High-reliability rigid thermoelectric device and preparation method thereof

Abstract

The invention discloses a high-reliability rigid thermoelectric device and a preparation method thereof, and relates to the technical field of thermoelectric device design. The thermoelectric device sequentially comprises a hot end substrate, a thermoelectric material particle layer and a cold end substrate from top to bottom. The thermoelectric material particle layer is composed of PN junctions composed of a plurality of thermoelectric material particles, the PN junctions form an electric path through an electric parallel connection and electric series connection alternating connection mode, and the heat path adopts a parallel connection mode; the hot end substrate and the cold end substrate are rigid ceramic substrates. According to the thermoelectric device, the unique electric parallel connection and electric series connection alternating structure design is adopted, the reliability of the thermoelectric device is greatly improved, when single thermoelectric material particles of the parallel connection part of one path are damaged, the other path can still keep electric connection, and it is guaranteed that the whole thermoelectric device can continuously and normally operate; the problem of overall failure caused by local damage of a traditional thermoelectric device with a full-series structure is effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric devices, and in particular to a high-reliability rigid thermoelectric device and a preparation method thereof. Background Art

[0002] In today's energy landscape, over two-thirds of global energy is lost to the atmosphere as heat during use. Efficiently capturing this waste heat and converting it into usable energy would bring significant economic and environmental benefits. Much of this untapped waste heat could actually be used to generate emission-free renewable energy. Given this enormous potential, thermoelectric technology based on the Seebeck effect has garnered significant attention over the past few decades and has gradually emerged in key areas such as specialty power supplies, green energy production, and industrial waste heat power generation. Notably, the Peltier effect, the reverse of the Seebeck effect, enables thermoelectric devices to precisely control cooling capacity and temperature. Compared to traditional compressor-based refrigeration technology, thermoelectric cooling offers significant advantages, including more precise temperature control, faster response times, and, due to its lack of moving parts, low maintenance and silent operation. Consequently, thermoelectric cooling systems have become an indispensable component in numerous high-tech fields, including infrared guidance, laser weapon systems, 5G / 6G communications infrastructure, new energy vehicles, biomedical equipment, integrated circuit cooling, and the defense industry.

[0003] As thermoelectric devices with both power generation and cooling functions are increasingly used in various high-tech fields, their importance is becoming more and more prominent. Taking the radioisotope thermoelectric generator (RTG) as an example, the thermoelectric devices therein can provide stable energy support for deep space probes, and the thermoelectric cooling devices can also ensure the temperature stability of the precision components inside the reconnaissance satellite camera. However, if these thermoelectric devices used in special scenarios fail to operate after launch, it will trigger a series of serious chain reactions. Therefore, while pursuing high conversion efficiency of thermoelectric devices, their service performance and service life have become important considerations that cannot be ignored. Failures of conventional thermoelectric devices are often closely related to their structural characteristics and working conditions. For example Figure 1 As shown, these thermoelectric devices typically consist of ten or even hundreds of basic thermoelectric PN junctions connected in series. During actual operation, thermal stress accumulates over time and as the temperature difference between the two ends of the device persists. This accumulated thermal stress can easily cause cracking in the connection layer between the P-leg, N-leg, and the connection interface. Once the connection layer cracks, the current transmission path is destroyed, and the entire thermoelectric device will fail completely. Therefore, effectively extending the service life of thermoelectric devices through scientific and rational device structural design has become a key issue that needs to be addressed and is of great practical significance. Summary of the Invention

[0004] The present invention aims to provide a high-reliability rigid thermoelectric device and its fabrication method. Compared to conventional thermoelectric devices, this device, which features alternating parallel and series connections, significantly improves reliability and effectively extends its service life. This device, with its superior properties, is particularly valuable in specialized applications in high-tech fields, where replacement of failed thermoelectric devices is impossible.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a high-reliability rigid thermoelectric device, which comprises, from top to bottom, a hot-end substrate, a thermoelectric material particle layer, and a cold-end substrate; the thermoelectric material particle layer is composed of a PN junction formed by a plurality of thermoelectric material particles, the PN junction forms an electrical path by alternating electrical parallel and electrical series connections, and the thermal path adopts a parallel connection; the hot-end substrate and the cold-end substrate are rigid ceramic substrates.

[0007] In a second aspect, the present invention provides a method for preparing a high-reliability rigid thermoelectric device, comprising the following steps:

[0008] Step 1: Preparation of thermoelectric material particles

[0009] P-type and N-type Bi2Te3 ingots are prepared by a zone melting process, then processed into wafers using a diamond wire saw. After being polished with coarse sandpaper, the surface is cleaned using an ultrasonic cleaning device. A contact layer is prepared by electroplating, and the wafers are cut into particles of a specific size to obtain the desired P-type and N-type thermoelectric material particles.

[0010] Step 2: Preparation of hot-end / cold-end substrates

[0011] Alumina or aluminum nitride plates are selected and cut. The cut plates are placed in a 25wt.% NaOH solution and ultrasonically cleaned at 50°C for 3-5 minutes. After ultrasonic cleaning, the plates are transferred to a 3wt.% dilute sulfuric acid solution and immersed for 30-60 seconds to perform a roughening process. After the roughening process is completed, the plates are removed, rinsed with clean water, and dried to obtain hot-end and cold-end substrates.

[0012] Step 3: Preparation of copper-clad electrode substrate

[0013] The prepared hot-end substrate and cold-end substrate are subjected to magnetron copper cladding to form a copper layer, and then a photosensitive resin is spin-coated on the surface of the copper layer. Then, exposure, development, electroplating thickening, demoulding and etching are sequentially performed to obtain a copper-clad electrode substrate;

[0014] Step 4: Preparation of thermoelectric devices

[0015] Qualified thermoelectric material particles are screened, packaged into braided tape, and solder is accurately printed on the prepared copper-clad electrode substrate using a screen printer. The thermoelectric particles are accurately placed on the substrate solder using a placement machine, and the device is assembled using a reflow soldering process.

[0016] Furthermore, the step 1 specifically includes the following steps:

[0017] Step 101: Select bismuth blocks, antimony blocks, tellurium blocks, selenium blocks and tellurium tetraiodide powder as raw materials to prepare P-type (Bi, Sb)2Te3 and N-type Bi2Te 2.79 Se 0.21 I 0.004 Thermoelectric materials, namely P-type and N-type Bi2Te3;

[0018] Step 102: The mixed raw materials are sealed in a quartz tube, and then placed in a rocking furnace and smelted at a high temperature of 800° C. for two hours.

[0019] Step 103: After the smelting is completed, the synthesized polycrystalline ingot is transferred to a self-made zone melting furnace to slowly grow crystals to obtain a P-type Bi2Te3 ingot and an N-type Bi2Te3 ingot with a length of about 31 cm.

[0020] Step 104: Cut the P-type and N-type Bi2Te3 ingots into thin slices with a thickness of about 6 mm, first grind the slices with coarse sandpaper, and then perform ultrasonic cleaning on the surfaces;

[0021] Step 105: preparing a barrier layer and a welding layer by electroplating process;

[0022] Step 106 : Cut the wafer coated with the barrier layer and the solder layer into particles to obtain P-type and N-type thermoelectric material particles.

[0023] Furthermore, in step 105, the barrier layer is a Ni barrier layer. In the electroplating process, the barrier layer Ni is electroplated at 40°C for 20 minutes to obtain a transition layer with a thickness of 40-50 μm. The welding layer is a Sn welding layer. During electroplating, the Sn welding layer is electroplated at room temperature for 15 minutes to obtain a welding layer with a thickness of 30-40 μm.

[0024] Furthermore, the step 3 specifically includes the following steps:

[0025] Step 301: The prepared hot-end substrate and cold-end substrate are subjected to magnetron sputtering treatment to cover the roughened substrate surfaces with a copper layer, and an electroplating thickening or photolithography-limited growth process is selected to further thicken the sputtered copper layer;

[0026] Step 302, performing photolithography limited growth: using a coating machine to evenly coat UV glue on the copper-clad substrate after magnetron sputtering, drying and developing at low temperature, and then performing electroplating thickening treatment;

[0027] Step 303: Transfer the alternating parallel and series electrical paths onto the electroplated substrate at a transfer temperature of 145° C.

[0028] Step 304: prepare a blue environmentally friendly etchant into an aqueous solution at a ratio of 1:4, and etch in a 70° C. environment for 5-10 minutes;

[0029] Step 305, cleaning: first clean the circuit with gasoline, then remove stains with ethanol, and finally obtain the prepared hot-end / cold-end copper-clad electrode substrate.

[0030] Furthermore, in step 301 , when performing magnetron sputtering, the magnetron power is 60 W and the magnetron time is 1 hour.

[0031] Furthermore, in step 4, when the device is assembled using a reflow soldering process, a layer of 0.2 mm thick Sn-Bi alloy solder is first applied on the inner sides of the hot-end substrate and the cold-end substrate respectively by screen printing.

[0032] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:

[0033] (1) The high-reliability rigid thermoelectric device provided by the present invention proposes a unique connection method, that is, connecting multiple thermoelectric PN junctions in a structure that alternates between electrical parallel and electrical series. Traditional thermoelectric devices are usually constructed by connecting multiple thermoelectric PN junctions in series. Under this structure, once one of the PN junctions is damaged, the entire device will directly lose its function. Based on the unique connection method, the present invention constructs a reliable "backup system" for thermoelectric devices. When the PN junction in a certain parallel circuit cannot be turned on, the other parallel circuits can still remain in the on state, which ensures that the entire thermoelectric device can continue to operate normally and effectively avoids the problem of overall failure of traditional full-series structure thermoelectric devices due to local damage. Compared with conventional thermoelectric devices, the high-reliability rigid thermoelectric device with an alternating structure of electrical parallel and electrical series significantly extends the service life of the device and has important practical value in special application scenarios such as aerospace and deep space exploration.

[0034] (2) The method for preparing a high-reliability rigid thermoelectric device provided by the present invention first separately prepares thermoelectric material particles, a common substrate, and a copper-clad electrode substrate, and then different welding and assembly methods can be selected according to actual needs to prepare a finished thermoelectric device. Compared with conventional thermoelectric devices, the product has a longer service life, excellent performance, and a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0036] Figure 1 Schematic diagram of the structural principle of a conventional thermoelectric device;

[0037] Figure 2 A schematic diagram of the structural principle of the high-reliability rigid thermoelectric device provided by the present invention;

[0038] Figure 3 Design of high reliability rigid thermoelectric device of the present invention Figure 1 ; a is the cold end substrate, b is the hot end substrate;

[0039] Figure 4 Design of high reliability rigid thermoelectric device of the present invention Figure 2 ; a is the cold end substrate, b is the hot end substrate;

[0040] Figure 5 This is a physical picture of the high-reliability rigid thermoelectric device of the present invention. DETAILED DESCRIPTION

[0041] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0042] The object of the present invention is achieved through the following technical solutions:

[0043] See also Figure 2-Figure 4 , the present invention provides a high reliability rigid thermoelectric device, which comprises, from top to bottom, a hot end substrate, a thermoelectric material particle layer and a cold end substrate;

[0044] The thermoelectric material particle layer is composed of a PN junction composed of multiple thermoelectric material particles. The PN junction forms an electrical path through alternating electrical parallel and electrical series connections, and the thermal path adopts a parallel connection; the hot end substrate and the cold end substrate are rigid ceramic substrates.

[0045] The present invention provides a high-reliability rigid thermoelectric device prepared by the following method:

[0046] Preparation of thermoelectric material particles: Bismuth, antimony, tellurium, selenium and tellurium tetraiodide powder were selected as raw materials. Based on the precise weight and composition of high-purity elements such as bismuth (Bi), antimony (Sb), tellurium (Te), selenium (Se) and tellurium tetraiodide (TeI4), P-type (Bi, Sb)2Te3 and N-type Bi2Te 2.79 Se 0.21 I 0.004 Thermoelectric materials are referred to as P-type and N-type Bi2Te3. To improve the uniformity of the ingot samples, the evenly mixed raw materials are first sealed in a quartz tube, and then placed in a rocking furnace and continuously smelted at a high temperature of 800°C for two hours. After smelting, the synthesized polycrystalline ingot is transferred to a homemade regional melting furnace to slowly grow crystals. Finally, a P-type Bi2Te3 ingot with a diameter of about 34 mm and an N-type Bi2Te3 ingot with a length of about 31 cm were successfully prepared. Next, the P-type and N-type Bi2Te3-based thermoelectric materials are cut into thin slices with a thickness of about 6 mm. To ensure the smooth progress of subsequent processes, the thin slices are first polished with coarse sandpaper, and then their surfaces are carefully cleaned with ultrasonic cleaning equipment. After cleaning, the barrier layer and solder layer are prepared by electroplating. The barrier layer is nickel (Ni layer): in the electroplating process, the barrier layer Ni is electroplated at 40°C for 20 minutes, and the solder layer Sn is electroplated at room temperature for 15 minutes, which can obtain a transition layer of 40 to 50 μm thick and a solder layer of 30 to 40 μm thick. Finally, the wafer with the barrier layer and solder layer is cut into pieces with a size of about 1×1×2.5 mm using a dicing machine or a diamond wire saw. 3 particles, thereby obtaining the P-type and N-type thermoelectric material particles we need.

[0047] Hot-end / cold-end substrate preparation: Alumina or aluminum nitride sheets are selected and cut into predetermined dimensions. Therefore, the high-reliability rigid thermoelectric device proposed in this invention is a rigid device. The cut ceramic plates are then ultrasonically cleaned in a 25wt.% NaOH solution at 50°C for 3-5 minutes. After ultrasonic cleaning, the plates are transferred to a 3wt.% dilute sulfuric acid solution and soaked for 30-60 seconds for roughening. After roughening, the plates are removed, rinsed with clean water, and dried for later use.

[0048] The pre-prepared substrate is then subjected to magnetron sputtering treatment. This treatment is to cover the surface of the roughened ceramic plate with a copper layer with a thickness of several hundred to several thousand nanometers, so that it has good electrical conductivity. The specific operation is to continue sputtering for 1 hour at a stable power of 60W. After the magnetron sputtering is completed, the electroplating thickening or photolithography limited growth process can be selected according to actual needs. The electroplating thickening process is to further thicken the copper layer formed by sputtering to several hundred microns by electroplating copper, which can not only greatly reduce the electrode resistance and improve the conductivity efficiency, but also provide convenience for the subsequent reflow soldering process, ensuring stable and reliable welding quality.

[0049] Then, photolithography-limited growth is carried out: UV glue is evenly coated on the copper-clad ceramic sheet after magnetron sputtering using a glue spreader. After low-temperature drying (avoiding light) and development steps, an electroplating thickening operation is performed. Subsequently, a thermal transfer process is implemented to transfer the designed electrical path in the form of alternating electrical parallel and electrical series to the electroplated substrate. The transfer temperature is about 145°C. After that, the blue environmentally friendly etchant is prepared into an aqueous solution in a ratio of 1:4 and etched in a 70°C environment for 5-10 minutes. The photolithography-limited growth process also requires demolding. Finally, cleaning is carried out. First, the circuit is cleaned with gasoline, and then stains are removed with ethanol, and finally the prepared hot end / cold end substrate is obtained.

[0050] Device construction: First, use a taping machine to encapsulate the processed P-type and N-type thermoelectric material particles into suitable tapes respectively. During this process, quality inspection work is carried out simultaneously to screen out thermoelectric particles that do not meet the quality standards to ensure that the thermoelectric particles entering the subsequent process are qualified products. Next, use a screen printer to accurately print the solder on the prepared hot end / cold end substrate. A steel mesh with a thickness of 0.1mm is selected to ensure the uniformity and accuracy of solder printing. Afterwards, the placement machine starts working according to a pre-set program. It can place the thermoelectric particles in the tape neatly and accurately on the solder of the hot end electrode plate. The placement position of each thermoelectric particle has been accurately calculated to ensure a tight fit and correct position. After the device is assembled, it is placed in the reflow soldering instrument. During the soldering operation stage, strictly follow the soldering temperature process corresponding to the Sn-Bi alloy solder, and accurately control key parameters such as temperature and time. Through this rigorous operation, the finished device that meets high quality requirements was finally successfully prepared. Figure 3 and Figure 4 There are two circuit diagrams designed based on the alternating parallel and series connection methods, such as Figure 5 As shown, according to the two designed circuits, a high-reliability rigid thermoelectric device was finally obtained after construction.

[0051] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high reliability rigid thermoelectric device, characterized in that: The thermoelectric device comprises, from top to bottom, a hot-end substrate, a thermoelectric material particle layer, and a cold-end substrate; The thermoelectric material particle layer is composed of a PN junction composed of multiple thermoelectric material particles. The PN junction forms an electrical path by alternating electrical parallel and electrical series connections, and the thermal path adopts a parallel connection. The hot end substrate and the cold end substrate are rigid ceramic substrates.

2. A method for preparing a high-reliability rigid thermoelectric device according to claim 1, characterized in that: The following steps are involved: Step 1: Preparation of thermoelectric material particles P-type and N-type Bi2Te3 ingots are prepared by a zone melting process, then processed into wafers using a diamond wire saw. After being polished with coarse sandpaper, the surface is cleaned using an ultrasonic cleaning device. A contact layer is prepared by electroplating, and the wafers are cut into particles of a specific size to obtain the desired P-type and N-type thermoelectric material particles. Step 2: Preparation of hot-end / cold-end substrates Alumina or aluminum nitride plates are selected and cut. The cut plates are placed in a 25wt.% NaOH solution and ultrasonically cleaned at 50°C for 3-5 minutes. After ultrasonic cleaning, the plates are transferred to a 3wt.% dilute sulfuric acid solution and immersed for 30-60 seconds to perform a roughening process. After the roughening process is completed, the plates are removed, rinsed with clean water, and dried to obtain hot-end and cold-end substrates. Step 3: Preparation of copper-clad electrode substrate The prepared hot-end substrate and cold-end substrate are subjected to magnetron copper cladding to form a copper layer, and then a photosensitive resin is spin-coated on the surface of the copper layer. Then, exposure, development, electroplating thickening, demoulding and etching are sequentially performed to obtain a copper-clad electrode substrate; Step 4: Preparation of thermoelectric devices Qualified thermoelectric material particles are screened, packaged into braided tape, and solder is accurately printed on the prepared copper-clad electrode substrate using a screen printer. The thermoelectric particles are accurately placed on the substrate solder using a placement machine, and the device is assembled using a reflow soldering process.

3. The method for preparing a high-reliability rigid thermoelectric device according to claim 2, wherein: The step 1 specifically includes the following steps: Step 101: Select bismuth blocks, antimony blocks, tellurium blocks, selenium blocks and tellurium tetraiodide powder as raw materials to prepare P-type (Bi, Sb)2Te3 and N-type Bi2Te 2.79 Se 0.21 I 0.004 Thermoelectric materials, namely P-type and N-type Bi2Te3; Step 102: The mixed raw materials are sealed in a quartz tube, and then placed in a rocking furnace and smelted at a high temperature of 800° C. for two hours. Step 103: After the smelting is completed, the synthesized polycrystalline ingot is transferred to a self-made zone melting furnace to slowly grow crystals to obtain a P-type Bi2Te3 ingot and an N-type Bi2Te3 ingot with a length of about 31 cm. Step 104: Cut the P-type and N-type Bi2Te3 ingots into thin slices with a thickness of about 6 mm, first grind the slices with coarse sandpaper, and then perform ultrasonic cleaning on the surfaces; Step 105: preparing a barrier layer and a welding layer by electroplating process; Step 106 : Cut the wafer coated with the barrier layer and the solder layer into particles to obtain P-type and N-type thermoelectric material particles.

4. The method for preparing a high-reliability rigid thermoelectric device according to claim 3, characterized in that: In step 105, the barrier layer is a Ni barrier layer. During the electroplating process, the barrier layer Ni is electroplated at 40°C for 20 minutes to obtain a transition layer with a thickness of 40-50 μm. The welding layer is a Sn welding layer. During the electroplating process, the Sn welding layer is electroplated at room temperature for 15 minutes to obtain a welding layer with a thickness of 30-40 μm.

5. The method for preparing a high-reliability rigid thermoelectric device according to claim 2, wherein: The step 3 specifically includes the following steps: Step 301: The prepared hot-end substrate and cold-end substrate are subjected to magnetron sputtering treatment to cover the roughened substrate surfaces with a copper layer, and an electroplating thickening or photolithography-limited growth process is selected to further thicken the sputtered copper layer; Step 302, performing photolithography limited growth: using a coating machine to evenly coat UV glue on the copper-clad substrate after magnetron sputtering, drying and developing at low temperature, and then performing electroplating thickening treatment; Step 303: Transfer the alternating parallel and series electrical paths onto the electroplated substrate at a transfer temperature of 145° C. Step 304: prepare a blue environmentally friendly etchant into an aqueous solution at a ratio of 1:4, and etch in a 70° C. environment for 5-10 minutes; Step 305, cleaning: first clean the circuit with gasoline, then remove stains with ethanol, and finally obtain the prepared hot end / cold end copper-clad electrode substrate.

6. The method for preparing a high-reliability rigid thermoelectric device according to claim 5, characterized in that: In step 301 , when performing magnetron sputtering processing, the magnetron power is 60 W and the magnetron time is 1 hour.

7. The method for preparing a high-reliability rigid thermoelectric device according to claim 2, wherein: In step 4, when the device is assembled using a reflow soldering process, a 0.2 mm thick layer of Sn-Bi alloy solder is first applied on the inner sides of the hot-end substrate and the cold-end substrate using screen printing.

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