Thermoelectric Module Electrode Silver Base Layer High-Temperature Stability
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Solution Overview
Problem
Thermoelectric conversion modules face reliability issues due to solder softening at high temperatures, potential breakage of ceramic substrates, and material dispersion when using traditional electrode materials and joining methods.
Innovation Solution
A thermoelectric conversion module design featuring electrode layers made of aluminum or aluminum alloy with a silver base layer on ceramic substrates, which provides excellent thermal resistance and prevents material dispersion, combined with heat-transfer metal layers to absorb thermal strain and prevent substrate breakage, and the use of metallized layers and barrier layers to enhance joint reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solder is used to join the electrode and thermoelectric conversion element, then the joining process is simple and reliable at low temperatures, but the solder layer softens at high temperatures (300°C to 500°C), deteriorating joint reliability
Solution Approach 1:
The patent changes the material parameter of the joining layer from solder to a metal that does not soften at high temperatures. The joining layer is made of a metal with a melting point higher than 500°C, which fundamentally changes the thermal stability parameter to maintain joint reliability at elevated temperatures up to 500°C and above.
Solution Approach 2:
The patent employs a composite structure consisting of multiple layers: the electrode layer, the joining layer made of high-temperature resistant metal, and the thermoelectric conversion element. This composite material approach combines the electrical conductivity of the electrode with the high-temperature stability of the specialized joining metal to achieve both electrical functionality and thermal reliability.
2Reliability
If a joint layer made of metal which is not softened even at high temperature is used instead of solder, then joint reliability at high temperature is improved, but breakage in the ceramic substrate may occur
Solution Approach 1:
The patent applies local quality by making the electrode layer and joining layer conform to the surface topology of the ceramic substrate. The layers are formed to follow the contours and local variations of the substrate surface, ensuring uniform stress distribution and preventing concentration of thermal stresses that could lead to ceramic breakage.
Solution Approach 2:
The patent addresses thermal expansion by selecting materials for the electrode and joining layers that have thermal expansion coefficients matched to the ceramic substrate. This material selection strategy ensures that during temperature cycling, the layers expand and contract at similar rates, minimizing differential thermal stress and preventing ceramic substrate breakage.
3Ease of manufacture
If traditional electrode materials are used, then the manufacturing process is simple, but material dispersion occurs at high temperature, deteriorating performance
Solution Approach 1:
The joining layer serves as an intermediary between the electrode layer and the thermoelectric conversion element. This intermediate metal layer acts as a barrier that prevents direct contact and potential dispersion between the electrode material and the thermoelectric element at high temperatures, while still maintaining electrical conductivity and mechanical bonding.
Solution Approach 2:
The patent uses a composite structure with the electrode layer, joining layer, and thermoelectric element as distinct material layers. This composite approach allows each layer to perform its specific function: the electrode provides electrical connectivity, the joining layer provides high-temperature stability and prevents material dispersion, and the thermoelectric element provides the conversion function.
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 ensures high reliability and stability of the thermoelectric conversion module at high temperatures by preventing solder softening, reducing thermal stress on ceramic substrates, and maintaining long-term performance by preventing material dispersion and substrate breakage.
Implementation Method 1
a silver base layer formed on a surface of the electrode layers at at least one of the wiring substrates, and connected to the thermoelectric conversion elements
Implementation Method 2
by arranging the thermoelectric conversion module in a state in which one of the wiring substrates is at a higher-temperature side and the other is at a lower-temperature side so as to apply difference in temperature between the wiring substrates, electromotive force is generated in each thermoelectric conversion element by a Seebeck effect
Implementation Method 3
when both the ends are connected to DC power source, heat is moved in each thermoelectric conversion element by a Peltier effect (the heat is moved in a same direction with the current in the P-type element, and in an opposite direction to the current in the N-type element)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A thermoelectric conversion module 1 which is obtained by connecting a plurality of thermoelectric conversion elements 3, 4 via a pair of wiring substrates 2A, 2B facing each other in such a state that the thermoelectric conversion elements 3, 4 are combined with each other between the wiring substrates 2A, 2B: each of the wiring substrates 2A, 2B is obtained by forming an electrode layer 12, 13 on one surface of a ceramic substrate 11, the electrode layer 12, 13 being connected to the thermoelectric conversion elements 3, 4 and being formed of aluminum or an aluminum alloy: at least the electrode layer 12 that is arranged on the high-temperature side is provided with a silver base layer 21, in which a glass layer and a silver layer are laminated in the surface; and the silver layer of the silver base layer 21 is bonded to the thermoelectric conversion elements 3, 4.