Transition Metal Oxide Joint Layer for Thermal Cycling
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Solution Overview
Problem
Existing joined bodies with metal joint layers experience degraded mechanical and electrical joining performance when subjected to repeated thermal histories, leading to reliability issues.
Innovation Solution
A joined body is formed by creating a joint layer with a transition metal powder and oxide powder, where the oxide powder constitutes 2-10% of the total mass, and firing in an oxidizing atmosphere at 750°C to 850°C for 5 hours or less, resulting in a mixed layer that enhances thermal history resistance and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a metal joint layer is used to join two members, then the joining process is simple, but the mechanical and electrical joining performance degrades when subjected to repeated thermal histories
Solution Approach 1:
The joint layer is designed as a composite material containing both metal powder (5-40 mass%) and oxide powder (60-95 mass%), where the metal provides ductility and bonding while the oxide provides thermal stability and resistance to thermal degradation. This composite structure resolves the contradiction by combining the advantages of both materials to achieve both ease of manufacture and reliability under thermal cycling.
Solution Approach 2:
The invention changes the compositional parameters of the joint layer by controlling the ratio of metal to oxide particles, their size distributions, and chemical compositions. By optimizing these parameters, the joint layer achieves both manufacturability (through appropriate melting and bonding characteristics) and thermal history resistance (through oxide stabilization that prevents excessive softening or degradation during repeated heating and cooling cycles).
2Reliability
If a metal joint layer is used, then the electrical conductivity is maintained, but the thermal history resistance is insufficient leading to performance degradation
Solution Approach 1:
The invention optimizes the oxide content parameter within a specific range (60-95 mass%) to balance thermal history resistance with electrical conductivity. By controlling the oxide particle size, metal particle size, and their distribution, the joint layer achieves sufficient thermal stability while maintaining adequate electrical conductivity for the application.
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 more reliable and thermally stable joint with improved mechanical and electrical conductivity, maintaining strength and conductivity even with members having significant differences in thermal expansion coefficients, especially under repeated heating cycles.
Implementation Method 1
firing in an oxidizing atmosphere at a firing temperature of 750°C to 850°C for a holding time of 5 hour or less so as to form a joint portion which at least partially includes a mixed layer containing metal of the transition metal and an oxide thereof
Data Source
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AI summary
A joined body 20 includes comprises a first member 21, a second member 22 having a high coefficient of thermal expansion as compared to that of the first member 21, and a joint portion 30 which at least partially includes a mixed layer 33 containing metal of a transition metal and an oxide of the transition metal and which joins the first member 21 and the second member 22. In this joint portion 30, a first layer 31 containing a first oxide of a transition metal, a second layer 32 containing a second oxide of a transition metal having a low valence as compared to that of the first oxide, and the mixed layer 33 containing metal of a transition metal and an oxide thereof preferably are formed so as to form a multilayer structure.