Multistage cryogenic thermoelectric refrigeration device and design method thereof, high-stability welding jig

Abstract

This application relates to the field of thermoelectric device fabrication, and more particularly to a multi-stage low-temperature thermoelectric refrigeration device and its fabrication method, and a high-stability welding fixture, comprising: a multi-stage device, each stage device including multiple pairs of thermocouples, the two ends of each pair of thermocouples being electrically connected by electrodes, and copper electrodes disposed on a substrate; wherein, each pair of thermocouples includes an n-type thermocouple arm and a p-type thermocouple arm, each stage device including a cold end and a hot end, and in two adjacent stages device, the cooling capacity of the cold end of the lower stage device is greater than the heat generation of the hot end of the upper stage device.

Description

Technical Field

[0001] This application relates to the field of thermoelectric device fabrication, and in particular to a multi-stage low-temperature thermoelectric refrigeration device and its design method, as well as a high-stability welding fixture. Background Technology

[0002] Infrared detectors are playing an increasingly crucial role in both military and civilian fields due to their excellent target recognition capabilities and all-weather operational performance. To achieve high-sensitivity detection, mid-infrared sensors based on narrow-bandgap semiconductors (such as PbTe) typically need to operate in cryogenic environments below 150 K to suppress dark currents caused by thermal noise, thereby improving the signal-to-noise ratio. Among various cooling technologies, thermoelectric cooling, with its advantages of high response speed, high control precision, high reliability, vibration caused by no moving parts, and all-solid-state structure, is particularly suitable for active cooling scenarios of infrared detectors with stringent requirements for size, weight, and stability. Thermoelectric devices can be simply divided into single-stage devices and multi-stage devices based on the number of stages. As the name suggests, single-stage devices are the most common type of planar cooling devices, while multi-stage devices are the accumulation of heat flow in the direction of single-stage devices, so their cooling performance is significantly better than that of single-stage devices. Multi-stage devices are generally pyramidal structures with a larger bottom and a smaller top. Typically, the lowest stage is in direct contact with the heat sink, while the cold end is in contact with the object to be cooled, achieving the cooling effect.

[0003] Existing numerical analysis-based multi-stage device design methods mostly treat key performance parameters of thermoelectric materials (such as Seebeck coefficient, resistivity, and thermal conductivity) in multi-stage thermoelectric devices as constant properties that do not change with temperature. This approach is significantly flawed. Multi-stage thermoelectric devices are arranged vertically in space and follow a bottom-up, stage-by-stage cooling mode, resulting in an extremely wide overall operating temperature range, with the cumulative temperature difference from the hot end to the cold end exceeding 160K. Such a large temperature difference means that the thermoelectric arms of each stage are actually in drastically different local temperature fields. Since the performance of thermoelectric materials is a function of temperature, the actual performance parameters of each stage vary significantly depending on its stage number and local operating temperature. If performance prediction is simplified by calculating constant properties based only on material parameters at the initial hot-end temperature, the calculated results will deviate significantly from the actual test results. Therefore, treating material properties as constant properties in calculations fails to reflect the true temperature distribution and material property gradients within the device, inevitably leading to a serious discrepancy between the design results and the actual operation of the device, thus affecting the accuracy of the design.

[0004] On the other hand, in the fabrication of multi-level devices, the integration process commonly employs step-by-step welding and one-step welding. Step-by-step welding uses a layer-by-layer welding strategy, first welding the bottom thermoelectric arm to the substrate, then welding the upper layers one by one, repeating this process until the entire device is assembled. This method often uses solder systems with different melting points, making the process relatively complex. Furthermore, the bottom welding interface is susceptible to thermal cycling loads during multiple high-temperature cycles, which may lead to reduced interfacial bonding strength and microstructure deterioration, thus affecting the electrical and thermal performance of the device. In contrast, one-step welding technology, through an integral fixture structure, achieves simultaneous bonding of all layers in a single thermal cycle. This process significantly reduces the number of thermal shocks experienced by each welding interface, effectively suppressing excessive growth and microstructural evolution of the interfacial reaction layer caused by repeated heating, thereby reducing the risk of welding interface performance degradation. Simultaneously, one-step welding significantly shortens the overall assembly time, reduces the cumulative errors caused by multiple alignment operations, and is beneficial for improving the integration accuracy and structural consistency of the device. However, existing technical solutions often involve complex assembly of integrated welding fixtures, and the pursuit of flexibility can lead to structural instability. Alternatively, pre-aligned components may need to be demolded and transferred to the welding platform before welding. Both of these scenarios can easily lead to assembly errors, especially for multi-stage components with a large number of stages. Therefore, designing highly stable assembly fixtures is crucial for the integration of multi-stage cryogenic thermoelectric refrigeration devices. Furthermore, neither of the above methods can apply pressure to the components during welding while maintaining accuracy. This can result in welding defects such as weld seams and voids at the welding interface, increasing the bond strength and interface resistance, thereby reducing the device's cooling performance and reliability.

[0005] Multi-level device integration is difficult, and the more levels there are, the greater the difficulty and the more complex the related fixtures become. Distributed welding often uses solder systems with different melting points, making the process more complex. Repeated heating welding can also lead to deterioration of the welding interface, affecting the electrical and thermal performance of the device. Common integrated welding fixtures have structural instability and cannot effectively limit the movement of multi-level devices during transfer and welding, reducing the efficiency and success rate of device integration. The inability to apply the correct pressure to the device during welding affects the device's cooling performance and reliability. Summary of the Invention

[0006] In view of this, this application provides a multi-stage low-temperature thermoelectric refrigeration device and its design method, along with a high-stability welding fixture, to solve the design defects of existing multi-stage devices and the technical problems of structural instability, inability to effectively limit positioning and pressurize during welding. To achieve one or more of the above objectives, or other objectives, this application proposes a multi-stage low-temperature thermoelectric refrigeration device and its design method, along with a high-stability welding fixture.

[0007] In a first aspect, this application provides a multi-stage low-temperature thermoelectric refrigeration device, comprising: A multi-stage device, each stage of which includes multiple pairs of thermocouples, the two ends of each pair of thermocouples being electrically connected by electrodes, the copper electrodes being disposed on a substrate; wherein each pair of thermocouples includes an n-type thermocouple arm and a p-type thermocouple arm. Each stage of the device includes a cold end and a hot end. In two adjacent stages, the cooling capacity of the cold end of the lower stage device is greater than the heat output of the hot end of the upper stage device.

[0008] Preferably, the cross-sectional area A and height H of the thermocouple arm in each thermocouple pair satisfy the following conditions: in, ρ is the thermal conductivity; n is the resistivity; n is the n-type thermoelectric arm; and p is the p-type thermoelectric arm.

[0009] Preferably, the heat flow constraints at the cold and hot ends of each stage of the device are as follows: In two adjacent stages of devices, the heat generated at the hot end of the previous stage device is: The cooling capacity of the cold end of the next stage device is: in, > Total Seebeck coefficient Total resistance Total thermal conductivity , These are the Seebeck coefficient, thermal conductivity, and resistivity of thermoelectric materials, respectively. A and H These represent the cross-sectional area and height of the thermocouple arm, respectively. m This represents the number of thermocouple pairs. I , where n is the input current, n is the n-type thermoelectric arm, and p is the p-type thermoelectric arm.

[0010] The second aspect of this application provides a design method for a multi-stage low-temperature thermoelectric refrigeration device, used to complete the design of the multi-stage low-temperature thermoelectric refrigeration device as described in any one of the above claims, including: The operating temperature range is set according to the material properties, the height of the p-type thermocouple and the n-type thermocouple are fixed, and the cross-sectional area of ​​the p-type thermocouple or the n-type thermocouple is fixed. The optimal cross-sectional area value of the n-type thermocouple or the p-type thermocouple in each pair of thermocouples without a fixed cross-sectional area is obtained through wide temperature range simulation. The extreme cold junction temperature of each stage of the device is obtained through simulation. The extreme cold junction temperature of the next stage device is the same as the hot junction temperature of the previous stage device. Based on the extreme cold junction temperature of each level, the height of the p-type thermoelectric arm and the n-type thermoelectric arm, and the cross-sectional area of ​​the p-type thermoelectric arm and the n-type thermoelectric arm, the number of thermocouple pairs contained in each level of the device is calculated. The assembly of thermocouple pairs in each stage of the device completes the design of a multi-stage low-temperature thermoelectric refrigeration device.

[0011] Preferably, the method for calculating the number of thermocouple pairs contained in each stage of the device based on the limiting cold junction temperature, the height of the p-type thermocouple arm and the n-type thermocouple arm, and the cross-sectional area of ​​the p-type thermocouple arm and the n-type thermocouple arm includes: Obtain the hot junction temperature of each stage of the device, the extreme cold junction temperature of each stage of the device, the cross-sectional area of ​​the p-type thermocouple and the n-type thermocouple, the height of the p-type thermocouple and the n-type thermocouple, the interface contact resistance, the number of first-stage thermocouple pairs, and the operating current; Within the temperature range formed by the extreme cold end temperature and the hot end temperature, the actual working temperature is selected by traversal, and the equivalent material parameters within the actual working temperature range corresponding to the actual working temperature are calculated using the integral median method. Based on the equivalent material parameters and the cold end cooling capacity, the actual working temperature corresponding to the cold end cooling capacity being greater than 0 is the target actual working temperature. Based on the target actual operating temperature as the hot end temperature of the next-level device, the target actual operating temperature of the next-level device is calculated within the corresponding temperature range. Combined with the material performance parameters, the values ​​of all thermocouple pairs with corresponding cold end cooling capacity greater than 0 are calculated. Repeat the above steps to calculate the values ​​of all thermocouple pairs whose cold junction cooling capacity is greater than 0 for each level of device; Based on the values ​​of all thermocouple pairs, and according to the cold and hot junction constraints of each stage of the device, the cooling capacity of the next stage is calculated. Q c, i Greater than the heat released by the previous stage Q h, i+1 To obtain the cooling capacity of the cold end when the cold end temperature of the top level is the same as the hot end temperature of the bottom level. Q c By considering both the maximum cooling temperature difference and the maximum cooling capacity, the device structure that meets the requirements is selected, namely the number of thermocouple pairs at each level.

[0012] A third aspect of this application provides a high-stability welding fixture for welding the multi-stage low-temperature thermoelectric refrigeration device described in any one of the above claims, comprising: Base; The base positioning pin is connected to the base. Multiple substrate limiting pieces are stacked in sequence. Each substrate limiting piece is provided with a first positioning hole that cooperates with the positioning pin of the base, and a limiting hole for accommodating and limiting the device to be welded. An increasing plate disposed between two adjacent substrate limiting plates; A top plate is provided on the limiting piece of the substrate, and the top plate is provided with a first top plate positioning hole that cooperates with the positioning pin of the base.

[0013] Preferably, the height-increasing plate is provided with a height-increasing plate positioning hole that cooperates with the positioning pin of the base; The projection of the contour of the height-increasing piece onto the horizontal plane lies within the solid area of ​​the substrate limiting piece, so as to avoid obscuring the limiting hole.

[0014] Preferably, it also includes a transition piece, the two ends of which are mounted on the heightening piece; The transition piece is provided with a transition piece positioning pin; The substrate limiting plate and the top plate are respectively provided with a second positioning hole and a second top plate positioning hole that cooperate with the positioning pin of the transition plate.

[0015] Preferably, the height-increasing plate is provided with mounting holes, and the transition plate is mounted on the mounting holes by mounting members provided at both ends.

[0016] Preferably, the base has a through hole in the area corresponding to the limiting hole.

[0017] Beneficial effects: This application optimizes the cross-sectional area ratio of the n / p type thermoelectric arm and configures the number of thermocouple pairs at each stage to meet the interstage heat flow matching conditions, ensuring effective heat transport and effectively avoiding interstage heat accumulation. This ensures that heat can be smoothly transferred from the low-temperature stage to the high-temperature stage and ultimately dissipated, which is the foundation for the device to achieve large temperature difference cooling. The design method emphasizes the geometric dimensions (cross-sectional area) of the thermoelectric arm. A With height H Asymmetric optimization. Based on theoretical relationships, the optimal size ratio of n-type and p-type thermocouple arms is customized to enable the thermocouple pair to obtain the best thermoelectric figure of merit and refrigeration efficiency in a specific operating temperature range, thereby improving the temperature difference refrigeration capacity of each stage.

[0018] A wide-temperature-range parametric simulation strategy is adopted to improve design accuracy. This strategy considers the temperature-dependent properties of materials during actual operation. By performing parametric simulations in different temperature ranges, the optimal geometry of the thermoelectric arm at its actual operating temperature is obtained. This makes the design results more consistent with the actual temperature distribution of the device, overcoming the errors introduced by traditional constant-property design and significantly improving the accuracy of performance prediction.

[0019] The unique limiting structure allows for safe and convenient application of vertical pressure on the top plate, overcoming the difficulty of applying pressure using traditional methods. This effectively eliminates interface defects such as weld seams, voids, and incomplete soldering caused by the inability to apply pressure, avoiding the risks of weakened interface bonding strength and increased interface resistance, directly improving the device's cooling performance and lifespan. During the welding process, continuous pressure forces the molten solder to flow uniformly and expel gases, ensuring close contact between the thermoelectric arm and the substrate. This overcomes the problems of complex step-by-step welding processes, numerous thermal cycles, and large cumulative errors, ensuring highly consistent performance and quality across different batches and manufactured by different personnel, laying the foundation for large-scale mass production.

[0020] All components are stacked using locating pins as guides, with clear steps that greatly reduce human alignment errors. Integrated welding is employed, with all weld points completed simultaneously in a single thermal cycle, avoiding interface material fatigue and performance degradation caused by multiple high-temperature thermal cycles in step-by-step welding. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] in: Figure 1 This is a schematic diagram of a three-stage thermoelectric refrigeration device in one embodiment; Figure 2 This is a schematic diagram of a single thermocouple pair structure in one embodiment; Figure 3 This is a flowchart illustrating the calculation of the maximum cooling temperature difference for a three-stage thermoelectric refrigeration device in one embodiment. Figure 4 This is a flowchart illustrating the calculation of the maximum cooling capacity of a three-stage thermoelectric refrigeration device in one embodiment. Figure 5 An exploded view of the structure of a three-stage low-temperature thermoelectric refrigeration device and its welding fixture after assembly in one embodiment; Figure 6 This is a schematic diagram of the installation structure of the transition piece in one embodiment; Figure 7 This is a schematic diagram of the base structure in one embodiment; Figure 8 This is a schematic diagram of the first-stage device assembly structure in one embodiment; Figure 9 This is a schematic diagram of the assembly structure of the second-level device in one embodiment; Figure 10This is a schematic diagram of the assembly structure of the third-level device in one embodiment; Figure 11 This is a schematic diagram of the mounting structure of the uppermost substrate limiting piece in one embodiment; Figure 12 This is a schematic diagram of the top plate mounting structure in one embodiment; Figure 13 This is a schematic diagram of the structure of a level 3 device in one embodiment. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Specific Implementation This application provides a multi-stage low-temperature thermoelectric refrigeration device, such as... Figure 1 and Figure 2 As shown, the multi-stage low-temperature thermoelectric refrigeration device 50 includes multiple stages of devices. Taking a three-stage device as an example, the first stage device 51, the second stage device 52, and the third stage device 53 are included.

[0025] Each stage of the device includes multiple pairs of thermocouples 501, with the two ends of each pair of thermocouples 501 electrically connected via copper electrodes 502, which are disposed on a substrate 503. Each stage of the device includes a cold end and a hot end. In two adjacent stages of the device, the cooling capacity of the cold end of the lower stage device is greater than the heat generation of the hot end of the upper stage device.

[0026] Each thermocouple pair 501 also includes a p-type thermocouple arm 5011 and an n-type thermocouple arm 5012.

[0027] Specifically, the principle of multi-stage thermoelectric cooling devices is based on the cascading of thermoelectric effects. Through a carefully designed pyramid structure and inter-stage heat flow matching, the cooling effects of multiple single stages are superimposed in a coupled operating mode of electrical series and thermal parallel connection, ultimately achieving extremely low temperatures or high-performance cooling that a single device cannot achieve. Heat flows from the hot end to the cold end of each stage, cascading the cold end of the next stage with the hot end of the previous stage to serve as a heat dissipation surface for the hot end of the previous stage, thus achieving heat flow matching. Theoretically, each stage can operate as a unipolar device, such as... Figure 1As shown in (a) and (b), the stacking and integration of multi-level devices can achieve better cooling effects. Each level of device is electrically connected via copper electrodes. Thermocouples are the "smallest functional unit" of thermoelectric cooling devices. They consist of one n-type and one p-type thermocouple arm (electrically connected via copper electrode 502). When current flows through, an endothermic effect (cold junction) is generated at one junction, and an exothermic effect (hot junction) is generated at the other junction. Each level of device contains multiple pairs of thermocouples, and its total cooling capacity is a multiple of the cooling capacity of a single thermocouple pair. In thermocouples, the n-type thermocouple arm mainly relies on electron conduction, while the p-type thermocouple arm mainly relies on hole conduction. Under the action of an electric field, charge carriers (electrons or holes) carry heat from the cold junction to the hot junction of the device, thereby achieving cooling. To obtain optimal performance, the cross-sectional area of ​​the n-type and p-type thermocouple arms ( A ) and height ( H They are usually designed to be asymmetric and need to satisfy specific geometric matching relationships.

[0028] The design concept of multi-stage thermoelectric cooling devices is to use the cold end of the next stage device as the heat dissipation surface of the hot end device of the previous stage device, achieving cumulative amplification of temperature difference through thermal cascading. These devices often employ a pyramid configuration. From a stacking structure perspective, the number of thermoelectric arms in the upper stage device is usually less than that in the lower stage device, to ensure that the cooling capacity of the lower stage is greater than the heat generation of the upper stage, thus achieving a gradual decrease in temperature from bottom to top. For each stage device, the cold end is the surface that absorbs heat and cools, and the hot end is the surface that dissipates heat. Spatially, they exhibit cooling at the top and heating at the bottom, with temperatures gradually increasing or decreasing. Typically, the devices are stacked in a pyramid shape, with the apex being the cold side and the base being the hot side. Figure 1 As shown, substrate 503 is an insulating substrate that supports thermocouple pair 501 and electrode 502. It typically possesses good thermal conductivity and electrical insulation. Preferably, substrate 503 is made of aluminum nitride (AlN) ceramic material. Copper lines are formed on substrate 503, connecting thermocouple pair 501, with the copper lines serving as electrodes 502 of thermocouple pair 501. In multi-stage devices, substrate 503 also acts as a thermal interface between stages, tightly connecting the hot end of the lower stage with the cold end of the upper stage, ensuring efficient heat transfer. The thermal conductivity of AlN is typically between 150-200 W / (m·K), much higher than that of aluminum oxide (Al2O3, approximately 20-30 W / (m·K)). High thermal conductivity is crucial for thermoelectric coolers because it ensures that heat is rapidly and efficiently conducted away from the "hot end," preventing heat accumulation that could degrade device performance. At the same time, aluminum nitride is a good insulator, which can effectively isolate the circuit, prevent short circuits, and ensure that the current flows only through the designed thermoelectric arm path. In some implementations, the cross-sectional area A and height H of the thermocouple arm in each thermocouple pair satisfy the following conditions: (1-1) In formula (1-1), ρ is the thermal conductivity; n is the resistivity; n is the n-type thermoelectric arm; and p is the p-type thermoelectric arm.

[0029] Specifically, in thermoelectric cooling devices, n-type and p-type thermoelectric materials are interconnected by copper electrodes to form the smallest functional unit, namely a thermocouple pair. This unit, as the basic building block, can also be regarded as the simplest thermoelectric device. In multi-stage devices, a large number of thermoelectric units are arranged in an array in three-dimensional space, achieving directional heat transport through thermal parallel connection and electrical series connection. If the materials and structures of each thermoelectric unit in the array are exactly the same, and under the same hot junction temperature and operating current conditions, the maximum cooling temperature difference that each unit can achieve is theoretically the same, then the total maximum cooling capacity of a single-stage device is m times the maximum cooling capacity of a single thermocouple (where m is the number of thermocouple pairs contained in the device).

[0030] Therefore, structural optimization of thermocouple pairs is crucial for improving the overall performance of the device. The geometric dimensions of the thermocouple arms, especially the cross-sectional area A and height H, directly determine the thermoelectric figure of merit (TFP) of the device and profoundly affect its cooling performance. Since the materials of the n-type and p-type thermocouple arms typically have different resistivities and thermal conductivityes, to obtain the optimal TFP and cooling efficiency, the geometric dimensions of the two types of thermocouple arms are usually designed as asymmetrical structures. Theoretical analysis shows that when the device achieves the optimal TFP, the geometric dimensions of the n-type and p-type thermocouple arms should satisfy the relationship between their resistivity and thermal conductivity according to Equation 1-1.

[0031] In some implementations, the heat generated at the hot end of the device in an adjacent stage is: (1-3) The cooling capacity of the cold end of the next stage device is: (1-4) in, > Total Seebeck coefficient Total resistance Total thermal conductivity , These are the Seebeck coefficient, thermal conductivity, and resistivity of thermoelectric materials, respectively. A and H These represent the cross-sectional area and height of the thermocouple arm, respectively. m This represents the number of thermocouple pairs. I , where n is the input current, n is the n-type thermoelectric arm, and p is the p-type thermoelectric arm.

[0032] Specifically, taking a three-stage device as an example, the thermal flow constraint for each stage is shown in the following formula: (1-2) (1-3) (1-4) (1-5) (1-6) (1-7) in > , > .

[0033] In the structural design of multi-stage thermoelectric cooling devices, the bottom layer is usually considered the first stage. Key parameters for the first-stage device include the number of thermocouple pairs. Cold end temperature Hot end temperature And the heat absorbed at both the hot and cold ends. With heat release The corresponding parameter for the second-stage device is the number of thermocouple pairs. Cold end temperature and heat flow and The corresponding parameter for the third-level device is the number of thermocouple pairs. Cold end temperature and heat flow and It is particularly important to note that, since the lower end face of the second stage is in direct contact with the upper end face of the first stage device, the downward heat dissipation process of the second stage device will directly affect the cooling interface of the first stage device. Therefore, to ensure the overall performance of the device, the heat flow matching condition must be met: the cold end of the first stage device must absorb heat... The heat dissipation needs to be greater than that of the hot junction of the second-stage device. ,Right now > This condition is fundamental to achieving effective interstage heat transport and avoiding heat accumulation; this heat flux matching principle also applies to other multistage structures. Similarly, since the lower end face of the third-stage device is in direct contact with the upper end face of the second-stage device, the downward heat dissipation process of the third-stage device will directly affect the cooling interface of the second-stage device. Therefore, to ensure the overall performance of the device, the heat flux matching condition must be met: the cold end of the second-stage device absorbs heat... The heat dissipation needs to be greater than that of the hot junction of the third-level device. ,Right now > .

[0034] In some embodiments, this application uses a series-connected power supply for multi-stage thermoelectric cooling devices in terms of circuit configuration. In this mode, the current flowing through each stage of the thermoelectric device has a strictly equal characteristic, meaning that the operating current of all devices is exactly the same. The essence of a multi-stage thermoelectric cooling device is to construct a temperature gradient through thermal series connection.

[0035] In some implementations, in a multi-stage thermoelectric refrigeration device, the first i hot end temperature of the stage Equal to the first i- Level 1 cold end temperature This creates a chain reaction of temperature gradients. Preferably, the total temperature difference of the system can be expressed as the algebraic sum of the temperature differences at each stage: in, , N It is a series.

[0036] This application optimizes the cross-sectional area ratio of the n / p type thermoelectric arm and configures the number of thermocouple pairs at each stage to meet the interstage heat flow matching conditions, ensuring effective heat transport and effectively avoiding interstage heat accumulation. This ensures that heat can be smoothly transferred from the low-temperature stage to the high-temperature stage and ultimately dissipated, which is the foundation for the device to achieve large temperature difference cooling. The design method emphasizes the geometric dimensions (cross-sectional area) of the thermoelectric arm. A With height H Asymmetric optimization. Based on theoretical relationships, the optimal size ratio of n-type and p-type thermocouple arms is customized to enable the thermocouple pair to obtain the best thermoelectric figure of merit and refrigeration efficiency in a specific operating temperature range, thereby improving the temperature difference refrigeration capacity of each stage.

[0037] This application provides a design method for a multi-stage low-temperature thermoelectric refrigeration device, used to implement the design of the aforementioned multi-stage low-temperature thermoelectric refrigeration device, including: S1: Set the working temperature range according to the material properties, fix the height of the p-type thermocouple and the n-type thermocouple, as well as the cross-sectional area of ​​the p-type thermocouple or the n-type thermocouple, and obtain the optimal cross-sectional area value of the n-type thermocouple or the p-type thermocouple in each pair of thermocouples without fixed cross-sectional area through wide temperature range simulation. S2: The extreme cold junction temperature of each level of device, the extreme cold junction temperature of the previous level device, and the hot junction temperature of the next level device are obtained through simulation. S3: Based on the extreme cold junction temperature of each level, the height of the p-type thermoelectric arm and the n-type thermoelectric arm, and the cross-sectional area of ​​the p-type thermoelectric arm and the n-type thermoelectric arm, the number of thermocouple pairs contained in each level of device, as well as the cooling temperature difference and cooling capacity of devices with different configurations are calculated. The design of a multi-stage low-temperature thermoelectric refrigeration device is completed by assembling the thermocouple pairs of each level of the device.

[0038] Specifically, the operating temperature range refers to the temperature at which a device operates normally, i.e., the range between the hot-junction temperature and the cold-junction temperature. Simulation refers to the process of creating a finite element simulation model based on... Figure 2 The device structure shown is used for calculations. Since the key performance parameters of thermoelectric materials (such as Seebeck coefficient, resistivity, and thermal conductivity) are all functions of temperature, different types of thermoelectric materials have different suitable operating temperature ranges. Therefore, when designing thermoelectric devices, the performance of the materials must be comprehensively considered. The choice of thermoelectric material is directly determined by the operating temperature range. For example, Bi2Te3-based materials, suitable for room temperature (~300K), experience severe performance degradation at low temperatures of 150K; conversely, BiSb-based materials designed for low temperatures perform excellently in the 100-150K range. The extreme cold junction temperature is a key performance parameter and calculation boundary condition in the design of multi-stage thermoelectric refrigeration devices. Specifically, it refers to the temperature at which a certain stage of the thermoelectric refrigeration device, under a given operating current and hot junction temperature, operates without an external heat load (i.e., cooling capacity). Q c When the temperature approaches 0, it represents the lowest possible temperature that the cold end can reach. In calculating the actual operating temperature and performance of multi-stage thermoelectric cooling devices, the "limiting cold end temperature" of each stage is creatively used as the key iterative calculation boundary and starting point, significantly improving the accuracy and reliability of the design. This ensures that the calculations are performed within the physically achievable temperature range of the device at that stage, fundamentally avoiding non-physical interpretations and making the performance prediction results more reliable.

[0039] In thermoelectric refrigeration devices, n-type and p-type thermoelectric arms made of n-type and p-type thermoelectric materials are interconnected by copper electrodes to form the smallest functional unit, namely a pair of thermocouples. Thermocouple pairs, as the basic thermoelectric unit, can also be considered the simplest thermoelectric devices. In multi-stage devices, a large number of thermocouple pairs are arrayed in three-dimensional space, achieving directional heat transport through thermal parallel connection and electrical series connection.

[0040] Preferably, the materials and structures of each thermocouple pair in the array are completely identical.

[0041] Specifically, if the materials and structures of each thermocouple pair are exactly the same, then under the same hot junction temperature and operating current conditions, the maximum cooling temperature difference that each unit can achieve is theoretically the same, and the total maximum cooling capacity of a single-stage device is m times the maximum cooling capacity of a single thermocouple (m is the number of thermocouple pairs contained in each stage of the device).

[0042] Structural optimization of thermocouple pairs is crucial for improving overall device performance. The geometric dimensions of the thermoelectric arms in a thermocouple pair, especially the cross-sectional area A and the height H of the thermoelectric arm, directly determine the thermoelectric figure of merit of the device and profoundly affect its cooling performance. Since the n-type and p-type materials constituting the thermocouple typically have different resistivities and thermal conductivities, to obtain the optimal thermoelectric figure of merit and cooling efficiency, the geometric dimensions of the two thermoelectric arms are usually designed as an asymmetric structure. Theoretical analysis shows that when the device achieves the optimal thermoelectric figure of merit, the geometric dimensions of the n-type and p-type thermoelectric arms should satisfy the following matching relationship with their resistivity and thermal conductivity: (1-1) Where A is the cross-sectional area of ​​the thermoelectric arm, H is the height of the thermoelectric arm, α is the Seebeck coefficient of the thermoelectric material, κ is the thermal conductivity, and ρ is the resistivity.

[0043] Assuming that each thermoelectric arm (including n-type and p-type thermoelectric arms) has the same height and the cross-section of the thermoelectric arm is square with a side length of L, the geometric dimensions of the n-type and p-type thermoelectric arms should satisfy the following matching relationship with their resistivity and thermal conductivity: (1-8) For example, this application uses finite element simulation software to design the thermoelectric arm of a thermoelectric cooling device. First, a single device model is established, such as... Figure 2 As shown.

[0044] This application employs a wide-temperature-range parametric simulation strategy. In multi-stage thermoelectric cooling devices, due to the wide overall operating temperature range, the thermoelectric arms of different stages are actually located in different local temperature fields, causing their thermoelectric transfer parameters (such as Seebeck coefficient, resistivity, and thermal conductivity) to vary with the stage. By conducting wide-temperature-range simulations, the optimal geometric dimensions of each stage's thermoelectric arm within its corresponding operating temperature range can be systematically obtained, providing an optimization basis for subsequent device size design that conforms to the actual temperature distribution. Comprehensive characterization of the device's thermoelectric behavior under different geometric dimensions and operating conditions provides a reliable numerical verification basis for theoretical optimization results.

[0045] Bi 1-x Sb x Taking a low-temperature multi-stage device as an example, simulations were performed in the temperature range of 100-150K with a step size of 10K. The heights of the p-type and n-type thermoelectric arms were set to be the same. H The cross-sectional dimensions of the p-type thermoelectric arm are also considered. Since the cross-section is square, the cross-sectional value can be directly derived from the side length. Changing the cross-sectional value of the n-type thermoelectric arm changes the side length of the n-type thermoelectric arm's cross-section. Simulations are performed to change the thermoelectric arm's geometric dimensions under different temperature ranges. G = Thermoelectric arm height H / Cross-sectional area of ​​the thermoelectric armA The effect of the device's cooling temperature difference. Within the temperature range of 100-150K, determining the optimal dimensions of the n-type thermoelectric arm's cross-section (or side length) when the maximum cooling temperature difference occurs will determine the device's performance. G = H / A The optimal value. The above method can also be used to simulate with a fixed cross-sectional size of the n-type thermoelectric arm to obtain the optimal cross-sectional size of the p-type thermoelectric arm.

[0046] The design method for the number of thermocouple pairs in each level of the device is as follows: Based on the initial hot junction temperature (e.g., 150 K) and material performance parameters, it is not possible to directly perform accurate calculations. This is mainly because the key parameters of thermoelectric materials (such as Seebeck coefficient, resistivity and thermal conductivity) are all functions of temperature. If they are simplified to physical property constants, the calculation results will deviate significantly from the actual test results. Therefore, how to accurately calculate the cooling performance of multi-stage devices has become the core challenge in its design process.

[0047] This application proposes using interstage deconstruction analysis as the core method for predicting the performance of multi-stage thermoelectric refrigeration devices. Based on the heat flow constraint relationship of each stage (see formulas (1-2) to (1-7)), the cooling capacity of a single-stage thermoelectric refrigeration device is related to its cooling temperature difference (Δ). T = The thermal conductivity and the number of thermocouple pairs are inversely proportional, and the slope of the curve is determined by both the total thermal conductivity of the material and the number of thermocouple pairs. When the externally applied heat load is much smaller than the device's own cooling capacity, the actual cooling temperature difference of each stage of the device will approach its theoretical maximum cooling temperature difference. Based on the above principle, the performance prediction process proposed in this application is as follows: First, the maximum cooling temperature difference that the first-stage thermoelectric unit can achieve at a given hot-end temperature is obtained through simulation or calculation, that is, the lowest temperature that its cold-end surface can reach; then, this cold-end temperature is used as the input of the hot-end temperature of the second stage, and the lowest cold-end temperature of the second stage is solved; by recursively repeating the above operation, the limiting cooling temperature difference of each stage in the entire multi-stage device can be systematically solved, thereby completing the accurate prediction of the overall cooling capacity of the device.

[0048] For example, taking a three-stage thermoelectric cooling device, the initial hot-end temperature of the first-stage thermoelectric cooling device is set to 150 K. The limiting cold-end temperature of the first stage in thermal equilibrium is obtained through single-stage simulation. ;Will Using the hot-end temperature of the second stage as the basis, a single-stage simulation is performed again to obtain the extreme cold-end temperature of the second stage. (This temperature also serves as the hot-end temperature of the third stage); by repeating the above recursive process, the ultimate cold-end temperature of the third stage can be obtained. This allows for the systematic prediction of the cooling temperature difference of the entire three-level device under specified operating conditions.

[0049] The preferred method for obtaining the number of thermocouple pairs is as follows: (1) Obtain the hot end temperature of each stage of the device, the extreme cold end temperature of each stage of the device, the cross-sectional area of ​​the thermoelectric arm, the height of the thermoelectric arm, the interface contact resistance, the number of thermocouple pairs in the first stage, and the operating current; (2) Within the temperature range formed by the extreme cold end temperature and the hot end temperature, the actual working temperature is selected by traversal, and the equivalent material parameters in the actual working temperature range corresponding to the actual working temperature are calculated by the integral median method. Based on the equivalent material parameters, the actual working temperature corresponding to the cold end cooling capacity is greater than 0, which is the target actual working temperature. (3) Based on the target actual working temperature as the hot end temperature of the next stage device, the target actual working temperature of the next stage device is calculated in the corresponding temperature zone. Combined with the material performance parameters, the values ​​of all thermocouple pairs with corresponding cold end cooling capacity greater than 0 are calculated. (4) Repeat the above steps to calculate the values ​​of all thermocouple pairs whose cold junction cooling capacity is greater than 0 for each level of device; (5) Based on the values ​​of all thermocouple pairs, and according to the cold and hot junction constraints of each stage of the device, the cooling capacity of the next stage is calculated. Q c, i Greater than the heat released by the previous stage Q h, i+1 And obtain the cold-end cooling capacity when the cold-end temperature of the top level is the same as the hot-end temperature of the bottom level. Q c By considering both the maximum cooling temperature difference and the maximum cooling capacity, the device structure that meets the requirements is selected, namely the number of thermocouple pairs at each level.

[0050] Specifically, the integral median method refers to the method of calculating the key thermoelectric performance parameters (Seebeck coefficient) of a material within its operating temperature range. α resistivity ρ Thermal conductivity κ The integral is performed, and its average value over the interval is calculated; this average value is the "integral median". The target value of the number of thermocouple pairs at each stage refers to the optimal value of the number of thermocouple pairs in the device design. To accurately predict the actual cooling performance of multi-stage thermoelectric refrigeration devices, this application uses Python software for calculation. Taking a three-stage structure design as an example, the final calculated number of thermocouple pairs in each stage is obtained. m 1. m 2 and m 3. And the maximum cooling temperature difference and maximum cooling capacity of the device. For example... Figure 3 As shown, the specific steps are as follows: (1) First, input the known initial parameters, including the hot end temperature and extreme cold end temperature of each thermoelectric cooling device, and the cross-sectional area of ​​the n-type thermoelectric arm and the p-type thermoelectric arm. A n and A p The uniform height of both n-type and p-type thermoelectric arms is... H Interface contact resistance R c (Known material properties) Number of thermocouple pairs in the first-stage device m 1 (initial design settings), and operating current. I Within a certain range, different input currents... I By iterating through the data, we can obtain the refrigeration temperature difference corresponding to the three-stage thermoelectric refrigeration devices with different structures.

[0051] (2) After completing the initial parameter settings, the parameters of the first-stage thermoelectric refrigeration device structure are calculated first. This is done at the known minimum limiting temperature. With hot end temperature T h Within the defined range, the actual operating temperature of the first-stage thermoelectric refrigeration device. T 1. Perform traversal calculations. During this process, when the first-stage thermoelectric arm is operating at... ~ T h When considering a specific temperature range, it is necessary to determine the key thermoelectric performance parameters of the material within that range (including the Seebeck coefficient). α 1. Resistivity ρ 1 and thermal conductivity κ 1) Perform the integral mean value calculation. Substitute the obtained equivalent material parameters into theoretical formulas (1-2) and (1-3) to calculate the heat absorption of the first-stage cold end. Heat release at the hot end .when When >0, the corresponding actual operating temperature is obtained. T 1. Proceed to the next level of calculation; if this condition is not met, a new selection is required. T 1 value and repeat this step to calculate until... >0.

[0052] (3) The actual working temperature obtained from the first stage calculation T 1 serves as the hot-end temperature input for the second stage, at the second stage's minimum limiting temperature. T 2,min and T Temperature calculations are performed across the temperature range defined by 1. T The actual value of 2. During this process, the Seebeck coefficient of the second-stage thermoelectric material within the corresponding operating temperature range needs to be determined. α 2. Resistivity ρ 2 and thermal conductivity κ 2. Integral median values ​​of key parameters are calculated. Based on the fundamental assumption of interstage heat balance, the cooling capacity of the first stage is set. Equal to the heat release of the second stage Substituting this thermal equilibrium condition and material parameters into the equations shown in formulas (1-4) and (1-5), the required number of thermocouple pairs for the second stage can be obtained through numerical solution. m 2 (rounded to the nearest integer) and the corresponding actual cooling capacity If both conditions are met... >0 and m 2< m If condition 1 is met, proceed to the next level of parameter calculation; otherwise, reselect the parameter. T Repeat this step to obtain a value of 2 until a feasible solution that satisfies all constraints is obtained.

[0053] (4) In the calculation of the third-level parameters, the actual operating temperature output from the second level is used. T 2 serves as the hot-end temperature input for the third stage. T 3,min to T Traversing the interval of 2 T The actual value of 3, and calculate the thermoelectric parameters of this grade of material in the corresponding temperature range ( α 3. ρ 3. κ 3). Based on the interstage heat balance assumption, let the cooling capacity of the second stage be... Q c, 2 Equal to the heat release of the third stage Q h, 3 Substituting into formula (1-7), we can obtain the number of thermocouple pairs required for the third stage. m 3 (rounded to the nearest integer) and actual cooling capacity Q c, 3 When both conditions are met Q c, 3 >0 and m 3< m Under condition 2, the output includes the hot end temperature. T h Operating temperatures at all levels T 1. T 2 and T 3 and the number of thermocouple pairs m 1. m 2 and m 3. Complete parameter set; otherwise, you need to select again. T 3. Iterative calculations are performed using different values ​​until a feasible solution that meets all constraints is obtained.

[0054] In the above calculation process, the temperature boundary conditions (such as hot and cold junction temperatures) of each stage of the device must first be fixed. Then, the optimal number of thermocouple pairs for each stage is solved numerically. Since the calculated number of thermocouple pairs is usually not an integer, while the number of thermocouples in an actual device must be an integer, the calculation results need to be rounded. This rounding process introduces errors, leading to unreasonable situations in the dataset where the thermocouple pair configuration is exactly the same but the calculated cold junction temperature values ​​are different. To ensure the validity and rationality of the results, when outputting performance data, only the maximum value among all possible cold junction temperatures under the same thermocouple pair configuration is selected as the limit cooling temperature difference achievable by that configuration and output.

[0055] Meanwhile, to examine the maximum cooling capacity of the device, the cooling capacity of the next stage is calculated based on the values ​​of all thermocouple pairs and the constraints of the cold and hot ends of each stage of the device. Q c, i Greater than the heat released by the previous stage Q h, i+1 And obtain the cold-end cooling capacity when the cold-end temperature of the top level is the same as the hot-end temperature of the bottom level. Q c The specific implementation method for selecting the device structure that meets the requirements by considering both the maximum cooling temperature difference and the maximum cooling capacity, i.e., the number of thermocouple pairs at each level, is as follows, and the calculation logic is as follows: Figure 4 As shown: (1) First, input the existing initial parameters: A n , A p , H , R c , I , m 1. m 2. m 3. T h and T c .in, A n The cross-sectional area of ​​the n-type thermoelectric arm. A p The cross-sectional area of ​​the p-type thermoelectric arm. H For the height of n-type and p-type thermoelectric arms, R c For contact resistance, I For input current, m 1. m 2. m 3 represents the thermocouple pair values ​​calculated for each corresponding level. T h and Tc These are the hot-end temperature of the top-level device and the cold-end temperature of the bottom-level device, respectively. Taking a three-level pyramid-shaped device as an example, the top-level device is the bottom device of the pyramid, and the bottom-level device is the top device of the pyramid. Calculated using the hot-end and cold-end constraint formulas (1-2)-(1-7), when... T c and T h When the cooling capacity of the device is the same, the thermocouple pair structure corresponding to the device with the maximum cooling capacity is the optimal device structure.

[0056] (2) Under the known minimum temperature limit of the first-stage device T 1, min With hot end temperature T h Within the defined operating temperature range, the actual operating temperature for the first level. T 1. Iterate through and retrieve values. For each... T 1. Take a value and calculate the median integral parameter of the material properties in this temperature range. Substitute this parameter into the theoretical formula (1-3) to solve for the first-stage cooling capacity under this condition. Q c, 1 If the calculation result satisfies Q c, 1 If the value is greater than 0, the first-level parameter calculation is completed and the next iteration begins; otherwise, a new parameter is automatically selected. T The current step is repeated for a value of 1 until the calculation result satisfies the condition. Q c, 1 >0.

[0057] (3) In T 1 and T 2,min Traversal within range T 2. Calculate the median integral of the material properties, and substitute it into formulas (1-4) and (1-5) to obtain... Q h, 2 and Q c, 2 The condition for determining interstage thermal balance is set as follows: the cooling capacity of the second stage... Q c, 2 The value is greater than 0, and the cooling capacity of the first stage is greater than the heat output of the second stage. This condition ensures that the cooling capacity generated by the first stage is slightly greater than the heat output of the second stage, which is consistent with actual conditions. If the calculation result satisfies both of the above conditions, the calculation process proceeds to the next stage; otherwise, a new interval needs to be selected within the current range. T The value of 2 is determined, and the iterative calculation of this step is repeated.

[0058] (4) In the third-level device (the topmost device), the calculation must meet the top temperature requirement. T c=T h The specific method is as follows: Calculate T 2 ~T c The median value of the integral of the properties of each material can be obtained by substituting it into formulas (1-6) and (1-7). Q h, 3 and Q c, 3 The condition for determining interstage thermal balance is set as follows: the cooling capacity of the third stage. Q c, 2 The output value is greater than 0, and the cooling capacity of the second stage is greater than the heat release of the third stage. If the calculation result satisfies both of the above conditions, then the output value is... m 1 、m 2 、m 3 and Q c, 3 Otherwise, you need to reselect within the current range. T The value of 2 is determined, and the iterative calculation of this step is repeated.

[0059] During the cooling capacity calculation process, the iterative program assumes that the temperatures of each level of the device meet the following requirements. T h > T 1> T Constraints 2. For some device structures, although the above temperature relationships are satisfied, the interstage thermal balance determination conditions are not met, and such structures are eliminated in the iteration. In addition, some device structures can adapt to multiple temperature range divisions and correspond to multiple possible cooling capacity values. The maximum value among them is uniformly selected as the representative cooling capacity of the structure.

[0060] In the design of multi-stage thermoelectric refrigeration devices, the maximum cooling temperature difference and the maximum cooling capacity are usually negatively correlated. Therefore, relying solely on a single performance indicator cannot effectively guide the structural optimization of the device. This application establishes a computational model that can simultaneously obtain the maximum temperature difference and maximum cooling capacity of devices with the same structure. By comprehensively balancing these two key performance parameters, device configurations with better overall performance in terms of temperature difference and cooling capacity are selected. This method provides a clear quantitative basis for subsequent device design and performance improvement for practical applications.

[0061] This application optimizes the cross-sectional area ratio of the n / p type thermoelectric arms and configures the number of thermocouple pairs at each stage to achieve interstage heat flow matching conditions, ensuring effective heat transport and effectively avoiding interstage heat accumulation. This ensures that heat can be smoothly transferred from the low-temperature stage to the high-temperature stage and ultimately dissipated, forming the foundation for the device to achieve large temperature difference cooling. The design method emphasizes asymmetric optimization of the thermoelectric arm geometry (cross-sectional area A and height H). Based on theoretical relationships, the optimal size ratio of the n-type and p-type thermoelectric arms is customized to enable the thermocouple pairs to obtain the best thermoelectric figure of merit and cooling efficiency in a specific operating temperature range, thereby improving the temperature difference cooling capacity of each stage.

[0062] A wide-temperature-range parametric simulation strategy is adopted to improve design accuracy. This strategy considers the temperature-dependent properties of materials during actual operation. By performing parametric simulations in different temperature ranges, the optimal geometry of the thermoelectric arm at its actual operating temperature is obtained. This makes the design results more consistent with the actual temperature distribution of the device, overcoming the errors introduced by traditional constant-property design and significantly improving the accuracy of performance prediction.

[0063] By employing interstage deconstruction and iterative calculations, the overall performance can be accurately predicted. Starting from initial conditions (such as hot-end temperature and current), key performance indicators such as the actual operating temperature, thermocouple pairs, and cooling capacity / temperature difference of each stage can be solved step by step. This method can systematically and accurately predict the ultimate cooling performance of the entire multi-stage device, providing a reliable basis for device design.

[0064] Another aspect of this application provides a high-stability welding fixture for multi-stage low-temperature thermoelectric refrigeration devices, taking a three-stage low-temperature thermoelectric refrigeration device as an example, such as... Figure 5 The device includes: a base 10; a base positioning pin 11 connected to the base 10; and substrate limiting pieces 21, 22, 23, and 24 stacked sequentially. Each substrate limiting piece 21, 22, 23, and 24 is provided with a first positioning hole 211, 221, 231, and 241 that mates with the base positioning pin 11, and limiting holes 213, 223, 233, and 243 for accommodating and limiting the substrate of the device 50 to be soldered; and a top plate 40 covering the substrate limiting piece 24, which is provided with a first top plate positioning hole 41 that mates with the base positioning pin 11.

[0065] Specifically, the base 10 serves as the foundation of the entire welding fixture, and various components and the device 50 to be welded are assembled via the base positioning pins 11. Preferably, the cross-section of the base is a regular shape, such as a circle or a regular polygon, to facilitate the shape design of other corresponding components, such as the riser plate 31, the substrate limiting plates 21 / 22 / 23 / 24, and the top plate 40. More preferably, the cross-section of the base is rectangular to facilitate the side-by-side arrangement of multiple welding fixtures. It is understood that the aforementioned welding fixture can be a single welding fixture or a unit among multiple identical welding fixtures, i.e., the base 10 has multiple welding fixture units, each welding fixture unit including a base unit, and each base unit can assemble one device 50 to be welded. The device 50 to be welded is a multi-stage low-temperature thermoelectric refrigeration device.

[0066] In some embodiments, there is at least one base positioning pin 11, which can be a cuboid, a cube, or a similar regular structure. The shape of the first substrate positioning hole 211 matches the cross-sectional shape of the base positioning pin 11. For example, when the base positioning pin 11 is a cuboid, its cross-sectional shape is rectangular, and the shape of the first positioning hole 211 is a rectangle with corresponding dimensions. When the first positioning hole 211 is fitted onto the base positioning pin 11, the mounting position of the substrate limiting piece 21 on the base is relatively fixed. Preferably, the base positioning pin 11 is a cuboid or a cube. When there is only one base positioning pin 11, a cuboid or cube-shaped base positioning pin 11 can effectively limit the substrate limiting piece 21. Similarly, the shape design and function of the corresponding first positioning holes 221, 231, and 241 on the substrate limiting pieces 22, 23, and 24 are the same as those of the first positioning hole 211.

[0067] In some embodiments, the base positioning pin 11 and the base 10 are integrally formed. This achieves a firm connection and fixation, resulting in high stability of the entire welding fixture.

[0068] In some embodiments, there may be one or more base positioning pins 11. At least one base positioning pin 11 may be provided on the same side of the base 10, or at least one base positioning pin 11 may be provided on multiple sides of the base 10. In this embodiment, there are two base positioning pins 11, located on opposite sides of the base. The substrate limiting piece 21 is limited by the two opposing base positioning pins 11. Regardless of the shape of the base positioning pins 11, the ideal limiting effect can be achieved. The two base positioning pins 11 located on opposite sides of the base 10 is the most preferred structure, which can achieve the most ideal positioning with the fewest number of pins.

[0069] In some embodiments, there are two or more substrate positioning pieces. This embodiment is as follows... Figure 1As shown, this is a welding fixture for a three-stage low-temperature thermoelectric refrigeration device, corresponding to at least four substrate limiting pieces 21, 22, 23, and 24. The specific installation method is as follows... Figures 7-12 As shown. In other embodiments, the number of substrate limiting plates can be different, depending on the stage requirements of the low-temperature thermoelectric refrigeration device.

[0070] The uppermost substrate limiting piece 24 can further limit the uppermost low-temperature thermoelectric cooling device substrate to prevent the uppermost low-temperature thermoelectric cooling device from being unable to be effectively limited and from moving slightly during reflow soldering, thereby affecting the alignment accuracy of each level of low-temperature thermoelectric cooling device and causing welding defects.

[0071] A heightening plate 31 is provided between two adjacent substrate limiting plates 21 and 22. The heightening plate 31 is provided on opposite sides of the substrate limiting plate 21 to support the upper substrate limiting plate 22 and increase the height between the two adjacent substrate limiting plates 21 and 22 to meet the installation requirements of low-temperature thermoelectric refrigeration devices of different sizes. The number of heightening plates 31 on each side can be the same or different, but the height increase is the same.

[0072] In some embodiments, the lifting plate 31 on each side of the substrate limiting plate 21 is one piece, that is, one piece on each opposite side. In other embodiments, there are multiple lifting plates on each opposite side of the lifting plate 31, and the number of lifting plates 31 on both sides may be equal or unequal, so that two adjacent substrate limiting plates 21 and 22 can remain parallel.

[0073] Specifically, for ease of installation, the substrate limiting plates 21 and 22 are designed to be relatively thin, typically less than the thickness of a single-stage low-temperature thermoelectric refrigeration device. Furthermore, during the installation of each stage of the low-temperature thermoelectric refrigeration device, thermoelectric material needs to be placed on the surface of each stage, further increasing its thickness. To ensure that the next stage of the low-temperature thermoelectric refrigeration device stacked upwards is accurately positioned by the substrate limiting plate 22, the bottom surfaces of the low-temperature thermoelectric refrigeration device and the substrate limiting plate 22 need to be approximately on the same horizontal plane. Therefore, the height of the substrate limiting plate 22 needs to be adjusted using the height-adjusting plate 31.

[0074] Furthermore, the thickness of each stage of the low-temperature thermoelectric cooling device is not necessarily the same. For example, it is difficult to make the height of a single height-increasing plate 31 after being stacked on the substrate limiting plate 21 exactly equal to that of the single-stage low-temperature thermoelectric cooling device. Therefore, a thinner height-increasing plate 31 is designed, and multiple height-increasing plates 31 are added or removed to ensure that the upper surface of the top height-increasing plate 31 is basically at the same level as the thermoelectric material on the single-stage low-temperature thermoelectric cooling device. The preferred thickness of the height-increasing plate 31 is 1 / 10 to 1 / 2 of the thickness of the single-stage low-temperature thermoelectric cooling device. If it is too thin, too many height-increasing plates 31 need to be stacked, increasing the workload. If it is too thick, the height difference between the upper surface of the top height-increasing plate 31 and the thermoelectric material on the low-temperature thermoelectric cooling device may be too large, affecting the installation of the next stage device.

[0075] Furthermore, the stacked height-increasing plates 31 can have the same or different thicknesses. Using height-increasing plates of different thicknesses together can achieve a more precise height increase. For example, if the height-increasing plates 31 are designed to be 1mm and 0.5mm thick, and a height increase of 1.5mm is required, only one 1mm and one 0.5mm height-increasing plate 31 are needed, or three 0.5mm height-increasing plates can be stacked. The thickness specifications of the height-increasing plates 31 can be flexibly customized according to the device height.

[0076] Specifically, the shape of the limiting hole 213 on the substrate limiting plate 21 is the same as the cross-sectional shape of the substrate of the corresponding low-temperature thermoelectric refrigeration device, which can achieve precise positioning and prevent it from moving in any direction during reflow soldering. Depending on the different cross-sectional dimensions of the substrates of different levels of low-temperature thermoelectric refrigeration devices, the sizes of the limiting holes 213, 223, 233, and 243 corresponding to the substrate limiting plates 21, 22, 23, and 24 are different. Therefore, the design of the substrate limiting plates 21, 22, and 23 and the corresponding limiting holes 213, 223, 233, and 243 can be pre-customized according to the standardized substrate size design of the device, allowing the welding fixture to be flexibly adapted to various devices.

[0077] For example, when low-temperature thermoelectric refrigeration devices are stacked, their dimensions gradually decrease, and the corresponding limiting holes 213, 223, 233, and 243 also decrease accordingly.

[0078] In some embodiments, the heightening plate 31 is provided with a heightening plate limiting hole 311 that cooperates with the base positioning pin 11; the projection of the outline of the heightening plate 31 on the horizontal plane is located in the solid area of ​​the substrate limiting plate 21 to avoid obstructing the limiting hole 211.

[0079] Specifically, by constraining the contour of the riser plate 31 within the solid area of ​​the substrate limiting plate 21, the pressure generated during the installation of the low-temperature thermoelectric cooling device 50 is avoided, ensuring the order and predictability of the multi-layer stacked structure. Simultaneously, the pressure borne by the riser plate 31 from the upper-layer components can be effectively transmitted downwards through its own solidity to the substrate limiting plate 21, and then through the substrate limiting plate 21 to the lower-layer structure. This direct, vertical force transmission path helps maintain the structural stability and rigidity of the entire fixture during stacking and pressurization processes.

[0080] In some embodiments, a transition piece 60 is also included, with both ends of the transition piece 60 mounted on the heightening piece 31; a transition piece positioning pin 61 is provided on the transition piece 60; and second positioning holes 212, 222, 232, 242 and a second top plate positioning hole 42 are respectively provided on the substrate limiting pieces 22, 23, 24 and the top plate 40 to cooperate with the transition piece positioning pin 61.

[0081] Specifically, when the low-temperature thermoelectric refrigeration device has too many stages (50 levels) or each stage is too high, the height of the base positioning pin 11 is insufficient to complete the installation of all components. Placing the transition plate 60 on the riser plate 31, which has already been stacked to a certain height, effectively establishes a new, higher positioning reference platform. The transition plate positioning pin 61 on the transition plate 60 provides longer positioning guidance for continuing to stack more substrate limiting plates 22, 23, 24 and the top plate 40.

[0082] Specifically, such as Figure 6 As shown, the transition plate 60 has a rectangular structure and is symmetrically arranged on opposite sides of the base 10. Its projected surface does not overlap with any of the limiting holes 212, 222, or 232 to avoid affecting the installation of the low-temperature thermoelectric refrigeration device 50. It is installed on any of the first-stage riser plates 31, for example, on the riser plate 31 after the first-stage low-temperature thermoelectric refrigeration device 51 has been installed, or on the riser plate 31 after the second-stage low-temperature thermoelectric refrigeration device 52 has been installed. When the two ends of the transition plate 60 are mounted on the riser plate 31, there is a certain height of suspension where it does not contact the riser plate 31. Therefore, the riser plate 31 needs to have a certain rigidity to support the mounting components above, and is preferably made of high-temperature resistant rigid materials such as metal or ceramic.

[0083] The transition piece 60 can be installed on the height-increasing piece corresponding to any of the base plate limiting pieces to solve the problem of insufficient height of the base positioning pin 11.

[0084] In some embodiments, the heightening plate 31 is provided with mounting holes 312, and the transition plate 60 is mounted on the mounting holes 312 by mounting members 62 provided at both ends.

[0085] Specifically, mounting component 62 refers to a structure that can temporarily fix or confine the transition piece 60 to the heightening piece 31, including a plug-in connection structure, a threaded connection structure, or a guide groove structure. Preferably, this application uses a plug-in connection structure, specifically a plug-in rod structure, which is a boss protruding towards the heightening pad 31 and integrally formed with the transition piece 60. During installation, this plug-in rod structure can be directly inserted into the mounting holes 312 at both ends of the heightening pad 31, allowing the transition piece 60 to be temporarily fixed to the heightening piece 31 and easily separated. This improves the flexibility and reusability of assembling the various components of the welding fixture.

[0086] Preferably, the mounting hole 312 is a through hole. When multiple heightening pads 31 are stacked, the multiple mounting holes 312 are connected in series to form a deeper guide hole, which provides a larger contact area and a longer guide depth for the mounting part 62, thereby ensuring that the transition piece can obtain more stable positioning in both the horizontal and vertical directions, and enhancing the overall stability of the fixture in subsequent operations (such as placing devices, applying pressure, etc.).

[0087] In some embodiments, the limiting substrates 22, 23, and 24 located above the transition plate 60 and the top plate 40 are hollowed out at the position of the mounting hole 312, without obstructing the mounting hole 312. This provides an interference-free through path for the insertion rod structure below the transition plate 60.

[0088] In some embodiments, all the limiting base plates 22, 23, 24 and the top plate 40 are hollowed out at the positions of the mounting holes 312, so as not to obstruct the mounting holes 312. Therefore, no matter how many layers are stacked, the positioning reference transfer chain from the base to the top layer is completely unobstructed in physical space, avoiding assembly difficulties or accuracy loss caused by minor obstructions.

[0089] In some embodiments, after the transition piece 60 is installed, the top of the transition piece positioning pin 61 is higher than the top of the base positioning pin 11. Specifically, the actual height of the transition piece positioning pin 61 is not necessarily greater than the height of the base positioning pin 11, but its height after installation is higher than that of the transition piece positioning pin 61, so as to enable the welding of more stages of low-temperature thermoelectric refrigeration devices 50.

[0090] In some embodiments, the base 10 is provided with a through hole 12 in the area corresponding to the limiting hole.

[0091] Specifically, such as Figure 6As shown, the through hole 12 is used to eject the multi-stage low-temperature thermoelectric cooling device 50 using a tool after welding, thus achieving easier demolding. There can be one or more through holes 12. When the multi-stage low-temperature thermoelectric cooling device 50 with a large bottom area is welded, multiple through holes 12 can be used during demolding to prevent stress concentration and damage to the multi-stage low-temperature thermoelectric cooling device 50 when ejecting it through a single hole.

[0092] This application provides a "dedicated mold" for each substrate and cryogenic thermoelectric cooling device through a base with positioning pins, substrate limiting plates, and raising pads, ensuring that each component is always in the correct position. After the cryogenic thermoelectric cooling device is pre-assembled in the fixture, it can be directly transferred to the welding furnace without demolding, eliminating the structural collapse risk that is most likely to occur during the transfer process in traditional methods. It effectively solves the problem of high assembly error rate caused by the structural instability or the need for demolding and transfer of existing integrated welding fixtures, especially for pyramid-shaped devices with many stages and fragile structures, significantly improving the first-time integration success rate.

[0093] The unique limiting structure allows for safe and convenient application of vertical pressure on the top plate, overcoming the difficulty of applying pressure using traditional methods. This effectively eliminates interface defects such as weld seams, voids, and incomplete soldering caused by the inability to apply pressure, avoiding the risks of weakened interface bonding strength and increased interface resistance, directly improving the device's cooling performance and lifespan. During the welding process, continuous pressure forces the molten solder to flow uniformly and expel gases, ensuring close contact between the thermoelectric arm and the substrate. This overcomes the problems of complex step-by-step welding processes, numerous thermal cycles, and large cumulative errors, ensuring highly consistent performance and quality across different batches and manufactured by different personnel, laying the foundation for large-scale mass production.

[0094] All components are stacked using locating pins as guides, with clear steps that greatly reduce human alignment errors. Integrated welding is employed, with all weld points completed simultaneously in a single thermal cycle, avoiding interface material fatigue and performance degradation caused by multiple high-temperature thermal cycles in step-by-step welding.

[0095] In some embodiments, this application also relates to a welding method for a multi-stage low-temperature thermoelectric refrigeration device. Using the aforementioned welding fixture, the multi-stage low-temperature thermoelectric refrigeration device 50 is welded. Taking the welding of a 3-stage thermoelectric refrigeration device as an example, the specific steps include: S1: The substrate limiting piece 21 is fitted onto the base positioning pin 11 through its first positioning hole 211, and the first substrate body 511 coated with solder paste is placed into its limiting hole 213.

[0096] Specifically, such as Figure 7As shown, after the substrate positioning piece 21 is fitted onto the base positioning pin 11, the substrate positioning piece 21 is mounted on the base 10, and its position is fixed by the base positioning pin 11. There are two base positioning pins 11, located on opposite sides of the base 10, to achieve stable positioning of the substrate positioning piece 21. The positioning hole 213 is used to position the first substrate body 511. Its shape and size match the first substrate body 511, so that the first substrate body 511 can be placed into the positioning hole 213, thereby making it less likely for the first substrate body 511 to move during subsequent reflow soldering. The first substrate body 511 is the substrate portion of the first substrate 51. The first substrate 51 includes the first substrate body 511 and thermoelectric material 512, which is thermoelectric particles.

[0097] S2: Place the heightening piece 31 on the base 10 in the area on both sides of the substrate limiting piece 21.

[0098] Specifically, such as Figure 8 As shown, the height-increasing piece 31 is used to increase the height of the substrate limiting piece 21. Since the substrate limiting piece 21 is a single sheet of material with an outer periphery similar to the base 10, although it has a centrally cutout forming a limiting hole 213, it should not be made too thick to avoid increasing installation difficulty. On the other hand, the thickness of the first substrate 51 is not a standardized thickness, making it difficult to customize the thickness of the substrate limiting piece 21. Therefore, the height of the substrate limiting piece 21 is increased using the height-increasing piece 31. The top surface of the height-increasing piece 31 is basically at the same level as the top surface of the first substrate 51, so it does not affect the installation of the next-stage welding fixture. Specifically, the height-increasing piece 31 is provided with a height-increasing piece positioning hole 311. Through the height-increasing piece positioning hole 311, the height-increasing piece 31 can be accurately installed on the base 10 and limited, preventing lateral movement or axial rotation.

[0099] S3: Place a mask on the substrate limiting piece 21, place the thermoelectric material 512 on the first substrate body 511 through the opening of the mask, and then remove the mask.

[0100] Specifically, such as Figure 8 As shown, the photomask is a planar material with a specific pattern cut out, and the cut-out areas correspond to the areas where the thermoelectric material 512 needs to be placed. The shape of the photomask is the same as that of the first substrate 511, so the photomask can be accurately placed on the first substrate 511 by positioning it around its perimeter. The thermoelectric material 512 can be accurately transferred to a predetermined position on the first substrate 511. After removing the photomask, the thermoelectric material 512 is patterned and placed at the predetermined position on the first substrate 511.

[0101] S4: Place the substrate limiting piece 22 onto the base positioning pin, and repeat the above steps of placing the limiting substrate, substrate raising piece, and thermoelectric material until the pre-assembly of the multi-level device is completed.

[0102] For details, please refer to Figures 9-13 Second-level device installation, such as Figure 9 As shown, the substrate limiting piece 22 is fitted onto the base positioning pin 11, and then the second substrate body 521 coated with solder paste is placed in. The thermoelectric material 522 is transferred to a predetermined position on the second substrate body 521 through a mask plate, completing the placement of the second substrate 52. Subsequently, an appropriate number of lifting pieces 31 are fitted onto the two base positioning pins 11, so that the top surface of the lifting pieces 31 is substantially at the same level as the top surface of the second substrate 52.

[0103] like Figure 10 As shown, the third-level device 53 and the welding fixture are installed. The limiting substrate 23 is fitted onto the base positioning pin 11, and then the third substrate body 531 coated with solder paste is placed in. The thermoelectric material 532 is transferred to the predetermined position of the third substrate body 531 through the mask plate to complete the placement of the third substrate 53. Then, the uppermost substrate 54 is placed on the uppermost thermoelectric material. The fourth substrate 54 does not include thermoelectric particles.

[0104] like Figure 11 As shown, a suitable number of heightening tabs 31 and the uppermost substrate limiting tabs 24 are respectively fitted onto the two base positioning pins 11, so that the top surface of the substrate limiting tab 24 and the top surface of the fourth substrate 54 are basically at the same level. A schematic diagram of the three-level device structure is shown below. Figure 13 As shown. The placement of the three-stage thermoelectric cooling device in this embodiment is completed according to the method described above. If other stages of thermoelectric cooling devices are to be installed, only the number of substrate limiting plates and heightening plates needs to be increased accordingly. The number of substrate limiting plates corresponds one-to-one with the substrate of the multi-stage device, and the shape and size of the limiting holes on the substrate limiting plates also correspond one-to-one with the substrate of the multi-stage device. Typically, the dimensional tolerance is in the millimeter range; preferably, the dimensional tolerance is 0.05-0.08 mm, meaning the limiting hole is larger than the outer dimensions of the substrate, but its assembly tolerance is 0.05-0.08 mm. S5: Place the top plate 40 on the uppermost substrate limiting piece.

[0105] Specifically, such as Figure 12 As shown, the top plate 40 is a plate without a hollow center. It is fitted onto the base positioning pin 11 through the first top plate positioning hole 41 to achieve temporary limiting and detachable fixing.

[0106] S6: Place the assembled welding fixture and the pre-assembled multi-stage components into the welding equipment for welding.

[0107] All components of the welding fixture are made of high-temperature resistant metals or inorganic non-metallic materials, preventing high-temperature deformation or embrittlement during reflow soldering. Therefore, when the assembled welding fixture is placed into the reflow soldering equipment along with the pre-assembled multi-stage components, stable positioning is maintained during the welding process, resulting in excellent welding performance. This allows for the simultaneous welding of multi-stage components, avoiding the technical problems associated with repeated heating and welding that lead to weld interface deterioration and negatively impact the electrical and thermal properties of the components.

[0108] After assembly using the steps described above, pressure can be applied freely above the top plate 40. Pressure is typically applied by adding weights or other heavy objects. Without a base limiting pin, placing heavy objects would be difficult and requires careful handling. With a limiting pin, you can simply place the heavy object on the top plate 40 without worrying about it tipping over due to the height difference caused by the melting solder paste during the welding process.

[0109] In some embodiments, after the step of laying the thermoelectric material, the method further includes: after laying the thermoelectric material unit and removing the mask, placing the riser sheet again so that its top is flush with the top of the thermoelectric material unit, and then placing the next substrate limiting sheet.

[0110] Specifically, taking the placement of the first-stage device as an example, before placing the first substrate 51, a small number of riser sheets 31 are placed first. After the first substrate 51 is placed, the number of riser sheets 31 is increased so that the top surface of the riser sheets is basically at the same level as the top surface of the first substrate 51. This is to prevent the height of the riser sheets 31 from accumulating too high in the first step, which would affect the placement of the thermoelectric material 512.

[0111] Because the substrate of the multi-stage cryogenic thermoelectric cooler 50 is effectively constrained in its design, it will not misalign under conditions of non-severe tilting or dropping, thus preventing failure of the multi-stage cryogenic thermoelectric cooler 50. Therefore, during the transfer or soldering process of the pre-assembled multi-stage cryogenic thermoelectric cooler 50, minor vibrations or solder paste melting will not cause misalignment of the substrates at each stage. This feature is crucial for the multi-stage cryogenic thermoelectric cooler 50 and can significantly improve the soldering success rate.

[0112] Furthermore, this welding fixture allows for flexible pressure application above the top plate 40, typically achieved using weights or other heavy objects. Without a limit switch, placing heavy objects requires caution and is difficult; however, with the limit switch design, heavy objects can be placed directly and stably on the pressure plate, eliminating concerns about tipping due to height differences caused by solder paste melting during welding. This solves the problem of traditional methods where the lack of pressure leads to excessively thick solder paste, potentially creating voids at the welding interface, deteriorating interface bonding, and affecting device performance.

[0113] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with the claims of this application shall still fall within the scope of this application.

Claims

1. A multi-stage low-temperature thermoelectric refrigeration device, characterized in that, include: A multi-stage device, each stage of which includes multiple pairs of thermocouples, the two ends of each pair of thermocouples being electrically connected by electrodes, the copper electrodes being disposed on a substrate; wherein each pair of thermocouples includes an n-type thermocouple arm and a p-type thermocouple arm. Each stage of the device includes a cold end and a hot end. In two adjacent stages, the cooling capacity of the cold end of the lower stage device is greater than the heat output of the hot end of the upper stage device.

2. The multi-stage low-temperature thermoelectric refrigeration device as described in claim 1, characterized in that, The cross-sectional area A and height H of the thermocouple arm in each thermocouple pair satisfy the following conditions: in, ρ is the thermal conductivity; n is the resistivity; n is the n-type thermoelectric arm; and p is the p-type thermoelectric arm.

3. The multi-stage low-temperature thermoelectric refrigeration device as described in claim 2, characterized in that, The constraints for the hot and cold ends of each stage of the device are as follows: In two adjacent stages of devices, the heat generated at the hot end of the previous stage device is: The cooling capacity of the cold end of the next stage device is: in, > Total Seebeck coefficient Total resistance Total thermal conductivity , These are the Seebeck coefficient, thermal conductivity, and resistivity of thermoelectric materials, respectively. A and H These represent the cross-sectional area and height of the thermocouple arm, respectively. m This represents the number of thermocouple pairs. I , where n is the input current, n is the n-type thermoelectric arm, and p is the p-type thermoelectric arm.

4. A design method for a multi-stage low-temperature thermoelectric refrigeration device, used to design the multi-stage low-temperature thermoelectric refrigeration device as described in any one of claims 1-3, characterized in that, include: The operating temperature range is set according to the material properties, the height of the p-type thermocouple and the n-type thermocouple are fixed, and the cross-sectional area of ​​the p-type thermocouple or the n-type thermocouple is determined. The cross-sectional area value of the n-type thermocouple or the p-type thermocouple in each pair of thermocouples without a fixed cross-sectional area is obtained through wide temperature range simulation. The extreme cold-end temperature of each stage of the device is obtained through simulation. The extreme cold-end temperature of the next stage device is the same as the hot-end temperature of the previous stage device. Based on the extreme cold junction temperature of each stage, the height of the p-type thermocouple and the n-type thermocouple, and the cross-sectional area of ​​the p-type thermocouple and the n-type thermocouple, the target value of the number of thermocouple pairs of each stage of the device is calculated. The multi-stage low-temperature thermoelectric refrigeration device design was completed by assembling the thermocouple logs of each stage of the device based on the calculated target values.

5. The design method of the multi-stage low-temperature thermoelectric refrigeration device as described in claim 4, characterized in that, The method for calculating the number of thermocouple pairs contained in each stage of the device based on the extreme cold junction temperature, the height of the p-type thermocouple arm and the n-type thermocouple arm, and the cross-sectional area of ​​the p-type thermocouple arm and the n-type thermocouple arm includes: Obtain the hot junction temperature of each stage of the device, the extreme cold junction temperature of each stage of the device, the cross-sectional area of ​​the p-type thermocouple and the n-type thermocouple, the height of the p-type thermocouple and the n-type thermocouple, the interface contact resistance, the number of first-stage thermocouple pairs, and the operating current; Within the temperature range formed by the extreme cold end temperature and the hot end temperature, the actual working temperature is selected by traversal, and the equivalent material parameters within the actual working temperature range corresponding to the actual working temperature are calculated using the integral median method. The cold end cooling capacity is calculated based on the equivalent material parameters. The actual working temperature corresponding to the cold end cooling capacity being greater than 0 is the target actual working temperature. Based on the target actual operating temperature as the hot end temperature of the next-level device, the target actual operating temperature of the next-level device is calculated within the corresponding temperature range. Combined with the material performance parameters, the values ​​of all thermocouple pairs with corresponding cold end cooling capacity greater than 0 are calculated. Repeat the above steps to calculate the values ​​of all thermocouple pairs whose cold junction cooling capacity is greater than 0 for each level of device; Based on the thermocouple pair values ​​calculated above, and according to the cold and hot junction constraints of each stage of the device, the cooling capacity of the next stage is calculated. Q c, i Greater than the heat released by the previous stage Q h, i+1 And obtain the cold-end cooling capacity when the cold-end temperature of the top level is the same as the hot-end temperature of the bottom level. Q c By combining the two performance indicators of maximum cooling temperature difference and maximum cooling capacity, the device structure that meets the requirements is selected, namely the number of thermocouple pairs at each level.

6. A high-stability welding fixture for multi-stage low-temperature thermoelectric refrigeration devices, characterized in that, For welding multi-stage low-temperature thermoelectric refrigeration devices as described in any one of claims 1-3, comprising: Base; The base positioning pin is connected to the base. Multiple substrate limiting pieces are stacked in sequence. Each substrate limiting piece is provided with a first positioning hole that cooperates with the positioning pin of the base, and a limiting hole for accommodating and limiting the substrate of the device to be welded. An increasing plate disposed between two adjacent substrate limiting plates; A top plate is provided on the limiting piece of the substrate, and the top plate is provided with a first top plate positioning hole that cooperates with the positioning pin of the base.

7. The high-stability welding fixture for multi-stage low-temperature thermoelectric refrigeration devices as described in claim 6, characterized in that, The height-increasing plate is provided with a height-increasing plate positioning hole that cooperates with the positioning pin of the base; The projection of the contour of the height-increasing piece onto the horizontal plane lies within the solid area of ​​the substrate limiting piece, so as to avoid obscuring the limiting hole.

8. The high-stability welding fixture for multi-stage low-temperature thermoelectric refrigeration devices as described in claim 6, characterized in that, It also includes a transition plate, the two ends of which are mounted on the height-increasing plate; The transition piece is provided with a transition piece positioning pin; The substrate limiting plate and the top plate are respectively provided with a second positioning hole and a second top plate positioning hole that cooperate with the positioning pin of the transition plate.

9. The high-stability welding fixture for multi-stage low-temperature thermoelectric refrigeration devices as described in claim 6, characterized in that, The height-increasing plate is provided with mounting holes, and the transition plate is mounted on the mounting holes by mounting members provided at both ends.

10. The high-stability welding fixture for multi-stage low-temperature thermoelectric refrigeration devices as described in claim 6, characterized in that, The base has a through hole in the area corresponding to the limiting hole.

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