Homogeneous connection method of thermoelectric material and metal electrode, thermoelectric device connection structure and application

Abstract

A method for homogenous connection of a thermoelectric material and a metal electrode, a thermoelectric device connection structure and application, the homogenous connection method comprising the following steps: S1, forming a metallization functional layer on the end face of a thermoelectric arm made of a thermoelectric material by using a solid-phase forming process; S2, forming a homogenous connection layer on the surface of the metallization functional layer by using a physical deposition process, the material of the homogenous connection layer being the same as the material of the metal electrode to be connected or the main component of the homogenous connection layer being the same as the main component of the metal electrode to be connected; S3, welding the metal electrode to the surface of the homogenous connection layer by using a solder. The thermoelectric device connection structure prepared by the above homogenous connection method comprises a thermoelectric arm, a metallization functional layer, a homogenous connection layer, a solder layer and an electrode layer, and can be directly used for manufacturing a thermoelectric device. The connection method does not need an electroplating step, is simple, universal, reliable and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of semiconductor thermoelectric technology, and more specifically, to a method for homogeneous connection of thermoelectric materials and metal electrodes, a connection structure for thermoelectric devices, and their applications. Background Technology

[0002] Thermoelectric devices utilize the Seebeck effect or Peltier effect of semiconductor thermoelectric materials to directly convert thermal energy into electrical energy. In order to improve the conversion efficiency, it is usually required that the thermoelectric material (such as bismuth telluride Bi2Te3, lead telluride PbTe, etc.) and the metal electrode (usually copper Cu) have a low contact resistance and a strong and reliable connection.

[0003] The current mainstream approach involves forming a metallized functional layer (such as nickel (Ni) as a diffusion barrier layer) on the surface of thermoelectric materials using electroplating or electroless plating, followed by tin (Sn) plating as a solderable layer, and finally soldering the solderable layer to copper electrodes using tin-based solder. This traditional process suffers from a long process chain, wastewater pollution, and in some cases, high interfacial resistance and insufficient soldering reliability. Furthermore, if more environmentally friendly physical deposition processes (such as arc spraying) are used to prepare the metallized functional layer, a solderable layer still needs to be prepared on the surface of the metallized functional layer. However, the surface characteristics of the physically deposited layer differ from those of the traditional electroplated substrate. If the traditional electroplating process is used to prepare the solderable layer (such as the tin layer), it often requires the redevelopment and optimization of electroplating parameters. This process is technically complex, highly experience-dependent, and increases process difficulty, cost, and production uncertainty, hindering efficient and stable large-scale manufacturing.

[0004] Therefore, there is an urgent need in this field for a simpler, more universal, reliable and environmentally friendly method for connecting thermoelectric materials and metal electrodes to overcome the complexity of traditional processes and improve the quality of the connection interface. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that the existing connection methods between thermoelectric materials and metal electrodes are complex, environmentally unfriendly and have low interface connection quality. In order to overcome the above defects of the prior art, the present invention provides a homogeneous connection method between thermoelectric materials and metal electrodes, a thermoelectric device connection structure and application.

[0006] The first objective of this invention is to provide a method for homogeneous connection of a thermoelectric material and a metal electrode, comprising the following steps: S1. A metallized functional layer is formed on the end face of a thermoelectric arm made of thermoelectric material using a solid-state molding process; S2. Using a physical deposition process, a homogeneous connection layer is formed on the surface of the metallized functional layer. The material of the homogeneous connection layer is the same as the material of the metal electrode to be connected, or the main components of the homogeneous connection layer are the same as the main components of the metal electrode to be connected. S3. The metal electrode is welded to the surface of the homogeneous connection layer using solder.

[0007] The above solution abandons the complex approach of fabricating a heterogeneous solderable layer on top of the heterogeneous functional layer (i.e., the metallized functional layer). Instead, it directly constructs a homogeneous connection layer with the same material or main components as the metal electrode on the surface of the metallized functional layer of the thermoelectric element through a physical deposition process. This transforms the connection interface into a more easily handled homogeneous or near-homogeneous interface, resulting in high-quality interface bonding. This connection method eliminates the need for electroplating, making it simple, universal, reliable, and environmentally friendly.

[0008] In one possible implementation, the thermoelectric material in step S1 is at least one of the following: bismuth telluride system, lead telluride system, germanium telluride system, cobaltite system, semi-Hessler system, magnesium-based system, and silicon-germanium system.

[0009] In one possible implementation, the material composition of the metallized functional layer in step S1 is selected from one or more of nickel, iron, molybdenum, chromium, zinc, niobium, titanium, aluminum and their alloys.

[0010] In one possible implementation, the solid-state forming process in step S1 is one of electroplating, chemical plating, flame spraying, arc spraying, plasma spraying, magnetron sputtering, and hot pressing sintering.

[0011] In one possible implementation, the physical deposition process in step S2 is one of arc spraying, cold spraying, plasma spraying, or magnetron sputtering.

[0012] In one possible implementation, the physical deposition process in step S2 is arc spraying.

[0013] In one possible implementation, the metal electrode in step S2 is made of one of copper, molybdenum, gold, aluminum, and their alloys.

[0014] In one possible implementation, the solder in step S3 is a tin-based solder.

[0015] A second aspect of the present invention provides a thermoelectric device connection structure, which is obtained by the above-described homogeneous connection method, comprising a thermoelectric arm made of the thermoelectric material and a metallized functional layer formed on the end face of the thermoelectric arm, a homogeneous connection layer formed on the surface of the metallized functional layer, and a metal electrode welded to the homogeneous connection layer by solder.

[0016] A third aspect of the present invention provides an application of the thermoelectric device connection structure obtained by the above-described homogeneous connection method in a thermoelectric device, wherein the thermoelectric device can be obtained by directly assembling the metal electrode of the thermoelectric device connection structure with a ceramic substrate.

[0017] The beneficial effects of this invention are as follows: 1) Simplified process and strong versatility: It provides a modular connection solution. Regardless of the composition of the metallized functional layer on the surface of the thermoelectric element or the process used for fabrication, a reliable connection with the electrode can be achieved through the final step of "physical deposition of a homogeneous connection layer", which greatly reduces the difficulty of process debugging and dependence on the previous process.

[0018] 2) Interface optimization and reliable connection: By constructing an interface system of "homogeneous connection layer-solder-electrode", the surface energy and physical properties of the same or similar materials are similar, which fundamentally improves the wettability and spreadability of the solder, promotes the formation of dense and high-strength metallurgical bond, and significantly improves the reliability of the connection.

[0019] 3) Low contact resistance: Excellent metallurgical bonding and pure homogeneous interface effectively reduce interface defects and harmful compound formation, thereby significantly reducing interface contact resistance.

[0020] 4) Green, environmentally friendly, and highly efficient: The entire process requires no electroplating / chemical plating solutions, eliminating the discharge of heavy metal wastewater. It employs physical deposition technology, particularly arc spraying, to form a bonding layer in one step, resulting in high deposition efficiency and suitability for large-scale production. Attached Figure Description

[0021] Figure 1 This is an exploded structural diagram of the thermoelectric connection structure obtained by the homogeneous connection method of the present invention.

[0022] Figure 2 The data shows the interfacial resistivity of Example 1 in the Bi2Te3 / Ni system.

[0023] Figure 3 The data shows the interfacial resistivity of Example 2 in the PbTe / Fe system.

[0024] Figure 4 The data provided are the interfacial resistivity data for Example 3 in the Bi2Te3 / Ni / Zn composite functional layer system.

[0025] Figure 5 The power data are for a thermoelectric device fabricated based on the thermoelectric element obtained in Example 1. Detailed Implementation

[0026] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.

[0027] It should be noted that the endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0028] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.

[0029] This invention provides a method for homogeneous connection of a thermoelectric material and a metal electrode, the process steps of which include: 1) A metallized functional layer is formed on the end face of a thermoelectric arm made of thermoelectric material using a solid-state molding process; 2) A homogeneous interconnect layer is formed on the surface of the metallized functional layer using a physical deposition process. The material of the homogeneous interconnect layer is the same as that of the metal electrode to be connected, or the main components of the homogeneous interconnect layer are the same as those of the metal electrode to be connected. 3) The metal electrode is welded to the surface of the homogeneous bonding layer using solder.

[0030] Preferably, the thermoelectric material is at least one of the following: bismuth telluride system, lead telluride system, germanium telluride system, cobaltite system, semi-Hessler system, magnesium-based system, and silicon-germanium system. The material composition of the metallized functional layer is selected from one or more of nickel, iron, molybdenum, chromium, and zinc. The metallized functional layer can be designed according to the thermoelectric material system and performance requirements. For example, it may include a nickel (Ni) layer, iron (Fe) layer, molybdenum (Mo) layer, chromium (Cr) layer, niobium (Nb) layer, titanium (Ti) layer, aluminum (Al) layer, etc., for blocking diffusion, or a zinc (Zn) layer, etc., for stress relief, or an alloy metal compound layer composed of the above-mentioned elements. The solid-state forming process is one of electroplating, chemical plating, flame spraying, arc spraying, plasma spraying, magnetron sputtering, and hot pressing sintering. The physical deposition process is arc spraying, cold spraying, plasma spraying, or magnetron sputtering, more preferably arc spraying, because it has high deposition efficiency and is suitable for continuous production. The metal electrode is one of copper, molybdenum, gold, aluminum, and their alloys, preferably copper or a copper alloy electrode, and the homogeneous bonding layer is correspondingly a copper or copper alloy layer. The solder is preferably a tin-based solder.

[0031] The present invention also provides a thermoelectric device connection structure prepared by the above method, such as... Figure 1 As shown, it includes a thermoelectric arm, a metallized functional layer, a homogeneous connection layer, a solder layer, and an electrode layer. The above-described thermoelectric device connection structure can be directly used to fabricate thermoelectric devices; during fabrication, the electrode layer of the thermoelectric device connection structure can be directly assembled with the ceramic component.

[0032] The technical effects of the present invention will be further illustrated below through specific embodiments.

[0033] Example 1: Bi2Te3 / Ni functional layer / copper electrode system A 10 μm thick nickel (Ni) layer was deposited on both ends of thermoelectric arms made of p-type and n-type Bi2Te3 thermoelectric materials, respectively, as a metallization functional layer, to obtain p-Bi2Te3 / Ni and n-Bi2Te3 / Ni elements.

[0034] Using an electric arc spraying process, a 5μm thick copper (Cu) layer is deposited on the metallization surface of the above-mentioned p-Bi2Te3 / Ni element and n-Bi2Te3 / Ni element as a homogeneous bonding layer to form a thermoelectric element.

[0035] The thermoelectric element with the aforementioned homogeneous bonding layer was soldered to a copper electrode using tin-based solder, forming a thermoelectric device connection structure of “p-Bi2Te3 / Ni / Cu (homogeneous bonding layer) / solder / Cu electrode” and a thermoelectric device connection structure of “n-Bi2Te3 / Ni / Cu (homogeneous bonding layer) / solder / Cu electrode”, respectively.

[0036] Interfacial resistance tests were performed on the connection structures of thermoelectric devices to measure the average interfacial contact resistivity of p-type and n-type elements. ρ c The values ​​are 3.76 μΩ•cm. 2 and 0.7 μΩ•cm 2 ,like Figure 2 As shown.

[0037] Thermoelectric devices were then fabricated based on this thermoelectric element.

[0038] Thermoelectric element fabrication: Φ30mm p-Bi2Te3 and n-Bi2Te3 ingots were prepared and sliced ​​using a cutting machine to obtain two Φ30mm×3mm sheets. The two sheets were then roughened by sandblasting. Arc spraying was performed on both sides of the sheets using a φ1.5mm nickel wire at 20V spraying voltage and 0.5MPa gas pressure to form a barrier layer on the material surface. Next, arc spraying was performed on both sides of the sheets using a φ1.5mm copper wire at 20V spraying voltage and 0.5MPa gas pressure to deposit a copper bonding layer on the surface of the nickel barrier layer. Finally, the sheets were cut into 2.3mm×2.3mm×3mm particles using a dicing machine to obtain n-Bi2Te3 and p-Bi2Te3 thermoelectric elements.

[0039] Thermoelectric device fabrication: Cold-end copper-clad ceramic substrates and hot-end copper-clad ceramic substrates of 20mm × 20mm × 1mm were prepared respectively. A 0.1mm thick solder layer was printed using screen printing. Using a mold, the prepared p-Bi2Te3 and n-Bi2Te3 elements were alternately filled into the cold-end substrate. After the thermoelectric elements were filled, the hot-end substrate with solder was covered on the upper surface. Then, welding was completed using a heating stage, and the thermoelectric device was obtained after cooling.

[0040] Figure 5 The power-temperature difference curves of the thermoelectric device fabricated using the above process and the thermoelectric device fabricated using conventional processes are shown. The black curve represents the thermoelectric device of this invention containing a homogeneous bonding layer, while the red curve represents the conventional tin-plated thermoelectric device. In the figure, point P1 represents the output power of the device containing the homogeneous bonding layer at a temperature difference of 250K, which is 1.73W, and point P2 represents the output power of the conventional device, which is 1.68W. This demonstrates that the homogeneous bonding method can successfully fabricate the device, and its power output has a certain advantage over the conventional device.

[0041] Example 2: PbTe / Fe functional layer / copper electrode system This embodiment demonstrates the application of the invention to another thermoelectric material system.

[0042] A 10 μm thick iron (Fe) layer was deposited on both ends of the thermoelectric arms made of p-type and n-type PbTe thermoelectric materials, respectively, as a metallization functional layer, to obtain p-PbTe / Fe elements and n-PbTe / Fe elements.

[0043] Using an electric arc spraying process, a 5μm thick copper (Cu) layer was deposited on the surface of both the p-PbTe / Fe element and the n-PbTe / Fe element as a homogeneous bonding layer to obtain the thermoelectric element.

[0044] The above-mentioned thermoelectric elements are soldered to copper electrodes using tin-based solder to form thermoelectric device connection structures of “p-PbTe / Fe / Cu (homogeneous bonding layer) / solder / Cu electrode” and “n-PbTe / Fe / Cu (homogeneous bonding layer) / solder / Cu electrode”, respectively.

[0045] Interfacial resistance tests were performed on the connection structures of thermoelectric devices to measure the average interfacial contact resistivity of p-type and n-type elements. ρ c The values ​​are 60.4 μΩ·cm. 2 and 36.7 μΩ·cm 2 ,like Figure 3 As shown, this resistivity value is slightly higher than that of the Bi2Te3 system, which may be related to the thermal expansion coefficient of the PbTe material itself and the interfacial reaction characteristics with the iron layer, but it is still much lower than the interfacial resistance when no effective metallization connection is made, and the connection reliability meets the application requirements.

[0046] Example 3: Bi2Te3 / Ni / Zn composite functional layer / copper electrode system This embodiment demonstrates the application of the invention to a thermoelectric element having a composite metallized functional layer.

[0047] Using a thermoelectric arm made of n-type Bi2Te3 thermoelectric material as a substrate, Ni and Zn composite functional layers are sequentially deposited on its end surface by arc spraying to obtain an n-Bi2Te3 / Ni / Zn element.

[0048] A 5μm thick copper (Cu) layer was deposited on the surface of the composite functional layer of the n-Bi2Te3 / Ni / Zn element as a homogeneous bonding layer using an arc spraying process to obtain the thermoelectric element.

[0049] The above-mentioned thermoelectric element is welded to the copper electrode using tin-based solder to form a thermoelectric device connection structure of "n-Bi2Te3 / Ni / Zn / Cu (homogeneous bonding layer) / solder / Cu electrode".

[0050] The interface resistance of the thermoelectric device connection structure was tested, and the average interface contact resistivity was measured. ρc The value is 2.74 μΩ·cm. 2 ,like Figure 4 As shown.

[0051] Comparative Example 1: Traditional Electroplating Path For comparison, this comparative example demonstrates the challenges of continuing to use the traditional electroplating path on physically deposited functional layers.

[0052] A thermoelectric arm was fabricated using n-type Bi2Te3 thermoelectric material, and an arc spraying process was used to sequentially deposit a Ni / Zn composite functional layer on the end surface of the thermoelectric arm.

[0053] Subsequently, a conventional electroplating process was used to electroplat a layer of tin (Sn) on the surface of the above-mentioned composite functional layer as a solderable layer.

[0054] The results showed that the uniformity, density, and adhesion of the obtained tin layer were all poor. Subsequent attempts to weld tin-based solder to copper electrodes revealed difficulties in solder wetting and spreading, easy peeling of the thermoelectric device connection structure, poor connection reliability, and high and unstable average interface resistivity.

[0055] This comparison shows that directly using traditional electroplating processes to prepare solderable layers on physically deposited functional layers faces significant challenges in process adaptability, making it difficult to achieve stable and high-quality production. However, the "physically deposited homogeneous bonding layer" solution provided by this invention (as in Example 3) effectively avoids this complexity, achieving a simple and reliable connection.

[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for homogeneous connection of a thermoelectric material and a metal electrode, characterized in that, Includes the following steps: S1. A metallized functional layer is formed on the end face of a thermoelectric arm made of thermoelectric material using a solid-state molding process; S2. Using a physical deposition process, a homogeneous connection layer is formed on the surface of the metallized functional layer of the thermoelectric arm. The material of the homogeneous connection layer is the same as the material of the metal electrode to be connected, or the main component of the homogeneous connection layer is the same as the main component of the metal electrode to be connected. S3. The metal electrode is soldered to the surface of the homogeneous connection layer of the thermoelectric arm using solder.

2. The homogeneous connection method according to claim 1, characterized in that, The thermoelectric material in step S1 is at least one of the following: bismuth telluride system, lead telluride system, germanium telluride system, cobaltite system, semi-Hessler system, magnesium-based system, and silicon-germanium system.

3. The homogeneous connection method according to claim 1, characterized in that, The material composition of the metallized functional layer in step S1 is selected from one or more of the following: nickel, iron, molybdenum, chromium, zinc, niobium, titanium, aluminum and their alloys.

4. The homogeneous connection method according to claim 1, characterized in that, The solid-state forming process in step S1 is one of electroplating, chemical plating, flame spraying, arc spraying, plasma spraying, magnetron sputtering, and hot pressing sintering.

5. The homogeneous connection method according to claim 1, characterized in that, The physical deposition process in step S2 is one of arc spraying, cold spraying, plasma spraying, or magnetron sputtering.

6. The homogeneous connection method according to claim 5, characterized in that, The physical deposition process in step S2 is arc spraying.

7. The homogeneous connection method according to claim 1, characterized in that, The metal electrode in step S2 is made of one of the following materials: copper, molybdenum, gold, aluminum, and their alloys.

8. The homogeneous connection method according to claim 1, characterized in that, The solder in step S3 is a tin-based solder.

9. A thermoelectric device connection structure, characterized in that, The product, manufactured by the homogeneous connection method according to any one of claims 1-8, includes a thermoelectric arm made of thermoelectric material, a metallized functional layer formed on the end face of the thermoelectric arm, a homogeneous connection layer formed on the surface of the metallized functional layer, and a metal electrode welded to the homogeneous connection layer by solder.

10. The application of the thermoelectric device connection structure according to claim 9 in the fabrication of thermoelectric devices, characterized in that, The thermoelectric device can be obtained by directly assembling the metal electrode of the thermoelectric device connection structure with the ceramic substrate.

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