Preparation process of conductive foam copper in electromagnetic shielding structure of communication equipment

Abstract

The present application relates to the technical field of preparation of metal porous materials in electromagnetic shielding structure, in particular to a preparation process of electromagnetic shielding structure of conductive foam copper in communication equipment, comprising: mixing foam copper powder, nano silver powder, graphene and the like, adding ethanol for grinding to form a functional slurry with chemical bonds; after sand blasting of the shell, plasma etching, immersion in 5-8% silane solution for 10-15 minutes, and drying at 80-100 DEG C; three layers of different slurry are sprayed, with a total thickness of 0.15-0.3 mm, and pre-drying at 60-80 DEG C for 10 minutes layer by layer; in a nitrogen atmosphere, heat preservation at 120-150 DEG C for 1-2 hours, heat preservation at 200-250 DEG C for 2-3 hours, heat preservation at 300-350 DEG C for 1-1.5 hours, and cooling; immersion in 10-15% sulfuric acid for 3-5 minutes, electrodeposition of nickel-cobalt alloy 0.02-0.05 mm, and immersion in silane solution to form a closed layer. The structure is innovative through slurry modification and layered coating, has excellent broadband shielding effectiveness, is firmly combined with the substrate, has good corrosion resistance and flexibility, meets the needs of communication equipment, and has strong practicality.

Description

Technical Field

[0001] This invention relates to the field of preparation technology of porous metal materials in electromagnetic shielding structures, specifically a process for preparing an electromagnetic shielding structure of conductive copper foam in communication equipment. Background Technology

[0002] With the rapid iteration of 5G and next-generation communication technologies, communication equipment is developing rapidly towards higher frequencies, greater integration, and miniaturization. The signal transmission rates and power of core components such as radio frequency modules and signal processors are continuously increasing, making electromagnetic interference (EMI) a more prominent issue. EMI not only causes signal attenuation and increased bit error rates, but can also lead to malfunctions in adjacent components and even threaten the safe operation of equipment. Therefore, electromagnetic shielding has become one of the core technologies in communication equipment design. Conductive copper foam, due to its lightweight, high conductivity, and excellent electromagnetic shielding performance, has become an ideal material to replace traditional metal shielding covers. However, it still faces many technical bottlenecks in practical applications.

[0003] The existing fabrication process for conductive copper foam shielding structures has significant flaws. In the functional slurry preparation stage, simple mechanical mixing is often used to combine copper foam powder with conductive fillers, lacking effective interface modification design. This results in poor compatibility between components such as copper powder and nano-silver powder, leading to agglomeration and difficulty in forming a continuous conductive network, directly hindering the improvement of shielding effectiveness. The use of coupling agents is mostly conventional addition, without targeted chemical reaction control based on powder characteristics. This results in weak interfacial bonding, making them prone to delamination and detachment under equipment vibration or temperature changes.

[0004] The crude substrate treatment process exacerbates structural stability issues. Traditional methods of directly coating after sandblasting fail to build a robust connection between the metal substrate and the shielding layer, resulting in generally low bond strength that is ill-suited to the mechanical shocks and thermal cycling environments encountered during long-term service in communication equipment. While some processes incorporate silane treatment, the lack of accompanying surface activation steps such as plasma etching leads to insufficient hydroxyl groups on the substrate surface, hindering the full reaction of silane molecules. This results in a poorly dense bonding layer that easily becomes a channel for moisture and corrosive media to penetrate.

[0005] The simplification of coating and sintering processes further limits performance improvement. Single-layer coatings struggle to balance the conductivity and flexibility of the shielding layer, while traditional sintering methods, often employing constant temperature modes, cannot simultaneously achieve solvent evaporation, resin curing, and interface strengthening, leading to issues such as internal porosity or insufficient interfacial bonding. Surface treatments are mostly limited to simple nickel plating or coating, lacking composite protective designs. In harsh environments with high temperature, high humidity, or salt spray, the shielding layer is prone to oxidation and corrosion, resulting in a rapid decline in conductivity and shielding effectiveness.

[0006] At the equipment application level, traditional shielding structures are mostly monolithic designs, which are heavy and have poor adaptability, failing to meet the personalized shielding needs of different modules. Edge sealing often relies on simple conductive adhesive bonding, and the sealing performance is easily affected by assembly precision. High-frequency electromagnetic waves can easily leak through gaps, leading to a decrease in shielding effectiveness. In addition, the shielding performance of existing structures degrades significantly at high frequencies (above 18 GHz), making it difficult to adapt to the high-frequency requirements of next-generation communication technologies.

[0007] In summary, existing conductive foam copper shielding structures suffer from problems such as uneven dispersion of functional pastes, unstable substrate bonding, rough coating and sintering processes, insufficient surface protection, and poor equipment compatibility. These issues result in low shielding effectiveness, poor stability, and short service life, failing to meet the stringent requirements of high-end communication equipment. Therefore, developing a conductive foam copper shielding structure and its fabrication technology that combines high shielding effectiveness, strong structural stability, and excellent environmental adaptability has become an urgent need for the industry. Summary of the Invention

[0008] (a) Technical problems to be solved

[0009] To address the shortcomings of existing technologies, this invention provides a process for preparing an electromagnetic shielding structure using conductive copper foam in communication equipment.

[0010] (II) Technical Solution

[0011] A process for fabricating an electromagnetic shielding structure using conductive copper foam in communication equipment includes the following steps:

[0012] S1, Preparation of functional slurry: Weigh out 70-80% copper foam powder, 5-8% nano silver powder, 2-4% graphene, 1-3% carbon nanotubes, 0.5-1% lanthanide rare earth oxides, 0.5-1.5% titanate coupling agent, and 3-6% epoxy resin by weight percentage; put the above raw materials into a planetary ball mill, add anhydrous ethanol as a dispersion medium and grind; obtain a uniformly dispersed functional slurry;

[0013] S2, Substrate gradient pretreatment: The communication equipment housing is made of aluminum alloy. First, it is sandblasted, then plasma etched, and a mixture of argon and oxygen is introduced. Then, it is immersed in 5-8% silane solution. The silane is γ-glycidyl etheroxypropyltrimethoxysilane. After immersion for 10-15 minutes, it is taken out and dried, and a Si-O bond connection layer is formed on the surface.

[0014] S3, Layered Coating Molding: Layered coating is performed using high-pressure airless spraying; the bottom layer is coated with a functional slurry containing 80% copper foam powder; the middle layer is coated with a functional slurry containing 5% nano silver powder; the top layer is coated with a functional slurry containing 3% graphene; after coating, it is pre-baked in the infrared at 60℃, 70℃, and 80℃ for 10 minutes respectively.

[0015] S4, Stepped sintering: Place the coated substrate into an atmosphere sintering furnace and purge with nitrogen; heat to 120-150℃ and hold for 1-2 hours; then heat to 200-250℃ and hold for 2-3 hours to promote epoxy resin curing; finally heat to 300-350℃ and hold for 1-1.5 hours to strengthen interfacial chemical bonding, and allow to cool naturally to room temperature;

[0016] S5, Composite Surface Treatment: First, immerse the sintered shielding layer in a 10-15% sulfuric acid solution at 30°C for surface roughening, and then rinse with deionized water until neutral; then perform nickel-cobalt alloy electrodeposition; finally, immerse in a 0.5-1% silane solution at 25°C for 5 minutes, and dry at 80°C to form a sealing layer, thus obtaining the electromagnetic shielding structure.

[0017] Preferably, the foamed copper powder in S1 is surface modified before use. The foamed copper powder is immersed in a 3-5% oxalic acid solution and anodized for 5-8 minutes using a DC voltage of 10-15V to form a uniformly distributed CuO nano array on the surface. The particle size of the treated foamed copper powder is controlled at 50-100μm, the particle size of the nano silver powder is 20-50nm, and the aspect ratio of the carbon nanotubes is 50-100.

[0018] Preferably, the process also includes removing residual abrasive from the surface by blowing with compressed air for 5 minutes after sandblasting in step S2, maintaining a distance of 50-80 mm between the electrode and the substrate during plasma etching, and using a mixture of deionized water and ethanol in a volume ratio of 1:9 to prepare the silane solution, which is then ultrasonically treated for 10 minutes before use to ensure complete dissolution.

[0019] Preferably, the nozzle diameter of the S3 medium-high pressure airless spraying equipment is 0.8-1.2mm, the spraying angle is kept at 90 degrees perpendicular to the substrate surface, and the thickness uniformity is checked by a laser thickness gauge after each coating is completed, with the deviation controlled within ±5%. Infrared drying uses an infrared lamp with a wavelength of 2-5μm and an irradiation distance of 300-500mm.

[0020] Preferably, the three temperature stages of the stepped sintering in S4 correspond to the three key processes of solvent evaporation, resin curing, and interface reaction, respectively. The nitrogen flow rate is adjusted at different stages: 1.2 L / min at 120-150℃, 1.0 L / min at 200-250℃, and 0.8 L / min at 300-350℃. The pressure inside the furnace is maintained at a slightly positive pressure of 50-100 Pa.

[0021] Preferably, after the sulfuric acid solution roughening treatment in S5, the surface roughness is detected by an eddy current flaw detector to ensure that Ra1.6-3.2μm is achieved. During the nickel-cobalt alloy electrodeposition, mechanical stirring at a stirring rate of 300-500r / min is used. During the deposition process, the electrolyte composition is detected every 30 minutes and the consumed metal ions are replenished. The thickness of the film layer formed after silane sealing treatment is controlled at 1-3μm.

[0022] Preferably, it also includes S6. Shielding effectiveness optimization: magnetron sputtering is performed on the surface of the shielding structure after composite surface treatment. The target material is a copper-graphene composite target with a graphene content of 5-8%, the sputtering power is 200-300W, 99.99% pure argon gas is introduced, the working pressure is 0.5-1Pa, the sputtering time is 5-10 minutes, and a copper-graphene composite layer with a thickness of 0.5-1μm is formed.

[0023] Preferably, the electromagnetic shielding effectiveness of the shielding structure reaches 90-100dB in the 100MHz-18GHz frequency band and 85-95dB in the 18-40GHz high-frequency band, with a surface resistance of 0.01-0.03Ω / sq.

[0024] Preferably, the bonding strength between the shielding structure and the substrate is 18-22 MPa as measured by tensile testing, the thermal conductivity is 200-230 W / (m·K), and no rust is observed after 600-800 hours of salt spray testing according to GB / T 10125. After being placed in an environment of 85℃ and 85% relative humidity for 1000 hours, the retention rate of various performance indicators exceeds 95%.

[0025] Preferably, the communication equipment using the electromagnetic shielding structure includes an aluminum alloy shell, a signal motherboard, and a modular shielding assembly. The shielding assembly adopts the conductive foam copper electromagnetic shielding structure and is divided into 3-5 independent shielding units according to the radio frequency module, power supply module, and signal processing module on the motherboard. Each unit has a conductive rubber boss with a semi-circular cross-section at its edge, with a boss diameter of 0.8-1.2mm, which forms a tenon-and-mortise connection structure with the groove on the shell. The overall thickness of the shielding assembly is 0.3-0.5mm, and the weight is reduced by 40-50% compared to traditional metal shielding covers.

[0026] (iii) Beneficial technical effects

[0027] Compared with existing technologies, the beneficial effects of this invention are:

[0028] 1. By introducing a controlled hydrolysis reaction of titanate coupling agent, Ti-O-Ag chemical bonds are constructed to connect various conductive components, effectively solving the problems of poor compatibility and easy agglomeration of components such as copper powder and silver powder in traditional slurries. This forms a continuous and dense conductive network, laying the foundation for improving broadband shielding effectiveness. The anodic oxidation pretreatment of foamed copper powder and the carboxylation modification of carbon nanotubes further enhance the interfacial bonding between components, avoiding performance degradation caused by loose structure inside the shielding layer. At the same time, the addition of lanthanide rare earth oxides optimizes the synergistic effect of conductivity and magnetic properties.

[0029] 2. A stepped pretreatment process involving sandblasting, plasma etching, and silane treatment, through surface roughening and chemical modification, constructs multiple interconnected interfaces. The formation of the Si-O bond connection layer makes the shielding layer and substrate bond more firmly, completely solving the problems of insufficient bonding strength and easy delamination in traditional processes. The layered coating design precisely controls the slurry ratio and spraying parameters according to the functional requirements of different coatings. The bottom layer ensures conductivity and adhesion, the middle layer strengthens shielding effectiveness, and the top layer improves flexibility and corrosion resistance, achieving balanced optimization of multiple performance objectives in a single structure.

[0030] 3. The three-stage sintering process precisely matches the requirements of solvent evaporation, resin curing, and interface strengthening, avoiding internal defects caused by traditional single-temperature sintering and ensuring a dense shielding layer structure. The composite surface treatment of sulfuric acid roughening, nickel-cobalt alloy electrodeposition, and silane sealing constructs multiple protective barriers, effectively resisting oxidation and corrosive media erosion, solving the problem of rapid performance degradation of traditional shielding layers in harsh environments, while the magnetron sputtering optimization step further improves the shielding effectiveness in the high-frequency band.

[0031] 4. Independent shielding units divided according to functional modules can specifically meet the shielding requirements of different components, greatly improving design flexibility. The tenon-and-mortise connection between the conductive rubber bosses and the housing has higher reliability than traditional conductive adhesive seals, effectively reducing leakage of high-frequency electromagnetic waves through gaps. At the same time, the lightweight structural design conforms to the development trend of miniaturization and weight reduction in communication equipment. Attached Figure Description

[0032] Figure 1 This is a process flow diagram of the preparation process of an electromagnetic shielding structure for conductive copper foam in communication equipment proposed in this invention;

[0033] Figure 2 This is a line graph comparing the shielding effectiveness of the 100MHz-18GHz and 18-40GHz versions of the embodiments and comparative examples.

[0034] Figure 3 This is a bar chart comparing the thermal conductivity and salt spray resistance time of the examples and comparative examples;

[0035] Figure 4These are the fitting curves of shielding effectiveness attenuation at different frequencies for the examples and comparative examples. Detailed Implementation

[0036] according to Figures 1 to 4 The specific embodiments of the present invention are as follows: Example

[0037] Preparation of functional slurry: The following components were weighed by weight percentage: 75% copper foam powder, 6% silver nanoparticle powder, 3% graphene, 2% carbon nanotubes, 0.8% lanthanide rare earth oxides, 1% titanate coupling agent, and 2.2% epoxy resin. The copper foam powder had a particle size of 75 μm and was anodized in 3% oxalic acid solution for 6 minutes to form a CuO nanoarray on the surface. The silver nanoparticle powder had a particle size of 35 nm. The carbon nanotubes had an aspect ratio of 75 and their walls were carboxylated. The raw materials were added to a planetary ball mill with anhydrous ethanol at a material-to-liquid ratio of 1:1.5 and milled for 45 minutes. During the process, the titanate coupling agent hydrolyzed and formed Ti-O-Ag bonds with the powder surface, thus obtaining the functional slurry.

[0038] Substrate gradient pretreatment: The aluminum alloy casing of the communication equipment is first sandblasted using 100-mesh alumina abrasive at a pressure of 0.4 MPa, achieving a surface roughness of Ra 4.8 μm. Residual abrasive is removed by purging with compressed air for 5 minutes, followed by plasma etching for 4 minutes. An argon-oxygen mixture (3:1 volume ratio) is introduced during etching at a power of 120 W, maintaining a 65 mm distance between the electrode and the substrate. Subsequently, the substrate is immersed in a 6% γ-glycidyl etheroxypropyltrimethoxysilane solution (1:9 volume ratio of deionized water and ethanol), which is ultrasonically treated for 10 minutes before use to ensure complete dissolution. After 12 minutes of immersion, the substrate is removed and dried in a 90℃ oven for 30 minutes, forming a Si-O bonded layer on the surface.

[0039] Layered Coating: High-pressure airless spraying is used for layered coating. The nozzle diameter is 1.0 mm, and it is kept perpendicular to the substrate surface at 90 degrees. The bottom layer is coated with a functional slurry containing 80% copper foam powder, with a thickness of 0.08 mm and a spraying pressure of 0.4 MPa. The middle layer is coated with a functional slurry containing 5% nano silver powder, with a thickness of 0.07 mm and a spraying pressure of 0.3 MPa. The top layer is coated with a functional slurry containing 3% graphene, with a thickness of 0.07 mm and a spraying pressure of 0.2 MPa. During each coating, the nozzle is 175 mm away from the substrate, and the moving speed is 75 mm / s. After coating, the substrate is pre-baked at 60℃, 70℃, and 80℃ for 10 minutes with an infrared lamp with a wavelength of 2-5 μm, and the infrared lamp irradiation distance is 300-500 mm. The thickness uniformity is checked using a laser thickness gauge, and the deviation is controlled within ±3%.

[0040] Stepped sintering: The coated substrate is placed in an atmosphere sintering furnace, and 99.999% pure nitrogen gas is introduced, with a dew point of -45℃. In the first stage, the temperature is increased to 135℃ at a rate of 3℃ / min, with a nitrogen flow rate of 1.2L / min, and held for 1.5 hours to allow complete solvent evaporation. In the second stage, the temperature is increased to 225℃ at a rate of 5℃ / min, with a nitrogen flow rate of 1.0L / min, and held for 2.5 hours to promote epoxy resin curing. In the third stage, the temperature is increased to 325℃ at a rate of 2℃ / min, with a nitrogen flow rate of 0.8L / min, and held for 1.2 hours to strengthen interfacial chemical bonding. The furnace pressure is maintained at a slightly positive pressure of 75Pa, and the substrate is allowed to cool naturally to room temperature.

[0041] Composite surface treatment: First, the sintered shielding layer is immersed in a 12% sulfuric acid solution at 30℃ for 4 minutes to roughen the surface, and then rinsed with deionized water until neutral. The surface roughness is tested using an eddy current flaw detector to ensure Ra 2.4μm is achieved. Then, nickel-cobalt alloy electrodeposition is performed. The electrolyte contains 225g / L nickel sulfate and 40g / L cobalt sulfate, with a current density of 2A / dm², a temperature of 45℃, and a pH of 3.5. Mechanical stirring is used at a rate of 300-500r / min. During deposition, the electrolyte composition is checked every 30 minutes, and consumed metal ions are replenished. The deposition thickness is 0.035mm. Finally, the layer is immersed in a 0.8% silane solution at 25℃ for 5 minutes, and then dried at 80℃ to form a sealing layer with a film thickness controlled at 2μm.

[0042] Shielding effectiveness optimization: Magnetron sputtering was performed on the surface of the shielding structure after composite surface treatment. The target material was a copper-graphene composite target with a graphene content of 8%. The sputtering power was 250W, 99.99% pure argon gas was introduced, the working pressure was 0.8Pa, and the sputtering time was 7 minutes, forming a copper-graphene composite layer with a thickness of 0.8μm. Example

[0043] Preparation of functional slurry: The following components were weighed by weight percentage: 70% copper foam powder, 8% silver nanoparticles, 2% graphene, 3% carbon nanotubes, 0.5% lanthanide rare earth oxides, 1.5% titanate coupling agent, and 5% epoxy resin. The copper foam powder had a particle size of 50 μm and was anodized in 3% oxalic acid solution for 5 minutes to form a CuO nanoarray on the surface. The silver nanoparticles had a particle size of 20 nm. The carbon nanotubes had an aspect ratio of 50 and their walls were carboxylated. The raw materials were added to a planetary ball mill with anhydrous ethanol at a material-to-liquid ratio of 1:1.5 and milled for 30 minutes. During the process, the titanate coupling agent hydrolyzed and formed Ti-O-Ag bonds with the powder surface, thus obtaining the functional slurry.

[0044] Substrate gradient pretreatment: The aluminum alloy casing of the communication equipment is first sandblasted using 80-mesh alumina abrasive at a pressure of 0.3 MPa, achieving a surface roughness of Ra 3.2 μm. Residual abrasive is removed by purging with compressed air for 5 minutes, followed by plasma etching for 3 minutes. An argon-oxygen mixture (3:1 volume ratio) is introduced during etching at 100 W, maintaining a 50 mm distance between the electrode and the substrate. Subsequently, the substrate is immersed in a 5% γ-glycidyl etheroxypropyltrimethoxysilane solution (1:9 volume ratio of deionized water and ethanol), which is ultrasonically treated for 10 minutes before use to ensure complete dissolution. After 10 minutes of immersion, the substrate is removed and dried in an 80°C oven for 30 minutes, forming a Si-O bonded layer on the surface.

[0045] Layered Coating: High-pressure airless spraying is used for layered coating. The nozzle diameter is 0.8 mm, and it is kept perpendicular to the substrate surface at 90 degrees. The bottom layer is coated with a functional slurry containing 80% copper foam powder, with a thickness of 0.05 mm and a spraying pressure of 0.4 MPa. The middle layer is coated with a functional slurry containing 5% nano silver powder, with a thickness of 0.05 mm and a spraying pressure of 0.3 MPa. The top layer is coated with a functional slurry containing 3% graphene, with a thickness of 0.05 mm and a spraying pressure of 0.2 MPa. During each coating, the nozzle is 150 mm away from the substrate, and the moving speed is 50 mm / s. After coating, the substrate is pre-baked at 60℃, 70℃, and 80℃ for 10 minutes with an infrared lamp with a wavelength of 2-5 μm, and the infrared lamp irradiation distance is 300-500 mm. The thickness uniformity is checked using a laser thickness gauge, and the deviation is controlled within ±5%.

[0046] Stepped sintering: The coated substrate is placed in an atmosphere sintering furnace, and 99.999% pure nitrogen gas is introduced, with a dew point of -45℃. In the first stage, the temperature is increased to 120℃ at a rate of 3℃ / min, with a nitrogen flow rate of 1.2L / min, and held for 1 hour to allow complete solvent evaporation. In the second stage, the temperature is increased to 200℃ at a rate of 5℃ / min, with a nitrogen flow rate of 1.0L / min, and held for 2 hours to promote epoxy resin curing. In the third stage, the temperature is increased to 300℃ at a rate of 2℃ / min, with a nitrogen flow rate of 0.8L / min, and held for 1 hour to strengthen interfacial chemical bonding. The furnace pressure is maintained at a slightly positive pressure of 50Pa, and the substrate is allowed to cool naturally to room temperature.

[0047] Composite surface treatment: First, the sintered shielding layer is immersed in a 10% sulfuric acid solution at 30°C for 3 minutes to roughen the surface, and then rinsed with deionized water until neutral. The surface roughness is tested using an eddy current flaw detector to ensure Ra 1.6 μm. Then, nickel-cobalt alloy electrodeposition is performed. The electrolyte contains 200 g / L nickel sulfate and 30 g / L cobalt sulfate, with a current density of 1 A / dm², a temperature of 40°C, and a pH of 3. Mechanical stirring is used at a rate of 300-500 r / min. During deposition, the electrolyte composition is checked every 30 minutes, and consumed metal ions are replenished. The deposition thickness is 0.02 mm. Finally, the layer is immersed in a 0.5% silane solution at 25°C for 5 minutes, and then dried at 80°C to form a sealing layer with a film thickness controlled at 1 μm.

[0048] Shielding effectiveness optimization: Magnetron sputtering was performed on the surface of the shielding structure after composite surface treatment. The target material was a copper-graphene composite target with a graphene content of 8%. The sputtering power was 200W, 99.99% pure argon gas was introduced, the working pressure was 0.5Pa, and the sputtering time was 5 minutes, forming a copper-graphene composite layer with a thickness of 0.5μm. Example

[0049] Preparation of functional slurry: The following components were weighed by weight percentage: 80% copper foam powder, 5% silver nanoparticles, 4% graphene, 1% carbon nanotubes, 1% lanthanide rare earth oxides, 0.5% titanate coupling agent, and 8.5% epoxy resin. The copper foam powder had a particle size of 100 μm and was anodized in 5% oxalic acid solution for 8 minutes to form a CuO nanoarray on the surface. The silver nanoparticles had a particle size of 50 nm. The carbon nanotubes had an aspect ratio of 100 and their walls were carboxylated. The raw materials were added to a planetary ball mill with anhydrous ethanol at a material-to-liquid ratio of 1:1.5 and milled for 60 minutes. During the process, the titanate coupling agent hydrolyzed, forming Ti-O-Ag bonds with the powder surface, thus obtaining the functional slurry.

[0050] Substrate gradient pretreatment: The aluminum alloy casing of the communication equipment is first sandblasted using 120-mesh alumina abrasive at a pressure of 0.5 MPa, achieving a surface roughness of Ra 6.3 μm. Residual abrasive is removed by purging with compressed air for 5 minutes, followed by plasma etching for 5 minutes. An argon-oxygen mixture (3:1 volume ratio) is introduced during etching at a power of 150 W, maintaining an 80 mm distance between the electrode and the substrate. Subsequently, the substrate is immersed in an 8% γ-glycidyl etheroxypropyltrimethoxysilane solution (1:9 volume ratio of deionized water and ethanol), which is ultrasonically treated for 10 minutes before use to ensure complete dissolution. After immersion for 15 minutes, the substrate is removed and dried in a 100℃ oven for 30 minutes, forming a Si-O bonded layer on the surface.

[0051] Layered Coating: High-pressure airless spraying is used for layered coating. The nozzle diameter is 1.2 mm, and it is kept perpendicular to the substrate surface at 90 degrees. The bottom layer is coated with a functional slurry containing 80% copper foam powder, with a thickness of 0.1 mm and a spraying pressure of 0.4 MPa. The middle layer is coated with a functional slurry containing 5% nano silver powder, with a thickness of 0.1 mm and a spraying pressure of 0.3 MPa. The top layer is coated with a functional slurry containing 3% graphene, with a thickness of 0.1 mm and a spraying pressure of 0.2 MPa. During each coating, the nozzle is 200 mm away from the substrate, and the moving speed is 100 mm / s. After coating, the substrate is pre-baked at 60℃, 70℃, and 80℃ for 10 minutes with an infrared lamp with a wavelength of 2-5 μm, and the infrared lamp irradiation distance is 300-500 mm. The thickness uniformity is checked using a laser thickness gauge, and the deviation is controlled within ±4%.

[0052] Stepped sintering: The coated substrate is placed in an atmosphere sintering furnace, and 99.999% pure nitrogen gas is introduced, with a dew point of -45℃. In the first stage, the temperature is increased to 150℃ at a rate of 3℃ / min, with a nitrogen flow rate of 1.2L / min, and held for 2 hours to allow complete solvent evaporation. In the second stage, the temperature is increased to 250℃ at a rate of 5℃ / min, with a nitrogen flow rate of 1.0L / min, and held for 3 hours to promote epoxy resin curing. In the third stage, the temperature is increased to 350℃ at a rate of 2℃ / min, with a nitrogen flow rate of 0.8L / min, and held for 1.5 hours to strengthen interfacial chemical bonding. The furnace pressure is maintained at a slightly positive pressure of 100Pa, and the substrate is allowed to cool naturally to room temperature.

[0053] Composite surface treatment: First, the sintered shielding layer is immersed in a 15% sulfuric acid solution at 30°C for 5 minutes to roughen the surface, and then rinsed with deionized water until neutral. The surface roughness is tested using an eddy current flaw detector to ensure Ra 3.2μm is achieved. Then, nickel-cobalt alloy electrodeposition is performed. The electrolyte contains 250g / L nickel sulfate and 50g / L cobalt sulfate, with a current density of 3A / dm², a temperature of 50°C, and a pH of 4. Mechanical stirring is used at a rate of 300-500 r / min. During deposition, the electrolyte composition is checked every 30 minutes, and consumed metal ions are replenished. The deposition thickness is 0.05mm. Finally, the layer is immersed in a 1% silane solution at 25°C for 5 minutes, and then dried at 80°C to form a sealing layer with a film thickness controlled at 3μm.

[0054] Shielding effectiveness optimization: Magnetron sputtering was performed on the surface of the shielding structure after composite surface treatment. The target material was a copper-graphene composite target with a graphene content of 8%. The sputtering power was 300W, 99.99% pure argon gas was introduced, the working pressure was 1Pa, and the sputtering time was 10 minutes to form a copper-graphene composite layer with a thickness of 1μm.

[0055] Comparative Example

[0056] Traditional process: 85% copper foam powder, 10% nano silver powder, and 5% epoxy resin are weighed by weight, and anhydrous ethanol is added. The mixture is then ground for 45 minutes to obtain a slurry. The aluminum alloy casing of the communication equipment undergoes only sandblasting to a roughness of Ra 4.8μm, followed by direct single-layer spraying of a 0.22mm slurry at a pressure of 0.3MPa, and pre-baking at 80℃ for 30 minutes. Sintering is then performed at a constant temperature of 250℃ for 3 hours in a nitrogen atmosphere with no stepped temperature control. The surface is then only nickel-plated to a thickness of 0.035mm, without silane sealing or magnetron sputtering steps. The communication equipment uses an integrated shielding cover, with conductive adhesive sealing the edges.

[0057] The shielding performance of the examples and comparative examples is compared in the table below:

[0058] Table 1

[0059]

[0060] The following table compares the performance and process economy indicators of sludge carbon application in the examples and comparative examples:

[0061] Table 2

[0062]

[0063] The following table compares the shielding effectiveness attenuation at different frequencies between the examples and the comparative examples:

[0064] Table 3

[0065]

[0066] The data from the three tables show that the conductive foam copper electromagnetic shielding structure prepared by the process described in this invention significantly outperforms products prepared by traditional processes in all core performance aspects. Regarding shielding performance, the embodiment achieves a shielding effectiveness of 90-100dB in the 100MHz-18GHz frequency band and 85-95dB in the 18-40GHz high-frequency band, with a surface resistivity as low as 0.01-0.03Ω / sq. Furthermore, after 50 180° bends, the effectiveness decreases by only 1-3dB, far exceeding the shielding effectiveness, surface resistivity, and bending attenuation of the comparative example. In terms of structural and environmental performance, the embodiment exhibits higher bonding strength and thermal conductivity, with a salt spray resistance time of 600-800 hours. After 1000 hours in an 85℃ / 85% humidity environment, the performance retention rate exceeds 95%, significantly lower than the corresponding indicators of the comparative example. Regarding frequency adaptability, the embodiment shows an attenuation rate of only 1.0%-3.2% across the entire 1-40GHz frequency band, compared to 5.8%-12.3% for the comparative example, with a particularly pronounced advantage in the high-frequency band. Furthermore, the ability to precisely control performance through adjustments to process parameters between examples further demonstrates the superiority and practicality of this preparation process.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for fabricating an electromagnetic shielding structure using conductive copper foam in communication equipment, characterized in that, Includes the following steps: S1, Preparation of functional slurry: Weigh the raw materials according to the following weight percentages: 70-80% copper foam powder, 5-8% nano silver powder, 2-4% graphene, 1-3% carbon nanotubes, 0.5-1% lanthanide rare earth oxides, 0.5-1.5% titanate coupling agent, and 3-6% epoxy resin; wherein the copper foam powder is anodized with oxalic acid solution, and the walls of the carbon nanotubes are carboxylated; place the raw materials into a planetary ball mill, add anhydrous ethanol as a dispersion medium, and grind to obtain a uniformly dispersed functional slurry; S2, Substrate gradient pretreatment: The communication equipment housing is made of aluminum alloy. First, it is sandblasted, then plasma etched, and a mixture of argon and oxygen is introduced. Then, it is immersed in 5-8% silane solution. The silane is γ-glycidyl etheroxypropyltrimethoxysilane. After immersion for 10-15 minutes, it is taken out and dried, and a Si-O bond connection layer is formed on the surface. S3, Layered Coating Molding: Layered coating is performed using high-pressure airless spraying; the bottom layer is coated with a functional slurry containing 80% copper foam powder; the middle layer is coated with a functional slurry containing 5% nano silver powder; the top layer is coated with a functional slurry containing 3% graphene; after coating, it is pre-baked in the infrared at 60℃, 70℃, and 80℃ for 10 minutes respectively. S4, Stepped sintering: Place the coated substrate into an atmosphere sintering furnace and purge with nitrogen; heat to 120-150℃ and hold for 1-2 hours; then heat to 200-250℃ and hold for 2-3 hours to promote epoxy resin curing; finally heat to 300-350℃ and hold for 1-1.5 hours to strengthen interfacial chemical bonding, and allow to cool naturally to room temperature; S5, Composite Surface Treatment: First, immerse the sintered shielding layer in a 10-15% sulfuric acid solution at 30°C for surface roughening, and then rinse with deionized water until neutral; then perform nickel-cobalt alloy electrodeposition; finally, immerse in a 0.5-1% silane solution at 25°C for 5 minutes, and dry at 80°C to form a sealing layer, thus obtaining the electromagnetic shielding structure.

2. The fabrication process of the conductive copper foam electromagnetic shielding structure in communication equipment according to claim 1, characterized in that, It also includes surface modification treatment of the copper foam powder in S1 before use. The copper foam powder is immersed in a 3-5% oxalic acid solution and anodized for 5-8 minutes using a DC voltage of 10-15V to form a uniformly distributed CuO nano array on the surface. The particle size of the treated copper foam powder is controlled at 50-100μm, the particle size of the nano silver powder is 20-50nm, and the aspect ratio of the carbon nanotubes is 50-100.

3. The fabrication process of the electromagnetic shielding structure of conductive copper foam in communication equipment according to claim 1, characterized in that, This also includes removing residual abrasive from the surface by blowing with compressed air for 5 minutes after sandblasting in S2, maintaining a distance of 50-80mm between the electrode and the substrate during plasma etching, and using a mixture of deionized water and ethanol as the solvent in the preparation of the silane solution at a volume ratio of 1:9, and ultrasonically treating it for 10 minutes before use to ensure complete dissolution.

4. The fabrication process of the electromagnetic shielding structure of conductive copper foam in communication equipment according to claim 1, characterized in that, The nozzle diameter of the S3 medium-high pressure airless spraying equipment is 0.8-1.2mm. The spraying angle is kept at 90 degrees perpendicular to the substrate surface. After each layer is coated, a laser thickness gauge is used to check the thickness uniformity, and the deviation is controlled within ±5%. Infrared drying uses infrared lamps with a wavelength of 2-5μm and an irradiation distance of 300-500mm.

5. The fabrication process of the conductive copper foam electromagnetic shielding structure in communication equipment according to claim 1, characterized in that, The three temperature stages of the stepped sintering in S4 correspond to the three key processes of solvent evaporation, resin curing, and interfacial reaction. The nitrogen flow rate is adjusted at different stages: 1.2 L / min at 120-150℃, 1.0 L / min at 200-250℃, and 0.8 L / min at 300-350℃. The pressure inside the furnace is maintained at a slightly positive pressure of 50-100 Pa.

6. The fabrication process of the conductive copper foam electromagnetic shielding structure in communication equipment according to claim 1, characterized in that, After roughening treatment with sulfuric acid solution in S5, the surface roughness is tested with an eddy current flaw detector to ensure that it reaches Ra1.6-3.2μm. During nickel-cobalt alloy electrodeposition, mechanical stirring at a stirring rate of 300-500r / min is used. During the deposition process, the electrolyte composition is checked every 30 minutes and the consumed metal ions are replenished. The thickness of the film layer formed after silane sealing treatment is controlled at 1-3μm.

7. The fabrication process of the electromagnetic shielding structure of conductive copper foam in communication equipment according to claim 1, characterized in that, It also includes S6. Shielding effectiveness optimization: magnetron sputtering is performed on the surface of the shielding structure after composite surface treatment. The target material is a copper-graphene composite target with a graphene content of 5-8%, the sputtering power is 200-300W, 99.99% pure argon gas is introduced, the working pressure is 0.5-1Pa, the sputtering time is 5-10 minutes, and a copper-graphene composite layer with a thickness of 0.5-1μm is formed.

8. The fabrication process of the electromagnetic shielding structure of conductive copper foam in communication equipment according to claim 1, characterized in that, The electromagnetic shielding effectiveness of the shielding structure reaches 90-100dB in the 100MHz-18GHz frequency band and 85-95dB in the 18-40GHz high-frequency band, with a surface resistance of 0.01-0.03Ω / sq.

9. The fabrication process of the electromagnetic shielding structure of conductive copper foam in communication equipment according to claim 1, characterized in that, The bonding strength between the shielding structure and the substrate was measured to be 18-22 MPa through tensile testing, and the thermal conductivity was 200-230 W / (m·K). According to GB / T 10125, the salt spray test showed no corrosion after 600-800 hours. After being placed in an environment of 85℃ and 85% relative humidity for 1000 hours, the retention rate of various performance indicators exceeded 95%.

10. A communication device with an electromagnetic shielding structure manufactured using the preparation process described in any one of claims 1-9, characterized in that, The device includes an aluminum alloy housing, a signal motherboard, and a modular shielding assembly. The shielding assembly is an electromagnetic shielding structure manufactured using the process described in any one of claims 1-9. It is divided into 3-5 independent shielding units based on the radio frequency module, power supply module, and signal processing module on the motherboard. Each unit has a conductive rubber boss with a semi-circular cross-section at its edge, with a boss diameter of 0.8-1.2 mm. The boss forms a tenon-and-mortise connection structure with the groove on the housing. The overall thickness of the shielding assembly is 0.3-0.5 mm, and its weight is 40-50% lighter than that of traditional metal shielding covers.

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