Ceramic-Copper Bonding Layer Composition for Continuous Brazing
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Solution Overview
Problem
Existing bonded methods for ceramic substrates and copper plates in circuit boards, such as those using active metal bonding with Ti, suffer from low mass productivity due to vacuum requirements and batch processing, leading to inefficiencies and potential oxidation or nitriding of Ti, which limits continuous production.
Innovation Solution
A bonding method using a brazing material with a controlled composition of Cu, Ti, and Sn/In, including Ti-rich and Ti-poor regions, allows for rapid heating and cooling rates, enabling bonding in a nitrogen atmosphere or vacuum, and suppressing diffusion to enhance bondability and reduce warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If active metal bonding method using Ti is employed, then bond strength between ceramic substrate and copper plate is improved, but Ti is easily nitrided or oxidized requiring vacuum environment
Solution Approach 1:
The bonding layer uses a composite material system consisting of Cu-Ti-Sn or Cu-Ti-In alloy, combining multiple elements to achieve both strong bonding capability and resistance to oxidation/nitriding. The specific composition (Cu: 60-80 mass%, Ti: 5-30 mass%, Sn: 5-30 mass% or In: 5-30 mass%) creates a composite structure that maintains bond strength while protecting Ti from harmful reactions.
Solution Approach 2:
The patent enables bonding in nitrogen atmosphere by using the Cu-Ti-Sn or Cu-Ti-In composite material system that resists nitriding. The Sn or In component forms protective layers that prevent nitrogen from reacting with Ti, allowing the use of inert nitrogen atmosphere instead of vacuum, thus simplifying the bonding apparatus.
2Object-affected harmful factors
If vacuum bonding is performed with batch processing, then Ti oxidation/nitriding is prevented, but production time exceeds 24 hours per batch reducing mass productivity
Solution Approach 1:
The patent enables continuous bonding processing by using the Cu-Ti-Sn or Cu-Ti-In material system that allows bonding in nitrogen atmosphere. The bonding apparatus can continuously convey workpieces through the bonding zone without repeated vacuum cycles, achieving continuous production while maintaining bond quality and preventing Ti oxidation/nitriding.
Solution Approach 2:
The patent changes the bonding atmosphere parameter from vacuum to nitrogen atmosphere, and adjusts bonding temperature (700-900°C) and time parameters to optimize the bonding process. These parameter changes enable continuous processing while maintaining effective oxidation/nitriding prevention through the protective effect of the Cu-Ti-Sn or Cu-Ti-In composite material.
3Ease of manufacture
If conventional brazing material composition is used, then bonding is achievable, but diffusion occurs leading to warping and reduced bondability
Solution Approach 1:
The patent precisely controls the composition parameters of the brazing material: Cu: 60-80 mass%, Ti: 5-30 mass%, Sn: 5-30 mass% or In: 5-30 mass%. This specific parameter range optimizes the balance between bonding capability and diffusion control, preventing excessive element diffusion that causes warping while maintaining effective bondability.
Solution Approach 2:
The patent creates local quality differences within the bonding layer by controlling the distribution of Ti-rich and Sn/In-rich regions. The Ti-rich areas provide strong bonding to ceramic substrate, while Sn/In-rich areas provide good bonding to copper plate and suppress diffusion. This local differentiation of composition optimizes both bondability and warping control.
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 approach improves bonding efficiency, reduces production time, and maintains bond strength while preventing Ti oxidation/nitriding, allowing for continuous processing and higher productivity.
Implementation Method 1
rapid heating and cooling rates, enabling bonding
Implementation Method 2
rapid heating and cooling rates, enabling bonding
Implementation Method 3
bonding in a nitrogen atmosphere or vacuum, and suppressing diffusion to enhance bondability
Data Source
AI summary
A bonded body according to an embodiment comprises a ceramic substrate, a copper plate, and a bonding layer provided on at least one surface of the ceramic substrate and bonding the ceramic substrate and the copper plate, in which the bonding layer contains Cu, Ti, and a first element being one or two selected from Sn and In, and the bonding layer includes a Ti-rich region in which a ratio (MTi/ME1) of a mass MTi of Ti to a mass ME1 of the first element being 0.5 or more and a Ti-poor region in which the ratio (MTi/ME1) being 0.1 or less.