Copper-Ceramic Bonded Body with Nitride Compound Layer
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Solution Overview
Problem
Existing bonding methods for copper and ceramic substrates, such as DBC and active metal brazing, face challenges including high temperatures that can deteriorate the ceramic substrate and result in crack formation in the nitride compound layer, leading to unreliable bonding and reduced insulation circuit substrate reliability.
Innovation Solution
A copper-ceramic bonded body is formed with a nitride compound layer containing Ti, Nb, Hf, or Zr, and an Ag-Cu eutectic layer, along with an intermetallic compound phase, where the nitride compound layer thickness is controlled between 0.15 μm and 1.0 μm, and Ag particles are dispersed to enhance bonding strength and prevent crack generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If DBC method is used to bond copper plates to ceramic substrate, then bonding strength is improved, but bonding temperature must be set to 1065°C or higher which deteriorates the ceramic substrate
Solution Approach 1:
A nitride compound layer containing Ti, Nb, Hf, or Zr is introduced as an intermediary layer between the copper member and silicon nitride ceramic member. This intermediate layer facilitates bonding at lower temperatures (800-950°C) by forming intermetallic compounds that bridge the copper-ceramic interface, eliminating the need for high-temperature DBC processing while maintaining bonding strength.
Solution Approach 2:
The invention changes the bonding temperature parameter from 1065°C or higher (DBC method) to 800-950°C by introducing the nitride compound layer. This parameter change allows bonding to proceed at lower temperatures while still achieving reliable bonding through the formation of intermetallic compound phases at the interface.
2Reliability
If active metal brazing method with Ag-Cu-Ti brazing filler material is used, then wettability and bonding are improved, but bonding temperature of 900°C deteriorates the ceramic substrate and causes crack formation in nitride compound layer
Solution Approach 1:
The invention extracts the Ti element from the traditional Ag-Cu-Ti brazing filler material and forms a separate nitride compound layer containing Ti, Nb, Hf, or Zr. This separation allows the nitride compound layer to form intermetallic compounds with copper at controlled temperatures, while the Ag-Cu eutectic layer provides low-temperature bonding, thereby reducing the overall bonding temperature and preventing ceramic substrate deterioration.
Solution Approach 2:
The bonding interface consists of a composite structure comprising a nitride compound layer (containing Ti, Nb, Hf, or Zr) and an Ag-Cu eutectic layer. This composite material structure combines the advantages of both layers: the nitride compound layer forms strong intermetallic bonds with copper, while the Ag-Cu eutectic layer provides excellent wettability and low-temperature bonding, achieving reliable bonding without excessive heat.
3Temperature
If bonding temperature is simply decreased, then ceramic substrate deterioration is reduced, but brazing filler material does not sufficiently react with ceramic substrate causing decrease in bonding rate
Solution Approach 1:
The nitride compound layer containing Ti, Nb, Hf, or Zr is formed in advance before the bonding process. This preliminary formation of the reactive nitride layer ensures that when bonding occurs at lower temperatures (800-950°C), the intermetallic compound phase can form immediately between the copper member and ceramic member, maintaining high bonding rate without requiring high temperatures.
4Reliability
If high bonding temperature is used with Ag-Cu-Ti brazing filler material, then bonding is achieved, but thick nitride compound layer forms causing crack generation
Solution Approach 1:
The invention changes the bonding temperature parameter to 800-950°C, which is lower than the traditional high-temperature brazing process. This temperature control prevents the formation of a thick nitride compound layer, thereby avoiding crack generation while still achieving reliable bonding through the formation of intermetallic compound phases at the copper-ceramic interface.
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
This configuration ensures reliable bonding between copper and silicon nitride ceramic members, suppressing crack formation and achieving high bonding strength without unreacted portions, thus enhancing the reliability of the insulation circuit substrate.
Implementation Method 1
a nitride compound layer including one or more nitride forming elements selected from Ti, Nb, Hf, and Zr
Implementation Method 2
an Ag—Cu eutectic layer are formed in order from the ceramic member side
Implementation Method 3
an intermetallic compound phase formed of an intermetallic compound that contains the nitride forming element and Si is present between the copper member and the ceramic member
Data Source
AI summary
In a copper-ceramic bonded body of the present invention, at a bonding interface of a copper member and a ceramic member, there are formed a nitride compound layer containing one or more nitride forming elements selected from Ti, Nb, Hf, and Zr, and an Ag—Cu eutectic layer, in order from the ceramic member side, the thickness of the nitride compound layer is 0.15 μm or more and 1.0 μm or less, an intermetallic compound phase formed of an intermetallic compound that contains the nitride forming element and Si is present between the copper member and the ceramic member, and Cu and Si are present at the grain boundary of the nitride compound layer.