Anisotropic thermally conductive filled thermoelectric refrigeration device and method of manufacture

Abstract

The application provides an anisotropic heat-conducting filled thermoelectric refrigeration device and a manufacturing method, and belongs to the technical field of thermoelectric refrigeration devices, and comprises the following steps: preparing an anisotropic heat-conducting slurry, which contains the following components: a polymer resin matrix, hexagonal boron nitride and a dispersing agent; pretreating the whole device; filling the anisotropic heat-conducting slurry into a gap under a vacuum environment; placing the thermoelectric refrigeration device filled with the slurry on a rotating heating table at the center of a magnetic field generating device, applying a constant horizontal magnetic field, and rotating the rotating heating table at a constant speed; in the state of keeping the magnetic field and rotation, in-situ heat curing is performed on the device; removing a protective film on the outer surface of the device and cleaning overflowed glue around the device; and performing secondary post-curing treatment on the device. The application utilizes an electromagnetic field to construct a directional heat transfer path with high horizontal heat conduction and high vertical thermal insulation, and provides stable mechanical support and protection while improving the thermal performance.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric refrigeration device technology, and more specifically, relates to an anisotropic thermally conductive filled thermoelectric refrigeration device and its manufacturing method. Background Technology

[0002] With the rapid development of modern microelectronics, optoelectronics, and aerospace technologies, the thermal management of high-power-density electronic components is becoming increasingly prominent due to the continuous improvement of device integration. Thermoelectric coolers (TECs), as solid-state cooling devices that utilize the Peltier effect to directly convert electrical energy into heat energy, have become indispensable key thermal management components in fields such as 5G optical modules, high-power laser diodes, infrared detectors, and biomedical chips due to their unique advantages, including no moving parts, no noise, small size, high temperature control accuracy (up to ±0.01℃), and the ability to achieve precise localized cooling.

[0003] In the aforementioned application scenarios, TEC devices not only need to possess extremely high thermoelectric conversion efficiency but must also be able to withstand harsh mechanical environments and long-term thermal cycling shocks. The core structure of a TEC typically consists of two ceramic substrates, upper and lower, sandwiched between P-type and N-type semiconductor thermally conductive arms (usually bismuth telluride-based materials), forming a π-type array. When current flows, heat is "pumped" from the cold-end ceramic substrate to the hot-end ceramic substrate, thus achieving cooling. However, with the miniaturization of device size and the increase in power density, the heat flux density per unit area has risen sharply, posing unprecedented challenges to the internal heat conduction mechanism of the TEC. Traditional heat dissipation designs often focus on external heat sinks, neglecting the thermal and mechanical behavior of the internal packaging structure of the TEC device.

[0004] Furthermore, TEC devices face extremely complex multi-physics coupling environments during actual service. On the one hand, the huge temperature difference between the hot and cold ends generates significant thermal expansion mismatch between the ceramic substrate and the heat-conducting arm, leading to enormous shear thermal stress. On the other hand, thermoelectric materials are inherently brittle and have extremely weak resistance to mechanical shock. In applications such as automotive radar and mobile terminals where frequent vibrations occur, unprotected TECs are highly susceptible to heat-conducting arm breakage or solder joint peeling failure. Therefore, how to synergistically optimize the thermal performance (cooling efficiency, heat dissipation capacity) and mechanical performance (structural strength, reliability) of TECs has become a common key challenge that urgently needs to be overcome in the field of thermoelectric technology.

[0005] The current field of thermoelectric coolers faces the challenge of simultaneously achieving high mechanical strength, excellent horizontal heat dissipation, and extremely low vertical parasitic thermal conductivity. Existing filling solutions, if prioritizing high mechanical strength through thermally conductive adhesives, inevitably lead to a decrease in vertical thermal resistance, causing thermal short circuits and sacrificing cooling efficiency. Conversely, using air or low-thermal-conductivity adhesives to maintain cooling efficiency fails to address the problem of thermal stress concentration caused by localized hot spots. As TEC devices evolve towards miniaturization and high heat flux density, localized hot spots have become a major cause of early device failure, and substrate-based heat dissipation alone is no longer sufficient. Therefore, a novel filling structure is urgently needed that can effectively control the direction of heat flow—acting as a "good conductor" in the horizontal direction to eliminate hot spots, an "insulator" in the vertical direction to prevent thermal short circuits, and simultaneously providing sufficient mechanical support. Summary of the Invention

[0006] Addressing the technical challenges of balancing mechanical strength and cooling efficiency in existing thermoelectric cooler packaging technologies, and the fact that conventional filling materials can lead to vertical thermal short circuits and internal hot spot accumulation, this invention aims to provide an anisotropic thermally conductive filled thermoelectric cooling device and its manufacturing method. By filling the cold and hot ends of the thermoelectric cooler with anisotropic thermally conductive hexagonal boron nitride (h-BN) material and utilizing an electromagnetic field to precisely construct a directional heat transfer path with "high horizontal thermal conductivity and high vertical thermal insulation," this device provides robust mechanical support and protection while rapidly eliminating in-plane hot spots and blocking interlayer heat recirculation. This effectively overcomes the technical bottleneck of traditional packaging technologies where thermal and mechanical properties cannot be simultaneously achieved.

[0007] To achieve the above objectives, the present invention provides a method for manufacturing an anisotropic thermally conductive filled thermoelectric refrigeration device, comprising the following steps:

[0008] An anisotropic thermally conductive paste is prepared, wherein the anisotropic thermally conductive paste contains the following components: a polymer resin matrix, hexagonal boron nitride, and a dispersant;

[0009] Select the welded thermoelectric cooler, clean the entire device and perform surface activation treatment; then, apply a protective film to the outer surface of the ceramic substrate.

[0010] In a vacuum environment, the anisotropic thermally conductive paste is filled into the gap between the ceramic substrate and the thermally conductive arm on both sides of the thermoelectric cooler; then, the thermoelectric cooler filled with paste is placed on the rotating heating stage at the center of the magnetic field generating device, a constant horizontal magnetic field is applied, and the rotating heating stage is rotated at a uniform speed; finally, while maintaining the magnetic field and rotation, the device is heated and cured in situ.

[0011] After the in-situ heating and curing is completed, the protective film on the outer surface of the device is removed and the excess adhesive around the device is cleaned; then, the device undergoes a second post-curing treatment.

[0012] Furthermore, the initial viscosity of the anisotropic thermally conductive slurry is 2000-5000 mPa·s.

[0013] Furthermore, in the anisotropic thermally conductive slurry, the polymer resin matrix is ​​an alicyclic epoxy resin or an addition-type liquid silicone rubber, the viscosity of the polymer resin matrix is ​​100-600 mPa·s, and the mass percentage of the hexagonal boron nitride is 30-55%.

[0014] Furthermore, the aspect ratio of the hexagonal boron nitride is 30-100, and the average sheet diameter is 10-50 μm.

[0015] Furthermore, the anisotropic thermally conductive slurry also contains negative thermal expansion powder.

[0016] Furthermore, before filling the anisotropic thermally conductive slurry, a silane coupling agent modification layer with a thickness of 0.5-5 μm is coated on the sidewall of the thermally conductive arm, and the modification layer forms a chemical bond with the polymer resin matrix.

[0017] Furthermore, the strength B of the horizontal magnetic field and the viscosity η of the anisotropic thermally conductive slurry satisfy the following relationship: B² / η ≥ 10 T 2 / (Pa·s).

[0018] Furthermore, the post-curing process employs a gradient temperature rise post-curing process.

[0019] Furthermore, the surface activation treatment employs argon plasma cleaning for a processing time of 60-120 seconds.

[0020] Furthermore, the method includes the following steps: after the surface activation treatment, a poly(p-xylene) film is deposited on the surface of the heat-conducting arm by vacuum phase deposition.

[0021] A second aspect of the present invention provides an anisotropic thermally conductive filled thermoelectric cooling device, manufactured using any of the manufacturing methods described above, comprising: two ceramic substrates on both sides, a P-type thermally conductive arm and an N-type thermally conductive arm connected between the two ceramic substrates on both sides, a heat sink connected to the ceramic substrate at the hot end, and an anisotropic thermally conductive paste filled in the gap between the two ceramic substrates on both sides and the P-type thermally conductive arm and the N-type thermally conductive arm, wherein the anisotropic thermally conductive paste contains the following components: a polymer resin matrix, hexagonal boron nitride, and a dispersant.

[0022] Compared with the prior art, the present invention has the following technical effects:

[0023] This invention discloses a method for manufacturing an anisotropic thermally conductive filled thermoelectric refrigeration device. It employs a rotating magnetic field and in-situ heating curing assisted orientation process to fill the thermoelectric cooler with a highly oriented hexagonal boron nitride composite material. By controlling the horizontally ordered arrangement of the hexagonal boron nitride filler layers, an anisotropic thermal management network with "efficient horizontal thermal conduction and effective vertical thermal insulation" is constructed. Furthermore, the polymer resin matrix in the anisotropic thermally conductive slurry, after curing, can fully encapsulate and support the fragile thermally conductive arm array. By replacing traditional air gaps with high-strength insulating composite material, the problem of easy breakage of the thermally conductive arms is solved without sacrificing electrical insulation performance, significantly improving the overall compressive strength, shear strength, and vibration resistance of the device. This invention significantly enhances the mechanical strength of the device while utilizing interlayer thermal barriers to block heat reflow and high in-plane thermal conductivity to eliminate hot spots, meeting the requirements of high-performance thermal management systems for high reliability, high cooling efficiency, and long service life. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A flowchart illustrating a method for manufacturing an anisotropic thermally conductive filled thermoelectric refrigeration device according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of an anisotropic thermally conductive filled thermoelectric refrigeration device provided in an embodiment of the present invention;

[0027] Figure 3 Microstructure diagram of hexagonal boron nitride provided in an embodiment of the present invention;

[0028] Figure 4 A simulation cloud diagram of the temperature field of a thermoelectric cooler with an air gap structure provided in an embodiment of the present invention;

[0029] Figure 5 A simulation cloud map of the temperature field of a thermoelectric cooler with an anisotropic thermally conductive filling structure provided in an embodiment of the present invention;

[0030] Figure 6 The simulation cloud map of the temperature field of the thermoelectric cooler with an isotropic thermally conductive filling structure provided in the embodiment of the present invention.

[0031] The following are the labeling elements in the figure:

[0032] 1. Ceramic substrate, 2. Anisotropic thermally conductive paste filling layer, 3. P-type thermally conductive arm, 4. N-type thermally conductive arm, 5. Heat sink, 6. Nitrogen atom, 7. Boron atom. Detailed Implementation

[0033] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0034] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0035] Existing thermoelectric coolers, whether traditional air-gap structures or isotropic filled structures, generally suffer from the following problems when addressing high-performance thermal management requirements: severe vertical thermal short-circuit effect; conventional filling materials conduct heat not only horizontally but also vertically, causing a large amount of heat to flow back from the hot end to the cold end, significantly reducing the maximum cooling temperature difference and cooling efficiency; poor horizontal heat dissipation capacity; both air and epoxy resin have poor thermal conductivity, failing to effectively diffuse the Joule heat and conductive heat generated by the heat-conducting arms and chip laterally within the layer, leading to excessively high local temperatures and the formation of hot spots; fragile structures with no or partial filling, unable to withstand impact and vibration; failure caused by thermal stress concentration; due to uneven internal temperature distribution, huge non-uniform thermal expansion stress is generated at the interface between the ceramic substrate and the heat-conducting arms, which can easily cause microcracks in the ceramic substrate or fatigue fracture of the solder joints.

[0036] To address the structural defects of existing thermoelectric coolers, this invention fills the space between the cold and hot ends of the thermoelectric cooler with hexagonal boron nitride and constructs a microscopically ordered directional heat transfer network using a rotating magnetic field and in-situ heating and curing assisted orientation process. This thermoelectric cooling device achieves synergistic optimization of "efficient heat distribution in the horizontal direction" and "effective heat insulation in the vertical direction," fundamentally resolving the contradiction between thermal short circuit and mechanical reinforcement, and balancing mechanical strength and thermal performance.

[0037] The manufacturing process of an anisotropic thermally conductive filled thermoelectric refrigeration device according to an embodiment of the present invention is as follows: Figure 1 As shown, it includes the following steps:

[0038] S1. Prepare anisotropic thermally conductive paste, which contains the following components: polymer resin matrix, hexagonal boron nitride and dispersant;

[0039] S2. Select the completed thermoelectric cooler, clean the entire device and perform surface activation treatment; then, apply a protective film to the outer surface of the ceramic substrate.

[0040] S3. In a vacuum environment, anisotropic thermally conductive paste is filled into the gap between the ceramic substrates and the thermally conductive arms on both sides of the thermoelectric cooler. Then, the thermoelectric cooler filled with paste is placed on a rotating heating stage at the center of a magnetic field generating device (such as a superconducting magnet), a constant horizontal magnetic field is applied, and the rotating stage is started to drive the component to rotate around the vertical axis (Z-axis), that is, to make the rotating heating stage rotate at a uniform speed. Finally, while maintaining the magnetic field and rotation, the device is heated and cured in situ.

[0041] S4. After in-situ heating and curing, remove the protective film on the outer surface of the device and clean up any excess adhesive around the device; then, perform a second post-curing treatment on the device.

[0042] In step S1 above, hexagonal boron nitride (h-BN) sheet particles with a high aspect ratio are preferred as the thermally conductive filler. These particles are mixed with a polymer resin matrix and a dispersant. Other necessary additives (such as negative thermal expansion powder) may also be added. To ensure uniform dispersion of the filler in the matrix and remove microbubbles, a vacuum planetary mixer is used to stir and degas the mixture, resulting in a highly thixotropic slurry. This high thixotropic property causes the slurry to reduce viscosity under shear stress to facilitate flow and orientation, while rapidly recovering viscosity at rest to maintain its structural morphology. In this embodiment of the invention, the anisotropic thermally conductive slurry contains the following components by weight: 44-60 parts of polymer resin matrix, 40-55 parts of hexagonal boron nitride, and 1-1.5 parts of dispersant; in addition to these components, it may also contain 1.5-2.5 parts of negative thermal expansion powder.

[0043] Preferably, the aspect ratio of hexagonal boron nitride is 30-100, and the average sheet diameter is 10-50 μm. Compared with conventional small-diameter (e.g., <5 μm) or low aspect ratio particles, the filler with this high aspect ratio has significant thermal advantages. On the one hand, the large-diameter h-BN can provide a longer phonon transport free path, significantly reducing the number of interfaces between the particles and the matrix. In the microscopic mechanism of heat conduction, interfacial thermal resistance is the main bottleneck limiting the thermal conductivity of composite materials. Reducing the number of interfaces means that heat encounters less scattering and obstruction when transported horizontally, thereby greatly improving horizontal thermal conductivity. On the other hand, the high aspect ratio sheets are prone to collapse under shear force, forming a dense stacked structure. This increases the tortuosity of the heat flow path in the vertical direction, forcing vertically propagating heat to pass through numerous layers of polymer matrix and h-BN interfaces, thereby increasing vertical thermal resistance and achieving a "vertical insulation" effect.

[0044] Preferably, the mass percentage of h-BN in the thermally conductive slurry is 30-55 wt%. This mass percentage is chosen based on a comprehensive consideration of the "percolation threshold" theory and rheological properties. This ratio ensures that the h-BN sheets overlap and form continuous pathways within the matrix, and that the slurry possesses suitable thixotropy, facilitating subsequent coating. When the h-BN mass percentage is less than 30%, continuous thermally conductive pathways cannot be formed between the sheets, resulting in a horizontal thermal conductivity below 10 W / (m·K). When the mass percentage is greater than 55%, the slurry viscosity exceeds 8000 mPa·s, resulting in poor flowability, inability to completely fill the gaps in the thermally conductive arms, and hindered sheet rotation, leading to a decrease in orientation.

[0045] Preferably, in the thermally conductive slurry, the polymer resin matrix is ​​a low-viscosity (100-600 mPa·s) alicyclic epoxy resin or addition-type liquid silicone rubber, and its initial viscosity after mixing is controlled at 2000-5000 mPa·s. Using a low-viscosity matrix provides more free rotational space for the h-BN sheets. At the same shear rate, the sheets experience less viscous resistance and can respond more quickly to changes in the flow field to achieve high orientation. Furthermore, the low-viscosity slurry can more easily penetrate into the tiny gaps and corners between the thermally conductive arm and the ceramic substrate.

[0046] Preferably, a small amount of zirconium tungstate negative thermal expansion material powder is added to the thermally conductive paste. Adding a negative thermal expansion material optimizes the thermal cycling characteristics of the TEC (thermoelectric thermoelectric system) and adjusts the overall thermal expansion coefficient of the thermally conductive paste, making it closer to that of semiconductor thermoelectric materials. Without thermal expansion coefficient matching, when the device operates under extreme temperature differences between its hot and cold ends, significant internal stress will arise between the filler material and the thermally conductive arm due to the different rates of thermal expansion and contraction. Prolonged use may lead to thermally conductive arm breakage or interface delamination.

[0047] In step S2 above, the entire device is precisely cleaned to remove flux residue and oil contaminants from the gaps. Subsequently, the device undergoes overall surface activation treatment (such as plasma cleaning) to enhance the interfacial adhesion between the thermally conductive filler and the inner surfaces of the upper and lower ceramic substrates and the sidewalls of the thermally conductive arms. After treatment, a protective film is applied to the outer surfaces (i.e., heat exchange surfaces) of the upper and lower ceramic substrates to prevent slurry contamination.

[0048] Preferably, the surface activation treatment employs argon plasma cleaning for 60-120 seconds. This process can thoroughly remove invisible organic contaminants and significantly improve the wettability of polymer resins on ceramic surfaces.

[0049] Preferably, after surface activation treatment, a nano-scale parylene film is deposited on the surface of the heat-conducting arm by vacuum phase deposition to form a nano-scale insulating and interface protection layer, thereby enhancing the long-term electrical insulation reliability and environmental aging resistance of the device, making it suitable for high humidity and salt spray application environments.

[0050] Preferably, before filling the anisotropic thermally conductive paste, a silane coupling agent modification layer with a thickness of 0.5-5 μm is coated on the sidewall of the thermally conductive arm. In this way, the modification layer can form a chemical bond with the polymer resin matrix in the anisotropic thermally conductive paste, enhance the interfacial shear strength between the filled layer and the thermally conductive arm after curing, and further improve the overall compressive strength, shear strength and vibration resistance of the device, making it suitable for applications with high vibration and high strength requirements.

[0051] In step S3 above, the thermally conductive paste is first heated to a suitable temperature to reduce its viscosity, and then slowly poured into the gap between the ceramic substrate and the thermoelectric arm after step S2 in a vacuum environment. In this step, utilizing the diamagnetism of h-BN material and its principle of minimum energy in a rotating magnetic field, the h-BN sheets inside the paste are forced to overcome resin resistance, tilting and adjusting their orientation in the horizontal plane, so that the height of the sheet plane is parallel to the direction of the ceramic substrate (the microstructure of the anisotropic h-BN filler material is as follows...). Figure 3 As shown, 6 represents nitrogen atoms and 7 represents boron atoms. Finally, while maintaining the magnetic field and rotation, the heating stage is turned on to heat and solidify the device in situ. The heating temperature is above the gel point of the polymer resin matrix, thereby locking the height-ordered arrangement of the h-BN sheets in the solidified polymer resin matrix.

[0052] Preferably, the intensity B(T) of the horizontal magnetic field and the viscosity η(Pa·s) of the anisotropic thermally conductive slurry satisfy the following relationship: B² / η ≥ 10 T² / (Pa·s), to ensure that the h-BN sheets are oriented before curing. In a specific embodiment, the intensity of the horizontal magnetic field is 6-10 T, and the rotation speed of the rotary heating table is 5-30 rpm. When the magnetic field intensity is below 6T, the magnetic torque on the h-BN sheets is insufficient to overcome the viscous resistance of the resin, resulting in a low degree of orientation and an inability to form an effective anisotropic thermally conductive network; when the magnetic field intensity is above 10T, the equipment cost increases sharply, and the improvement in orientation is not significant, resulting in poor economic efficiency. Utilizing the diamagnetic anisotropy of h-BN materials, a high magnetic field strength can generate a sufficiently large magnetic torque on h-BN sheets suspended in a viscous polymer resin matrix, causing them to rotate against fluid resistance. The uniform rotation around the vertical axis averages the magnetic field vector over time, forcing the sheets to be strictly confined to a horizontal plane (i.e., perpendicular to the rotation axis) to maintain a minimum energy state. Compared to fluid shearing processes, the magnetic field has volumetric penetrability and is completely unaffected by the geometric obstruction of the heat-conducting arm array, thus ensuring a highly consistent horizontal orientation of the filler from the device center to the edge, and from the surface to the deep gaps, eliminating orientation dead zones.

[0053] The in-situ heating curing method of this invention employs a dynamic magnetic field locking strategy. This involves heating the polymer resin above its gel point while the magnetic field remains on and the component continues to rotate. This dynamic curing strategy utilizes the dynamic equilibrium characteristics of h-BN in a rotating magnetic field to lock the horizontal orientation of the layers in real time at the moment the resin matrix undergoes a cross-linking reaction and the viscosity rapidly increases from liquid to solid. This prevents the layers from rapidly relaxing and disorienting due to Brownian motion if the magnetic field is removed or rotation stops in the liquid state. Furthermore, the continuous rotation counteracts the unidirectional sedimentation of the filler under gravity, preventing resin-filler delamination and ensuring that the final cured composite thermally conductive material has a uniform component distribution and stable thermal properties in the vertical direction.

[0054] In step S4 above, in order to eliminate the internal stress generated during the in-situ curing process and ensure that the performance of the polymer resin reaches the optimal level, the device is subjected to a second high-temperature post-curing treatment to obtain a high-performance thermoelectric cooler with an anisotropic h-BN filled structure.

[0055] Preferably, post-curing employs a gradient temperature curing process. For example, after removing the magnetic field, the device is placed in an oven and sequentially heated to 100 °C for 1 hour, 120 °C for 1 hour, and 150 °C for 2 hours. Since the finished TEC is a multi-layered composite structure, direct high-temperature curing can easily lead to delamination caused by thermal expansion mismatch. Gradient temperature curing effectively releases the internal stress generated by resin curing shrinkage, preventing the ceramic substrate from cracking and ensuring that the filled device has extremely high mechanical reliability.

[0056] The structure of the thermoelectric refrigeration device manufactured in the embodiments of the present invention is as follows: Figure 2 As shown, the device includes: two ceramic substrates 1 on both sides, a P-type thermally conductive arm 3 and an N-type thermally conductive arm 4 connecting the two ceramic substrates 1 on both sides, a heat sink 5 connected to the hot end of the ceramic substrate 1, and an anisotropic thermally conductive paste filling layer 2 filling the gaps between the two ceramic substrates 1 on both sides and the P-type thermally conductive arms 3 and N-type thermally conductive arms 4. The anisotropic thermally conductive paste contains the following components: a polymer resin matrix, hexagonal boron nitride, and a dispersant. The heat sink 5 can dissipate heat using liquid cooling or air cooling, etc.

[0057] This invention achieves dual optimization of mechanics and thermal properties by filling the space between the cold and hot ends of a thermoelectric cooler with a highly horizontally oriented anisotropic thermally conductive paste filling layer 2. Using a magnetic field and in-situ heating curing process, the h-BN sheets are induced to align parallel to the insulating ceramic substrate 1. This filling layer not only provides robust mechanical support and moisture protection for the fragile thermally conductive arms, but also utilizes the layered crystal properties of h-BN to construct a microscopic anisotropic heat transfer network with "high horizontal conductivity and high vertical impedance," thereby physically enhancing the cooling system while avoiding the thermal short-circuit risk associated with traditional material filling.

[0058] In the thermoelectric cooling device structure manufactured in this embodiment of the invention, the h-BN filling layer plays a crucial dual role of "horizontal heat equalization" and "vertical heat insulation." When the device mounted on the cold end generates high-density heat, the filling layer utilizes the extremely high in-plane thermal conductivity of h-BN to rapidly diffuse the accumulated heat under the chip horizontally in all directions, assisting in temperature equalization at the cold end and preventing localized heat accumulation. Simultaneously, heat is "pumped" to the hot end through the heat-conducting arms. Due to the high thermal resistance between h-BN layers, the filling layer effectively blocks the backflow of heat from the hot end to the cold end, thereby maintaining the device's cooling efficiency while ensuring efficient heat dissipation of the chip.

[0059] Through the above design, the embodiments of the present invention effectively solve the technical challenges of "difficult elimination of local hot spots" and "thermal short circuit in TEC packaging" coexisting in the heat dissipation of high-power electronic devices. It not only eliminates the hidden danger of ceramic substrate cracking caused by thermal stress concentration, but also significantly reduces the operating temperature of the chip while enhancing the mechanical reliability of the device, providing a highly efficient and reliable solution for the thermal management of 5G optical modules, high-power laser diodes, and high-performance computing chips.

[0060] The following specific embodiments further illustrate an anisotropic thermally conductive filled thermoelectric refrigeration device and its manufacturing method according to an embodiment of the present invention.

[0061] Example 1

[0062] Step 1: Preparation of highly thixotropic anisotropic thermally conductive paste

[0063] A highly thixotropic thermally conductive slurry for filling was prepared using a low-viscosity alicyclic epoxy resin (model: TTA21, chemical composition: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate) as the matrix. The core filler was highly crystalline hexagonal boron nitride (h-BN) powder with an average flake diameter of 30 μm and an aspect ratio as high as 40:1. 45 wt% h-BN (approximately 32% by volume) was pre-modified with 1 wt% silane coupling agent (i.e., dispersant, γ-glycidoxypropyltrimethoxysilane) to reduce interfacial thermal resistance. Then, 52 wt% alicyclic epoxy resin system and 2 wt% zirconium tungstate negative thermal expansion regulating powder were added. The mixture was placed in a vacuum planetary centrifuge and stirred at 2000 rpm for 5 minutes to break up agglomerates, followed by degassing at 2200 rpm for 10 minutes under vacuum. The final slurry has a viscosity of approximately 3500 mPa·s, exhibiting excellent thixotropic properties that meet the requirements of precision orientation processes.

[0064] Step 2: Device Pretreatment and Protection

[0065] The successfully soldered thermoelectric cooling device was selected and ultrasonically cleaned sequentially in acetone and anhydrous ethanol for 5 minutes each to remove flux residue from the gaps. After drying, it was placed in a plasma cleaner and treated with argon (Ar) gas at 200W RF power and 100 sccm flow rate for 90 seconds to activate the internal gap surface. Following treatment, a 2μm thick parylene film was deposited on the surface of the heat-conducting arm using vacuum phase deposition to provide nanoscale electrical insulation and moisture protection. Subsequently, high-temperature resistant polyimide tape was applied to the outer surfaces of the upper and lower ceramic substrates to prevent contamination of the heat exchange surface during subsequent processes.

[0066] Step 3: Rotating magnetic field-assisted in-situ curing

[0067] The slurry prepared in step one was preheated to 40°C to reduce its viscosity. It was then injected into the gap between the heat-conducting arm and the ceramic substrate until the slurry completely submerged the heat-conducting arm and extended approximately 0.5 mm above the top. Subsequently, the assembly was placed at the center of a superconducting magnet with a magnetic induction intensity of 8 T and fixed on a heated rotating stage. The rotating stage was activated, causing the assembly to rotate uniformly around its vertical axis at 30 rpm. Under the combined effect of the strong horizontal magnetic field and rotation, the h-BN sheets overcame resin resistance and achieved a highly horizontal alignment. While maintaining the magnetic field and rotation without interruption, the heating stage was turned on, raising the temperature to 120°C at a rate of 5°C / min and holding it at that temperature for 30 minutes. During this process, the epoxy resin underwent a cross-linking reaction, reaching its gel point and locking the horizontal orientation of the h-BN sheets within the cured matrix.

[0068] Step 4: Post-treatment and secondary curing

[0069] After the device has initially cured and cooled, remove it, peel off the protective tape, and scrape off any excess adhesive from the sides. Place the device in a precision oven for secondary curing in a magnetic field-free environment: hold at 120°C for 1 hour, then raise the temperature to 150°C and hold for 2 hours. This completely eliminates internal residual stress and completes the cross-linking of the resin. The final device has a clean appearance, its internal filling layer has an excellent horizontal orientation structure, and its mechanical strength is significantly improved.

[0070] Example 2

[0071] Step 1: Preparation of highly thixotropic anisotropic thermally conductive paste

[0072] A thermally conductive slurry for filling was prepared using an addition-type liquid silicone rubber (composed of vinyl-terminated polydimethylsiloxane and hydrogen-containing polymethylsiloxane) with a viscosity of approximately 500 mPa·s as the matrix. The core filler was hexagonal boron nitride (h-BN) powder with an average flake diameter of 30 μm and an aspect ratio of 30:1. To reduce the slurry viscosity, 1 wt% of a polyether-modified polysiloxane dispersant was added. 40% h-BN (approximately 28% by volume) and 59% silicone rubber system were weighed out according to mass percentage. The mixture was placed in a vacuum planetary centrifuge and stirred at 1500 rpm for 5 minutes, followed by degassing at 2000 rpm under vacuum for 15 minutes. The final slurry had a viscosity of approximately 2800 mPa·s, exhibiting good fluidity and a longer pot life.

[0073] Step 2: Device Pretreatment and Protection

[0074] The devices were sequentially cleaned and dried in acetone and anhydrous ethanol. They were then placed in a plasma cleaner and treated with oxygen (O2) at 300W RF power for 60 seconds. This oxygen plasma treatment not only removed organic contaminants but also introduced a large number of hydroxyl groups onto the ceramic surface, significantly enhancing the chemical adhesion between the hydrophobic silicone rubber and the hydrophilic ceramic substrate. Subsequently, a Teflon protective film was applied to the outer surfaces of both the upper and lower ceramic substrates, utilizing its low surface energy to prevent overflowing silicone from adhering to the substrate.

[0075] Step 3: Rotating magnetic field-assisted in-situ curing

[0076] The prepared silicone thermally conductive slurry was preheated to 50°C. Using a vacuum side-dispensing process, the slurry was completely drawn into the gap between the thermally conductive arm and the ceramic substrate under a vacuum of -95 kPa via capillary action. The assembly was then placed at the center of a superconducting magnet with a magnetic induction intensity of 6 T and fixed on a heated rotating stage. The rotating stage was started to rotate the assembly at a uniform speed of 20 rpm. Due to the low viscosity of the silicone matrix and the moderate particle size of h-BN, the layers quickly responded to the magnetic field and achieved horizontal alignment. Maintaining the rotation and magnetic field, the heating stage was turned on and the temperature was raised to 100°C and held for 60 min. Under these conditions, the silicone rubber underwent a hydrosilylation reaction, completing cross-linking and curing, locking the orientation structure of h-BN.

[0077] Step 4: Post-treatment and secondary curing

[0078] Remove the device, peel off the protective film, and trim the edges. Place the device in an oven for secondary curing in a magnetic field-free environment: hold at 150℃ for 4 hours. This step ensures complete cross-linking of the silicone rubber molecular chains and removes reaction byproducts. The final device exhibits excellent flexibility, and the low-modulus filler layer effectively buffers the enormous shear stress generated during thermal cycling.

[0079] Example 3

[0080] Step 1: Preparation of highly thixotropic anisotropic thermally conductive paste

[0081] To achieve higher thermal conductivity, a "bimodal particle size distribution" strategy was adopted. Low-viscosity alicyclic epoxy resin (TTA21) was selected as the matrix. The filler consisted of two different sizes of h-BN: large-diameter h-BN (D50=40μm, aspect ratio 50:1) and small-diameter h-BN (D50=5μm, aspect ratio 10:1), with a mass ratio of 7:3. In addition, 1wt% of a phosphate ester wetting and dispersing agent was added. The total mass fraction of h-BN filler was 55% (approximately 40% by volume), and the mass fraction of the alicyclic epoxy resin matrix was 44%. Utilizing the steric hindrance effect of the dispersant, despite the high filler content, the slurry viscosity was still controlled at around 4000 mPa·s after treatment in a vacuum planetary mixer (2500 rpm for strong dispersion), with no residual bubbles.

[0082] Step 2: Device Pretreatment and Protection

[0083] After welding, the thermoelectric cooling devices were cleaned and dried, and then subjected to argon plasma activation treatment (200W, 120 seconds). To enhance the chemical bonding between the filler material layer and the sidewall of the heat-conducting arm, an ethanol solution of 2% (by mass) silane coupling agent (model: KH-560) was prepared. The solution was coated onto the surface of the heat-conducting arm and dried at 110°C for 30 minutes, thereby forming a silane coupling agent chemically modified layer with a thickness of approximately 0.5-5 μm on the sidewall of the heat-conducting arm and the surface of the substrate. This modified layer can form a strong chemical bond with the subsequently poured alicyclic epoxy resin matrix. After treatment, thickened polyimide tape was applied to the outer surfaces of the upper and lower ceramic substrates to prevent slurry overflow and contamination in subsequent processes.

[0084] Step 3: Rotating magnetic field-assisted in-situ curing

[0085] A vacuum immersion method was employed: the device was completely immersed in a slurry bath preheated to 60°C, and a vacuum of -100 kPa was maintained for 10 minutes to allow the slurry to thoroughly penetrate the micro-gap. After removing the device and wiping off excess slurry, it was placed in the center of a strong magnetic field with a magnetic induction intensity of 10 T (higher field strength is required for high-viscosity systems). The rotating stage was started and rotated at a low speed of 10 rpm (to prevent centrifugal separation of the high-viscosity slurry). The heating stage was then turned on, and a gradient temperature increase was adopted: first, the temperature was kept constant at 80°C for 60 minutes (slow gelation, allowing sufficient rotation time for large particles), and then the temperature was increased to 120°C and kept constant for 30 minutes to lock the structure. Small particles filled the gaps between large particles, and the large particles were horizontally oriented under the magnetic field, constructing a dense horizontal thermally conductive network.

[0086] Step 4: Post-treatment and secondary curing

[0087] After curing, clean the device and peel off the film. Perform high-temperature post-treatment: hold at 120℃ for 1 hour, then at 160℃ for 2 hours. The resulting device has extremely high horizontal thermal conductivity and extremely high vertical thermal resistance. Furthermore, due to its dense packing structure, the device's compressive strength is far higher than that of traditional air-gap devices, making it suitable for applications that withstand high installation pressure.

[0088] To verify the thermal performance of the anisotropic thermally conductive filled thermoelectric refrigeration device prepared in Embodiment 1 of this invention, multiphysics coupling simulation was performed using COMSOL Multiphysics software. In the simulation, the input current was set to 2 A, the horizontal thermal conductivity of the intermediate h-BN filler was set to 40 W / (m·K), the vertical thermal conductivity was set to 0.5 W / (m·K), the initial temperature of the entire system was set to 20 ℃, the temperature of the lower ceramic substrate was set to 60 ℃, and the heat source was the four chips above, each with a power of 1 W. In the above multiphysics simulation model, the thermal conductivity parameters of the anisotropic thermally conductive filler layer were set based on the theoretical expectation model derived from the high filler content (approximately 32 vol%) and highly horizontally oriented microstructure of this embodiment. Specifically, its horizontal thermal conductivity is set to 40 W / (m·K). This is because the intrinsic thermal conductivity within the plane of the high aspect ratio h-BN single crystal is extremely high (>300 W / (m·K)), forming a continuous and dense phonon conduction network under the induction of a strong magnetic field, which significantly reduces the in-plane interfacial thermal resistance. Simultaneously, its vertical thermal conductivity is set to 0.5 W / (m·K). This is because the intrinsic thermal conductivity between h-BN layers is extremely poor (only about 2 W / (m·K)), and interfacial thermal resistance scattering occurs when vertically penetrating the interface between the stacked h-BN layers and the epoxy resin, making the overall vertical thermal resistance approximately equal to the resin matrix thermal resistance in a series model. (Comparison) Figure 4 (Air gap, ideal thermal state) and Figure 5 (The filled device of Embodiment 1 of the present invention) can be seen as follows: Figure 4 The lowest cold junction temperature of the unfilled device is 39°C; while Figure 5 After the anisotropic thermally conductive material of this embodiment was filled in the middle, the lowest temperature at the cold end was maintained at 41.8°C. This means that although a solid filler material was introduced to enhance mechanical strength, heat backflow was effectively suppressed due to the high thermal resistance of h-BN in the vertical direction, and the cooling performance of the device only decreased slightly (increasing by about 2.8°C). As a comparative verification, under the same simulation conditions, the middle filler layer was replaced with conventional isotropic thermally conductive silicone (the thermal conductivity of each filler material was set to 40 W / (m·K) in the simulation), and the simulation results are as follows. Figure 6As shown, the lowest temperature at the cold end rises sharply to 45.7°C, and the cooling temperature difference decreases. Therefore, it is evident that the anisotropic filling structure of this invention is far superior to traditional isotropic thermally conductive adhesive filling in terms of cooling performance. Meanwhile, in comparison... Figure 4 and Figure 5 The highest temperature distribution on the middle heat-conducting arm is visible. Figure 4 In the (unfilled) heat-conducting arm area, due to poor heat dissipation, the highest temperature reached 62.5℃ due to localized heat accumulation; while... Figure 5 In this embodiment, the highest temperature decreased to 61.9℃. This indicates that the horizontally oriented h-BN in the anisotropic thermally conductive filler material of this invention constructs a highly efficient lateral thermal diffusion network, which can rapidly conduct and homogenize the Joule heat generated by the thermally conductive arms to the surrounding filler medium. This excellent horizontal homogenization not only reduces the peak temperature inside the device and eliminates potential local hot spots, but also significantly reduces the internal temperature gradient, thereby reducing destructive thermal stress and effectively preventing cracking failure of the ceramic substrate under long-term high-load operation.

[0089] This invention constructs a microscopically ordered hexagonal boron nitride (h-BN) anisotropic filling structure, enabling active regulation of heat flow within the thermoelectric cooler. Utilizing the inherently high thermal resistance formed by van der Waals forces connecting the h-BN layers, and the dense stacking of layers in the vertical direction, an effective "thermal barrier" is constructed within the gaps of the heat-conducting arms. This significantly blocks the parasitic backflow of heat from the hot end to the cold end (thermal short circuit), thereby ensuring that the device, while achieving mechanical filling enhancement, still maintains near-vacuum-sealed maximum cooling temperature difference and cooling efficiency.

[0090] This invention utilizes the tight wrapping and support of the cured polymer resin matrix on the heat-conducting arm to improve the overall mechanical strength and impact resistance of the device. Compared to other air gap or vacuum encapsulation structures, this invention completely solves the defects of easy breakage and poor shock resistance of the heat-conducting arm; compared to conventional isotropic thermally conductive adhesive filling technology, this invention avoids the attenuation of cooling performance caused by excessive heat conduction in the vertical direction while providing the same mechanical support.

[0091] This invention utilizes a rotating strong magnetic field combined with in-situ heating and curing to assist in orientation, resulting in a highly horizontally ordered arrangement of high thermal conductivity fillers within the filler layer. This achieves the effect of constructing a highly efficient lateral heat diffusion network within the device. This structure fully leverages the ultra-high in-plane thermal conductivity of hexagonal boron nitride, rapidly and uniformly dissipating the high-density heat generated by cold-end power devices or the localized heat accumulation during the operation of the heat-conducting arms. This mechanism effectively eliminates localized hot spots, significantly reduces destructive thermal stress caused by uneven temperature distribution, thereby preventing cracking of the ceramic substrate and extending the device's service life under varying operating conditions.

[0092] This invention achieves excellent weather resistance and electrical insulation reliability through an interface enhancement design that combines overall surface activation pretreatment with an impregnation process. The plasma-activated heat-conducting arm sidewalls are tightly adhered to a preferred parylene film interface layer, forming a first dense barrier. Combined with bubble-free dense filling, this isolates external moisture, oxygen, and contaminants from eroding the internal fine solder joints and semiconductor materials, effectively suppressing electrochemical migration and material oxidation. This comprehensive protective design enables the thermoelectric cooler of this invention to withstand harsh conditions such as high humidity and salt spray, significantly improving the long-term operational stability of the device.

[0093] This invention utilizes a "monolithic in-situ curing with rotating magnetic field" manufacturing process to achieve a highly uniform microstructure with no orientation dead zones. Leveraging the volumetric penetrability of the magnetic field, it is unaffected by the shielding of the heat-conducting arm array, ensuring that all fillers from the device center to the edge, and from the surface to the deep interlayer gaps, achieve a highly consistent horizontal orientation. Furthermore, the dynamic in-situ curing strategy effectively prevents the layers from settling and disorienting under gravity, ensuring the continuity of the heat dissipation network in the overall structure, resulting in a final product with extremely high performance consistency and yield.

[0094] The above embodiments merely illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for manufacturing an anisotropic thermally conductive filled thermoelectric refrigeration device, characterized in that, Includes the following steps: An anisotropic thermally conductive paste is prepared, wherein the anisotropic thermally conductive paste contains the following components: a polymer resin matrix, hexagonal boron nitride, and a dispersant; Select the welded thermoelectric cooler, clean the entire device and perform surface activation treatment; then, apply a protective film to the outer surface of the ceramic substrate. In a vacuum environment, the anisotropic thermally conductive paste is filled into the gap between the ceramic substrate and the thermally conductive arm on both sides of the thermoelectric cooler; then, the thermoelectric cooler filled with paste is placed on the rotating heating stage at the center of the magnetic field generating device, a constant horizontal magnetic field is applied, and the rotating heating stage is rotated at a uniform speed; finally, while maintaining the magnetic field and rotation, the device is heated and cured in situ. After the in-situ heating and curing is completed, the protective film on the outer surface of the device is removed and the excess adhesive around the device is cleaned; then, the device undergoes a second post-curing treatment.

2. The manufacturing method of an anisotropic thermally conductive filled thermoelectric refrigeration device as described in claim 1, characterized in that, The initial viscosity of the anisotropic thermally conductive slurry is 2000-5000 mPa·s.

3. The manufacturing method of an anisotropic thermally conductive filled thermoelectric refrigeration device as described in claim 1, characterized in that, In the anisotropic thermally conductive paste, the polymer resin matrix is ​​an alicyclic epoxy resin or an addition-type liquid silicone rubber, the viscosity of the polymer resin matrix is ​​100-600 mPa·s, and the mass percentage of the hexagonal boron nitride is 30-55%.

4. The manufacturing method of an anisotropic thermally conductive filled thermoelectric refrigeration device as described in claim 1, characterized in that, The hexagonal boron nitride has an aspect ratio of 30-100 and an average sheet diameter of 10-50 μm; and / or the anisotropic thermally conductive paste also contains negative thermal expansion powder.

5. The manufacturing method of an anisotropic thermally conductive filled thermoelectric refrigeration device as described in claim 1, characterized in that, Before filling the anisotropic thermally conductive slurry, a silane coupling agent modified layer with a thickness of 0.5-5 μm is coated on the sidewall of the thermally conductive arm, and the modified layer forms a chemical bond with the polymer resin matrix.

6. The manufacturing method of an anisotropic thermally conductive filled thermoelectric refrigeration device as described in claim 1, characterized in that, The strength B of the horizontal magnetic field and the viscosity η of the anisotropic thermally conductive slurry satisfy the following relationship: B² / η ≥ 10T 2 / (Pa·s).

7. The manufacturing method of an anisotropic thermally conductive filled thermoelectric refrigeration device as described in claim 1, characterized in that, The post-curing process employs a gradient temperature rise post-curing process.

8. The manufacturing method of an anisotropic thermally conductive filled thermoelectric refrigeration device as described in claim 1, characterized in that, The surface activation treatment uses argon plasma cleaning, and the treatment time is 60-120 seconds.

9. A method for manufacturing an anisotropic thermally conductive filled thermoelectric refrigeration device as described in any one of claims 1-4 and 6-8, characterized in that, It also includes the following steps: After the surface activation treatment, a poly(p-xylene) film is deposited on the surface of the heat-conducting arm by vacuum phase deposition.

10. An anisotropic thermally conductive filled thermoelectric cooling device, characterized in that, The material is manufactured using the manufacturing method according to any one of claims 1-9, comprising: two ceramic substrates on both sides, a P-type thermally conductive arm and an N-type thermally conductive arm connected between the two ceramic substrates on both sides, a heat sink connected to the ceramic substrate at the hot end, and an anisotropic thermally conductive paste filled in the gap between the two ceramic substrates on both sides and the P-type thermally conductive arm and the N-type thermally conductive arm, wherein the anisotropic thermally conductive paste contains the following components: a polymer resin matrix, hexagonal boron nitride, and a dispersant.

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