Electromagnetic shielding material and preparation process thereof

Abstract

The invention relates to the field of electromagnetic shielding materials, and particularly discloses an electromagnetic shielding material and a preparation process thereof.A titanium roller with specific roughness is used as a cathode roller, nickel foil with a certain rough morphology is directly prepared, and after plasma treatment, the nickel foil is directly compounded with PAI / PI, so that the electromagnetic shielding material is obtained. The prepared electromagnetic shielding material is ultrathin and has high strength and electromagnetic shielding performance at the same time, compared with an electromagnetic shielding material prepared by directly pasting a thermosetting adhesive in a metal foil and a high polymer material, the electromagnetic shielding material has higher high-temperature-resistant and flame-retardant effects, the temperature-resistant limitation of a glue composite hierarchical structure is avoided, and the instantaneous high temperature resistance can reach 280 DEG C.

Description

Technical Field

[0001] This application relates to the field of nickel foil composite electromagnetic shielding materials, and more specifically, it relates to an electromagnetic shielding material and its preparation process. Background Technology

[0002] With the rapid development of electronic devices towards higher frequencies, higher densities, higher integration, and wireless connectivity, electromagnetic interference problems are becoming increasingly prominent. Electromagnetic compatibility design has become a key aspect of ensuring stable and reliable operation of equipment, and lightweighting of electromagnetic shielding materials is one of the most direct and effective means of suppressing electromagnetic interference.

[0003] In applications such as SMT conductive pads, antenna / RF module shielding covers, I / O interfaces, slots, through-hole seals, and chassis / rack shielding, conductive cloth wrapped around conductive foam is often used as a lightweight electromagnetic shielding material to provide dual shielding of reflection and absorption. However, the electromagnetic shielding performance of conductive cloth composite electromagnetic shielding materials is limited. The thinnest traditional conductive cloth can only be controlled at 0.016-0.018mm, at which point the electromagnetic shielding effectiveness is usually only 59-68dB, which cannot meet the requirements for higher electromagnetic shielding performance. Because non-woven cloth contains plastic components, its recyclability is also insufficient compared to pure metal foil. The adhesive layer in the metal foil and polymer composite material made by thermosetting adhesive will fail at temperatures above 250°C, and may also cause delamination between the metal foil and the polymer layer. Moreover, the flame retardant effect is not good. Furthermore, conductive cloth is easily stretched and deformed during processing and use, further reducing the shielding effect.

[0004] The high reflectivity of nickel foil and the high absorption enhancement effect of PAI and PI make it a promising candidate for lightweight, ultrathin electromagnetic shielding materials. However, due to bottlenecks such as the preparation of ultrathin nickel foil and the control of the interfacial bonding strength and stability with PAI and PI, it has not yet been able to form a prominent competitive advantage in the field of electromagnetic shielding materials. Therefore, it is of great research value to provide an electromagnetic shielding material that has an ultrathin thickness, high mechanical strength, recyclability, and good electromagnetic shielding effect, while breaking through the temperature resistance limitations of the adhesive layer of traditional composite materials and being less prone to breakage or delamination failure during use. Summary of the Invention

[0005] In order to achieve high strength and high electromagnetic shielding effect of ultrathin electromagnetic shielding materials, this application provides an electromagnetic shielding material and its preparation process.

[0006] In a first aspect, this application provides a process for preparing an electromagnetic shielding material, comprising the following preparation steps: S1. Preprocessing: S1.1 Preparation of pretreated cathode rollers: Prepare pretreated titanium cathode rollers that have undergone electrolytic polishing and have a surface roughness of 0.25-0.45μm; S1.2 Electrolyte purification: The electrolyte is precision filtered through a pore size of ≤0.2μm to remove impurity ions Fe. 2+ <5ppm, Cu 2+ <10ppm, the electrolyte includes nickel aminosulfonate 240-260g / L, boric acid 35-45g / L, and stress reliever 0.01-1.0g / L; S2. Electrolytic nickel foil production: Electrolytic nickel is used as the anode, and a pretreated titanium cathode roller is used as the cathode. The pretreated titanium cathode roller is rotated and electrolytically deposited in the electrolyte. Then, the nickel foil is washed with deionized water and dried to obtain nickel foil. The nickel foil includes a smooth surface and a rough surface. The side near the pretreated titanium cathode roller is rough surface with a roughness of 0.25-0.45 μm and a dyne value > 42. S3. Nickel foil pretreatment: The rough surface is subjected to plasma treatment to obtain pretreated nickel foil; S4. Coating: A 5-10 micrometer thick wet film of slurry is coated on the plasma-treated side of the pretreated nickel foil to obtain an intermediate nickel foil. The slurry includes one or more of PAI slurry or PI slurry with a solid content of 20-30 wt%. S5. Thermal curing: Electromagnetic shielding material is obtained by thermal curing intermediate nickel foil.

[0007] Preferably, the surface roughness is 0.30-0.40 μm.

[0008] This application innovatively utilizes a titanium roller with specific roughness as the cathode roller to directly prepare nickel foil with a certain rough morphology. By increasing the contact area between the nickel foil and the PAI / PI slurry, limiting the solid content of the slurry, and activating it through plasma treatment, a relatively tight bond is achieved between the nickel foil and the polymer layer. This avoids the thickness and high-temperature resistance limitations of traditional adhesives. The resulting nickel foil-polymer composite material has an ultra-thin structure. The nickel foil first reflects most of the electromagnetic waves, while the unreflected electromagnetic waves enter the polymer layer and are absorbed. The combination of the two avoids the problems of secondary radiation pollution caused by single reflection or insufficient absorption efficiency. At the same time, there is no delamination between the interfaces, resulting in stable shielding performance. By precisely limiting the roughness, the nickel foil achieves both good interface bonding and high mechanical stability and electromagnetic reflection effect. The above preparation process is simple. By adjusting the process parameters, various specifications such as 6 μm nickel foil + 6 μm PAI, 4+6, 4+4, and 6+18 can be produced. The resulting ultra-thin electromagnetic shielding material has high strength and high electromagnetic shielding effect.

[0009] Preferably, the electrolysis current density in S2 is 14-22 A / dm³. 2 The cathode roller speed is 8-10 r / min, the electrolyte temperature is 48-52℃, and the pH value is 3.8-4.2.

[0010] At this point, the deposition rate is neither too low nor too high, which would cause uneven distribution of surface current. The nickel atoms are arranged more densely, reducing porosity and lowering electromagnetic wave transmission.

[0011] Preferably, the coating in S4 includes gravure coating, which is performed using a 40-60 mesh anilox roller.

[0012] By using micro-gravure coating and a specific mesh anilox roller, the amount of slurry transferred is precisely controlled, avoiding localized slurry accumulation or missed coating caused by the rough surface of the nickel foil. This achieves uniform PAI / PI wet film thickness without bubbles, providing a matrix foundation for the effective dispersion of conductive fillers.

[0013] Preferably, the slurry in S4 includes a PAI slurry with a solid content of 20-30 wt%, wherein the PAI slurry comprises the following raw materials in the following mass ratio: 20-24 wt% PAI, 0.1-0.7 wt% aminosilane coupling agent, 0.1-0.3 wt% polydimethylsiloxane, 2-4 wt% conductive filler, and the balance being a mixed solvent of N-methylpyrrolidone and dimethylformamide in a volume ratio of 7:(2.5-3.5).

[0014] This application provides a specific PAI slurry configuration that achieves high adhesion, high flexibility, and low internal stress in the PAI layer. The conductive filler is stably dispersed, and after curing, it forms a high-strength film that supports the conductive filler without easily cracking. Simultaneously, its polar groups can combine with the surface-active groups of the nickel foil, enhancing interlayer adhesion. The amino and siloxane bonds at both ends of the aminosilane coupling agent molecule act as molecular bridges between the nickel foil and the PAI layer, further improving interfacial bonding. Low-molecular-weight PDMS fills the gaps between the PAI molecular chains, reducing internal stress during thermosetting and preventing PAI layer cracking, while also improving material flexibility. The product can be further coated with conductive foam for use. PAI provides the strength and adhesion foundation, the coupling agent strengthens the interfacial bond, and PDMS optimizes toughness. The combined effect of these three factors effectively solves the problems of easy cracking of the polymer layer and easy peeling from the nickel foil.

[0015] Preferably, the plasma treatment in S3 includes the following preparation steps: first, treatment with a power of 600-800W for 2-4 minutes, with a gas volume ratio of Ar:O2 = 4:1, and then treatment with an ammonia atmosphere of 200-300W for 1-2 minutes.

[0016] The above steps involve a two-stage plasma treatment. First, high-energy particles are used to etch the rough surface of the nickel foil, enriching the microscopic depressions. Simultaneously, oxygen-containing active groups are introduced onto the nickel foil surface, enhancing surface polarity and further increasing the dyne value to >50, thus improving wettability with PAI slurry. Further ammonia plasma treatment introduces active amino groups onto the nickel foil surface, forming hydrogen bonds with the imide bonds of PAI, further strengthening interfacial bonding.

[0017] Preferably, the conductive filler is a carboxylated modified conductive filler, and the preparation steps include: adding the conductive filler and carboxysilane coupling agent to an ethanol aqueous solution, dispersing them evenly, heating to react, filtering, washing, and drying to obtain the carboxylated modified conductive filler.

[0018] By modifying the conductive filler with carboxylation, the conductive filler is not only more uniformly distributed and more tightly bonded to the PAI matrix, but the carboxyl groups may also react with the amino groups in the PAI system and the active amino groups on the surface of the nickel foil during the thermosetting process, which further improves the interfacial bonding strength and the stability of dielectric loss. The resulting electromagnetic shielding material exhibits better performance.

[0019] Preferably, the conductive filler comprises nano-silver powder, MXene, and rGO in a mass ratio of (2-3):(1-2):1, wherein the nano-silver powder has a particle size of 20-50 nm, the MXene has a sheet size of 10-100 nm, and the rGO has a specific surface area of ​​500-700 m². 2 / g.

[0020] Nano-silver powder has extremely high conductivity, which can quickly form the main conductive pathway and reduce the percolation threshold of the conductive network. MXene has a certain layered structure, with abundant hydroxyl / fluorine groups on the surface and a high dielectric constant. It can consume electromagnetic wave energy through interlayer polarization and interfacial polarization. At the same time, the layered structure can block some electromagnetic waves and assist in reflection. The rGO sheet structure has a large specific surface area, which can load more nano-silver powder / MXene and reduce agglomeration. Meanwhile, surface defects can enhance dipole polarization, and the sheet structure can form a maze effect, prolonging the propagation path of electromagnetic waves inside the material. This further limits the type, size and mass ratio of conductive fillers. Preferably, the thermosetting in S5 includes the following steps: hot air tunnel curing, with a tunnel temperature of 110-150℃, a total tunnel length of 5-8m, and a speed of 1-2m / min.

[0021] By adopting the above-mentioned curing process, the low temperature of the first temperature zone pre-evaporates the solvent to avoid the generation of bubbles, and the high temperature of the second temperature zone promotes the cross-linking of PAI, achieving densification, uniform shrinkage, and sufficient curing, which is suitable for the setting of PAI slurry in this application. After curing, the different conductive fillers in the system have suitable settling speeds, which can form a stable continuous network structure and are tightly bonded to the PAI matrix, ensuring the stability of absorption performance.

[0022] Preferably, the coating speed during the coating process is 1.5±0.2m / min, the doctor blade angle is 35±5°, and the coating pressure is 0.15±0.02MPa.

[0023] Through the above-described process, the slurry forms a uniform liquid film on the nickel foil surface after coating, ensuring that the coating adheres to the rough surface of the nickel foil. Simultaneously, the conductive fillers nano-silver powder, MXene, and rGO used in this application exhibit different settling velocities without compressing the already settled conductive fillers. After electromagnetic waves are incident, they may form the following path: first reflected by the nickel foil, then reflected sequentially by MXene and rGO, absorbed by the dielectric polarization of nano-silver powder and MXene, and then dissipated through multiple reflections and heat. The resulting electromagnetic shielding material exhibits better electromagnetic shielding performance. Furthermore, due to the formation of a strength structure with a certain gradient after settling, the stress distribution under stress is more reasonable, resulting in better strength performance.

[0024] Preferably, the pretreatment of the titanium cathode roller includes the following pretreatment steps: electrolytic polishing, with a treatment temperature of 50-60℃ and a current density of 12-15A / dm³. 2 Polishing time is 10-15 minutes, followed by washing and drying. Then, the surface is polished to a roughness of 0.30μm-0.40μm to obtain a pretreated titanium cathode roller.

[0025] The pretreated titanium cathode roller has a suitable surface roughness, which effectively improves the surface roughness of the prepared metal foil, thus facilitating better bonding of the metal foil.

[0026] Secondly, this application provides an electromagnetic shielding material, prepared using the above-mentioned process, comprising a nickel foil layer and a polymer material layer, wherein the nickel foil layer and the polymer material layer form a two-layer thin film structure, and the polymer material layer comprises one or more of a PAI layer or a PI layer.

[0027] By using a titanium roller with a specific roughness as the cathode roller, nickel foil with a certain rough morphology is directly prepared. After plasma treatment, it is directly composited with PAI / PI. The resulting electromagnetic shielding material is ultra-thin while having high strength and electromagnetic shielding performance. It avoids the temperature resistance limitation of glue composite layer structure and can withstand instantaneous high temperature up to 280℃.

[0028] Thirdly, this application provides an electromagnetic shielding multilayer composite material, including a foam layer and an electromagnetic shielding material layer, wherein the foam layer and the electromagnetic shielding material layer are bonded together by conductive adhesive, and the electromagnetic shielding material layer includes the aforementioned electromagnetic shielding material.

[0029] Preferably, the electromagnetic shielding material is wrapped around the outside of the foam layer, and the side of the electromagnetic shielding material coated with PI / PAI paste is close to the foam side.

[0030] By combining the electromagnetic shielding material obtained in this application with foam to prepare a multilayer composite material, especially by coating the electromagnetic shielding material on the outside of the foam layer, the electromagnetic shielding effect is further improved through the multilayer structure. At the same time, it has good applicability for scenarios requiring lightweight filling performance of electromagnetic shielding materials. Compared with the traditional preparation method of coating the foam with conductive cloth, this avoids the reduction in shielding effect caused by the conductive cloth being easily stretched and deformed during processing and use. The electromagnetic shielding performance of the resulting multilayer composite material is more stable.

[0031] In summary, this application has the following beneficial effects: This application provides a process for preparing an electromagnetic shielding material. By using a titanium roller with a specific roughness as the cathode roller, a nickel foil with a certain rough morphology is directly prepared. After plasma treatment, it is directly composited with PAI / PI. The resulting electromagnetic shielding material is ultra-thin while having high strength and electromagnetic shielding performance. It avoids the temperature resistance limitation of glue composite layer structure and can withstand instantaneous high temperature up to 280℃.

[0032] This application further optimizes the plasma treatment process to introduce a large number of active groups that form physical and chemical connections with the conductive fillers in the PAI system, resulting in high interfacial connection strength. By limiting the process parameters of the thermosetting and coating processes, the transmission path of electromagnetic waves after entry and the combination of electromagnetic shielding effect are further optimized, resulting in electromagnetic shielding material with better electromagnetic shielding performance.

[0033] By providing an electromagnetic shielding multilayer composite material, a lightweight electromagnetic shielding multilayer composite material with more stable performance and filling function is provided, avoiding the limitation of the traditional conductive cloth covering foam processing pulling that reduces the shielding effect. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the electromagnetic shielding material structure obtained in this application.

[0035] Figure 2 This is a schematic diagram of the electromagnetic shielding multilayer composite material structure obtained in this application.

[0036] Figure 3 This is a schematic diagram of the pretreated titanium cathode roller structure used in the preparation process of this application.

[0037] Explanation of reference numerals in the attached figures: 1. Roller body; 11. Shaft; 12. Bearing. Detailed Implementation

[0038] To further aid in understanding the technical solution of the present invention, several specific embodiments are provided to describe the technical solution of the present invention in more detail. All described embodiments are only some embodiments of the present invention, not all of them; embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The following embodiments are further illustrations of the present invention, but the present invention is not limited thereto.

[0039] The raw materials used in the embodiments and preparation examples of this application are all conventional commercially available brands, or can be obtained according to conventional processes.

[0040] PAI was purchased from Yuanye T25305; polydimethylsiloxane was purchased from Ecosol / Yousuo 350CS; nano silver powder was purchased from Shanghai Chaowei Nano CW-Ag-001; MXene was purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd. XFDZ12; rGO was purchased from Shanghai Najiu Intelligent Technology Co., Ltd. NJ-rGO-1000-p0; foam was Kanglida SMD-G-KLD-1.8-2-2-F; conductive cloth was Kanglida copper-nickel conductive cloth; conductive adhesive was purchased from Shanghai Tengshuo Electronic Materials Co., Ltd. TS-0220F.

[0041] Preparation Example 17.8 g of allyltrimethoxysilane was dispersed in 200 ml of methanol, and 2 g of sodium hydroxide was added to adjust the pH to 8-9. Then, 600 ml of 5 wt% KMnO4 aqueous solution was slowly added dropwise over 30 minutes. The mixture was heated to 45 ± 2 °C and stirred for 3.5 hours. 12.6 g of sodium sulfite was slowly added and stirred for 15 minutes. The filtrate was collected by suction filtration, and concentrated hydrochloric acid was added dropwise until the pH reached 2-3. The acidified filtrate was then extracted with 50 g of ethyl acetate and allowed to stand for separation. The upper organic phase was collected. The extraction was repeated twice, and the organic phases were combined. 10 g of anhydrous sodium sulfate was added to the organic phase, and the mixture was allowed to stand and dry for 2 hours until the solution was clear. The sodium sulfate was removed by filtration, and the filtrate was transferred to a rotary evaporator and distilled under reduced pressure at 90 °C / 1 kPa to obtain the carboxysilane coupling agent.

[0042] Add 5g of nano silver powder and 1g of carboxysilane coupling agent to 100ml of 50vt% ethanol aqueous solution, disperse evenly, heat at 60℃ for 4 hours, filter, wash with deionized water, and dry to obtain carboxylated modified nano silver powder.

[0043] Add 5g of MXene and 1g of carboxysilane coupling agent to 100ml of 50vt% ethanol aqueous solution, disperse evenly, heat at 60℃ for 4 hours, filter, wash with deionized water, and dry to obtain carboxylated modified MXene.

[0044] 5g g rGO and 1g carboxysilane coupling agent were added to 100ml of 50vt% ethanol aqueous solution, dispersed evenly, heated at 60℃ for 4 hours, filtered, washed with deionized water, and dried to obtain carboxylated modified rGO. Example

[0045] Example 1: S1. Preprocessing: S1.1 Preparation of Pretreated Cathode Roller: Prepare a pretreated titanium cathode roller with a surface roughness of 0.30 μm after electrolytic polishing. Electrolytic polishing conditions: temperature 60℃, current density 15 A / dm³. 2 The polishing time is 15 minutes. After polishing, the surface is rinsed with deionized water 3 times and then dried with nitrogen. Then, it is polished with 8000-mesh diamond cloth until the surface roughness is 0.30μm to obtain a pretreated titanium cathode roller. S1.2 Electrolyte purification: The electrolyte is precision filtered through a pore size of ≤0.2μm to remove impurity ions Fe. 2+ <5ppm, Cu 2+ <10ppm, the electrolyte contains nickel sulfamate 250g / L, boric acid 40g / L, sodium saccharin 0.3g / L, and water as the solvent; S2. Electrolytic nickel foil production: Electrolytic nickel is used as the anode, and a pretreated titanium cathode roller is used as the cathode. The pretreated titanium cathode roller is rotated in the electrolyte for electrolytic deposition. The electrolytic current density is 18 A / dm³. 2 The cathode roller rotates at 8 r / min, the electrolyte temperature is 50℃, and the pH value is 4. Then, the nickel foil is obtained by washing with deionized water and drying. The nickel foil includes a smooth surface and a rough surface. The side near the pretreated titanium cathode roller is rough, with a roughness of 0.30 μm and a dyne value of >42. S3. Nickel foil pretreatment: The rough surface is subjected to plasma treatment to obtain pretreated nickel foil. First, it is treated at 800W for 3 minutes with a gas volume ratio of Ar:O2 = 4:1, and then treated at 300W in an ammonia atmosphere for 1 minute. S4. Coating: An 8-micrometer thick PAI slurry wet film is micro-grooved onto the plasma-treated side of the pretreated nickel foil to obtain an intermediate nickel foil. During the coating process, the coating speed is 1.5±0.2m / min, the doctor blade angle is 35°, and the coating pressure is 0.15±0.02MPa. The slurry is prepared by uniformly mixing the following raw materials by weight: 20g PAI, 0.5g aminosilane coupling agent KH792, 0.2g polydimethylsiloxane, 2g carboxylated modified nano silver powder prepared in the preparation example, 1g carboxylated modified MXene prepared in the preparation example, and 1g carboxylated modified rGO prepared in the preparation example. The balance is a total of 74.3ml of N-methylpyrrolidone and dimethylformamide mixed solvent in a volume ratio of 7:3. S5. Thermal curing: The intermediate nickel foil is cured in a hot air drying tunnel with a temperature of 140℃, a total tunnel length of 6m, and a speed of 1m / min to obtain the electromagnetic shielding material.

[0046] Example 2 The only difference between this embodiment and Example 1 is that the PAI slurry is prepared by uniformly mixing the following raw materials: 20g PAI, 0.2g polydimethylsiloxane, 2g nano silver powder, 1g MXene and 1g rGO, with the remainder being a total of 74.3ml of N-methylpyrrolidone and dimethylformamide mixed solvent in a volume ratio of 7:3.

[0047] Example 3 The only difference between this embodiment and Embodiment 1 is that the plasma treatment preparation steps are as follows: 800W power for 3 minutes, gas volume ratio Ar:O2 = 4:1.

[0048] Example 4 The only difference between this embodiment and Embodiment 1 is that the coating speed during the coating process is 1.5±0.2m / min, the doctor blade angle is 35°, and the coating pressure is 0.25±0.02MPa. Example 5 The only difference between this embodiment and Embodiment 1 is that the coating speed during the coating process is 1.5±0.2 m / min, the doctor blade angle is 35°, and the coating pressure is 0.10±0.02 MPa. Example 6 The conductive fillers in the PAI slurry are 2g of nano silver powder, 1g of MXene, and 1g of rGO.

[0049] Example 7 The conductive fillers in the PAI slurry are 1g of carboxylated modified silver nanopowder prepared in the preparation example, 2g of carboxylated modified MXene prepared in the preparation example, and 1g of carboxylated modified rGO prepared in the preparation example.

[0050] Example 8 The electromagnetic shielding material prepared in Example 1 was coated with PAI paste on one side and then bonded to the outside of the foam with conductive adhesive to obtain a multilayer electromagnetic shielding composite material.

[0051] Comparative Example Comparative Example 1 S1. Preprocessing: S1.1 Preparation of Pretreated Cathode Roller: Prepare a pretreated titanium cathode roller with a surface roughness of 0.20 μm after electrolytic polishing. Electrolytic polishing conditions: temperature 60℃, current density 15A / dm³. 2The polishing time is 15 minutes. After polishing, the surface is rinsed with deionized water 3 times and then dried with nitrogen. Then, it is polished with 8000-mesh diamond cloth until the surface roughness is 0.20 μm to obtain a pretreated titanium cathode roller. S1.2 Electrolyte purification: The electrolyte is precision filtered through a pore size of ≤0.2μm to remove impurity ions Fe. 2+ <5ppm, Cu 2+ <10ppm, the electrolyte contains nickel sulfamate 250g / L, boric acid 40g / L, sodium saccharin 0.3g / L, and water as the solvent; S2. Electrolytic nickel foil production: Electrolytic nickel is used as the anode, and a pretreated titanium cathode roller is used as the cathode. The pretreated titanium cathode roller is rotated in the electrolyte for electrolytic deposition. The electrolytic current density is 18 A / dm³. 2 The cathode roller rotates at 8 r / min, the electrolyte temperature is 50℃, and the pH value is 4. Then, the nickel foil is washed with deionized water and dried to obtain a nickel foil. The nickel foil includes a smooth surface and a rough surface. The side near the pretreated titanium cathode roller is rough surface with a roughness of 0.20 μm. S3. Nickel foil pretreatment: The rough surface is subjected to plasma treatment to obtain pretreated nickel foil. First, it is treated with 800W power for 3 minutes, with a gas volume ratio of Ar:O2 = 4:1 and a treatment distance of 10mm. Then, it is treated with 300W power in an ammonia atmosphere for 1 minute and a treatment distance of 10mm. S4. Coating: An 8-micrometer thick PAI slurry wet film is micro-grooved onto the plasma-treated side of the pretreated nickel foil to obtain an intermediate nickel foil. During the coating process, the coating speed is 1.5±0.2m / min, the doctor blade angle is 35°, and the coating pressure is 0.15±0.02MPa. The slurry is prepared by uniformly mixing the following raw materials by weight: 20g PAI, 0.5g aminosilane coupling agent KH792, 0.2g polydimethylsiloxane, 2g carboxylated modified nano silver powder prepared in the preparation example, 1g carboxylated modified MXene prepared in the preparation example, and 1g carboxylated modified rGO prepared in the preparation example. The balance is a total of 74.3ml of N-methylpyrrolidone and dimethylformamide mixed solvent in a volume ratio of 7:3. S5. Thermal curing: The intermediate nickel foil is cured in a hot air drying tunnel with a temperature of 140℃, a total tunnel length of 6m, and a speed of 1m / min to obtain the electromagnetic shielding material.

[0052] Comparative Example 2 S1. Preprocessing: S1.1 Preparation of Pretreated Cathode Roller: Prepare a pretreated titanium cathode roller with a surface roughness of 0.50 μm after electrolytic polishing. Electrolytic polishing conditions: temperature 60℃, current density 15A / dm³. 2The polishing time is 15 minutes. After polishing, the surface is rinsed with deionized water 3 times and then dried with nitrogen. Finally, it is polished with 8000-mesh diamond cloth until the surface roughness is 0.50 μm to obtain a pretreated titanium cathode roller. S1.2 Electrolyte purification: The electrolyte is precision filtered through a pore size of ≤0.2μm to remove impurity ions Fe. 2+ <5ppm, Cu 2+ <10ppm, the electrolyte contains nickel sulfamate 250g / L, boric acid 40g / L, sodium saccharin 0.3g / L, and water as the solvent; S2. Electrolytic nickel foil production: Electrolytic nickel is used as the anode, and a pretreated titanium cathode roller is used as the cathode. The pretreated titanium cathode roller is rotated in the electrolyte for electrolytic deposition. The electrolytic current density is 18 A / dm³. 2 The cathode roller rotates at 8 r / min, the electrolyte temperature is 50℃, and the pH value is 4. Then, the nickel foil is washed with deionized water and dried to obtain a nickel foil. The nickel foil includes a smooth surface and a rough surface. The side near the pretreated titanium cathode roller is rough surface with a roughness of 0.50 μm. S3. Nickel foil pretreatment: The rough surface is subjected to plasma treatment to obtain pretreated nickel foil. First, it is treated at 800W for 3 minutes with a gas volume ratio of Ar:O2 = 4:1, and then treated at 300W in an ammonia atmosphere for 1 minute. S4. Coating: An 8-micrometer thick PAI slurry wet film is micro-grooved onto the plasma-treated side of the pretreated nickel foil to obtain an intermediate nickel foil. During the coating process, the coating speed is 1.5±0.2m / min, the doctor blade angle is 35°, and the coating pressure is 0.15±0.02MPa. The slurry is prepared by uniformly mixing the following raw materials by weight: 20g PAI, 0.5g aminosilane coupling agent KH792, 0.2g polydimethylsiloxane, 2g carboxylated modified nano silver powder prepared in the preparation example, 1g carboxylated modified MXene prepared in the preparation example, and 1g carboxylated modified rGO prepared in the preparation example. The balance is a total of 74.3ml of N-methylpyrrolidone and dimethylformamide mixed solvent in a volume ratio of 7:3. S5. Thermal curing: The intermediate nickel foil is cured in a hot air drying tunnel with a temperature of 140℃, a total tunnel length of 6m, and a speed of 1m / min to obtain the electromagnetic shielding material.

[0053] Comparative Example 3 Electromagnetic shielding multilayer composite material is prepared by coating and bonding conductive cloth to the outside of foam with conductive adhesive.

[0054] Performance testing The electromagnetic shielding material was subjected to performance testing.

[0055] Test 1: Electromagnetic shielding effectiveness of 10MHz-10GHz was tested according to GJB 8820-2015 "Method for Measurement of Shielding Effectiveness of Electromagnetic Shielding Materials"; Test 2: Tensile strength was tested according to IPC-TM-650.

[0056] The test results are shown in Table 1.

[0057] Table 1 Test 3: The electromagnetic shielding effectiveness of the electromagnetic shielding multilayer composite materials prepared in Example 8 and Comparative Example 3 was tested according to GJB 8820-2015 "Method for Measurement of Shielding Effectiveness of Electromagnetic Shielding Materials" for 10MHz-10GHz. Test 4: Then, referring to IPC-TM-650 at 20 kgf / mm 2 The electromagnetic shielding multilayer composite material was repeatedly stretched 20 times under the tensile strength. The electromagnetic shielding effectiveness 2 of the electromagnetic shielding multilayer composite material under simulated processing conditions was obtained by repeated test 3. The shielding effectiveness reduction rate was calculated by referring to the formula: shielding effectiveness reduction rate = (electromagnetic shielding effectiveness 1 - electromagnetic shielding effectiveness 2) / electromagnetic shielding effectiveness 1 × 100%.

[0058] The test results are shown in Table 1.

[0059] Table 2 Shielding effectiveness 1 dB Shielding effectiveness reduction rate (%) Example 8 105.4 2.1 Comparative Example 3 65.7 12.0 Combining Examples 1-3, Comparative Examples 1-2, and Table 1, this application innovatively limits the titanium cathode roller to a certain roughness, allowing for the direct lamination of nickel foil after plasma treatment with a specially formulated PAI slurry. The resulting electromagnetic shielding material can achieve an ultra-thin thickness while possessing superior shielding effectiveness and tensile strength. Furthermore, the resulting electromagnetic shielding material shows no significant change in tensile and electromagnetic shielding properties after instantaneous heating to 280°C for 1-10 seconds, avoiding the temperature limitations of traditional adhesive-based composite layer structures.

[0060] In conjunction with Examples 1, 4-5 and Table 1, this application achieves a better gradient sedimentation effect of the components in the slurry by limiting the coating process and the thermosetting process, resulting in a more reasonable reflection and absorption network, uniform and sufficient curing, and the electromagnetic shielding material obtained has better performance.

[0061] In conjunction with Examples 1, 6-7 and Table 1, this application achieves a certain gradient of sedimentation by adding a certain mass ratio of conductive filler and modifying it with carboxylation, thereby further optimizing the interfacial bonding through a combination of physical and chemical effects.

[0062] In conjunction with Example 8, Comparative Example 3 and Table 2, this application obtains an ultra-thin, lightweight electromagnetic shielding material to replace the conductive cloth covering the outside of the foam, avoiding the decrease in surface conductivity and damage to the shielding path caused by repeated squeezing and stretching during the processing and use of the conductive cloth, resulting in a more stable shielding effect.

[0063] 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 preparation process for an electromagnetic shielding material, characterized in that, Includes the following steps: S1. Preprocessing: S1.1 Preparation of pretreated cathode roller: Prepare a pretreated titanium cathode roller that has been electrolytically polished and has a surface roughness of 0.25-0.45μm; S1.2 Electrolyte purification: The electrolyte is precisely filtered through a pore size of ≤0.2μm, with impurity ions Fe²⁺<5ppm and Cu²⁺<10ppm. The electrolyte includes nickel sulfamate 240-260g / L, boric acid 35-45g / L, and stress reliever 0.01-1.0g / L. S2. Electrolytic nickel foil production: Electrolytic nickel is used as the anode, and a pretreated titanium cathode roller is used as the cathode. The pretreated titanium cathode roller is rotated and electrolytically deposited in the electrolyte. Then, the nickel foil is washed with deionized water and dried to obtain nickel foil. The nickel foil includes a smooth surface and a rough surface. The side near the pretreated titanium cathode roller is rough surface with a roughness of 0.25-0.45 μm and a dyne value > 42. S3. Nickel foil pretreatment: The rough surface is subjected to plasma treatment to obtain pretreated nickel foil; S4. Coating: A 5-10 micrometer thick wet film of slurry is coated on the plasma-treated side of the pretreated nickel foil to obtain an intermediate nickel foil. The slurry includes one or more of PAI slurry or PI slurry with a solid content of 20-30 wt%. S5. Thermal curing: Electromagnetic shielding material is obtained by thermal curing intermediate nickel foil.

2. The preparation process of the electromagnetic shielding material according to claim 1, characterized in that, In S2, the electrolysis current density is 14-22 A / dm², the cathode roller speed is 8-10 r / min, the electrolyte temperature is 48-52℃, and the pH value is 3.8-4.

2.

3. The preparation process of the electromagnetic shielding material according to claim 1, characterized in that, The slurry in S4 includes PAI slurry with a solid content of 20-30 wt%. The PAI slurry includes the following raw materials in the following mass ratio: PAI 20-24 wt%, aminosilane coupling agent 0.1-0.7 wt%, polydimethylsiloxane 0.1-0.3 wt%, conductive filler 2-4 wt%, and the balance is a mixed solvent of N-methylpyrrolidone and dimethylformamide in a volume ratio of 7:(2.5-3.5).

4. The preparation process of the electromagnetic shielding material according to claim 1, characterized in that, The plasma treatment in S3 includes the following preparation steps: first, treatment with a power of 600-800W for 2-4 minutes, with a gas volume ratio of Ar:O2=4:1, and then treatment with an ammonia atmosphere of 200-300W for 1-2 minutes.

5. The preparation process of the electromagnetic shielding material according to claim 3, characterized in that, The conductive filler is a carboxyl-modified conductive filler, and the preparation steps include: adding the conductive filler and carboxylsilane coupling agent to an ethanol aqueous solution, dispersing them evenly, heating to react, filtering, washing, and drying to obtain the carboxyl-modified conductive filler.

6. The preparation process of the electromagnetic shielding material according to claim 3, characterized in that, The conductive filler comprises nano-silver powder, MXene, and rGO in a mass ratio of (2-3):(1-2):1, with the nano-silver powder having a particle size of 20-50 nm, the MXene having a sheet size of 10-100 nm, and the rGO having a specific surface area of ​​500-700 m² / g.

7. The preparation process of the electromagnetic shielding material according to claim 1, characterized in that, The coating process in S4 includes gravure coating, which is performed using a 40-60 mesh anilox roller. The coating speed during the coating process is 1.5±0.2m / min, the doctor blade angle is 35±5°, and the coating pressure is 0.15±0.02MPa.

8. The preparation process of the electromagnetic shielding material according to claim 1, characterized in that, The pretreated titanium cathode roller includes the following pretreatment steps: electrolytic polishing, treatment temperature 50-60℃, current density 12-15A / dm², polishing time 10-15min, water washing, drying, and then grinding to a surface roughness of 0.30μm-0.40μm to obtain the pretreated titanium cathode roller.

9. An electromagnetic shielding material prepared according to the preparation process of electromagnetic shielding material according to any one of claims 1-8, characterized in that, The electromagnetic shielding material is a double-layer or multi-layer composite film, including a nickel foil layer and a polymer material layer, wherein the nickel foil layer and the polymer material layer are connected, and the polymer material layer includes one or more of PAI layer or PI layer.

10. A multilayer electromagnetic shielding composite material, characterized in that, It includes a foam layer and an electromagnetic shielding material layer, which are bonded together by conductive adhesive. The electromagnetic shielding material layer includes the electromagnetic shielding material as described in claim 9.

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