Copper-Ceramic Brazing Composition for High-Strength Ag-Free Joints
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Solution Overview
Problem
The existing copper-ceramic joint techniques face challenges in achieving high joint strength, particularly due to issues like Ag migration and high costs, as well as the formation of brittle intermetallic compounds and large voids that reduce the strength of the joint.
Innovation Solution
A copper-ceramic joint body is developed using a brazing member with a composition of 65-95% Cu, 4.5-33% Mg, and 0.1-7% active metal elements like Ti, Zr, or Hf, which forms a joint layer with a solid solution phase and intermetallic compounds, preventing the localization of brittle phases and voids, thereby enhancing the joint's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an active metal brazing member containing silver is used for joining copper and ceramic members, then joint strength is improved, but Ag migration occurs and cost increases
Solution Approach 1:
The patent removes silver from the brazing member composition entirely, extracting the harmful element that causes migration while maintaining joint strength through alternative alloying elements and controlled microstructure formation
Solution Approach 2:
The patent changes the compositional parameters of the brazing member by specifying precise ranges of Cu (65-95 at%), Mg (4.5-33 at%), and active metal elements (0.1-7 at%), transforming the material system from Ag-containing to Ag-free while achieving comparable or superior joint strength
2Object-generated harmful factors
If a brazing member without silver is used to reduce cost and prevent Ag migration, then cost and harmful effects are reduced, but joint strength becomes insufficient
Solution Approach 1:
The patent creates a composite microstructure in the joint layer consisting of multiple phases (Cu-rich phase, Mg-rich phase, and intermetallic compounds), where each phase contributes different properties that collectively achieve high joint strength without silver
Solution Approach 2:
The patent creates localized regions with different compositions and microstructures within the joint layer, including Cu-rich regions for ductility and Mg-rich regions for strength, with each local area optimized for specific mechanical properties
3Ease of manufacture
If conventional brazing methods are used, then joining is achieved, but brittle intermetallic compounds and large voids form reducing joint strength
Solution Approach 1:
The patent specifies precise parameter ranges for brazing temperature (700-900°C), time (5-120 minutes), and atmosphere (vacuum or inert gas) to control the formation of intermetallic compounds and minimize void formation, transforming the manufacturing process from conventional to optimized
Solution Approach 2:
The patent uses magnesium as an intermediary element that facilitates controlled reaction between copper and ceramic members, forming a transition layer that prevents direct formation of excessive brittle intermetallic compounds and reduces void formation
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 significantly increases the shear and tensile strength of the copper-ceramic joint to at least 10 MPa and 17.3 MPa, respectively, by ensuring a strong connecting structure and minimizing void formation, making the joint more reliable.
Implementation Method 1
a joint layer formed on joint surfaces of the copper member and the ceramic member, and containing Cu and Mg and further containing at least one type of active metal elements
Implementation Method 2
forms a joint layer with a solid solution phase and intermetallic compounds
Data Source
AI summary
A copper-ceramic joint body having high joint strength is provided. The copper-ceramic joint body includes: a copper member made of Cu or Cu alloy; a ceramic member joined to the copper member and made of nitride of Si or Al; and a joint layer formed on joint surfaces of the copper member and the ceramic member, and containing Cu and Mg and further containing at least one type of active metal elements selected from a group of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd and Er, and shear strength of the joint layer is equal to or higher than 10 MPa.