Thermoelectric Module Joining Layer Thermal Stress Mitigation
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Solution Overview
Problem
Existing thermoelectric conversion modules are not durable enough to withstand large temperature differences between high-temperature and low-temperature portions, leading to thermal stress and potential breakage due to differences in thermal expansion coefficients between thermoelectric elements and electrodes.
Innovation Solution
A thermoelectric conversion module with a joining layer thickness of 30 μm or more, comprising a first layer with an average crystal grain diameter of 1-10 μm and a second layer with grains over 10 μm, formed by sintering metal particles smaller than 100 nm, to mitigate thermal stress and enhance electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a joining layer is formed using fine metal particles to connect thermoelectric elements and electrodes, then electrical conductivity is improved, but thermal stress causes breakage or failure of the joining layer under large temperature differences
Solution Approach 1:
The patent changes the physical parameters of the joining layer by controlling crystal grain size (creating a gradient from fine to coarse grains) and thickness (30 μm or more). This parameter optimization allows the joining layer to simultaneously achieve good electrical conductivity through fine metal particles and resistance to thermal stress through appropriate grain size distribution and sufficient thickness
Solution Approach 2:
The joining layer is formed as a composite structure with a gradient of crystal grain sizes, combining fine-grained regions (for electrical conductivity) and coarse-grained regions (for mechanical strength and thermal stress resistance). This composite approach allows the single joining layer to fulfill multiple functional requirements that cannot be met by a uniform structure
2Strength
If the joining layer thickness is increased to mitigate thermal stress, then thermal stress resistance is improved, but manufacturing complexity and material consumption increase
Solution Approach 1:
The patent specifies a minimum thickness parameter of 30 μm for the joining layer, which is optimized to provide sufficient thermal stress mitigation without excessive material consumption. This parameter setting balances mechanical strength requirements with manufacturing efficiency and material usage
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 effectively prevents breakage and maintains thermoelectric conversion efficiency by reducing thermal stress and increasing the strength and conductivity of the joining layer, allowing the module to operate reliably across significant temperature differences.
Implementation Method 1
a large temperature difference is caused between the high-temperature portion and the low-temperature portion in the thermoelectric conversion module, and a large temperature difference is also caused between the thermoelectric element and an electrode. Generally, since the thermoelectric element and the electrode have totally different components, in an operation environment in which a large temperature difference is caused, the degrees of thermal expansion are significantly different at the thermoelectric element and the electrode, and a large thermal stress is caused between the thermoelectric element and the electrode
Implementation Method 2
forming paste including metal particles smaller than 100 nm between the electrodes and the thermoelectric element, and sintering the paste so as to form a joining layer which joins the electrodes and the thermoelectric element
Data Source
AI summary
A thermoelectric conversion module includes a pair of substrates, electrodes formed on the facing surfaces of a pair of the electrodes, a thermoelectric element disposed between the electrodes, and a joining layer that joins the electrodes and the thermoelectric element, in which the thickness of the joining layer is 30 μm or more, and is formed by sintering paste including metal particles smaller than 100 nm.