Copper-Ceramic Bonded Body With Low-Impurity Interface Control
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Solution Overview
Problem
Insulating circuit substrates face challenges in withstanding severe thermal cycles due to the formation of hard and brittle TiN layers at the ceramic-copper interface, leading to potential breaking during thermal loading, especially when using Cu-Mg-Ti-based brazing materials with high impurity concentrations.
Innovation Solution
A copper/ceramic bonded body is developed with controlled concentrations of Al, Si, Zn, and Mn at the bonded interface, limited to 3 atom % or less, to suppress the precipitation of fine intermetallic compounds and prevent ceramic substrate breaking during severe thermal cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Cu-Mg-Ti-based brazing material is used to bond copper sheet to ceramic substrate, then bonding strength is improved, but TiN layer forms at the bonded interface causing brittleness and potential breaking during thermal cycles
Solution Approach 1:
The invention changes the chemical composition parameters of the brazing material by strictly controlling impurity elements (Al, Si, Zn, Mn) to 3 atom% or less. This parameter change prevents the formation of harmful TiN layer while maintaining the bonding strength provided by Cu-Mg-Ti-based material, thereby resolving the contradiction between bonding strength and thermal cycle reliability.
Solution Approach 2:
The invention converts the potentially harmful effect of impurity elements into a benefit by establishing precise compositional boundaries. By limiting Al, Si, Zn, and Mn to 3 atom% or less, the impurities that would normally cause TiN formation and brittleness are transformed into controlled constituents that do not harm the bonded interface, thus improving thermal cycle reliability while maintaining bonding strength.
2Ease of manufacture
If high concentration of impurity elements (Al, Si, Zn, Mn) is present at the bonded interface, then liquid phase formation during bonding is improved, but fine intermetallic compounds precipitate causing precipitation hardening and potential breaking during thermal cycles
Solution Approach 1:
The invention applies parameter changes by precisely defining the concentration limits of impurity elements (Al, Si, Zn, Mn) at 3 atom% or less. This controlled parameter change ensures that while sufficient liquid phase forms for proper bonding, the concentration remains below the threshold that triggers harmful precipitation hardening, thus maintaining both manufacturability 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 controlled impurity concentrations effectively prevent ceramic substrate breaking and enhance thermal cycle reliability by reducing precipitation hardening at the bonded interface, ensuring the substrate's integrity under severe thermal conditions.
Implementation Method 1
When a Cu—Mg—Ti-based brazing material is used as in Patent Document 2, a liquid phase of Cu and Mg is formed at the bonded interface
Implementation Method 2
in a case where a large amount of impurity elements are present at the bonded interface, fine intermetallic compounds are precipitated when the liquid phase at the bonded interface is solidified
Implementation Method 3
the vicinity of the bonded interface between the ceramic substrate and the copper sheet is precipitated and hardened
Implementation Method 4
heating at 560° C. to 800° C. in a nitrogen gas atmosphere, and Mg in a Cu—Mg—Ti alloy is sublimated and does not remain at a bonded interface
Data Source
AI summary
A copper/ceramic bonded body is provided, including: a copper member made of copper or a copper alloy; and a ceramic member, the copper member and the ceramic member being bonded to each other, in which a total concentration of Al, Si, Zn, and Mn is 3 atom % or less when concentration measurement is performed by an energy dispersive X-ray analysis method at a position 1000 nm away from a bonded interface between the copper member and the ceramic member to a copper member side, assuming that a total value of Cu, Mg, Ti, Zr, Nb, Hf, Al, Si, Zn, and Mn is 100 atom %.