Copper-AlN Bonding with an Mg Solid Solution Interface
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Solution Overview
Problem
Existing bonding methods for copper and ceramic substrates, such as DBC and active metal brazing, face issues like ceramic deterioration, partial discharge, and intermetallic compound formation, which can lead to ceramic breaking during high-temperature operation.
Innovation Solution
A copper/ceramic bonded body with a Mg solid solution layer between the copper and ceramic members, where Mg is diffused and reacted to form a reliable bond, avoiding the use of Ti, Zr, Nb, and Hf to prevent nitride phase and intermetallic compound formation, and using a vacuum atmosphere with controlled pressing load and temperature to ensure strong and durable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If DBC method is used to bond copper sheets to ceramic substrate, then bonding strength is improved, but ceramic substrate deteriorates due to high bonding temperature (1065°C or higher)
Solution Approach 1:
The invention changes the bonding temperature parameter from 1065°C (DBC eutectic point) to a lower range of 500-850°C by using Mg as an intermediate layer, which forms a eutectic reaction with copper at lower temperatures, thus bonding the copper sheets to the ceramic substrate without deteriorating the ceramic
Solution Approach 2:
The invention introduces Mg as an intermediate layer between the copper sheets and ceramic substrate. This Mg layer acts as a mediator that facilitates bonding at lower temperatures through eutectic reaction with copper, preventing direct high-temperature contact between copper and ceramic that would cause ceramic deterioration
2Reliability
If bonding is performed in nitrogen gas atmosphere, then oxidation is prevented, but partial discharge occurs due to atmospheric gas remaining at bonded interface
Solution Approach 1:
The invention uses a vacuum atmosphere (1×10⁻⁶ to 5×10⁻² Pa) during bonding instead of nitrogen gas atmosphere. This vacuum environment prevents oxidation while eliminating atmospheric gases that would remain at the bonded interface and cause partial discharge, thus resolving both concerns
3Strength
If Ag—Cu—Ti-based brazing material is used, then wettability is improved and bonding is reliable, but nitride phases and intermetallic compounds form causing ceramic breaking during high-temperature operation
Solution Approach 1:
The invention extracts and removes Ti, Zr, Nb, and Hf elements from the bonding material composition. By eliminating these active metals that form problematic nitride phases and intermetallic compounds, the invention prevents ceramic breaking during high-temperature operation while maintaining bonding reliability through Mg-based eutectic reaction
4Temperature
If Cu—Mg—Ti alloy paste is used for bonding, then bonding is achieved at 560°C to 800°C, but Mg sublimation and organic matter residue remain at bonded interface causing insufficient bonding
Solution Approach 1:
The invention optimizes the Mg layer thickness parameter to 0.17-3.48 mg/cm² and controls bonding temperature to 500-850°C. This parameter control ensures complete Mg diffusion and reaction without excessive sublimation, and the vacuum atmosphere prevents organic matter residue, achieving high-quality bonded interfaces
Solution Approach 2:
The invention applies Mg as a thin film layer beforehand on the copper sheet surface before bonding. This preliminary Mg layer is carefully controlled in thickness and composition, ensuring it provides sufficient reaction material for eutectic bonding while minimizing excess Mg that would sublime and cause interface defects
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 achieves reliable bonding between copper and ceramic substrates with excellent migration resistance and suppressed ceramic breaking during high-temperature operation, ensuring high reliability under high-voltage conditions.
Implementation Method 1
a Mg solid solution layer is provided between the copper member and the ceramic member and contains Mg in a state of a solid solution in a Cu primary phase
Implementation Method 2
a Mg solid solution layer is provided between the copper member and the ceramic member and contains Mg in a state of a solid solution in a Cu primary phase
Implementation Method 3
the copper sheets and the ceramic substrate are bonded by generating a liquid phase at the interfaces between the copper sheets and the ceramic substrate using a eutectic reaction of copper and copper oxides
Implementation Method 4
since the brazing material containing Ti as an active metal is used, the wettability between the molten brazing material and the ceramic substrate is improved
Implementation Method 5
the brazing material containing Ti as an active metal is used, the wettability between the molten brazing material and the ceramic substrate is improved
Implementation Method 6
Mg in the Cu—Mg—Ti alloy sublimates and does not remain at the bonded interface
Data Source
AI summary
A copper/ceramic bonded body includes: a copper member made of copper or a copper alloy; and a ceramic member made of an aluminum nitride, wherein, the copper member and the ceramic member are bonded to each other, and a Mg solid solution layer is provided between the copper member and the ceramic member and contains Mg in a state of a solid solution in a Cu primary phase.