Packaging method and packaging structure for flexible thermoelectric element

Abstract

The invention discloses a packaging method and a packaging structure for a flexible thermoelectric element, and relates to the technical field of semiconductor device preparation, and the packaging method comprises the steps: preparing a thermoelectric series structure which comprises an electrode layer, a P-type thermoelectric arm and an N-type thermoelectric arm; the electrode layer is composed of a plurality of metal electrodes; coating the outer surface of the electrode layer with cloth glue; a first packaging layer is attached to the outside of the electrode layer on one side of the thermoelectric series structure; a second packaging layer is attached to the outside of the electrode layer on the other side of the thermoelectric series structure; and finally, the packaging of the flexible thermoelectric element is completed after static pressure molding. According to the invention, a discontinuous bonding structure of the packaging cloth is adopted to package the thermoelectric element, and a traditional compact polymer packaging material is replaced; and the unique packaging mode of point-like adhesion and planar ventilation between the packaging cloth and the device is utilized, so that the structural stability and comfort of the device are ensured.

Description

Technical Field

[0001] This invention generally relates to the field of semiconductor device fabrication technology, and specifically to a packaging method and packaging structure for flexible thermoelectric elements. Background Technology

[0002] Thermoelectric devices enable direct conversion between thermal and electrical energy, showing significant application potential in energy recovery and self-powered sensing systems. Wearable thermoelectric devices, in particular, can continuously generate electricity by utilizing the temperature difference between human skin and ambient air, providing energy support for low-power wearable electronic devices without the need for charging, and have therefore attracted widespread attention.

[0003] For wearable applications, thermoelectric devices need to possess good flexibility and mechanical reliability to adapt to complex deformations such as bending, stretching, and torsion during human movement. Currently, the flexible encapsulation of existing wearable thermoelectric devices mainly uses polymer materials, such as polydimethylsiloxane (PDMS), polyurethane (PU) foam, and polyimide (PI) film. These encapsulation methods typically employ a monolithic potting or overlay structure, encapsulating the thermoelectric leg array, electrodes, and electrical connection structure entirely within the polymer matrix to achieve flexibility and electrical insulation protection.

[0004] These encapsulation structures have a dense physical morphology, with a water vapor permeability typically below 50 g / m² / 24h. When the device is worn in close contact with the skin for extended periods, not only does the encapsulation structure become less skin-friendly, but it also prevents sweat from effectively escaping through the encapsulation layer. Sweat accumulates at the interface between the encapsulation layer and the skin, significantly impacting the wearing comfort and long-term reliability of the thermoelectric device. Summary of the Invention

[0005] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a packaging method and packaging structure for flexible thermoelectric elements.

[0006] In a first aspect, the present invention provides a packaging method for flexible thermoelectric elements, comprising: A thermoelectric series structure is fabricated, comprising an electrode layer, a P-type thermoelectric arm, and an N-type thermoelectric arm, wherein the P-type and N-type thermoelectric arms are connected in series through the electrode layer; the electrode layer is composed of a plurality of metal electrodes. A fabric adhesive with a thickness of 10~100μm is coated on the outer surface of the electrode layer; The first encapsulation layer is attached to the outside of one side electrode layer of the thermoelectric series structure; The second encapsulation layer is attached to the other side of the electrode layer of the thermoelectric series structure, and the first encapsulation layer and the second encapsulation layer form a continuous air-permeable channel in the region corresponding to the gap between the electrode layers. Static pressure molding: Under a set temperature range, a set pressure range is applied synchronously and uniformly to the first encapsulation layer and the second encapsulation layer, and the pressure is maintained for a set time to complete the encapsulation of the flexible thermoelectric element.

[0007] According to the technical solution provided by the present invention, the set temperature range is 140℃~150℃; the set pressure range is 5N~10N; and the set time is 120min~140min.

[0008] According to the technical solution provided by the present invention, the first encapsulation layer and the second encapsulation layer are breathable fabric structures; the breathable fabric structure is a woven or knitted fabric made of natural fibers or chemical fibers.

[0009] According to the technical solution provided by the present invention, the preparation of the thermoelectric series structure includes the following steps: S11: Multiple P-type thermoelectric arms and N-type thermoelectric arms are alternately arranged in the positioning mold to form an array of thermoelectric leg pairs; S12: Apply solder paste to one end of the arranged P-type thermoelectric arm and N-type thermoelectric arm, attach the metal electrode to the solder paste, and dry it in a drying oven at a temperature of 50℃~70℃, so that each metal electrode is initially bonded to one end of the thermoelectric leg pair to form a preliminary thermoelectric series structure. S13: After the initial bonding of the preliminary thermoelectric series structure is flipped over, it is placed back into the positioning mold. Step S12 is repeated to apply solder paste to the other end of the preliminary thermoelectric series structure. After drying, the thermoelectric series structure to be solidified is obtained. S14: Place the thermoelectric series structure to be solidified in a reflow oven and maintain it for a set time within the set temperature range and set pressure range to solidify it into the final thermoelectric series structure.

[0010] According to the technical solution provided by the present invention, both the first encapsulation layer and the second encapsulation layer are provided with hydrophobic regions and hydrophilic regions: The hydrophobic region is provided correspondingly to the metal electrode; The hydrophilic region is positioned corresponding to the position of the non-metallic electrode on the electrode layer; The hydrophilic region consists of a hydrophobic layer, a water-absorbing layer, and a hydrophilic layer arranged sequentially from the inside to the outside of the component.

[0011] According to the technical solution provided by the present invention, the first encapsulation layer and the second encapsulation layer are provided with a directional moisture-wicking area in the region that is offset from the thermoelectric series structure, which is connected to the hydrophilic area to form a sweat outward transport path.

[0012] According to the technical solution provided by the present invention, the preparation of the thermoelectric series structure further includes the following steps: S15: Spray-applied gradient intermediate layer; The process of spraying the gradient intermediate layer includes the following steps: Spray the first layer of mixed slurry onto the outer surface of the metal electrode and pre-cur it at 80~100℃ for 1~3 minutes; A second layer of mixed slurry and a third layer of mixed slurry are sprayed sequentially on the outside of the first layer of mixed slurry. The proportions of high-modulus phase and low-modulus phase in the first layer of mixed slurry, the second layer of mixed slurry, and the third layer of mixed slurry gradually decrease; The third layer of mixed slurry remains in a semi-cured state; during the static pressure molding process, the fabric adhesive and the semi-cured third layer of mixed slurry undergo interfacial fusion to form an integrated adhesive structure.

[0013] According to the technical solution provided by the present invention, the high modulus phase content in the first mixed slurry layer is 80-95 wt%, and the low modulus phase content is 5-20 wt%; the high modulus phase content in the second mixed slurry layer is 50-80 wt%, and the low modulus phase content is 20-50 wt%; the high modulus phase content in the third mixed slurry layer is 0-30 wt%, and the low modulus phase content is 70-100 wt%.

[0014] In a second aspect, the present invention provides a packaging structure for flexible thermoelectric elements, comprising: The thermoelectric body includes: an electrode layer, a P-type thermoelectric arm, and an N-type thermoelectric arm, wherein the P-type thermoelectric arm and the N-type thermoelectric arm are connected in series through the electrode layer; the electrode layer is composed of a plurality of metal electrodes; An adhesive layer is coated on the outside of the metal electrode; The encapsulation fabric layer includes a first encapsulation layer and a second encapsulation layer. The first encapsulation layer and the second encapsulation layer are respectively bonded to the outside of the electrode layers located at both ends of the thermoelectric body by the adhesive layer, thereby encapsulating the flexible thermoelectric element.

[0015] According to the technical solution provided by the present invention, the ends of both the P-type thermoelectric arm and the N-type thermoelectric arm are provided with an integrally machined transition layer, which is used to improve the wettability of the solder to each thermoelectric arm.

[0016] In summary, this technical solution specifically discloses a packaging method and packaging structure for flexible thermoelectric elements. The packaging method includes: preparing a thermoelectric series structure, which comprises an electrode layer, a P-type thermoelectric arm, and an N-type thermoelectric arm, the P-type and N-type thermoelectric arms being connected in series through the electrode layer; the electrode layer is composed of several metal electrodes; coating the outer surface of the electrode layer with a 10-100 μm thick adhesive; attaching a first encapsulation layer to one side of the electrode layer of the thermoelectric series structure; attaching a second encapsulation layer to the other side of the electrode layer of the thermoelectric series structure, with the first and second encapsulation layers forming a continuous venting channel in the region corresponding to the gap between the electrode layers; and static pressure molding: simultaneously and uniformly applying a static pressure within a set pressure range to the first and second encapsulation layers within a set temperature range, maintaining the pressure for a set duration to complete the packaging of the flexible thermoelectric element.

[0017] Beneficial effects: (1) The present invention uses a discontinuous adhesive structure of encapsulation fabric to encapsulate thermoelectric elements, replacing the traditional dense polymer encapsulation material. The porous structure of the encapsulation material effectively improves the water vapor permeability of the encapsulation structure compared to polymer materials. At the same time, this unique encapsulation structure enables the encapsulation fabric and the device to achieve a unique combination of "point-like adhesion and surface-like air permeability", ensuring the structural stability of the device.

[0018] (2) When the device is worn against the skin, the sweat produced by the human body can be smoothly discharged in the form of water vapor through the breathable channels of the encapsulation layer, avoiding the accumulation of sweat at the interface between the encapsulation layer and the skin. This not only eliminates discomfort such as stuffiness and dampness, but also reduces the risk of skin allergies, enabling the device to meet the wearability needs of scenarios such as long-term health monitoring and sports assistance.

[0019] (3) The present invention does not require complex molds and multi-step potting. It can complete the encapsulation in just three steps: applying glue, attaching cloth, and static pressure, which significantly reduces manufacturing costs and improves production efficiency. Attached Figure Description

[0020] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of a fabric-encapsulated device; Figure 2 This is a schematic diagram of the thermoelectric units of the device connected in series; Figure 3 This is a schematic diagram of the connection of the basic thermoelectric unit of the device; Figure 4 For device fabrication process; Figure 5 For device fabrication steps; Figure 6This represents the rate of change of the bending resistance of the packaged device. Figure 7 The current-voltage (IV) curves of the device under a fixed temperature difference; Figure 8 The device current-power (IP) curve is shown under a fixed temperature difference. Figure 9 The open-circuit voltage of the device under different temperature differences; Figure 10 The output power density of the device under different temperature differences; Figure 11 The open-circuit voltage of the device varies under different movement states when worn on the human wrist; Figure 12 IV curves of the device under different motion states when worn on the human wrist; Figure 13 IP curves of the device under different motion states when worn on the human wrist; Figure 14 The IV curve of the device when it is integrated into a hat and worn; Figure 15 IP profile of the device when integrated into a hat for wear; Figure 16 The curve showing the change in voltage opening time (tV) when the device is integrated into the hat and worn for an extended period of time.

[0021] The labels in the diagram are: 1. Electrode layer; 2. P-type thermoelectric arm; 3. N-type thermoelectric arm; 4. Encapsulation fabric layer; 5. Transition layer; 6. Gradient intermediate layer. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] Example 1 To make the technical solutions of the embodiments of the present invention clearer and easier to understand, the application background of the embodiments of the present invention will be introduced below.

[0025] With the development of the Internet of Things (IoT) and flexible electronics, thermoelectric devices that utilize human body heat to generate electricity have become an ideal alternative to batteries. These devices are typically attached to the wrist, arm, chest, or neck, powering low-power sensors by collecting the temperature difference between the skin and the environment (usually between 5°C and 15°C). In practical wearable scenarios, thermoelectric devices face challenges related to wearing comfort and dynamic reliability. Specifically, human skin is the primary organ for sweating and heat dissipation. Traditional polymer encapsulations (such as PDMS and PI films) have extremely low water vapor permeability, easily leading to sweat accumulation at the skin interface, causing stuffiness, redness, and even skin allergies. This not only affects the user experience, but the salt in sweat can also corrode the electrodes, shortening the device's lifespan. Furthermore, wearable parts (such as joints and arms) undergo complex deformations during movement. In existing technologies, there is a significant modulus difference between rigid thermoelectric arms and flexible encapsulations. When bent, stress concentrates at the welding interface, easily causing solder joint cracking and a surge in contact resistance, leading to device failure after only a few hundred bends.

[0026] While attempts have been made to improve breathability using porous polymers, these often come at the cost of structural strength. Although flexible circuit boards have been used as electrodes, they are costly and do not adhere well to human skin. Therefore, there is an urgent need for an encapsulation solution that can guarantee excellent breathability while enhancing bending stability. To address these issues, this invention proposes a solution that uses an encapsulation fabric to form breathable channels, employing discontinuous bonding and a synergistic stress-bearing structure to solve these problems.

[0027] For details, please refer to Figure 1 The schematic diagram shown in this embodiment illustrates a packaging method for flexible thermoelectric elements, including: S1: Fabricate a thermoelectric series structure, which includes an electrode layer, a P-type thermoelectric arm, and an N-type thermoelectric arm. The P-type and N-type thermoelectric arms are connected in series through the electrode layer. The electrode layer is composed of several metal electrodes. A 10-100 μm thick fabric adhesive is coated on the outer surface of the electrode layer; The first encapsulation layer is attached to the outside of one electrode layer of the thermoelectric series structure; The second encapsulation layer is attached to the other side of the electrode layer of the thermoelectric series structure, and the first encapsulation layer and the second encapsulation layer form a continuous venting channel in the region corresponding to the gap between the electrode layers. S2: Static pressure molding: Under a set temperature range, static pressure within a set pressure range is applied synchronously and uniformly to the first and second encapsulation layers, and maintained for a set time to complete the encapsulation of the flexible thermoelectric element.

[0028] For example, the temperature range is set to 140℃~150℃; the pressure range is set to 5N~10N; and the time is set to 120min~140min. However, these parameters may be adjusted according to actual needs, and the present invention does not impose any special limitations on them.

[0029] In this embodiment of the invention, the P-type thermoelectric arm can be selected from Bi. 0.5 Sb 1.5 Te3 thermoelectric material has a thermoelectric figure of merit of over 1.0 at room temperature and needs to be cut into cubes of 1.3 × 1.3 × 2.1 mm before use. The end of the P-type thermoelectric arm is pre-plated with a transition layer, which can be a Ni / Ag composite transition layer or a transition layer containing only Ni. The Ni layer acts as a barrier layer to prevent element diffusion, while the Ag layer acts as a wetting layer to improve solderability.

[0030] The N-type thermoelectric arm can be made of Ag2Se thermoelectric material, which has good mechanical properties and room temperature thermoelectric properties. Its size is the same as that of the P-type thermoelectric arm, and a transition layer is also prepared at the end. This transition layer is a Ni / Cu composite transition layer formed by synchronous hot pressing, or it can be a transition layer containing only Ni. No special limitation is made here. The metal electrode can be made of 0.1mm thick copper foil with a conductivity ≥58 MS / m. It can be cut into 1.3×5.6mm rectangular strips, ensuring its projected area on the horizontal plane is larger than the end face area of ​​the thermoelectric arm. This creates an extension beyond the edge of the thermoelectric arm, providing ample bonding area for the adhesive and forming an integrated stress-bearing structure, ensuring device structural stability. When the device is bent, external stress first acts on the large-area encapsulation layer and is then evenly dispersed through the encapsulation layer and the underlying metal electrode extension, preventing stress concentration at the fragile solder interface and significantly improving the device's electrical stability under dynamic wear conditions.

[0031] In practical applications, the metal electrode and the N-type thermoelectric arm are connected to the P-type thermoelectric arm via solder paste, and the solder paste layer can be made of Sn. 42 Bi 58 This lead-free low-temperature solder paste has a melting point of 138°C, a particle size of 20~38μm, and a flux content of approximately 11wt%. This solder paste melts at relatively low temperatures, avoiding thermal damage to thermoelectric materials.

[0032] For the fabric adhesive layer, polyamide hot melt adhesive can be selected, with a softening point of approximately 115~125℃ and a melt viscosity of approximately 3000~8000 mPa. The coating thickness is controlled at around 50μm to ensure sufficient adhesion without excessive penetration and clogging of the fabric pores.

[0033] The first and second encapsulation layers can be selected from one or more of knitted fabric, non-woven fabric, or functional composite fabric, with a weight of 120g / m², a thickness of approximately 0.3mm, and an air permeability of approximately 300mm / s. This fabric possesses good elasticity and skin-friendliness, as well as excellent abrasion resistance. The special encapsulation structure formed by the first and second encapsulation layers ensures that the gap area between the thermoelectric arms after encapsulation is an adhesive-free area, preserving the original pore structure of the encapsulation layers and forming highly efficient ventilation channels. Therefore, water vapor generated from the evaporation of sweat when the flexible thermoelectric element is worn can be smoothly discharged through the ventilation channels in the gap area.

[0034] It should be noted that the ventilation channel has the characteristics of longitudinal continuity, lateral connection, and non-clogging. Longitudinal continuity means that the pores of the first and second encapsulation layers are aligned in the thickness direction, forming a continuous vertical airflow path. Lateral connection means that the electrode gap areas are interconnected, forming a ventilation network covering the entire device surface. Non-clogging means that the adhesive layer does not penetrate into the cloth encapsulation layer. When the device is worn against the skin, the sweat produced by the human body, in the form of water vapor, passes through the pores of the first encapsulation layer, enters the electrode gap area, and then passes through the pores of the second encapsulation layer, and is finally discharged into the external environment, effectively avoiding the accumulation of sweat at the interface between the encapsulation layer and the skin.

[0035] The choice of solder paste is crucial in this process. Low-temperature solder pastes, such as Sn, are preferred. 42 Bi 58 (Melting point 138℃), Sn 43 Bi 57 (Melting point 139℃) or In 52 Sn 48 (Melting point 118℃), its melting point is below 200℃, so welding can be completed at a lower temperature, avoiding thermal damage to thermoelectric materials (such as Bi2Te3-based materials may degrade in performance above 250℃) caused by high temperature. It is recommended to control the thickness of the solder paste coating to 10~100μm. Too thin a coating can easily lead to poor soldering, while too thick a coating may cause solder to overflow and short circuit.

[0036] During the hydrostatic pressing process, the encapsulation effect can be further improved by optimizing the process parameters. For example, the preferred temperature range is 140℃~150℃; the preferred pressure range is 5N~10N; and the preferred time is 120min~140min. Within this parameter range, the fabric adhesive can fully melt and wet the encapsulation layer fibers, forming a strong mechanical anchor, while avoiding fabric deformation or excessive adhesive penetration that could clog pores due to excessive temperature or pressure.

[0037] Therefore, unlike the overall potting or full coverage methods used in traditional polymer encapsulation, this invention achieves a unique effect of "point-like adhesion and surface-like breathability." Point-like adhesion refers to the fact that this invention only coats the outer surface of the metal electrodes with fabric adhesive, forming discrete adhesion points corresponding to the metal electrodes one-to-one. The adhesion thickness is controlled at 10-100 μm, filling only the tiny gaps between the encapsulation layer and the metal electrodes without wetting into the encapsulation layer itself. This ensures the structural stability between the thermoelectric body and the encapsulation layer while maximizing the space for breathable areas. Surface-like breathability is achieved through the surface structure of the first and second encapsulation layers. That is, except for the area where the metal electrodes are located, the surface structure of the first and second encapsulation layers themselves forms comprehensive breathable channels on the device surface. Furthermore, the breathability automatically increases with the amount of perspiration (the more you sweat, the greater the water vapor partial pressure difference, and the faster the expulsion), effectively improving the long-term wearing comfort of wearable thermoelectric devices.

[0038] In a preferred embodiment, the first encapsulation layer and the second encapsulation layer are breathable fabric structures; the breathable fabric structure is a woven or knitted fabric made of natural or chemical fibers.

[0039] Specifically, to ensure breathability and structural stability, the first and second sealing layers are preferably made of breathable fabric. This breathable fabric can be a woven or knitted fabric made of natural fibers (such as cotton, linen, and silk) or chemical fibers (such as polyester, nylon, and modal). The porosity of these materials is typically between 30% and 70%, providing ample channels for water vapor transport. For example, using 60-count double-knitted pure cotton fabric can achieve an air permeability of 200-400 mm / s, ensuring both good breathability and sufficient structural strength.

[0040] In a preferred embodiment, S1: The fabrication of the thermoelectric series structure includes the following steps: S11: Multiple P-type thermoelectric arms and N-type thermoelectric arms are alternately arranged in the positioning mold to form an array of thermoelectric leg pairs; S12: Apply solder paste to one end of the arranged P-type thermoelectric arm and N-type thermoelectric arm, attach the metal electrodes to the solder paste, and dry them in a drying oven at a temperature of 50℃~70℃, so that each metal electrode is initially bonded to one end of the thermoelectric leg pair to form a preliminary thermoelectric series structure. S13: After the initial bonding of the preliminary thermoelectric series structure is flipped over, it is placed back into the positioning mold. Step S12 is repeated to apply solder paste to the other end of the preliminary thermoelectric series structure. After drying, the thermoelectric series structure to be solidified is obtained. S14: Place the thermoelectric series structure to be solidified in a reflow oven and maintain it for a set time within a set temperature and pressure range to solidify it into the final thermoelectric series structure.

[0041] Specifically, in practical applications, the process of fabricating a thermoelectric series structure can be understood as follows: Using a precision CNC-machined PTFE positioning mold (hole position accuracy ±0.02mm), P-type and N-type thermoelectric arms coated with a transition layer are alternately arranged into a 15×15 rectangular array, with a total array size of approximately 75×75mm and a gap of approximately 3mm between the thermoelectric arms. At one end of the array, a 300-mesh stainless steel screen printing template is used to coat a Sn42Bi58 solder paste, with a solder paste layer thickness of approximately 100μm. Metal electrodes are then attached to the solder paste, ensuring the electrode center is aligned with the thermoelectric arm center. The assembly is then placed in a 60℃ drying oven for 15 minutes to allow the solvent in the solder paste to evaporate, thus initially fixing the metal electrodes to the P-type and N-type thermoelectric arms. Flip the pre-fixed device and remove the positioning mold, repeating step S12. Attach metal electrodes to the other end according to the designed configuration. Then, place the pre-constructed thermoelectric series structure with electrodes on both sides into a reflow oven. Place a precision-ground stainless steel pressure block on each of the upper and lower surfaces of the device and apply a pressure of 8N. Further, set the reflow profile: heat to 150°C at 5°C / min, hold for 5 minutes, and then allow to cool naturally to room temperature. During this process, the solder paste melts, forming a reliable intermetallic compound bond between the metal electrodes and the thermoelectric arm transition layer.

[0042] Next, after reflow soldering, adhesive is applied to the upper and lower surfaces of the device using dispensing or micro-grooving methods, applying the adhesive only to the outer surface of the extensions of the metal electrodes to form an adhesive layer, ensuring that there is no adhesive in the electrode gap area. The pre-cut first and second encapsulation layers are then placed over the adhesive-coated area, and a stainless steel block weighing approximately 500g is placed on its surface to apply pressure. The device is then left to stand at a constant temperature of 25°C for 2 hours to allow the first and second encapsulation layers to fully bond with the metal electrodes located at both ends of the P-type and N-type thermoelectric arms, resulting in a complete device.

[0043] In a preferred embodiment, both the first encapsulation layer and the second encapsulation layer are provided with hydrophobic regions and hydrophilic regions: The hydrophobic region is set correspondingly to the metal electrode; The hydrophilic region is positioned correspondingly to the non-metallic electrodes on the electrode layer; The hydrophilic zone consists of a hydrophobic layer, a water-absorbing layer, and a hydrophilic layer arranged sequentially from the inside to the outside of the component.

[0044] To further enhance wearing comfort, especially for the need for perspiration wicking during exercise, this invention also provides a preferred embodiment with directional moisture-wicking function. In this embodiment, both the first and second encapsulation layers are provided with hydrophobic and hydrophilic regions. The hydrophobic region is positioned corresponding to the metal electrode. This region can be coated with a fluorocarbon or silicon-based hydrophobic finishing agent (concentration 10~30g / L) to make the contact angle between the fabric surface and water greater than 120°, thus preventing sweat from wetting the electrode area and causing short circuits or corrosion. The hydrophilic region is positioned corresponding to the position of the non-metallic electrode on the electrode layer (the area between the electrode layers). This region can be modified by plasma treatment or hydrophilic finishing agents (such as polyethylene glycol derivatives) to make the contact angle between the fabric surface and water less than 60°, thus enabling rapid moisture absorption. The hydrophilic region consists of a hydrophobic layer, a water-absorbing layer, and a hydrophilic layer arranged sequentially from the inside to the outside of the element. The hydrophobic layer (e.g., a PTFE porous membrane with a pore size of 0.2~0.5μm) prevents sweat backflow. The water-absorbing layer (e.g., highly absorbent polyester nonwoven fabric with a basis weight of 30~80g / m²) absorbs and diffuses sweat laterally through capillary action. The hydrophilic layer (e.g., hydrophilic modified cotton fabric) rapidly conducts sweat to the external environment for evaporation. This not only avoids the impact of sweat on the thermoelectric series structure but also allows sweat to absorb heat through evaporation in the external environment, enhancing the effective temperature difference collected by the flexible thermoelectric element between the skin and the environment, and improving the heating efficiency of the thermoelectric device.

[0045] Furthermore, in the regions of the first and second encapsulation layers that are offset from the thermoelectric series structure, there are also directional moisture-wicking areas that communicate with the hydrophilic areas, forming a sweat outflow path. This area can achieve unidirectional sweat outflow by printing alternating hydrophobic and hydrophilic patterns (such as strip-shaped hydrophilic channels with a width of 0.5~2mm) on the fabric, utilizing capillary pressure gradients. This design allows liquid sweat on the skin surface to be quickly absorbed and outflowed along a predetermined path, while the hydrophobic area protects the metal electrode area from sweat corrosion, achieving an excellent effect of sweat wicking without soaking.

[0046] Specifically, in practical applications, the hydrophobic area fabric is treated with a padding method: the fabric is immersed in a finishing solution containing 30 g / L of fluorocarbon hydrophobic agent (such as Daikin TG-580) and 5 g / L of crosslinking agent, with a padding rate of 70%, and then dried at 150°C for 2 minutes. After treatment, the contact angle of the fabric in this area can reach 135°, and sweat will bead up and roll off its surface without wetting the electrode area. The hydrophilic region corresponds to the gap area on the electrode layer. The hydrophilic region consists of a hydrophobic layer, a water-absorbing layer, and a hydrophilic layer, arranged sequentially from the inside near the skin outwards. The hydrophobic layer uses a PTFE hydrophilic modified microporous membrane with a thickness of 30μm and a pore size of 0.45μm, which can prevent liquid sweat from flowing back while allowing water vapor to pass through. The water-absorbing layer uses a highly absorbent polyester spunlace nonwoven fabric with a basis weight of 50g / m² and a fiber fineness of 1.2dtex. It is hydrophilic treated (containing 5% hydrophilic agent SILASTOL PHP 26) and has excellent capillary water absorption performance, with a water retention rate of up to 8 times its own weight. The hydrophilic layer uses 40-count hydrophilic modified cotton plain weave fabric, which is plasma treated (power 500W, treatment time 1min) to reduce the contact angle to 35°, which can quickly diffuse the absorbed sweat to the surface for evaporation. The directional moisture-wicking area has a 2mm wide strip-shaped hydrophilic channel at the edge of the encapsulation fabric layer (away from the thermoelectric array) that is connected to the hydrophilic region. This channel is formed by printing a hydrophobic barrier pattern, which uses capillary pressure gradients to guide sweat from the hydrophilic area to the edge, where it eventually drips or evaporates.

[0047] In a real-world experimental environment, simulation tests of perspiration management, electrode corrosion resistance, and sports wearability can be conducted to continuously refine the product design. Specifically, the perspiration management simulation test involves, for example, placing the device under test (DUT) onto simulated skin (made of medical-grade silicone, 2mm thick, with thermal properties similar to human skin) in a constant temperature and humidity environment of 25±2℃ and 50±5%RH. Technicians continuously deliver artificial sweat (prepared according to ISO 3160 standards) to the interface between the DUT and the simulated skin using a micro-injection pump at a flow rate of 0.5mL / h for 4 hours. Subsequently, a temperature and humidity sensor (accuracy ±2%RH) monitors the relative humidity changes at the interface in real time, recording data every 10 seconds. Finally, three samples are tested in each group, and the average value is taken as the test result. The electrode corrosion resistance simulation test involves placing the DUT in a constant temperature and humidity chamber at 60℃ and 85% relative humidity for 500 hours of continuous aging. Every 100 hours, the device is removed, cooled to room temperature, and its internal resistance is measured using the four-wire method. The rate of change of internal resistance is then calculated. The process for simulating wearable sports testing is as follows: using a flexible circuit board bending tester, the device under test is attached to the surface of a silicone prosthesis simulating an arm. The bending angle is set to 0-90°, the bending frequency to 30 times / minute, and the device is bent continuously for 1000 times. Finally, the internal resistance of the device is measured before and after bending, and the adhesion between the device and the prosthesis surface is observed. The above process is not limited to the experimental steps specified in this invention.

[0048] In a preferred embodiment, the fabrication of the thermoelectric series structure further includes spraying a gradient intermediate layer. Specifically, the process of spraying the gradient intermediate layer includes the following steps: Spray the first layer of mixed slurry onto the outer surface of the metal electrode and pre-cur it at 80~100℃ for 1~3 minutes; A second layer of mixed slurry and a third layer of mixed slurry are sprayed sequentially on the outside of the first layer of mixed slurry. The proportions of high-modulus phase and low-modulus phase in the first, second, and third mixed slurry layers gradually decrease. The third layer of mixed slurry remains in a semi-cured state; during the static pressure molding process, the fabric adhesive and the semi-cured third layer of mixed slurry undergo interfacial fusion to form an integrated adhesive structure.

[0049] For example, the high-modulus phase content in the first mixed slurry layer is 80-95 wt%, and the low-modulus phase content is 5-20 wt%; the high-modulus phase content in the second mixed slurry layer is 50-80 wt%, and the low-modulus phase content is 20-50 wt%; the high-modulus phase content in the third mixed slurry layer is 0-30 wt%, and the low-modulus phase content is 70-100 wt%; and in the first, second, and third mixed slurry layers, the high-modulus phase content decreases sequentially, and the low-modulus phase content increases sequentially, forming a gradient transition structure from high modulus to low modulus.

[0050] The high-modulus phase refers to the component with a high elastic modulus in the composite slurry system. After curing, it mainly serves as a structural support, improving the overall structural stiffness and maintaining the geometric stability of the device, while also forming a good mechanical match with the high-modulus metal electrode. The low-modulus phase refers to the component with a low elastic modulus in the composite slurry system. After curing, it mainly provides a flexible buffering effect, absorbing and dissipating deformation energy to alleviate interfacial stress concentration, and achieving a mechanical match with the flexible encapsulation layer or substrate.

[0051] In practical applications, the high-modulus phase can be selected from rigid materials such as epoxy resin (modulus of approximately 3~5 GPa) and phenolic resin (modulus of approximately 5~7 GPa) to provide structural support; the low-modulus phase can be selected from flexible materials such as polyurethane (modulus of approximately 10~100 MPa), silicone (modulus of approximately 1~10 MPa), and acrylate to provide deformation capability. By adjusting the ratio of the two, the modulus can be continuously adjusted.

[0052] Preferably, the high-modulus phase content in the first mixed slurry layer is 80-95 wt%, and the low-modulus phase content is 5-20 wt%, so that its modulus is close to that of the metal electrode (the modulus of copper is about 110 GPa, and the modulus of aluminum is about 70 GPa), achieving rigidity matching; the high-modulus phase content in the second mixed slurry layer is 50-80 wt%, and the low-modulus phase content is 20-50 wt%, with the modulus in an intermediate transition state; the high-modulus phase content in the third mixed slurry layer is 0-30 wt%, and the low-modulus phase content is 70-100 wt%, with the modulus close to that of the flexible encapsulation fabric (such as the modulus of cotton fabric is about 0.1-1 GPa), achieving flexibility matching.

[0053] Therefore, to further improve the bending resistance and long-term reliability of the device, this embodiment sprays a gradient intermediate layer on the outside of the metal electrode. This gradient intermediate layer design enables a smooth transition of mechanical properties between the high-modulus metal electrode and the low-modulus encapsulation material, effectively eliminating stress abrupt change points. According to finite element simulation analysis, the maximum stress at the interface can be effectively reduced after adopting this gradient buffer layer, thereby improving the bending life of the device.

[0054] In practical applications, the first mixed slurry layer adheres closely to the metal electrode, with a ratio of 90wt% epoxy resin (E-51 type) and 10wt% polyurethane (Bayer Desmocap 12), with a small amount of defoamer and leveling agent added. After curing, this layer has a modulus of approximately 2.8 GPa, close to the modulus of the metal electrode, achieving rigidity matching and ensuring effective stress transfer. The second mixed slurry layer sits above the first layer, with a ratio of 60wt% epoxy resin and 40wt% polyurethane. After curing, this layer has a modulus of approximately 680 MPa, serving as an intermediate transition layer and acting as a stress buffer. The third mixed slurry layer is the outermost layer, with a ratio of 20wt% epoxy resin and 80wt% polyurethane. This layer remains in a semi-cured state before encapsulation, with a modulus of approximately 85 MPa, close to the modulus of the encapsulation fabric (approximately 120 MPa), achieving flexibility matching. It should be noted that the semi-cured state gives its surface a certain degree of tackiness, facilitating interfacial fusion with the subsequent fabric adhesive.

[0055] In practical applications, precision spraying equipment is used to spray a first mixed slurry layer onto the surface of the metal electrode, controlling the wet film thickness to approximately 20 μm. This layer is then pre-cured on a 90°C hot plate for 2 minutes to achieve a surface-dry state. Next, a second mixed slurry layer is sprayed onto the first layer, with a wet film thickness of approximately 20 μm, and pre-cured at 90°C for 1.5 minutes. Finally, a third mixed slurry layer is sprayed, with a wet film thickness of approximately 15 μm, and pre-cured at 80°C for 1 minute to maintain a semi-cured state with a still tacky surface. The encapsulation process then proceeds: an adhesive layer is directly coated onto the surface of the third mixed slurry layer (at this point, the adhesive layer can partially dissolve with the semi-cured third layer), followed by the attachment of the encapsulation fabric layer and hydrostatic pressing. During hydrostatic pressing, the adhesive layer and the semi-cured third mixed slurry layer undergo interfacial fusion, forming an integrated, interface-free adhesive structure. This completely eliminates the interlayer interface, effectively alleviating stress concentration and thermal stress caused by mismatched coefficients of thermal expansion. It should be further noted that the bending life test in this invention also shows that the resistance of the device of this invention did not change significantly after 1000 bends, while the resistivity of the conventional packaged device increased by 50% after 100 bends, ensuring the electrical connection reliability of the device under repeated deformation.

[0056] Example 2 The above text combined Figures 4-16 A packaging method for flexible thermoelectric elements provided by an embodiment of the present invention has been described in detail below. Figures 1-3 The structure provided in the embodiments of the present invention will be described.

[0057] The packaging structure is prepared by the packaging method of Example 1, and includes: The thermoelectric body includes: electrode layer 1, P-type thermoelectric arm 2 and N-type thermoelectric arm 3, which are connected in series through electrode layer 1; electrode layer 1 is composed of several metal electrodes. An adhesive layer is coated on the outside of the metal electrode; for example, a fabric adhesive. The encapsulation fabric layer 4 includes a first encapsulation layer and a second encapsulation layer. The first encapsulation layer and the second encapsulation layer are respectively bonded to the outside of the electrode layers 1 located at both ends of the thermoelectric body by adhesive layers to encapsulate the flexible thermoelectric element. The first encapsulation layer and the second encapsulation layer form a continuous air-permeable channel in the area corresponding to the gap between the electrode layers.

[0058] Among them, the ends of the P-type thermoelectric arm 2 and the N-type thermoelectric arm 3 are provided with an integrally machined transition layer 5, which is used to improve the wettability of the solder to each thermoelectric arm.

[0059] Specifically, the transition layer 5 can be prepared using processes such as integral hot pressing, electroplating, chemical plating, magnetron sputtering, or vacuum evaporation. For example, on the surface of a Bi2Te3-based thermoelectric material, layer 5 can be electroplated first. Ni is used as a barrier layer, followed by electroplating or sputtering of 0.3μm Ag as a wetting layer; Ag2Se-based thermoelectric arms are formed by directly adding Ni / Cu metal powder to both ends during sintering, followed by hot pressing. The presence of transition layer 5 effectively prevents diffusion reactions between the thermoelectric material and the electrode metal during welding, increases the wettability of the thermoelectric arm and the solder, and reduces interface resistance. In addition, to further improve the bending resistance and long-term reliability of the device, a gradient intermediate layer 6 is sprayed on the outside of the electrode layer 1. The design of this gradient intermediate layer 6 enables a smooth transition of mechanical properties from the high-modulus metal electrode to the low-modulus packaging material, effectively eliminating stress abrupt change points.

[0060] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects: (1) Improve wearing comfort: The fabric is used as the encapsulation material, and the structure design of dot-bonding and surface breathability effectively improves the water vapor permeability compared with traditional polymers, effectively wicking away sweat and avoiding stuffiness and dampness. At the same time, the soft touch of the fabric is far superior to that of polymer encapsulation, improving skin-friendliness.

[0061] (2) Improved dynamic electrical stability: Through the synergistic stress-bearing structure of "large-size metal electrode - adhesive layer - fabric", bending stress is dispersed, avoiding stress concentration at the welding interface. Experiments show that the resistance of the device using the present invention does not change significantly after 1000 bends, while the resistivity of the traditional packaged device increases by 50% after 100 bends, ensuring the reliability of the electrical connection of the device under repeated deformation.

[0062] (3) High functional expandability: By introducing a directional moisture-wicking structure, the interface humidity can be reduced by more than 60%; by introducing a gradient stress buffer structure, the interface stress can be reduced by 70%, and the bending life can be increased by more than 5 times. These functions can be selected and combined according to different application scenarios (such as daily wear, strenuous exercise, medical monitoring).

[0063] (4) Simple process and low cost: No complicated molds and multi-step potting process are required. Encapsulation can be completed in just three steps: applying glue, attaching cloth and static pressure. The production cycle can be shortened from tens of hours in the traditional process to less than 2 hours, which reduces the manufacturing cost and is suitable for large-scale production.

[0064] (5) Wide material applicability: The method and structure of the present invention are not only applicable to traditional Bi2Te3-based thermoelectric materials, but also to various thermoelectric material systems such as Ag2Se-based, Mg3Bi2-based, SnSe-based, and Cu2Se-based, and have good universality.

[0065] Finally, this invention uses an output performance testing device to test the device's performance. A heating stage and Peltier device are used to create a temperature difference, a dual-channel thermometer is used to calibrate the hot and cold junction temperatures, and a digital source meter is used to test the device's voltage and current changes. Ultimately, examples of the beneficial effects are analyzed below, using bending resistance testing and output performance testing as examples: See Figure 6 Bending resistance test: 1000 cyclic bending tests were conducted at a bending radius of 20mm, with the internal resistance recorded every 100 bends. In this embodiment, the initial internal resistance of the device was approximately 12.5Ω, and after 1000 bends, the internal resistance was 12.675Ω, with a resistance change rate of only 1.4%. This indicates that the present invention effectively protects the welding interface through the synergistic stress-bearing structure of the "metal electrode extension – adhesive layer – fabric".

[0066] See Figures 7-10 Output performance test: Under a temperature difference ΔT = 50K, the wearable thermoelectric device of this embodiment of the invention achieves an output power of 2.1 mW and an output power density of 4.5 μW cm⁻¹. -2 It meets the power supply needs of low-power wearable electronic devices and also meets the intermittent operation needs of devices such as low-power Bluetooth sensors.

[0067] Figures 11-13 Wearable sports test: The open circuit voltage of the device was tested when the human body was in different sports states (sitting, walking and running). As the intensity of the exercise increased, the open circuit voltage of the device showed an increasing trend. In the jogging state, the open circuit voltage and output power reached 80 mV and 290 μW, respectively.

[0068] Figures 14-16Device integration wearable test: When the packaged device is integrated into the hat and subjected to actual wear test, the open circuit voltage reaches 92 mV, the output power reaches 300 μW, and the open circuit voltage does not show significant decay within the 200 s test duration.

[0069] An encapsulation structure for a flexible thermoelectric element according to an embodiment of the present invention is prepared based on the method described in the embodiments of the present invention, and the above-mentioned and other operations and / or functions of the various components of the encapsulation structure are respectively for realizing Figure 1 The corresponding process of the method in the illustrated embodiment will not be described in detail here for the sake of brevity.

[0070] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention is not limited to the specific combination of the above-described technical features, but also includes other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this invention.

Claims

1. A packaging method for flexible thermoelectric elements, characterized in that, Includes the following steps: A thermoelectric series structure is fabricated, comprising an electrode layer, a P-type thermoelectric arm, and an N-type thermoelectric arm, wherein the P-type and N-type thermoelectric arms are connected in series through the electrode layer; the electrode layer is composed of a plurality of metal electrodes. A fabric adhesive with a thickness of 10~100μm is coated on the outer surface of the electrode layer; The first encapsulation layer is attached to the outside of one side electrode layer of the thermoelectric series structure; The second encapsulation layer is attached to the other side of the electrode layer of the thermoelectric series structure, and the first encapsulation layer and the second encapsulation layer form a continuous air-permeable channel in the region corresponding to the gap between the electrode layers. Static pressure molding: Under a set temperature range, a set pressure range is applied synchronously and uniformly to the first encapsulation layer and the second encapsulation layer, and the pressure is maintained for a set time to complete the encapsulation of the flexible thermoelectric element.

2. The packaging method for flexible thermoelectric elements according to claim 1, characterized in that, The set temperature range is 140℃~150℃; the set pressure range is 5N~10N; and the set time is 120min~140min.

3. The packaging method for flexible thermoelectric elements according to claim 1, characterized in that, The first encapsulation layer and the second encapsulation layer are breathable fabric structures; the breathable fabric structure is a woven or knitted fabric made of natural or chemical fibers.

4. The packaging method for flexible thermoelectric elements according to any one of claims 1-3, characterized in that, The preparation of the thermoelectric series structure includes the following steps: S11: Multiple P-type thermoelectric arms and N-type thermoelectric arms are alternately arranged in the positioning mold to form an array of thermoelectric leg pairs; S12: Apply solder paste to one end of the arranged P-type thermoelectric arm and N-type thermoelectric arm, attach the metal electrode to the solder paste, and dry it in a drying oven at a temperature of 50℃~70℃, so that each metal electrode is initially bonded to one end of the thermoelectric leg pair to form a preliminary thermoelectric series structure. S13: After the initial bonding of the preliminary thermoelectric series structure is flipped over, it is placed back into the positioning mold. Step S12 is repeated to apply solder paste to the other end of the preliminary thermoelectric series structure. After drying, the thermoelectric series structure to be solidified is obtained. S14: Place the thermoelectric series structure to be solidified in a reflow oven and maintain it for a set time within the set temperature range and set pressure range to solidify it into the final thermoelectric series structure.

5. The packaging method for flexible thermoelectric elements according to any one of claims 1-3, characterized in that, Both the first and second encapsulation layers have hydrophobic and hydrophilic regions: The hydrophobic region is provided correspondingly to the metal electrode; The hydrophilic region is positioned corresponding to the position of the non-metallic electrode on the electrode layer; The hydrophilic region consists of a hydrophobic layer, a water-absorbing layer, and a hydrophilic layer arranged sequentially from the inside to the outside of the component.

6. The packaging method for flexible thermoelectric elements according to claim 5, characterized in that, In the first and second encapsulation layers, in areas offset from the thermoelectric series structure, there are directional moisture-wicking areas that are connected to the hydrophilic areas to form a sweat outward transport path.

7. The packaging method for flexible thermoelectric elements according to any one of claims 1-3, characterized in that, The preparation of the thermoelectric series structure further includes the following steps: S15: Spray-applied gradient intermediate layer; The process of spraying the gradient intermediate layer includes the following steps: Spray the first layer of mixed slurry onto the outer surface of the metal electrode and pre-cur it at 80~100℃ for 1~3 minutes; A second layer of mixed slurry and a third layer of mixed slurry are sprayed sequentially on the outside of the first layer of mixed slurry. The proportions of high-modulus phase and low-modulus phase in the first layer of mixed slurry, the second layer of mixed slurry, and the third layer of mixed slurry gradually decrease; The third layer of mixed slurry remains in a semi-cured state; during the static pressure molding process, the fabric adhesive and the semi-cured third layer of mixed slurry undergo interfacial fusion to form an integrated adhesive structure.

8. The packaging method for flexible thermoelectric elements according to claim 7, characterized in that, The first layer of mixed slurry contains 80-95 wt% high-modulus phase and 5-20 wt% low-modulus phase; the second layer of mixed slurry contains 50-80 wt% high-modulus phase and 20-50 wt% low-modulus phase; and the third layer of mixed slurry contains 0-30 wt% high-modulus phase and 70-100 wt% low-modulus phase.

9. A packaging structure for flexible thermoelectric elements, characterized in that, include: The thermoelectric body includes: an electrode layer, a P-type thermoelectric arm, and an N-type thermoelectric arm, wherein the P-type thermoelectric arm and the N-type thermoelectric arm are connected in series through the electrode layer; the electrode layer is composed of a plurality of metal electrodes; An adhesive layer is coated on the outside of the metal electrode; The encapsulation fabric layer includes a first encapsulation layer and a second encapsulation layer. The first encapsulation layer and the second encapsulation layer are respectively bonded to the outside of the electrode layers located at both ends of the thermoelectric body by the adhesive layer, thereby encapsulating the flexible thermoelectric element.

10. A packaging structure for a flexible thermoelectric element according to claim 9, characterized in that, Both the P-type and N-type thermoelectric arms have an integrally machined transition layer at their ends, which is used to improve the wettability of the solder to each thermoelectric arm.

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