Thermoelectric Module Bonding with Silver Oxide Paste
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Solution Overview
Problem
Conventional thermoelectric conversion modules face challenges in maintaining high performance due to the use of metal materials that melt during soldering or brazing, leading to oxidation issues and difficulty in achieving stable long-term power generation, especially at high temperatures up to 500°C, and the bonding process is not suitable for mass production.
Innovation Solution
A thermoelectric conversion module is developed with a half-Heusler structured n-type thermoelectric element and an oxide-based p-type element, using a silver paste with additives like silver oxide or titanium oxide to reduce bond resistance and enhance thermal stability, allowing for efficient electrical connection and improved durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal materials are used for soldering or brazing to bond thermoelectric conversion elements and conductive members, then electrical connection is achieved, but the materials melt at high temperatures (500°C) causing oxidation and performance degradation
Solution Approach 1:
The patent changes the material parameters by using silver paste containing silver oxide or titanium oxide instead of conventional metal soldering materials. This allows the bonding process to occur at lower temperatures while maintaining electrical conductivity, enabling the module to operate stably at high temperatures up to 500°C without melting or oxidation of the conductive material
Solution Approach 2:
The patent employs a composite conductive paste consisting of silver powder, silver oxide, and titanium oxide. This composite material combines the electrical conductivity of silver with the high-temperature stability and oxidation resistance of metal oxides, creating a bonding material that maintains performance at elevated temperatures
2Reliability
If conventional conductive paste containing silver, gold, or platinum is used to bond n-type thermoelectric conversion elements, then electrical connection is established, but bond resistance is high reducing power generation efficiency
Solution Approach 1:
The patent modifies the compositional parameters of the conductive paste by incorporating silver oxide or titanium oxide alongside silver powder. This chemical composition change reduces the bond resistance at the interface between the n-type thermoelectric conversion element and the conductive member, thereby improving power generation efficiency by reducing energy losses
Solution Approach 2:
The silver oxide or titanium oxide acts as an intermediary substance that facilitates better electrical contact between the thermoelectric element and the conductive member. These oxide particles improve the interfacial properties, reducing contact resistance and enhancing overall electrical conductivity of the bonding structure
3Reliability
If vacuum conditions are used to prevent oxidation of conductive materials at high temperatures, then oxidation resistance is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The conductive paste formulation inherently provides oxidation resistance through the inclusion of silver oxide or titanium oxide, which are stable at high temperatures. This self-protecting property eliminates the need for external vacuum environments, allowing the module to operate in ambient air while maintaining oxidation resistance and simplifying the overall system design
Solution Approach 2:
The metal oxide components create a chemically stable, oxidation-resistant environment at the bonding interface, effectively creating a localized inert atmosphere that protects the conductive materials from oxidation without requiring the entire device to be operated in vacuum conditions
4Strength
If copper brazing in vacuum is used to bond thermoelectric conversion elements, then strong bonding is achieved, but the process is not suitable for mass production
Solution Approach 1:
The patent replaces the complex mechanical brazing process requiring vacuum equipment with a simpler paste application and low-temperature firing process. The silver-based conductive paste can be applied using conventional printing or coating methods and bonded at relatively low temperatures, making the process highly suitable for automated mass production while maintaining strong bonding strength
Solution Approach 2:
The patent changes the bonding parameters by using a lower bonding temperature with silver paste compared to high-temperature copper brazing. This temperature reduction enables the use of simpler equipment and faster cycle times, significantly improving manufacturability for mass production while achieving adequate bond strength through the reactive properties of the silver-based paste
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 module maintains excellent performance with minimal output decrease over time, achieving high thermoelectric conversion efficiency and oxidation resistance across a wide temperature range from 50°C to 500°C, suitable for continuous operation without the need for vacuum conditions.
Implementation Method 1
The thermoelectric conversion utilizes the Seebeck effect, and is an energy conversion method in which a temperature difference between both ends of a thermoelectric conversion material generates a potential difference to generate power
Data Source
AI summary
This thermoelectric conversion module is formed by electrically connecting, by a conductive member, one end of an n-type thermoelectric conversion element having a negative Seebeck coefficient and having a half-Heusler structure to one end of a p-type thermoelectric conversion element containing an oxide having a positive Seebeck coefficient at a temperature of 25° C. or higher. The conductive member is connected to the n-type thermoelectric conversion element and the p-type thermoelectric conversion element through a connection layer containing a conductive metal comprising silver, and the connection layer is characterized by further containing an oxide to reduce the bond resistance between the n-type thermoelectric conversion element and/or the p-type thermoelectric conversion element.