A metal injection molding method of high-density special-shaped structure pure copper heat dissipation device

Abstract

This application relates to a metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device, comprising the following steps: S1, mixing coarse and fine copper powder to form pure copper powder, adding 0.01%-0.05% rare earth oxides and 0.01%-0.1% nano-copper oxide and / or nano-cuprous oxide by mass of the total pure copper powder, mixing evenly, then adding a binder for kneading and granulation to obtain a pure copper heat dissipation device masterbatch; S2, molding the pure copper heat dissipation device masterbatch using an injection molding machine to obtain an irregularly shaped heat dissipation device green blank, and performing degreasing treatment; S3, sintering the degreased irregularly shaped heat dissipation device green blank in an atmosphere furnace, and obtaining a high-density, irregularly shaped pure copper heat dissipation device after cooling. This application utilizes the synergistic reduction effect of rare earth oxides and nano-copper oxides to generate highly active copper in situ and purify particle boundaries during sintering, enabling the pure copper heat dissipation device to achieve high relative density, complete irregular structure, and high thermal conductivity.

Description

Technical Field

[0001] This application relates to the field of metal injection molding technology, and in particular to a metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device. Background Technology

[0002] Pure copper, due to its excellent thermal conductivity, is widely used in heat dissipation devices in the electronics, communications, power, and new energy fields. As equipment integration increases, the structures of heat dissipation devices are becoming increasingly complex. Shapes such as irregularly shaped air ducts, curved fins, and through-type irregular channels offer advantages in improving heat dissipation efficiency. While traditional manufacturing methods, such as machining (e.g., CNC milling, wire cutting), offer high precision, they are difficult to process internal irregular structures, resulting in low material utilization, high cost, and low efficiency, making them unsuitable for mass production. Profile extrusion molding is only suitable for simple shapes with uniform cross-sections and cannot form irregular internal cavities or complex three-dimensional structures.

[0003] Metal injection molding (MIM) combines plastic injection molding and powder metallurgy technologies, enabling the efficient manufacture of complex-shaped metal parts. It has been widely applied in stainless steel, titanium alloys, and cemented carbide. Some research has also attempted to use MIM for the fabrication of pure copper heat sinks, theoretically solving the molding problem for complex structures. However, practical applications have revealed that pure copper powder has high sintering activity and is easily oxidized. Furthermore, the binder systems and sintering regimes used in conventional MIM processes struggle to achieve high densification; in most cases, the relative density after sintering is below 95%, or even less than 90%, affecting thermal conductivity. In addition, pure copper is prone to deformation or collapse during sintering, especially thin-walled or irregularly shaped structures, resulting in low yields. Therefore, current MIM technology cannot stably and efficiently manufacture pure copper heat sinks that combine irregular structures and high density.

[0004] Therefore, there is an urgent need for a metal injection molding method that can simultaneously manufacture irregularly shaped pure copper heat dissipation devices and achieve one-time molding and high-density sintering of complex structures to meet the production requirements of high thermal conductivity, low cost, and mass production. Summary of the Invention

[0005] In order to achieve one-time molding and high-density sintering of irregularly shaped pure copper heat dissipation devices, this application provides a metal injection molding method for high-density irregularly shaped pure copper heat dissipation devices.

[0006] A metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device includes the following steps: S1. Mix coarse copper powder and fine copper powder to form pure copper powder, add 0.01%-0.05% rare earth oxides and 0.01%-0.1% nano copper oxide and / or nano cuprous oxide according to the total mass of the pure copper powder, mix evenly, then add binder for kneading, and granulate to obtain pure copper heat dissipation device masterbatch; S2. The pure copper heat dissipation device masterbatch obtained in step S1 is formed by injection molding machine to obtain a green blank of irregular structure heat dissipation device, and then degreased. S3. The degreased green blank of the irregular structure heat dissipation device obtained in step S2 is sintered in an atmosphere furnace, and after cooling, the high-density irregular structure pure copper heat dissipation device is obtained.

[0007] The inventors discovered that adding rare earth oxides and nano-copper oxide and / or nano-cuprous oxide to the process of preparing irregularly shaped pure copper heat dissipation devices, through the synergistic effect of in-situ synergistic reduction and interface activation diffusion, enables the irregularly shaped pure copper heat dissipation devices to possess excellent performance in terms of high density and complete forming of complex irregular structures.

[0008] Specifically, during the sintering heating process, nano-copper oxide (CuO) or nano-cuprous oxide (Cu2O) is first reduced by hydrogen at a relatively low temperature (within the range of 400℃-600℃) to generate highly active nano-copper particles. These in-situ generated nano-copper particles have extremely high surface energy and preferentially fill the micropores between coarse and fine particles, forming "activated necking". At the same time, the active oxygen generated by the reduction reaction is carried away by hydrogen, avoiding obstruction by the oxide film.

[0009] Subsequently, rare earth oxides (such as La2O3 and CeO2) are gradually reduced to rare earth elements (La and Ce) under the catalysis of nano-copper and in a hydrogen atmosphere. The reduced rare earth elements have a strong interface purification effect, preferentially agglomerating at the grain boundaries and surface of copper particles, and combining with residual oxygen, sulfur and other impurities to form stable compounds, thereby cleaning the particle interface and reducing the atomic diffusion barrier.

[0010] Under the aforementioned synergistic effect, the mass migration rate between copper particles is significantly improved. The densification process, which originally required higher temperatures or external pressure, can be completed rapidly at conventional sintering temperatures of 1020℃-1060℃. At the same time, because the sintering temperature is not excessively increased, irregularly shaped structures (such as square through-ducts and curved fins) will not soften, deform, or collapse locally, thus maintaining structural integrity and dimensional accuracy while achieving high density.

[0011] Preferably, the rare earth oxide in step S1 is selected from one or both of lanthanum oxide and cerium oxide.

[0012] More preferably, the rare earth oxide includes lanthanum oxide and cerium oxide, wherein the mass ratio of lanthanum oxide to cerium oxide is 1:(0.5-2).

[0013] Through extensive experimentation, the inventors discovered that when lanthanum oxide and cerium oxide are compounded in the aforementioned mass ratio and added to pure copper powder as rare earth oxides, irregularly shaped pure copper heat dissipation devices can achieve a unified high-density, fine-grained structure, and complete forming of complex shapes. Specifically, lanthanum oxide and cerium oxide produce a "relay reduction" and "interfacial synergistic segregation" effect during the reduction process: cerium oxide is preferentially reduced due to its lower standard reduction potential, forming cerium-rich active sites, which further catalyze the reduction of lanthanum oxide at even lower temperatures; the reduced lanthanum and cerium atoms co-segregate at the grain boundaries of copper particles, where lanthanum preferentially combines with residual oxygen, sulfur, and other impurities to form diffusely distributed nanoscale oxide clusters, effectively purifying the grain boundaries, while cerium reduces the self-diffusion activation energy of copper atoms, promoting interparticle material migration. The synergistic effect of both optimizes the grain boundary mobility, avoiding abnormal grain growth caused by excessive densification and eliminating grain boundary brittleness caused by impurity segregation.

[0014] However, excessive lanthanum oxide can lead to incomplete reduction and residual oxide inclusions, reducing thermal conductivity and densification effect. Excessive cerium oxide can easily cause abnormal growth of copper grains, precipitation of brittle phases at grain boundaries, and even local overheating, resulting in deformation or cracking of the irregular structure. Therefore, controlling the mass ratio of the two oxides within the range of 1:(0.5-2) is key to achieving high density, fine-grained structure, excellent thermal conductivity, and complete forming of irregular structures.

[0015] Preferably, the mass ratio of coarse copper powder to fine copper powder in step S1 is (2.33-9):1.

[0016] By controlling the mass ratio of coarse to fine copper powder, a bimodal particle size distribution of "skeleton-filler" can be formed: coarse particles form a supporting skeleton, maintaining the shape stability of the irregular structure; fine particles fill the gaps between coarse particles, preferentially densifying in the early stage of sintering, generating capillary force to drive the rearrangement of coarse particles, thereby achieving high-density packing without external pressure. If the proportion of coarse particles is too high and the proportion of fine particles is insufficient, the gaps in the skeleton cannot be effectively filled, leaving a large number of closed pores after sintering, and the relative density is significantly reduced; if the proportion of fine particles is too high, the shrinkage rate of the green body increases, the irregular structure is prone to distortion and deformation, and the agglomeration of fine particles leads to local overburning. The preferred mass ratio range of this application ensures a stable and high relative density after sintering, while guaranteeing the dimensional accuracy of complex structures such as irregular air ducts and curved fins.

[0017] Preferably, the adhesive used in step S1 is selected from one or more of polyoxymethylene, polyethylene, polypropylene, and paraffin.

[0018] More preferably, the adhesive comprises polyoxymethylene, polyethylene and paraffin wax, wherein the mass ratio of polyoxymethylene, polyethylene and paraffin wax is (16-18):(0.5-1.5):1.

[0019] The inventors discovered that by using the above-mentioned ternary compound binder, the carbon residue after sintering can be significantly reduced while ensuring the fluidity of injection molding and the strength of the green body.

[0020] Specifically, polyoxymethylene (POM) serves as the main framework and rapidly decomposes into gaseous formaldehyde through depolymerization during the catalytic degreasing stage, leaving interconnected channels. Paraffin melts and seeps out in the early stages of degreasing, further opening the pores. By adding an appropriate amount of polyethylene, not only are carbon sources that are difficult to completely remove at high temperatures reduced, but the amount of residual carbon is also controlled at a low level, preventing carbon from accumulating at copper grain boundaries, thereby eliminating the obstruction of carbon to copper atom diffusion and increasing sintering density.

[0021] Experiments show that if the proportion of polyethylene is too high, the carbon residue increases and the density decreases; if the proportion of polyethylene is too low, the green body of the irregularly shaped heat dissipation device lacks toughness, and the irregularly shaped thin-walled structure (such as the edge of the air duct) is prone to micro-cracks during demolding. Therefore, the preferred ratio in this application achieves the best balance between low carbon residue and good formability, and can simultaneously achieve high density and complete molding of irregularly shaped structures.

[0022] More preferably, the adhesive further includes a sintering activator comprising 0.1%-1% of the total mass of the adhesive, wherein the sintering activator is selected from one or two of boric acid and borax.

[0023] By employing the above technical solution, boric acid or borax in the binder partially remains in the green body during the degreasing stage. Upon entering the sintering stage, it undergoes thermal decomposition, generating active boron oxides or a low-melting-point copper borate transition phase. These active substances accumulate at the copper particle contact interface, reducing the solid-phase diffusion activation energy, promoting copper atom interface migration, and accelerating the densification process. Simultaneously, boron atoms segregate at grain boundaries, pinning grain migration and inhibiting abnormal grain growth, resulting in a uniform and fine grain structure in the sintered body. Insufficient addition leads to inadequate activation, while excessive addition easily forms brittle boride phases at grain boundaries, reducing material toughness. The preferred addition range in this application achieves a balance between promoting densification and maintaining material toughness, enabling the complete molding of high-density and irregularly shaped structures.

[0024] Preferably, the degreasing process in step S2 is performed using catalytic degreasing or thermal degreasing.

[0025] By employing the above technical solutions, catalytic debinding utilizes an acidic atmosphere to rapidly depolymerize polyoxymethylene into gaseous monomers, resulting in high debinding efficiency and good green body shape retention, making it suitable for thin-walled or complex irregular structures. Thermal debinding, through stepwise heating, gradually decomposes the binder, offering a wide process window suitable for large-sized or thick-walled parts. Both methods effectively remove the binder, providing a clean particle interface for subsequent sintering and preventing residual carbon from hindering densification.

[0026] Preferably, the sintering atmosphere in the atmosphere furnace in step S3 is a mixture of hydrogen and nitrogen, and the volume ratio of hydrogen to nitrogen is 1:(3-4).

[0027] By employing the above technical solution, hydrogen provides a reducing environment, effectively removing oxides from the surface and interior of copper particles and maintaining the cleanliness of the particle interface. Nitrogen, as a diluent gas, reduces the hydrogen concentration, preventing localized overheating or deformation of irregular structures during sintering due to excessive hydrogen concentration. Furthermore, by adjusting the atmosphere ratio, the sintering shrinkage rate is controlled, ensuring dimensional stability of the irregular structure during densification. Maintaining the hydrogen-to-nitrogen volume ratio within the range of 1:3 to 1:4 ensures sufficient reduction capability while providing a suitable gaseous environment to inhibit abnormal grain growth, thereby obtaining a high-density, well-shaped pure copper heat sink. If the hydrogen ratio is too high, localized overheating or deformation may occur; if the hydrogen ratio is too low, insufficient reduction results in oxide residues hindering densification. The atmosphere range selected in this application balances the reduction effect and structural stability of the irregularly shaped pure copper heat sink during sintering.

[0028] Preferably, the sintering temperature of the atmosphere furnace in step S3 is 1020-1060°C.

[0029] By employing the above-mentioned technical solution and controlling the sintering temperature between 1020℃ and 1060℃, copper particles can achieve sufficient diffusion and densification while avoiding abnormal grain growth or localized overheating. Below this temperature range, the atomic diffusion rate is insufficient, leading to inadequate necking between particles, more residual porosity, and difficulty in achieving high density. Above this temperature range, grain boundary migration is too rapid, grains coarsen, and irregular structures (such as thin-walled air ducts or curved fins) are prone to collapse or deformation due to softening. The temperature range selected in this application, combined with the aforementioned rare earth oxides, nano-copper oxides, and boride activators, achieves high densification at relatively low temperatures while maintaining the shape integrity and dimensional accuracy of irregular structures.

[0030] In summary, this application includes at least one of the following beneficial technical effects: 1. This application utilizes the synergistic addition of rare earth oxides with nano-copper oxide and / or nano-cuprous oxide, and leverages in-situ reduction and interfacial activation diffusion to enable pure copper heat dissipation devices to achieve high density at conventional sintering temperatures, while maintaining the integrity of complex structures such as irregular air ducts and curved fins, without the need for subsequent machining.

[0031] 2. This application uses a ternary composite binder of polyoxymethylene, polyethylene and paraffin, and optimizes the relative ratio of the three components. While ensuring the fluidity of injection molding and the strength of the green body, it significantly reduces the carbon residue after sintering, avoids the obstruction of copper atom diffusion by carbon, thereby improving the densification effect and reducing the risk of cracking of thin-walled irregular structures during demolding. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the overall structure of a pure copper heat sink with a square through-flow channel, which is fabricated using the metal injection molding method of Embodiment 1 of this application. Detailed Implementation

[0033] The present application will be further described in detail below with reference to embodiments and comparative examples: Some of the raw materials used in the examples and comparative examples: The coarse-particle copper powder, model number ML-Cu-PW20, has an average particle size of 20 μm; the fine-particle copper powder, model number ML-Cu-PW01, has an average particle size of 1 μm. Both were purchased from Zhejiang Manli Nanotechnology Co., Ltd.

[0034] Lanthanum oxide (serial number 0326957), analytical grade; cerium oxide (serial number 02652999), analytical grade, both purchased from Qinghe County Zhongzhou Alloy Materials Co., Ltd.

[0035] Polyoxymethylene, polyethylene, paraffin wax, and boric acid were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0036] Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available products. Example

[0037] Example 1 The fabrication of a high-density, irregularly shaped pure copper heat dissipation device is as follows: S1. Mix 82 parts by weight of coarse copper powder and 18 parts by weight of fine copper powder to form pure copper powder. Add 0.015 parts by weight of lanthanum oxide, 0.015 parts by weight of cerium oxide and 0.05 parts by weight of nano copper oxide, mix evenly, add 9 parts by weight of polyoxymethylene, 0.5 parts by weight of polyethylene, 0.5 parts by weight of paraffin wax and 0.05 parts by weight of boric acid for kneading. The kneading temperature is 180℃ and the time is 90 minutes. Granulate to obtain pure copper heat dissipation device masterbatch. S2. The pure copper heat dissipation device masterbatch obtained in step S1 is formed by injection molding machine with barrel temperature of 190℃, mold temperature of 65℃, and injection pressure of 110MPa to obtain a green blank of irregular structure heat dissipation device, and then degreased (fumigated with nitric acid vapor at 135℃ for 2.5 hours). S3. The degreased irregular-shaped heat dissipation device blank obtained in step S2 is sintered in a furnace with a hydrogen and nitrogen atmosphere in a volume ratio of 1:3.5. The sintering temperature is 1040°C, and the temperature is held for 2 hours. After cooling, a high-density irregular-shaped pure copper heat dissipation device is obtained.

[0038] Example 2 The only difference between Example 2 and Example 1 is that in step S1 of Example 2, 0.015 parts by weight of lanthanum oxide and 0.015 parts by weight of cerium oxide are replaced with 0.02 parts by weight of lanthanum oxide and 0.01 parts by weight of cerium oxide.

[0039] Example 3 The difference between Example 3 and Example 1 is that in step S1 of Example 3, 0.015 parts by weight of lanthanum oxide and 0.015 parts by weight of cerium oxide are replaced with 0.005 parts by weight of lanthanum oxide and 0.025 parts by weight of cerium oxide.

[0040] Example 4 The only difference between Example 4 and Example 1 is that in step S1 of Example 4, 0.015 parts by weight of lanthanum oxide and 0.015 parts by weight of cerium oxide are replaced with 0.03 parts by weight of lanthanum oxide.

[0041] Example 5 The only difference between Example 5 and Example 1 is that in step S1 of Example 5, 0.015 parts by weight of lanthanum oxide and 0.015 parts by weight of cerium oxide are replaced with 0.03 parts by weight of cerium oxide.

[0042] Example 6 The only difference between Example 6 and Example 1 is that in step S1 of Example 6, 9 parts by weight of polyoxymethylene, 0.5 parts by weight of polyethylene, and 0.5 parts by weight of paraffin are replaced with 8.5 parts by weight of polyoxymethylene, 1 part by weight of polyethylene, and 0.5 parts by weight of paraffin.

[0043] Example 7 The only difference between Example 7 and Example 1 is that in step S1 of Example 7, 9 parts by weight of polyoxymethylene, 0.5 parts by weight of polyethylene, and 0.5 parts by weight of paraffin are replaced with 9.3 parts by weight of polyoxymethylene, 0.2 parts by weight of polyethylene, and 0.5 parts by weight of paraffin.

[0044] Example 8 The difference between Example 8 and Example 1 is that in step S1 of Example 7, 9 parts by weight of polyoxymethylene, 0.5 parts by weight of polyethylene, and 0.5 parts by weight of paraffin are replaced with 9.5 parts by weight of polyoxymethylene and 0.5 parts by weight of paraffin.

[0045] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that 0.05 parts by weight of nano-copper oxide was not added in step S1 of Comparative Example 1. The preparation steps are as follows: S1. Mix 82 parts by weight of coarse copper powder and 18 parts by weight of fine copper powder to form pure copper powder. Add 0.015 parts by weight of lanthanum oxide and 0.015 parts by weight of cerium oxide and mix evenly. Add 9 parts by weight of polyoxymethylene, 0.5 parts by weight of polyethylene, 0.5 parts by weight of paraffin wax and 0.05 parts by weight of boric acid and knead at 180°C for 90 minutes. Granulate to obtain pure copper heat dissipation device masterbatch. S2. The pure copper heat dissipation device masterbatch obtained in step S1 is formed by injection molding machine with barrel temperature of 190℃, mold temperature of 65℃, and injection pressure of 110MPa to obtain a green blank of irregular structure heat dissipation device, and then degreased (fumigated with nitric acid vapor at 135℃ for 2.5 hours). S3. The degreased irregular-shaped heat dissipation device blank obtained in step S2 is sintered in a furnace with a hydrogen and nitrogen atmosphere in a volume ratio of 1:3.5. The sintering temperature is 1040°C, and the temperature is held for 2 hours. After cooling, a high-density irregular-shaped pure copper heat dissipation device is obtained.

[0046] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that 0.015 parts by weight of lanthanum oxide and 0.015 parts by weight of cerium oxide were not added in step S1 of Comparative Example 1. The preparation steps are as follows: S1. Mix 82 parts by weight of coarse copper powder and 18 parts by weight of fine copper powder to form pure copper powder. Add 0.05 parts by weight of nano copper oxide and mix evenly. Add 9 parts by weight of polyoxymethylene, 0.5 parts by weight of polyethylene, 0.5 parts by weight of paraffin wax and 0.05 parts by weight of boric acid and knead at 180°C for 90 minutes. Granulate to obtain pure copper heat dissipation device masterbatch. S2. The pure copper heat dissipation device masterbatch obtained in step S1 is formed by injection molding machine with barrel temperature of 190℃, mold temperature of 65℃, and injection pressure of 110MPa to obtain a green blank of irregular structure heat dissipation device, and then degreased (fumigated with nitric acid vapor at 135℃ for 2.5 hours). S3. The degreased irregular-shaped heat dissipation device blank obtained in step S2 is sintered in a furnace with a hydrogen and nitrogen atmosphere in a volume ratio of 1:3.5. The sintering temperature is 1040°C, and the temperature is held for 2 hours. After cooling, a high-density irregular-shaped pure copper heat dissipation device is obtained.

[0047] The high-density, irregularly shaped pure copper heat dissipation devices prepared in each embodiment and comparative example were tested for relative density according to GB / T 3850-2015, thermal conductivity according to GB / T 22588-2008, and grain size according to GB / T6394-2017. The irregularly shaped air ducts (square through-air ducts) and the edges of curved fins were observed under a stereomicroscope to check for defects such as cracks, microcracks, deformation, collapse, or blockage.

[0048] Table 1. Performance data of high-density irregular-shaped pure copper heat dissipation devices prepared in each embodiment and comparative example. Group Relative density (%) Thermal conductivity (W / (m·K)) Grain size (μm) Irregular structure integrity Example 1 98.2 374 15 intact Example 2 97.8 368 18 intact Example 3 96.5 356 38 Micro-deformation Example 4 95.8 348 12 intact Example 5 96.2 352 50 Localized brittle fracture Example 6 96.8 360 18 intact Example 7 97.5 365 15 microcracks Example 8 97.0 360 15 Obvious cracks Comparative Example 1 93.5 335 12 intact Comparative Example 2 94.2 340 30 intact As can be seen from Examples 1-8 and Table 1, the synergistic addition of rare earth oxides and nano-copper oxide has a decisive influence on the overall performance of pure copper heat dissipation devices. When lanthanum oxide and cerium oxide are mixed in a 1:1 mass ratio, they produce a relay reduction and interfacial synergistic segregation effect during the reduction process: cerium oxide is preferentially reduced to form cerium-rich active sites, catalyzing the reduction of lanthanum oxide at a lower temperature; the reduced lanthanum atoms purify the grain boundaries and combine with impurities, while cerium atoms reduce the copper self-diffusion activation energy, jointly optimizing the grain boundary mobility. Example 1, using a 1:1 mixture of lanthanum oxide and cerium oxide, showed the best performance in terms of relative density, thermal conductivity, grain size, and integrity of the irregular structure. Example 2, adjusting the ratio to 2:1, still achieved good results, but the grain size increased slightly and the thermal conductivity decreased slightly. Example 3, adjusting the ratio to 1:5, resulted in abnormal grain growth due to excessive cerium content, micro-deformation of the irregular structure, and a significant decrease in thermal conductivity. Example 4, with only lanthanum oxide added but no cerium oxide, resulted in incomplete reduction of some lanthanum oxide due to the lack of cerium's catalytic reduction effect, leading to significantly lower density and thermal conductivity. Example 5, with only cerium oxide added but no lanthanum oxide, resulted in grain coarsening and localized brittleness due to the lack of lanthanum's grain boundary purification effect. This indicates that the ratio of lanthanum oxide to cerium oxide must be controlled within a reasonable range; both are indispensable.

[0049] In terms of binder formulation, the ternary ratio of polyoxymethylene (POM), polyethylene (PE), and paraffin wax has a crucial impact on carbon residue and green body formability. Example 1 uses a POM, PE, and paraffin wax formulation of 18:1:1. The moderate PE ratio ensures both green body toughness and keeps carbon residue at a low level, achieving high density and complete molding. Example 6 increases the PE ratio; the higher PE content leads to increased carbon residue, hindering copper atom diffusion and reducing density and thermal conductivity. Example 7 reduces the PE ratio; although carbon residue is lower, green body toughness is insufficient, and microcracks appear in the irregular thin-walled structure during demolding. Example 8 completely omits PE; the green body brittleness increases significantly, with obvious cracks appearing during demolding, and structural integrity is compromised. This indicates that the PE ratio needs to be controlled within a moderate range; too high a ratio increases carbon residue, while too low a ratio results in insufficient green body toughness.

[0050] Combining Example 1 and Comparative Examples 1-2 with Table 1, it can be seen that the individual roles and synergistic effects of nano-copper oxide and rare earth oxides have been clearly verified. In Comparative Example 1, without the addition of nano-copper oxide, both density and thermal conductivity decreased significantly, indicating that nano-copper oxide played an irreplaceable role in the initial sintering process of reduction to highly active nano-copper, filling micropores, and catalyzing the reduction of rare earth oxides. In Comparative Example 2, without the addition of rare earth oxides, density and thermal conductivity were also significantly lower, while grain size increased, indicating that rare earth oxides made a unique contribution to purifying grain boundaries and reducing diffusion barriers. The performance of both was significantly lower than that of Example 1, demonstrating a significant synergistic effect between nano-copper oxide and rare earth oxides.

[0051] This application employs a preferred ratio of coarse and fine copper powder to form a bimodal particle size distribution of skeleton and filler, enabling the sintered body to achieve close packing under pressureless conditions. Simultaneously, rare earth oxides composed of lanthanum oxide and cerium oxide are added, utilizing relay reduction and interfacial synergistic segregation effects to purify grain boundaries and optimize grain boundary mobility. Furthermore, nano-copper oxide is added as a reduction aid, generating highly active nano-copper in situ during the early stages of sintering, filling micropores and catalyzing the reduction of rare earth oxides. The binder is a ternary compound of polyoxymethylene, polyethylene, and paraffin, with the polyethylene ratio controlled within a preferred range to significantly reduce carbon residue while ensuring green body formability. Boric acid is further added to the binder as a sintering activator, decomposing to generate active borides to lower the diffusion barrier and inhibit grain growth. Combined with a sintering atmosphere of 1:3.5 hydrogen to nitrogen volume ratio and a sintering temperature of 1040℃, pure copper heat dissipation devices can achieve high density and complete irregular structures at conventional sintering temperatures. Therefore, this application realizes the one-time molding and high-density sintering of irregularly shaped pure copper heat dissipation devices, which can be widely used in fields such as electronics, communications, power and new energy where heat dissipation performance requirements are stringent.

[0052] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device, characterized in that, Includes the following steps: S1. Mix coarse copper powder and fine copper powder to form pure copper powder, add 0.01%-0.05% rare earth oxides and 0.01%-0.1% nano copper oxide and / or nano cuprous oxide according to the total mass of the pure copper powder, mix evenly, then add binder for kneading, and granulate to obtain pure copper heat dissipation device masterbatch; S2. The pure copper heat dissipation device masterbatch obtained in step S1 is formed by injection molding machine to obtain a green blank of irregular structure heat dissipation device, and then degreased. S3. The degreased green blank of the irregular structure heat dissipation device obtained in step S2 is sintered in an atmosphere furnace, and after cooling, the high-density irregular structure pure copper heat dissipation device is obtained.

2. The metal injection molding method for the high-density, irregularly shaped pure copper heat dissipation device according to claim 1, characterized in that, The rare earth oxides mentioned in step S1 are selected from one or both of lanthanum oxide and cerium oxide.

3. The metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device according to claim 2, characterized in that, The rare earth oxides include lanthanum oxide and cerium oxide, wherein the mass ratio of lanthanum oxide to cerium oxide is 1:(0.5-2).

4. The metal injection molding method for the high-density, irregularly shaped pure copper heat dissipation device according to claim 1, characterized in that, The mass ratio of coarse copper powder to fine copper powder in step S1 is (2.33-9):

1.

5. The metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device according to claim 1, characterized in that, The adhesive used in step S1 is selected from one or more of polyoxymethylene, polyethylene, polypropylene, and paraffin.

6. The metal injection molding method for the high-density, irregularly shaped pure copper heat dissipation device according to claim 5, characterized in that, The adhesive comprises polyoxymethylene, polyethylene and paraffin wax, wherein the mass ratio of polyoxymethylene, polyethylene and paraffin wax is (16-18):(0.5-1.5):

1.

7. The metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device according to claim 5, characterized in that, The adhesive also includes a sintering activator comprising 0.1%-1% of the total mass of the adhesive, wherein the sintering activator is selected from one or two of boric acid and borax.

8. The metal injection molding method for the high-density, irregularly shaped pure copper heat dissipation device according to claim 1, characterized in that, In step S2, the degreasing process is carried out using catalytic degreasing or thermal degreasing.

9. The metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device according to claim 1, characterized in that, In step S3, the sintering atmosphere in the atmosphere furnace is a mixture of hydrogen and nitrogen, and the volume ratio of hydrogen to nitrogen is 1:(3-4).

10. The metal injection molding method for a high-density, irregularly shaped pure copper heat dissipation device according to claim 1, characterized in that, The sintering temperature of the atmosphere furnace in step S3 is 1020-1060°C.

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