Copper-Silicon Nitride Bonding Structure for High-Voltage Reliability
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Solution Overview
Problem
Existing bonding methods for copper and ceramic substrates, such as DBC, active metal brazing, and Cu-Mg-Ti alloy pastes, lead to ceramic deterioration, partial discharge, and intermetallic compound phases that cause breaking during high-temperature operation, limiting their use in high-voltage applications.
Innovation Solution
A copper/ceramic bonded body with a magnesium oxide layer and Mg solid solution layer, where Mg reacts with nitrogen to form a magnesium nitride phase, ensuring reliable bonding without Ti, Zr, Nb, and Hf, and limiting intermetallic compound phases to 15% or less, using a vacuum and controlled heating to suppress breaking and enhance migration resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DBC method is used to bond copper sheets to ceramic substrate, then bonding is achieved, but bonding temperature must be set to 1065°C or higher causing ceramic substrate deterioration
Solution Approach 1:
A Cu-Mg-Ti alloy intermediate layer is introduced between the copper sheet and ceramic substrate. The Mg component reacts with the ceramic substrate at lower temperatures (560-800°C) to form a bonding interface, while the Cu provides metallurgical bonding to the copper sheet. This intermediary layer enables bonding at temperatures below the ceramic deterioration threshold.
Solution Approach 2:
The bonding process utilizes phase change parameters by controlling the heating temperature range (560-800°C) to trigger specific reactions in the Cu-Mg-Ti alloy. At this temperature range, Mg reacts with the ceramic substrate while avoiding the high-temperature eutectic reaction required in conventional DBC, thus changing the bonding mechanism from high-temperature direct bonding to low-temperature reactive bonding.
2Reliability
If bonding is performed in nitrogen gas atmosphere, then bonding is achieved, but atmospheric gas remains at bonded interface causing partial discharge
Solution Approach 1:
The patent employs a vacuum environment during the bonding process to eliminate atmospheric gases. By performing bonding under vacuum conditions, nitrogen and other atmospheric gases are removed from the bonding interface, preventing their entrapment and subsequent partial discharge issues during high-voltage operation.
3Reliability
If Cu-Mg-Ti alloy paste is used for bonding, then bonding is achieved, but Ti forms intermetallic compound phases causing ceramic breaking during high-temperature operation
Solution Approach 1:
The patent严格控制 the bonding temperature range (560-800°C) to prevent excessive Ti diffusion and intermetallic compound formation. By controlling the temperature parameter, the reaction between Ti and ceramic is limited, avoiding the formation of brittle intermetallic phases that would cause ceramic breaking during high-temperature operation.
Solution Approach 2:
The Cu-Mg-Ti alloy is designed with specific compositional ratios where Mg is the primary reactive component (5-20 mass%) that interacts with the ceramic substrate, while Ti (1-5 mass%) is present in controlled amounts to provide reinforcement without excessive intermetallic formation. This local compositional optimization ensures bonding reliability while preventing ceramic damage.
4Reliability
If active metal brazing method is used, then wettability is improved, but Ag migration occurs reducing high-voltage application suitability
Solution Approach 1:
The patent removes Ag from the bonding material composition entirely, replacing it with a Cu-Mg-Ti alloy system. This extraction of the migratory Ag component eliminates the migration issue while maintaining bonding effectiveness through the reactive Mg component that forms strong bonds with the ceramic substrate without exhibiting migration behavior.
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 reliable bonding with excellent migration resistance and suppresses ceramic breaking during high-temperature operation, ensuring high-voltage and high-temperature reliability.
Implementation Method 1
Mg reacts with nitrogen to form a magnesium nitride phase
Implementation Method 2
using a vacuum and controlled heating to suppress breaking and enhance migration resistance
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A copper/ceramic bonded body includes: a copper member (22) made of copper or a copper alloy; and a ceramic member (11) made of a silicon nitride, wherein the copper member (22) and the ceramic member (11) are bonded to each other, a magnesium oxide layer (31) is provided on a ceramic member (11) side of a bonded interface between the copper member (22) and the ceramic member (11), a Mg solid solution layer (32) is provided between the magnesium oxide layer (31) and the copper member (22) and contains Mg in a state of a solid solution in a Cu primary phase, and a magnesium nitride phase (35) is present on a magnesium oxide layer (31) side of the Mg solid solution layer (32).