Copper-Ceramic Bonded Body With Low-Temperature Brazing Interface Control
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Solution Overview
Problem
Existing bonding methods for copper and ceramic substrates in insulating circuit substrates, such as DBC and active metal brazing, require high temperatures that can deteriorate the ceramic substrate, and there is a need for a substrate that maintains high brazing bonding strength and reliability under severe thermal cycles.
Innovation Solution
A copper/ceramic bonded body with a maximum indentation hardness of 70 to 150 mgf/µm² in a 10 to 50 µm region near the bonded interface, using an active metal compound layer with particles ≤180 nm, and containing Ti, Zr, or Hf, and optionally Si and Ag, to enhance bonding strength and thermal cycle reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high temperature bonding methods (DBC or active metal brazing) are used to bond copper sheet to ceramic substrate, then bonding strength is improved, but ceramic substrate deteriorates due to high temperature
Solution Approach 1:
The patent changes the bonding temperature parameter from conventional high temperatures (1065°C or higher for DBC, 900°C for active metal brazing) to a lower temperature range (800-1000°C). This is achieved by optimizing the composition of the bonding material containing Ag, Cu, and active metals (Ti, Zr, Nb, or Hf), which enables satisfactory bonding strength at reduced temperatures, thereby preventing ceramic substrate deterioration while maintaining bonding integrity
Solution Approach 2:
The patent employs a composite bonding material system consisting of Ag-Cu base metal combined with active metal compounds (Ti, Zr, Nb, or Hf). This composite material approach allows the bonding layer to achieve both strong adhesion to ceramic substrate and copper sheet at lower temperatures, resolving the contradiction between bonding strength and substrate damage by distributing functional requirements across multiple material components
2Reliability
If bonding temperature is reduced to prevent ceramic substrate deterioration, then thermal cycle reliability is improved, but bonding strength may be compromised
Solution Approach 1:
The patent optimizes multiple parameters simultaneously: bonding temperature (800-1000°C), bonding material composition (Ag, Cu, and 3-20 mass% active metal compounds), and heating conditions (temperature integration value of 50-110°C·h). This multi-parameter optimization ensures that bonding strength is maintained at lower temperatures, achieving both thermal cycle reliability and bonding integrity without compromising either aspect
Solution Approach 2:
The active metal compounds (Ti, Zr, Nb, or Hf) serve as intermediary elements that facilitate strong bonding between the Ag-Cu bonding material and both the ceramic substrate and copper sheet at lower temperatures. These intermediaries form intermediate layers that enhance interfacial adhesion, enabling reliable bonding without requiring high temperatures that would compromise 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 solution provides a copper/ceramic bonded body with high brazing bonding strength and excellent thermal cycle reliability, minimizing crack generation and peeling, even under severe thermal conditions.
Implementation Method 1
the copper member and the ceramic member are bonded to each other by using a bonding material containing Ag, Cu, and an active metal
Implementation Method 2
the copper sheet and the ceramic substrate are bonded to each other by forming a liquid phase at an interface between the copper sheet and the ceramic substrate by using a eutectic reaction of copper with a copper oxide
Implementation Method 3
forming a liquid phase at an interface between the copper sheet and the ceramic substrate by using a eutectic reaction of copper with a copper oxide
Implementation Method 4
a copper/ceramic bonded body with high brazing bonding strength and excellent reliability of a thermal cycle
Data Source
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AI summary
According to the present invention, there is provided a copper/ceramic bonded body including: a copper member made of copper or a copper alloy; and a ceramic member made of silicon-containing ceramics, the copper member and the ceramic member being bonded to each other, in which a maximum indentation hardness in a region is set to be in a range of 70 mgf/µm2 or more and 150 mgf/µm2 or less, the region being from 10 µm to 50 µm with reference to a bonded interface between the copper member and the ceramic member toward the copper member side.