peeling occurs at the bonded interface under high temperature thermal cycles
Solution Approach 1:
The patent changes the chemical composition parameters of the titanium layer by adding specific amounts of aluminum (0.1-10 at%) and copper (0.1-10 at%) to form an intermetallic compound layer. This compositional modification transforms the bonding interface from a pure titanium layer that peels under thermal stress to a controlled intermetallic compound structure that resists peeling while maintaining bonding reliability.
Solution Approach 2:
The patent creates a composite intermetallic compound layer at the titanium-copper interface containing multiple elements (Ti, Cu, Al) in specific ratios. This composite structure combines the advantages of different materials: titanium's reactivity for bonding, copper's conductivity, and aluminum's thermal stability, resulting in an interface that resists peeling under thermal cycling while maintaining electrical and thermal performance.
2Reliability
If the intermetallic compound unformed part is large at the bonded interface, then manufacturing is easier, but peeling occurs under thermal cycle load
Solution Approach 1:
The patent establishes specific parameter ranges for aluminum and copper content (0.1-10 at% each) in the titanium layer to control intermetallic compound formation. By adjusting these compositional parameters, the patent ensures complete or near-complete intermetallic compound formation across the bonding interface, eliminating the unformed regions that cause peeling while maintaining manufacturability through controlled diffusion processes.
Solution Approach 2:
The patent performs preliminary compositional design of the titanium layer before bonding by pre-alloying or co-deposition of Ti, Al, and Cu in specific ratios. This preliminary preparation ensures that the intermetallic compound forms uniformly during the bonding process itself, eliminating the need for post-bonding treatments and ensuring complete coverage without requiring extremely tight manufacturing tolerances.
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 peeling at the bonded interface even under high thermal cycles, enhancing the reliability of insulating circuit substrates, power modules, LED modules, and thermoelectric modules by maintaining excellent bonding between copper and titanium layers.
Implementation Method 1
an intermetallic compound containing Cu and Ti is formed at a bonded interface of the copper member and the titanium layer
Data Source
AI summary
In a copper/titanium/aluminum bonded body of the present invention, a copper member made of copper or a copper alloy and an aluminum member made of aluminum or an aluminum alloy are bonded via a titanium layer, an intermetallic compound containing Cu and Ti is formed at a bonded interface of the copper member and the titanium layer, and a maximum value of a length Li of an intermetallic compound unformed part along the bonded interface is 20 μm or less in the bonding interface of the copper member and the titanium layer, the intermetallic compound unformed part being a part free of formation of the intermetallic compound, and a ratio ΣLi/L0 is 0.16 or less, ΣLi being a total length of the intermetallic compound unformed part along the bonded interface and of L0 being a total length of the bonded interface along the bonded interface.