Copper-Ceramic Bonding via Cu-Sn-O Eutectic Reaction
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Solution Overview
Problem
Existing copper/ceramic bonding methods face issues such as ceramic substrate deterioration, migration problems due to silver presence, and uneven interfacial reactions, particularly in high-temperature applications and high-voltage environments.
Innovation Solution
A copper/ceramic bonded body is formed with an active metal nitride layer on the ceramic side and a Mg solid solution layer between the ceramic and copper members, using active metals like Ti, Zr, or Hf, which enhances interfacial reactions and prevents silver migration, ensuring reliable bonding and improved migration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the DBC method is used to bond copper plates to ceramic substrate, then bonding is achieved, but the bonding temperature must be set to 1065°C or higher which causes ceramic substrate deterioration
Solution Approach 1:
The patent changes the bonding parameters by using a lower eutectic temperature system (Cu-Sn-O at 780-850°C) instead of the conventional Cu-CuO system (1065°C or higher). This is achieved by introducing tin oxide (SnO2) particles into the copper plate, which enables the formation of a liquid phase at lower temperatures through the Cu-Sn-O eutectic reaction, thereby bonding the copper plate to the ceramic substrate without causing deterioration
Solution Approach 2:
The patent introduces an intermediary substance (SnO2 particles) into the copper plate that facilitates the bonding process. The SnO2 particles react with copper to form a liquid phase at lower temperatures, acting as a mediator that enables bonding between copper and ceramic without requiring high temperatures that would damage the substrate
2Reliability
If active metal brazing method with Ag-Cu-Ti brazing material is used, then wettability is improved and reliable bonding is achieved, but Ag migration occurs and high voltage applications cannot be achieved
Solution Approach 1:
The patent extracts and removes silver (Ag) from the bonding interface by replacing the conventional Ag-Cu-Ti brazing material with a copper plate containing SnO2 particles. This elimination of silver prevents migration issues while maintaining bonding reliability through the Cu-Sn-O eutectic reaction mechanism
Solution Approach 2:
The patent replaces expensive silver-based brazing materials with a copper-based system containing tin oxide particles. The copper plate with SnO2 serves as a cost-effective alternative that achieves reliable bonding without the migration problems associated with silver, making the system suitable for high voltage applications
3Temperature
If Cu-Mg-Ti alloy powder paste is used as brazing material in nitrogen gas atmosphere, then bonding is achieved at 560°C to 800°C, but gas remains at bonding interface causing partial discharge
Solution Approach 1:
The patent employs a vacuum atmosphere during the bonding process to prevent gas entrapment at the bonding interface. By conducting the eutectic bonding in vacuum conditions, harmful gases are evacuated from the interface, eliminating the cause of partial discharge while maintaining the low temperature bonding advantage
Solution Approach 2:
The patent replaces the chemical brazing process (using Cu-Mg-Ti alloy powder paste) with a physical eutectic bonding mechanism. Instead of relying on complex alloy reactions in nitrogen atmosphere, the system uses the Cu-Sn-O eutectic reaction combined with vacuum processing to achieve clean bonding without gas entrapment
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 provides a robust and reliable copper/ceramic bond with excellent migration resistance, suitable for high-pressure and high-temperature conditions, by promoting uniform interfacial reactions and eliminating silver from the bonding interface.
Implementation Method 1
the copper plates and the ceramic substrate are bonded by generating a liquid phase at the interfaces between the copper plates and the ceramic substrate using a eutectic reaction of copper and copper oxides
Implementation Method 2
a Mg solid solution layer in which Mg is dissolved in a Cu matrix phase is formed between the active metal nitride layer and the copper member
Implementation Method 3
an active metal nitride layer containing a nitride of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic member side between the copper member and the ceramic member
Data Source
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AI summary
There is provided a copper/ceramic bonded body of the present invention in which a copper member made of copper or a copper alloy and a ceramic member made of aluminum nitride or silicon nitride are bonded to each other, in which an active metal nitride layer containing a nitride of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic member side between the copper member and the ceramic member, a Mg solid solution layer in which Mg is dissolved in a Cu matrix phase is formed between the active metal nitride layer and the copper member, and the active metal is present in the Mg solid solution layer.