Ceramic-Metal Joint with Ti-Rich Interface and Porous Brazing Layer
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Solution Overview
Problem
Existing joined bodies of ceramic and metallic members often lack sufficient strength, and may crack during thermal cycles due to inadequate bonding and porosity issues.
Innovation Solution
A joined body comprising a ceramic member with a recess and a metallic member coated with Ni or Au, bonded using a joint layer containing Au, Sn, Ag, Cu, and Ti, with a Ti-rich interface and porosity ratio of 0.1 to 15%, which enhances strength and prevents cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional brazing joint layer is used to join ceramic and metallic members, then the joining process is simple, but the strength is insufficient and cracking occurs during thermal cycles
Solution Approach 1:
The joint layer is segmented into multiple functional layers: a Ti-rich reaction layer at the ceramic interface for anchoring, a intermediate layer containing Au, Sn, Ag, Cu for bonding, and a porous structure distributed throughout. This segmentation allows each layer to perform its specific function optimally, achieving high strength while preventing cracking during thermal cycles.
Solution Approach 2:
The joint layer is designed as a composite material system combining multiple elements (Ti, Au, Sn, Ag, Cu) with controlled porosity (0.1 to 15%). The Ti-rich phase provides strong chemical bonding to the ceramic, while the porous structure accommodates thermal expansion differences, creating a composite that resists both high strength requirements and thermal stress.
2Reliability
If the joint layer is made completely dense to prevent leakage, then sealing is improved, but cracking occurs and strength decreases after thermal cycles
Solution Approach 1:
The joint layer intentionally incorporates a porous structure with porosity controlled at 0.1 to 15%. These pores act as stress relief zones that accommodate thermal expansion mismatches between the ceramic and metallic members during thermal cycling. The porous structure prevents cracking while maintaining sufficient mechanical strength, resolving the contradiction between crack resistance and strength.
3Strength
If Ti content at the ceramic interface is increased to improve bonding, then anchoring strength is enhanced, but excessive reaction may occur
Solution Approach 1:
The joint layer exhibits local quality variation with a Ti-rich concentration specifically at the ceramic interface to maximize anchoring strength through chemical reaction. As one moves away from the ceramic interface into the bulk of the joint layer, the Ti concentration decreases while Au, Sn, Ag, and Cu dominate. This gradient structure ensures strong bonding at the interface while preventing excessive Ti-Al2O3 reaction that would compromise the overall joint layer composition and properties.
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 joined body with high initial and thermal cycle strength, preventing cracking and ensuring durability by anchoring the joint layer through Ti reaction and optimal porosity.
Implementation Method 1
Ti reacts with the ceramic at the joint interface and may serve to anchor the joint layer
Implementation Method 2
the first brazing material is heated in a vacuum atmosphere at 1,050° C. for 5 minutes to form a metallized layer
Implementation Method 3
These components are heated in a vacuum atmosphere at 800° C. for 5 minutes to form a brazing joint layer
Data Source
AI summary
A joined body 10 is manufactured by joining a Mo- or Ti-made terminal 14 having a Ni coating, a Au coating, a Ni—Au coating (with Ni Serving as a base) to a recess 12a formed in a plate-shaped ceramic member 12 made of alumina or aluminum nitride through a joint layer 16. The joint layer 16 contains Au, Sn, Ag, Cu, and Ti and is in contact with a bottom surface of the recess 12a and with at least part of a side surface of the recess 12a (the entire side surface in this case). In the joint layer 16, its joint interface with the ceramic member 12 is Ti-rich. When the joined body 10 is cut in its thickness direction, the ratio of the total cross sectional area of pores to the cross-sectional area of the joint layer 16 (porosity) is 0.1 to 15%.