Copper-Ceramic Bonding Interface for Thermal Cycle Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing insulating circuit substrates face issues with thermal cycle reliability due to the hardening of the bonded interface between copper and ceramic members, leading to potential breaking during severe thermal cycles, especially when using bonding materials containing active metals like Ti.
Innovation Solution
The formation of an active metal compound layer with controlled area rate and thickness, combined with an Ag-Cu alloy layer, at the bonded interface, along with a carbon component discharge process during bonding, to suppress the hardening and enhance thermal cycle reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bonding material containing active metal (Ti) is used to bond copper sheet to ceramic substrate, then the wettability and brazing bonding strength are improved, but the bonded interface becomes hard and breaking occurs during thermal cycle
Solution Approach 1:
The patent applies local quality by creating distinct regions within the bonding material with different compositions and functions. The bonding material contains a first region with active metal particles (Ti) for reacting with ceramic to improve wettability and bonding strength, and a second region with softer metal particles (Ag, Cu, Au) that prevent hardening and improve thermal cycle reliability. This spatial differentiation of material properties resolves the contradiction between achieving strong bonding and maintaining thermal cycle reliability.
2Strength
If active metal reacts with ceramic substrate to improve wettability, then bonding strength increases, but the interface hardening causes breaking under thermal stress
Solution Approach 1:
The patent uses softer metal particles (Ag, Cu, Au) as intermediaries between the active metal particles and the ceramic substrate. These intermediary particles prevent the direct transmission of thermal stress to the hardened interface region while still allowing the active metal to react with the ceramic for improved bonding. The softer metals act as a buffer that mediates between the hard bonding interface and the external thermal environment, preventing breaking during thermal cycling.
3Stability of the object's composition
If carbon is present at bonded interface, then active metal forms carbide and cures the interface, but this hardening reduces thermal cycle reliability
Solution Approach 1:
The patent applies local quality by spatially separating the carbide formation region from the stress-bearing region. Carbon is allowed to react with active metal particles to form carbides in the first region, providing interface curing and stability. Meanwhile, the second region contains softer metals that do not form hard carbides and instead provide flexibility and stress relief during thermal cycling. This localized differentiation resolves the contradiction between interface curing and thermal cycle 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 suppresses the hardening of the bonded interface, ensuring the copper/ceramic assembly maintains structural integrity under severe thermal cycles, thereby enhancing the thermal cycle reliability of the insulating circuit substrate.
Implementation Method 1
Ti which is an active metal reacts with the ceramic substrate; and thereby, the wettability of the bonding material is improved, and the brazing bonding strength between the copper sheet and the ceramic substrate is improved
Implementation Method 2
carbon is present at the bonded interface when a ceramic member and a copper member have been bonded using a bonding material containing an active metal, the active metal reacts with the carbon to form an active metal carbide, and the bonded interface is hardened due to curing by the active metal carbide
Implementation Method 3
subjecting the copper member and the ceramic member laminated with the bonding material being interposed therebetween to a heating treatment, in a state of being pressurized in a lamination direction, generating a liquid phase at an interface between the copper member and the ceramic substrate, and subsequently solidifying the liquid phase by carrying out cooling to bond the copper member to the ceramic member
Data Source
AI summary
This copper/ceramic assembly includes: a copper member consisting of copper or a copper alloy; and a ceramic member, wherein the copper member and the ceramic member are bonded to each other. At a bonded interface between the ceramic member and the copper member, an active metal compound layer is formed on a side of the ceramic member. In a region extending by 10 μm from the active metal compound layer toward a side of the copper member, an area rate of an active metal carbide is 8% or less.