Multilayer helically oriented high thermal conductive metal-based shielding and absorbing sheet and method of making same

Abstract

The present application relates to a kind of multilayer spiral orientation high thermal conductivity metal-based shielding wave-absorbing sheet and its preparation method, including base layer and wave-absorbing layer, the base layer includes metal foil base layer, metal foil base layer is formed with multilayer thermal conductive wave-absorbing layer on one side, thermal conductive wave-absorbing layer includes adhesive polymer material and anisotropic hybrid thermal conductive wave-absorbing filler, the thermal conductive wave-absorbing filler of each thermal conductive wave-absorbing layer is respectively oriented in multiple predetermined orientations, the thermal conductive wave-absorbing filler of each thermal conductive wave-absorbing layer is respectively oriented in predetermined angle oblique to the horizontal direction of film by electric field induction, and the thermal conductive wave-absorbing filler of multilayer is arranged in whole upright spiral structure in sheet.The wave-absorbing sheet is obtained by electrostatic self-assembly one-dimensional or two-dimensional thermal conductive filler loaded with soft magnetic wave-absorbing material, different direction oblique orientation of each layer material is induced by dielectrophoresis force using external electric field, each layer has different orientation, and good compatibility of high thermal conductivity and wideband wave-absorbing performance is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of manufacturing of electrical component assemblies, and in particular to a multi-layer helically oriented high-thermal-conductivity metal-based shielding and wave-absorbing sheet and a preparation method thereof. BACKGROUND

[0002] With the wide application of current electronic and electrical equipment and components, especially in high-precision and high-end equipment or components, the heat of electrical components is easily increased when the equipment or components are running at high power, which may cause local overheating. At the same time, electronic and electrical components usually have the need for electromagnetic shielding to avoid interference with the normal operation of the equipment and components.

[0003] Existing electrical component assemblies usually use wave-absorbing and heat-conducting gaskets to solve the problem of heat dissipation and electromagnetic shielding. In the process of using heat-conducting gaskets to solve the problem of equipment heat dissipation, people gradually realize that the problems of electromagnetic pollution and information leakage caused by electronic equipment are also increasing. However, since heat-conducting silicone rubber has occupied most of the thickness space, there is no additional thickness space for the application of wave-absorbing materials from the perspective of structural design. Therefore, heat-conducting and wave-absorbing shielding materials emerge as the times require, which are innovative materials with the dual characteristics of heat conduction and electromagnetic compatibility, and are widely used in the internal key electronic components of optical communication, servers, 5G communication equipment, signal receiving modules, etc.

[0004] Orientation technology is an effective method to improve the heat conduction performance or wave-absorbing and shielding performance. The orientation and arrangement structure of the heat-conducting and wave-absorbing filler in the composite material are changed by means of external electromagnetic field or mechanical orientation, etc. At present, there are few studies on improving the performance by using material orientation technology in the field of heat-conducting and wave-absorbing shielding materials. The existing heat-conducting and wave-absorbing shielding materials generally use two fillers with heat-conducting function and wave-absorbing and shielding function respectively to be compounded in the matrix, and a few studies and patents use orientation technology to improve the performance.

[0005] A preparation method of an oriented multilayer heat-conducting wave-absorbing body is disclosed in Chinese Patent No. CN116470299A. The patent uses graphene sheets as heat-conducting and wave-absorbing fillers, uses horizontal magnetic orientation to prepare the wave-absorbing layer, and uses vertical magnetic orientation to prepare the heat-conducting layer, and prepares the heat-conducting wave-absorbing body by multilayer compounding. The heat-conducting path of the heat-conducting wave-absorbing body prepared by the patent is blocked in the horizontal orientation layer, and the vertical direction heat-conducting effect is not ideal. Moreover, the reflection effect is dominant when graphene is used as a wave-absorbing agent, and the wave-absorbing effect is not obvious. Chinese Patent No. CN116042188A uses self-made spiral carbon fibers and high-permeability materials compounded with silicone oil, and then obtains a heat-conducting wave-absorbing material by baking under an applied magnetic field. The patent method is relatively complex and the cost is high, and the wave-absorbing performance of the material is insufficient. Chinese Patent No. CN116333498A discloses a preparation method of a high-heat-conducting wave-absorbing gasket. The method selects fibers / inorganic heat-conducting fillers with a length-diameter ratio or an aspect ratio and microcrystalline metal powder wave-absorbing fillers to be compounded in a matrix, and realizes the orientation of the fiber heat-conducting fillers by high shear force. However, the orientation of the fillers is only realized in the flow direction of the material, and the vertical heat-conducting performance is insufficient.

[0006] In addition, the currently marketed or researched heat-conducting wave-absorbing materials are generally polymer-based composites. It is difficult for pure polymer matrix and composites to achieve good compatibility of high heat conductivity and wide-band wave-absorbing performance.

[0007] At the same time, the existing wave-absorbing materials and shielding materials have obvious boundaries. Single use of high shielding materials may cause interference of reflected electromagnetic waves on self components. The existing polymer-based wave-absorbing materials have poor absorption of high-voltage and high-frequency electromagnetic waves, and there is electromagnetic radiation leakage. Most of the products prepared by induction orientation process or mechanical orientation process have poor orientation effect, or the process is relatively complex and has no industrial significance. Non-radar stealth civilian electronic shielding wave-absorbing materials also need to have good shielding performance to prevent mutual interference of equipment. Most heat-conducting wave-absorbing products only have good thermal conductivity and good absorption and attenuation functions of electromagnetic waves, but the shielding efficiency of the products is not good. SUMMARY

[0008] Therefore, a multilayer spiral oriented high-heat-conducting metal-based shielding wave-absorbing sheet and a preparation method thereof are provided. One-dimensional or two-dimensional heat-conducting fillers loaded with soft magnetic wave-absorbing materials are obtained by electrostatic self-assembly, different direction oblique orientation of each layer of materials is induced by dielectrophoresis force under an applied electric field, and a multilayer spiral oriented high-heat-conducting metal-based shielding wave-absorbing material is prepared.

[0009] A multilayer helically oriented high-thermal-conductivity metal-based shielding and absorbing sheet includes a base layer and a shielding and absorbing layer formed on the base layer, the base layer includes a metal foil base layer, the metal foil base layer has a single side formed with a plurality of layers of a thermal-conductivity and shielding and absorbing layer, the thermal-conductivity and shielding and absorbing layer includes a bonding polymer material and an anisotropic hybrid thermal-conductivity and shielding and absorbing filler, the anisotropic hybrid thermal-conductivity and shielding and absorbing filler of each thermal-conductivity and shielding and absorbing layer is alternately oriented in a plurality of predetermined orientations, the anisotropic hybrid thermal-conductivity and shielding and absorbing filler of each thermal-conductivity and shielding and absorbing layer is alternately oriented at a predetermined angle inclined to a horizontal direction of the sheet by electric field induction, and the anisotropic hybrid thermal-conductivity and shielding and absorbing filler of the plurality of layers is arranged in an overall upright helical structure in the sheet.

[0010] In one specific technical solution, each of the thermal-conductivity and shielding and absorbing layers includes 5-35 parts by weight of the bonding polymer material, 40-80 parts of the anisotropic hybrid thermal-conductivity and shielding and absorbing filler, and 2-15 parts of an auxiliary agent; each of the thermal-conductivity and shielding and absorbing layers is prepared by mixing the components, ball milling, defoaming to prepare a thermal-conductivity and shielding and absorbing slurry, coating, orienting in an electric field, and pre-solidifying.

[0011] Preferably, the anisotropic hybrid thermal-conductivity and shielding and absorbing filler of each thermal-conductivity and shielding and absorbing layer is arranged into multiple rows by electric field induction, and the filler of each row is arranged into a row according to the same orientation and the same predetermined angle.

[0012] Preferably, the anisotropic hybrid thermal-conductivity and shielding and absorbing filler of each thermal-conductivity and shielding and absorbing layer is alternately oriented at a predetermined angle inclined to a horizontal direction of the sheet in four directions of front, back, left, and right; preferably, the anisotropic hybrid thermal-conductivity and shielding and absorbing filler of each thermal-conductivity and shielding and absorbing layer is oriented according to an inclined orientation in a height direction or a thickness direction.

[0013] Preferably, the anisotropic hybrid thermal-conductivity and shielding and absorbing filler of each thermal-conductivity and shielding and absorbing layer is alternately oriented at a predetermined angle of 30-60° inclined to a horizontal direction of the sheet in four directions of front, back, left, and right by electric field induction.

[0014] Preferably, the metal foil base layer is one of a copper foil, an aluminum foil, a nickel foil, and a silver foil, and has a thickness of 10-200 um; the metal foil base layer has at least one layer of the thermal-conductivity and shielding and absorbing layer on a single side or both sides, the number of layers of the thermal-conductivity and shielding and absorbing layer on the single side of the metal foil base layer is 0-10 layers; more preferably, each layer has a thickness of 10-400 um.

[0015] Preferably, the bonding polymer material includes one or a mixture of two or more of an epoxy resin, a silicone, an acrylate, a polyamide, an amino resin, a polyethylene terephthalate, a polyphenylene sulfide sulfone, a polyurethane, a chlorosulfonated polyethylene, and a polyvinylidene fluoride resin. Preferably, the anisotropic hybrid thermal-conductivity and shielding and absorbing filler is a hybrid filler formed by electrostatic self-assembly of sheet-shaped thermal-conductivity filler with negative charge and spherical magnetic filler with positive charge.

[0016] Preferably, the sheet-shaped thermally conductive filler with negative charge is a mixture of one or two of the following: negatively charged modified sheet-shaped boron nitride, graphene sheet. Preferably, the sheet-shaped thermally conductive filler has a length-diameter of 1-10 um and a sheet thickness of 0.005-0.05 um. Preferably, the spherical magnetic filler with positive charge is one or a mixture of two or more of the following: positively charged modified carbonyl iron, magnetite, ferrite, iron-silicon-aluminum, iron nitride, iron-nickel alloy, etc. Preferably, the spherical magnetic filler has a D50 of 0.01-0.5 um.

[0017] Furthermore, a preparation method of the multilayer spiral oriented high thermal conductivity metal-based shielding and absorbing sheet is provided, which comprises the following steps:

[0018] The sheet-shaped thermally conductive filler with negative charge and the magnetic filler with positive charge are prepared by ball milling, and the anisotropic hybrid thermally conductive and absorbing filler is prepared by electrostatic self-assembly.

[0019] The adhesive polymer material, the anisotropic hybrid thermally conductive and absorbing filler, the polar solvent, and the auxiliary agent are mixed and ball milled for 2-5 h, and defoaming is performed to obtain a thermally conductive and absorbing coating slurry.

[0020] The prepared thermally conductive and absorbing coating slurry is coated on the metal foil base layer, and after coating, the sheet is placed horizontally, oriented in an alternating current field with the orientation direction inclined to the coating horizontal direction, and the solvent is dried and pre-solidified at the same time, and the orientation direction is marked; the step is repeated to coat at least one layer of the thermally conductive and absorbing coating slurry on the metal foil base layer, and each time the oriented pre-solidified sheet is horizontally rotated by 90° compared with the orientation direction of the previous layer, so that the filler orientation direction is different from that of the previous thermally conductive and absorbing layer, and after all the layers are coated, the whole is solidified to obtain the multilayer spiral oriented high thermal conductivity metal-based shielding and absorbing sheet.

[0021] Preferably, the preparation of the sheet-shaped thermally conductive filler with negative charge comprises the following steps: mixing 20-50 parts of thermally conductive filler, 80-100 parts of deionized water, and 1-10 parts of sodium poly-styrene sulfonate, adjusting the pH value to be less than the isoelectric point of the thermally conductive filler, ball milling for 12-48 h, and drying to obtain the sheet-shaped thermally conductive filler with negative charge.

[0022] The preparation of the magnetic filler with positive charge comprises the following steps: mixing 20-50 parts of magnetic filler, 80-100 parts of deionized water, and 1-10 parts of poly-diallyl dimethyl ammonium chloride, adjusting the pH value to be greater than the isoelectric point, ball milling for 12-48 h, and drying to obtain the magnetic filler with positive charge.

[0023] The electrostatic self-assembly comprises the following steps: dispersing 5-20 parts of the mass ratio of 1:0.5-1.5 of the sheet-shaped thermally conductive filler with negative charge and the magnetic filler with positive charge in 60 parts of deionized water, stirring at 100-200 r / min for 15-60 min, standing for 15-30 min, and then washing the sodium chloride salt with deionized water after suction filtration, and drying to obtain an anisotropic hybrid thermally conductive and wave-absorbing filler;

[0024] The method for coating the prepared thermally conductive and wave-absorbing coating slurry on the metal foil base layer is one of blade coating, spraying, slot coating and dipping;

[0025] The orientation pre-curing method comprises the following steps: placing the coated sheet in a vacuum oven, the vacuum oven is provided with two electrode plates which are parallel to each other but are inclined to the horizontal plane as a whole, the angle between the electrode plate and the horizontal plane is 30-60°, the electrode plate is connected with a voltage with an amplitude of 500-3000 v and a frequency of 1-10 Hz, and the sheet is pre-cured in the electric field at a temperature lower than the curing temperature for 10-30 min to lock the orientation of the filler and ensure that the filler will not collapse.

[0026] The above multi-layer spiral orientation high-thermal-conductivity metal-based shielding and wave-absorbing sheet and the preparation method have at least the following beneficial effects:

[0027] 1. The sheet-shaped filler is inclined to be oriented, which not only constructs the thermal conduction path of the layered material in the thickness direction, but also realizes the uniform distribution of the wave-absorbing filler in the horizontal direction, solving the problem of the compromise between the thermal conductivity and the wave-absorbing performance in the previous single vertical or horizontal orientation technology.

[0028] 2. The multi-layer thermally conductive and wave-absorbing material is prepared by using a layer-by-layer coating process, the orientation directions of the fillers between the layers are designed differently, the spiral thermally conductive and wave-absorbing structure is realized, the incident wave is internally reflected and attenuated in different directions when entering different thermally conductive and wave-absorbing layers, and the wave-absorbing performance of the material is greatly improved.

[0029] 3. The metal foil has high thermal conductivity and high electromagnetic shielding effect, so that the wave-absorbing and heat-conducting functions and the shielding function are combined, and the internal space is saved. The metal foil layer and the thermally conductive and wave-absorbing composite layer also have a large electromagnetic wave interface scattering effect, and the overall wave-absorbing performance of the material is more excellent.

[0030] 4. The surface zeta potential of the filler is controlled by using a ball milling method, the sheet-shaped thermally conductive filler is modified by using an anionic polyelectrolyte through ball milling, the anionic groups of the anionic polyelectrolyte are easily intercalated between the sheet-shaped fillers, the zeta potential of the thermally conductive filler is successfully reduced, and the sheet-shaped filler is effectively peeled off. The surface of the wave-absorbing magnetic filler is positively charged by using a cationic polyelectrolyte, and the thermally conductive and wave-absorbing hybrid integrated material is prepared by using electrostatic self-assembly, so as to realize the overall control of the filler and improve the performance of the material. Attached Figure Description

[0031] Figure 1 This is a three-dimensional exploded structural diagram of a multi-layered spiral-oriented high thermal conductivity metal-based shielding and absorbing sheet provided in an embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the internal structure of a multi-layered spiral-oriented high thermal conductivity metal-based shielding and absorbing sheet in the wave propagation direction provided by an embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the internal structure of a multi-layered spiral-oriented high thermal conductivity metal-based shielding and absorbing sheet in the direction of heat conduction, provided in an embodiment of the present invention.

[0034] Figure 4 This is a schematic diagram of the structure of a vacuum oven used in the method for preparing multi-layered spiral-oriented high thermal conductivity metal-based shielding and absorbing thin films applied in embodiments of the present invention.

[0035] The following are labeled in the figure: 1. Thermally conductive and microwave absorbing layer; 2. Anisotropic hybrid thermally conductive and microwave absorbing filler; 3. Metal foil base layer; 4. Electrode plate; 5. Insulating fixture; 6. Film material to be oriented; 7. Vacuum oven; 8. Polymer material. Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0037] Please see Figure 1 As shown in the figure, this embodiment of the invention provides a multilayer spiral-oriented high thermal conductivity metal-based shielding and absorbing sheet, which includes a base layer and absorbing layers formed on the base layer. As shown in the figure, the base layer includes a metal foil base layer 3, on which multiple thermally conductive and absorbing layers 1 are formed on one side. The thermally conductive and absorbing layers 1 contain an adhesive polymer material 8 and anisotropic hybrid thermally conductive and absorbing fillers 2. The anisotropic hybrid thermally conductive and absorbing fillers 2 of each thermally conductive and absorbing layer 1 are alternately oriented in multiple predetermined orientations. The anisotropic hybrid thermally conductive and absorbing fillers 2 of each thermally conductive and absorbing layer 1 are alternately oriented at predetermined angles inclined to the horizontal direction of the film by electric field induction. The multiple anisotropic hybrid thermally conductive and absorbing fillers 2 are arranged in an upright spiral structure in the sheet.

[0038] Specifically, each of the heat-conducting wave-absorbing layers 1 comprises 5-35 parts by weight of a bonding polymer material 8, 40-80 parts of an anisotropic hybrid heat-conducting wave-absorbing filler, and 2-15 parts of an auxiliary agent. The above components are mixed, ball-milled, and defoamed to obtain a heat-conducting wave-absorbing slurry for coating. After coating, the heat-conducting wave-absorbing slurry is oriented in an electric field, pre-solidified, and coated multiple times, and then oriented in an electric field and pre-solidified to form the heat-conducting wave-absorbing layers 1 on the metal foil base layer 3. The bonding polymer material 8 preferably comprises one or more than two of an epoxy resin, a silicone, an acrylate, a polyamide, an amino resin, a polyethylene terephthalate, a polyphenylene sulfide sulfone, a polyurethane, a chlorosulfonated polyethylene, and a polyvinylidene fluoride resin. The bonding polymer material 8 serves as a base material of the heat-conducting wave-absorbing layers 1. The anisotropic hybrid heat-conducting wave-absorbing filler 2 is preferably a hybrid filler formed by electrostatic self-assembly of a sheet-shaped heat-conducting filler with negative charges and a spherical magnetic filler with positive charges. The auxiliary agent preferably comprises one or more than one of a dispersing agent, a leveling agent, a curing agent, and an accelerator, and the appropriate auxiliary agent is selected according to the selected bonding polymer material and the overall formulation requirements. The dispersing agent is preferably a high-molecular-weight alkyl ammonium salt copolymer. The adhesion accelerator is a silane coupling agent, such as γ-glycidoxypropyltrimethoxysilane, which is an epoxy-functional silane and is beneficial to adhesion promotion.

[0039] Preferably, the sheet-shaped heat-conducting filler with negative charges is one or a mixture of two of a sheet-shaped boron nitride modified with negative charges and a graphene sheet. More preferably, the sheet-shaped heat-conducting filler is a mixture of the sheet-shaped boron nitride and the graphene sheet, and the mass ratio of the sheet-shaped boron nitride to the graphene sheet is preferably 1:1-2:1. Preferably, the sheet-shaped heat-conducting filler has a length-diameter of 1-10 um and a sheet thickness of 0.005-0.05 um. Preferably, the spherical magnetic filler with positive charges is one or a mixture of two or more than two of carbonyl iron modified with positive charges, magnetite, ferrite, iron-silicon-aluminum, iron nitride, and iron-nickel alloy. More preferably, the spherical magnetic filler is a mixture of two or more than two of the carbonyl iron, the magnetite, the ferrite, the iron-silicon-aluminum, the iron nitride, and the iron-nickel alloy, and the mixing ratio is preferably 1:1. Preferably, the spherical magnetic filler has a D50 of 0.01-0.5 um. Preferably, the sheet-shaped heat-conducting filler with negative charges and the spherical magnetic filler with positive charges are dispersed in deionized water at a predetermined mass ratio to obtain a suspension with a solute content of 100-300 g / L, ultrasonic dispersion stirring is performed for 3-6 h, the suspension is allowed to stand for 1-3 h, and freeze-drying is performed to obtain the anisotropic hybrid heat-conducting wave-absorbing filler. The predetermined mass ratio of the sheet-shaped heat-conducting filler with negative charges to the spherical magnetic filler with positive charges is 1:0.5-1:6, and is preferably 1:3-1:5. The molar ratio of the sheet-shaped heat-conducting filler with negative charges to the spherical magnetic filler with positive charges is preferably 1:0.5-1.5. According to the experimental results, the carbonyl iron modified with positive charges and the sheet-shaped heat-conducting filler with negative charges are selected in the embodiment, and are mixed at the preferred ratio to favorably balance the heat-conducting performance and the wave-absorbing performance of the wave-absorbing sheet.

[0040] Preferably, the metal foil base layer 3 is one of copper foil, aluminum foil, nickel foil, silver foil, and has a thickness of 10-200 um; the heat-conducting wave-absorbing layer 1 is attached to the upper and lower surfaces or a single surface of the metal foil base layer 3, i.e., with the metal foil base layer 3 as the center, a single surface or both surfaces of the metal foil base layer has at least one layer of the heat-conducting wave-absorbing layer, and the number of layers of the heat-conducting wave-absorbing layer on a single surface of the metal foil base layer is 0-10; more preferably, each layer has a thickness of 10-400 um.

[0041] Preferably, the anisotropic hybrid heat-conducting wave-absorbing filler 2 of each heat-conducting wave-absorbing layer 1 is arranged in multiple rows by electric field induction, and each row of filler is arranged in a row according to the same orientation and the same predetermined angle. More preferably, the orientations of the anisotropic hybrid heat-conducting wave-absorbing filler 2 of two adjacent layers are relatively rotated by 90 degrees.

[0042] Preferably, the anisotropic hybrid heat-conducting wave-absorbing filler 2 of each heat-conducting wave-absorbing layer 1 is alternately oriented in the four directions of front, back, left, and right at a predetermined angle oblique to the horizontal direction of the film. Preferably, the anisotropic hybrid heat-conducting wave-absorbing filler of each heat-conducting wave-absorbing layer is obliquely oriented according to the height direction or the thickness direction. Since the filler is preferentially flaky, the flakes are oriented in an oblique manner according to the length direction. In this way, the heat-conducting performance in the length direction is achieved, and the wave-absorbing performance is greatly taken into account, thereby successfully solving the problem that the heat-conducting performance and the wave-absorbing performance cannot be taken into account simultaneously in the prior art single vertical or horizontal orientation technology.

[0043] Preferably, the anisotropic hybrid heat-conducting wave-absorbing filler 2 of each heat-conducting wave-absorbing layer 1 is alternately oriented in the four directions of front, back, left, and right at a predetermined angle oblique to the horizontal direction of the film. Preferably, the anisotropic hybrid heat-conducting wave-absorbing filler 2 of two adjacent layers is relatively rotated by 90 degrees, and the angles of oblique of the anisotropic hybrid heat-conducting wave-absorbing filler 2 are preferably equal. For example, the anisotropic hybrid heat-conducting wave-absorbing filler 2 is alternately oriented in the four directions of front, back, left, and right at a predetermined angle of 45 degrees oblique to the horizontal direction of the film.

[0044] In another aspect of the embodiment of the present application, a preparation method of the multilayer high-heat-conducting metal-based shielding wave-absorbing sheet with spiral orientation is provided, which comprises the following steps:

[0045] Filler electrostatic self-assembly: flaky heat-conducting fillers with negative charges and magnetic fillers with positive charges are respectively prepared by ball milling, and the anisotropic hybrid heat-conducting wave-absorbing filler 2 is prepared by electrostatic self-assembly;

[0046] Preparation of coating slurry: the adhesive polymer material 8, the anisotropic hybrid heat-conducting wave-absorbing filler 2, the polar solvent, and the auxiliary agent are mixed by ball milling for 2-5 h and defoaming to prepare the heat-conducting wave-absorbing coating slurry;

[0047] Coating, electric field orientation and pre-curing: coating the prepared heat-conducting wave-absorbing coating slurry on the metal foil base layer 3, after coating, the sheet is placed horizontally, oriented in an alternating current electric field with the direction inclined to the horizontal direction of coating, and the solvent is dried and pre-cured while being oriented, and the orientation direction is marked;

[0048] The steps of coating, electric field orientation and pre-curing are repeated to coat at least one layer of heat-conducting wave-absorbing coating slurry on the metal foil base layer 3, and each time the oriented pre-cured sheet is horizontally rotated 90° compared to the orientation direction of the previous layer, so that the filler orientation direction is different from the orientation of the previous heat-conducting wave-absorbing layer 1. After all layers are coated, overall curing is performed to obtain the multi-layer spiral-oriented high-thermal-conductivity metal-based shielding and wave-absorbing sheet.

[0049] Preferably, the preparation of the sheet-shaped heat-conducting filler with negative charge comprises the following steps: mixing 20-50 parts of heat-conducting filler, 80-100 parts of deionized water and 1-10 parts of sodium poly (p-phenylene sulfonate), adjusting the pH value to be less than the isoelectric point of the heat-conducting filler, ball milling for 12-48 hours and drying to obtain the sheet-shaped heat-conducting filler with negative charge. Sodium poly (p-phenylene sulfonate) helps to uniformly disperse the heat-conducting filler, and through ball milling, two or more sheet-shaped boron nitride and graphene sheets can be uniformly mixed.

[0050] The preparation of the magnetic filler with positive charge comprises the following steps: mixing 20-50 parts of magnetic filler, 80-100 parts of deionized water and 1-10 parts of poly (diallyldimethylammonium chloride), adjusting the pH value to be greater than the isoelectric point, ball milling for 12-48 hours and drying to obtain the magnetic filler with positive charge. Poly (diallyldimethylammonium chloride) is easily soluble in water, has strong condensation and good hydrolysis stability, and can effectively promote the uniform mixing of two or more magnetic fillers.

[0051] The electrostatic self-assembly of the filler comprises the following steps: dispersing 5-20 parts by weight of the sheet-shaped heat-conducting filler with negative charge and the magnetic filler with positive charge in a mass ratio of 1:0.5-1.5 in 60 parts of deionized water, stirring at 100-200 r / min for 15-60 min, standing for 15-30 min, washing with deionized water and sodium chloride salt after suction filtration, and drying to obtain the anisotropic hybrid heat-conducting wave-absorbing filler 2. The mass ratio of the two fillers is 1:0.5-1.5, and the total amount is 5-20 parts:60 parts of deionized water.

[0052] Preparation of coating slurry: the bisphenol F epoxy resin (Epon 862), vinyl silicone oil, anisotropic hybrid heat-conducting and wave-absorbing hybrid filler, dispersant BYK-9076, adhesion promoter KH560, and organic solvent are weighed according to a predetermined mass ratio, and are dispersed in a ball mill tank at a rotation speed of 300 rmp / min for 2-4 h. After ball milling, 10-30 g of a curing agent, a cycloaliphatic amine, is added, and the mixture is dispersed in the ball mill tank at a rotation speed of 350 rmp / min for 15-60 min. After 200-mesh screening, the mixture is placed in a planetary debubbling machine to remove bubbles, thereby obtaining a heat-conducting and wave-absorbing coating slurry. The polar solvent or the organic solvent can be selected from any one or a combination of two or more of acetone, cyclohexanone, ethanol, N-methyl pyrrolidone, and N,N-dimethylformamide. The adjuvant preferably comprises a dispersant and an adhesion promoter. The dispersant is preferably a high-molecular-weight alkyl ammonium salt copolymer. The adhesion promoter is a silane coupling agent, for example, γ-glycidoxypropyltrimethoxysilane, which is an epoxy-functional silane and is conducive to adhesion promotion.

[0053] The method for coating the prepared heat-conducting and wave-absorbing coating slurry on the metal foil base layer 3 is one of blade coating, spray coating, slot coating, and dip coating. The metal foil base layer 3 is preferably cut before coating, and then the prepared heat-conducting and wave-absorbing coating slurry is coated on the cut metal foil base layer 3. Specifically, preparation of a multilayer spiral-oriented high-thermal-conductivity metal-based shielding and wave-absorbing sheet: a copper foil is coated with the heat-conducting and wave-absorbing coating slurry by a coating machine, and the coated sheet is placed on an insulating jig in a vacuum oven. The vacuum oven is provided with upper and lower electrode plates that are inclined at an angle of about 45° to the horizontal plane. The electrode plates are connected to a voltage with an amplitude of 1000 V and a frequency of 3 Hz. After 10 min of pre-curing at 100°C, a double-sided single-layer oriented heat-conducting and wave-absorbing layer is obtained. The double-layer slurry is again coated by slot coating, and the orientation direction is rotated by 90° relative to the previous orientation direction. The sheet is again oriented and pre-cured in the vacuum oven for 10 min. The coating and pre-curing are repeated three times in the same manner, thereby obtaining a multilayer spiral-oriented high-thermal-conductivity metal-based shielding and wave-absorbing sheet having multiple layers (such as 4 layers or 8 layers) of heat-conducting and wave-absorbing layers on the upper and lower surfaces of the copper foil. Each coating layer has a thickness of 0.15 mm, and the total thickness of the sheet is 2.43 mm.

[0054] The orientation and pre-curing method comprises the following steps: placing the coated sheet in a vacuum oven, and placing two electrode plates that are parallel to each other but are inclined to the horizontal plane as a whole in the vacuum oven. The angle between the electrode plates and the horizontal plane is 30°-60°. The electrode plates are connected to a voltage with an amplitude of 500-3000 V and a frequency of 1-10 Hz. The sheet is pre-cured in the electric field at a temperature lower than the curing temperature for 10-30 min to lock the orientation of the filler and ensure that the filler does not collapse.

[0055] As shown in FIG. 1, Figure 4 Pre-curing is mainly performed in a vacuum oven, Figure 4The example is the structure of a vacuum oven 7, which is provided with an insulation jig electrode plate 4, an insulation jig 5, and a to-be-oriented film material 6 after spraying is completed, which is placed in the jig and in the vacuum oven. The vacuum oven 7 is provided with two electrode plates 4 which are parallel to each other but are inclined to the horizontal plane as a whole, and the included angle between the electrode plate 4 and the horizontal plane is 30°-60°. The two electrode plates 4 are arranged in a diagonal parallel manner, and the two electrode plates 4 correspond to two sides of a parallelogram, and the insulation jig 5 is horizontally placed and corresponds to the diagonal of the same parallelogram. Thus, by setting the inclination angle of the two electrode plates 4, the fillers of each layer can be oriented correspondingly. In addition, during the orientation and pre-curing process, the electrode plate is connected with a voltage with an amplitude of 500-3000v and a frequency of 1-10Hz, and the pre-curing is performed in the electric field at a temperature lower than the curing temperature for 10-30min to lock the orientation of the fillers and ensure that the fillers will not collapse.

[0056] The above multi-layer spiral oriented high thermal conductivity metal-based shielding and wave-absorbing sheet and the preparation method have at least the following beneficial effects:

[0057] 1. The sheet-shaped fillers are inclined and oriented, which not only constructs the thermal conduction path of the layered material in the thickness direction, but also realizes the uniform distribution of the wave-absorbing fillers in the horizontal direction, solving the problem of the compromise between the thermal conductivity and the wave-absorbing performance in the previous single vertical or horizontal orientation technology.

[0058] 2. The multi-layer thermal conduction and wave-absorbing material is prepared by using a layer-by-layer coating process, the orientation direction of the fillers between the layers is designed differently, the spiral thermal conduction and wave-absorbing structure is realized, and when the incident wave enters different thermal conduction and wave-absorbing layers 1, it is subjected to internal reflection and attenuation in different directions, greatly increasing the wave-absorbing performance of the material.

[0059] 3. The metal foil has high thermal conductivity and high electromagnetic shielding effect, so that the wave-absorbing and thermal conduction functions and the shielding function are combined, and the internal space is saved. The metal foil layer and the thermal conduction and wave-absorbing composite layer also have a large electromagnetic wave interface scattering effect, and the overall wave-absorbing performance of the material is more excellent.

[0060] 4. The surface zeta potential of the fillers is controlled by using a ball milling method, the sheet-shaped thermal conductive fillers are modified by using an anionic polyelectrolyte through ball milling, the anionic groups of the anionic polyelectrolyte are easily intercalated between the sheet-shaped fillers, and the sheet-shaped fillers are effectively peeled off while the zeta potential of the thermal conductive fillers is successfully reduced. The surface of the wave-absorbing magnetic fillers is positively charged by using a cationic polyelectrolyte, and the thermal conduction and wave-absorbing hybrid integrated material is prepared by using electrostatic self-assembly, so as to realize the overall control of the fillers and improve the performance of the material.

[0061] The preparation method of the multi-layer spiral oriented high thermal conductivity metal-based shielding and wave-absorbing sheet, the prepared positive electrode material, and the performance of the battery and other aspects are illustrated by multiple examples.

[0062] Example 1

[0063] Surface treatment of metal foil: Take 450mm x 450mm / 35um rolled copper foil, clean and dry the surface, and perform two plasma treatments on the upper and lower surfaces respectively by plasma surface treatment machine.

[0064] Preparation of anisotropic hybrid heat-conducting and wave-absorbing filler: 108 g of boron nitride nanosheet with an average flake diameter of 5.4 um and an average flake thickness of 30 nm, 80 g of graphene flake with an average flake diameter of 7 um and an average flake thickness of 50 nm, 42.7 g of sodium poly (p-styrenesulfonate), and 769.2 g of deionized water were mixed, and then taken out after being ball-milled at 400 r / min for 5 minutes in a zirconium oxide ball mill tank. Dilute HCl was added to adjust the pH to 3-4, and then re-ball-milled at 280 r / min for 6 h. The beads were filtered and dried to obtain a negatively charged modified heat-conducting filler. 104 g of nanometer carbonyl iron powder with an average particle size of 220 nm, 104 g of ferroferric oxide with an average particle size of 100-120 nm, 41.7 g of poly (diallyldimethylammonium chloride), and 750 g of deionized water were mixed, and then taken out after being ball-milled at 400 r / min for 5 min. Ammonia water was added to adjust the pH to 8-9, and then the ball-milling was continued at 280 r / min for 6 h. The beads were filtered and dried. The negatively charged modified heat-conducting filler and the positively charged modified wave-absorbing filler were dispersed in deionized water at a mass ratio of 1:3 to obtain a suspension with a solute content of 200 g / L. Ultrasonic dispersion and stirring were performed for 5 h, the suspension was left to stand for 1 h, and then freeze-drying was performed to obtain an anisotropic hybrid heat-conducting and wave-absorbing filler.

[0065] Preparation of coating slurry: 68 g of bisphenol F epoxy resin (Epon 862), 24 g of vinyl silicone oil, 308 g of anisotropic hybrid heat-conducting and wave-absorbing filler, 2 g of dispersant BYK-9076, 4 g of KH560, 50 g of acetone were dispersed and ball-milled in a ball mill tank at a speed of 300 rpm / min for 2.5 h. After ball-milling, 10 g of curing agent alicyclic amine was added, and the ball-milling was continued at a speed of 350 rpm / min for 15 min. After being filtered through a 200-mesh bead, the product was placed into a planetary debubbling machine to remove bubbles to obtain a heat-conducting and wave-absorbing coating slurry.

[0066] Preparation of multi-layer helical oriented high thermal conductive metal-based shielding and absorbing sheet: Copper foil is coated with thermal conductive and absorbing coating paste by a doctor blade coater. After coating, the sheet is placed on an insulating fixture in a vacuum oven. The oven is equipped with upper and lower electrodes that are inclined at an angle of about 45° to the horizontal plane. The electrodes are connected to a voltage with an amplitude of 1000 V and a frequency of 3 Hz. After 10 minutes of pre-curing at 100°C, a single layer of oriented thermal conductive and absorbing layer is obtained. The paste is coated again, and the orientation direction is rotated by 90° relative to the previous orientation direction. The sheet is again oriented in an electric field in the vacuum oven and pre-cured for 10 minutes. The coating and pre-curing process is repeated 7 times in the same way. Then, the sheet is baked at 160°C for 3 minutes to obtain a multi-layer helical oriented high thermal conductive metal-based shielding and absorbing sheet with 8 layers of thermal conductive and absorbing layers on the copper foil. Each coating layer has a thickness of 0.15 mm, and the total thickness of the sheet is 1.23 mm.

[0067] Example Two

[0068] Surface treatment of metal foil: A 450 mm x 450 mm / 35 um calendered copper foil is taken, the surface is cleaned and dried, and the upper and lower surfaces are each subjected to two plasma treatments by a plasma surface treatment machine.

[0069] Preparation of anisotropic hybrid thermal conductive and absorbing filler: 188 g of graphene sheets with an average flake diameter of 6 um and an average flake thickness of 50 nm, 42.7 g of sodium poly (p-phenylene sulfonate), and 769.2 g of deionized water are mixed, and then ball-milled in a zirconium oxide ball mill at 400 r / min for 5 minutes. The pH is adjusted to 5-6 by adding dilute HCl, and the mixture is re-ball-milled at 280 r / min for 12 hours. The mixture is filtered and dried to obtain negatively charged modified graphene sheets. 104 g of nano-carbonyl iron powder with an average particle size of 220 nm, 104 g of ferroferric oxide with an average particle size of 100-120 nm, and 41.7 g of polydiallyldimethylammonium chloride are mixed with 750 g of deionized water, and then ball-milled at 400 r / min for 5 minutes. Ammonia water is added to adjust the pH to 8-9, and the mixture is continuously ball-milled at 280 r / min for 6 hours. The mixture is filtered and dried. The negatively charged modified graphene sheets and the positively charged modified absorbing filler are dispersed in deionized water at a mass ratio of 1:5.36 to obtain a suspension with a solute content of 200 g / L. The mixture is ultrasonically dispersed and stirred for 5 hours, allowed to stand, and freeze-dried to obtain an anisotropic hybrid thermal conductive and absorbing filler.

[0070] Preparation of coating paste: 68 g of bisphenol F epoxy resin (Epon 862), 24 g of vinyl silicone oil, 308 g of anisotropic hybrid thermal conductive and absorbing filler, 2 g of dispersant BYK-9076, 4 g of KH560, and 50 g of acetone are dispersed and ball-milled in a ball mill at a speed of 300 rpm / min for 2.5 hours. After ball-milling, 10 g of curing agent alicyclic amine is added, and the mixture is dispersed and ball-milled at a speed of 350 rpm / min for 15 minutes. The mixture is filtered through a 200-mesh screen and then placed in a planetary debubbling machine to remove bubbles to obtain a thermal conductive and absorbing coating paste.

[0071] Preparation of multi-layer spiral oriented high thermal conductive metal-based shielding and absorbing sheet: Copper foil is coated with thermal conductive and absorbing coating paste by a doctor blade coater. After coating, the sheet is placed on an insulating fixture in a vacuum oven. The oven is equipped with upper and lower electrodes that are inclined at an angle of about 45° to the horizontal plane. The electrodes are connected to a voltage with an amplitude of 1000 V and a frequency of 3 Hz. After 10 minutes of pre-curing at 100°C, a single layer of oriented thermal conductive and absorbing layer is obtained. The paste is coated again, and the orientation direction is rotated by 90° relative to the previous orientation direction. The sheet is again oriented in an electric field in the vacuum oven and pre-cured for 10 minutes. The coating and pre-curing process is repeated 7 times in the same way. Then, the sheet is baked at 160°C for 3 minutes to obtain a multi-layer spiral oriented high thermal conductive metal-based shielding and absorbing sheet with 8 layers of thermal conductive and absorbing layers on the copper foil. Each coating layer has a thickness of 0.15 mm, and the total thickness of the sheet is 1.23 mm.

[0072] Example Three

[0073] Surface treatment of metal foil: A 450 mm x 450 mm / 35 um calendered copper foil is taken, the surface is cleaned and dried, and the upper and lower surfaces are each subjected to two plasma treatments by a plasma surface treatment machine.

[0074] Preparation of anisotropic hybrid thermal conductive and absorbing filler: 80 g of graphene sheets with an average flake diameter of 6 um and an average flake thickness of 50 nm, 108 g of boron nitride nanosheets with an average flake diameter of 5.4 um and an average flake thickness of 30 nm, 42.7 g of sodium poly-styrene sulfonate, and 769.2 g of deionized water are mixed. After 5 minutes of ball milling at 400 r / min in a zirconium oxide ball mill jar, the mixture is taken out, diluted HCl is added to adjust the pH to 3-4, and the mixture is re-ball milled at 280 r / min for 12 hours. The mixture is filtered and dried. 208.3 g of nano-carbonyl iron powder with a particle size of 200-600 nm, 41.7 g of poly-diallyl dimethyl ammonium chloride, and 750 g of deionized water are mixed. After 5 minutes of ball milling at 400 r / min, the mixture is ball milled at 280 r / min for 12 hours. The mixture is filtered and dried. The negatively charged modified graphene sheets and the positively charged modified nano-carbonyl iron powder are dispersed in deionized water at a mass ratio of 1:5.36 to obtain a suspension with a solute content of 200 g / L. The mixture is ultrasonically dispersed and stirred for 5 hours, allowed to stand, and freeze-dried to obtain an anisotropic hybrid thermal conductive and absorbing filler.

[0075] Preparation of coating paste: 68 g of bisphenol F epoxy resin (Epon 862), 24 g of chlorosulfonated polyethylene, 308 g of anisotropic hybrid thermal conductive and absorbing filler, 2 g of dispersant BYK-9076, 4 g of KH560, and 50 g of xylene are dispersed and ball milled in a ball mill jar at a speed of 300 rpm / min for 2.5 hours. After ball milling, 10 g of curing agent alicyclic amine is added, and the mixture is dispersed and ball milled at a speed of 350 rpm / min for 15 minutes. The mixture is filtered through a 200 mesh screen bead and then placed in a planetary debubbling machine to remove bubbles to obtain a thermal conductive and absorbing coating paste.

[0076] Preparation of multilayer spiral oriented high thermal conductive metal-based shielding and absorbing sheet: Copper foil is coated with thermal conductive absorbing coating paste by a doctor blade coater. After coating, the sheet is placed on an insulating fixture in a vacuum oven, which is equipped with upper and lower electrodes with a normal line inclined at an angle of about 45° to the horizontal plane, and the electrodes are connected to a voltage with an amplitude of 1000V and a frequency of 3Hz. After 10 minutes of pre-curing at 100℃, a single layer of oriented thermal conductive absorbing layer is obtained. The paste is coated again, and the orientation direction is rotated 90° relative to the previous orientation direction. The paste is oriented and pre-cured again in the vacuum oven for 10 minutes. The coating and pre-curing process is repeated 7 times in the same way, and then the copper foil is baked at 160℃ for 3 minutes to obtain a multilayer spiral oriented high thermal conductive metal-based shielding and absorbing sheet with 8 layers of thermal conductive absorbing layers on the copper foil, with a thickness of 0.15mm for each coating layer and a total thickness of 1.23mm for the film.

[0077] Comparative Example 1

[0078] The remaining technical solutions of Comparative Example 1 are the same as those of Example 1, except that there is no electric field orientation step.

[0079] Comparative Example 2

[0080] The remaining technical solutions of Comparative Example 2 are the same as those of Example 1, except that the coating is oriented and cured in an external electric field perpendicular to the horizontal direction of the coating.

[0081] Comparative Example 3

[0082] The remaining technical solutions of Comparative Example 1 are the same as those of Example 1, except that the coating is oriented and cured in an external electric field parallel to the horizontal direction of the coating.

[0083] The thermal absorbing materials prepared in Examples 1 to 4 are tested according to the standards as follows

[0084] 1. Thermal conductivity test

[0085] 2. Absorbing performance test

[0086] 3. Shielding effectiveness test

[0087] Table 1 Performance test results of multilayer spiral oriented high thermal conductive metal-based shielding and absorbing sheet

[0088]

[0089] It should be noted that the present application is not limited to the above-mentioned embodiments, and other changes can be made by those skilled in the art according to the inventive spirit of the present application. Any changes made in accordance with the inventive spirit of the present application should be included within the scope of the present application.

Claims

1. A multilayer spiral oriented high thermal conductive metal based shielding and absorbing sheet, comprising a base layer and an absorbing layer formed on the base layer, characterized in that, The base layer comprises a metal foil base layer, and a plurality of heat-conducting and wave-absorbing layers are formed on one side of the metal foil base layer. The heat-conducting and wave-absorbing layers comprise a bonding polymer material and anisotropic hybrid heat-conducting and wave-absorbing fillers. The anisotropic hybrid heat-conducting and wave-absorbing fillers of each heat-conducting and wave-absorbing layer are alternately oriented in a plurality of predetermined directions. The anisotropic hybrid heat-conducting and wave-absorbing fillers of each heat-conducting and wave-absorbing layer are alternately oriented at a predetermined angle oblique to the horizontal direction of the film by electric field induction. The anisotropic hybrid heat-conducting and wave-absorbing fillers of the plurality of layers are arranged in an overall upright spiral structure in the sheet. The bonding polymer material comprises one or more than two of epoxy resin, silicone, acrylate, polyamide, amino resin, polyethylene terephthalate, polyphenylene sulfide sulfone, polyurethane, chlorosulfonated polyethylene, and fluorinated ethylene propylene resin. The anisotropic hybrid heat-conducting and wave-absorbing fillers are hybrid fillers formed by electrostatic self-assembly of sheet-shaped heat-conducting fillers with negative charges and spherical magnetic fillers with positive charges. The sheet-shaped heat-conducting fillers with negative charges are one or a mixture of sheet-shaped boron nitride with negative charge modification and graphene sheet. The sheet-shaped heat-conducting fillers have a length-diameter of 1-10 um and a sheet thickness of 0.005-0.05 um. The spherical magnetic fillers with positive charges are one or a mixture of more than two of carbonyl iron with positive charge modification, magnetite, ferrite, iron-silicon-aluminum, iron nitride, and iron-nickel alloy. The spherical magnetic fillers have a D50 of 0.01-0.5 um.

2. The multilayer, spirally oriented, high thermal conductivity, metal-based, shield and absorbent foil of claim 1 wherein, Each heat-conducting and wave-absorbing layer comprises 5-35 parts by weight of the bonding polymer material, 40-80 parts of the anisotropic hybrid heat-conducting and wave-absorbing fillers, and 2-15 parts of an auxiliary agent. Each heat-conducting and wave-absorbing layer is prepared by mixing the components, ball milling, defoaming, coating to prepare heat-conducting and wave-absorbing slurry, orienting in an electric field, and pre-solidifying.

3. The multi-layer, spirally oriented, high thermally conductive, metal-based, shield and absorbent foil of claim 1, wherein, The anisotropic hybrid heat-conducting and wave-absorbing fillers of each heat-conducting and wave-absorbing layer are arranged in multiple rows by electric field induction. The fillers in each row are arranged in the same direction and at the same predetermined angle.

4. The multi-layer, spirally oriented, high thermally conductive, metal-based, shield and absorbent foil of claim 3, wherein, The anisotropic hybrid heat-conducting and wave-absorbing fillers of each heat-conducting and wave-absorbing layer are alternately oriented in four directions of front, back, left, and right at a predetermined angle oblique to the horizontal direction of the film. The anisotropic hybrid heat-conducting and wave-absorbing fillers of each heat-conducting and wave-absorbing layer are arranged in a slanting orientation in the height direction or the thickness direction.

5. The multilayer, spirally oriented, high thermal conductivity, metal matrix gasketing and shielding absorbent foil of claim 1, wherein, The anisotropic hybrid heat-conducting and wave-absorbing fillers of each heat-conducting and wave-absorbing layer are alternately oriented in four directions of front, back, left, and right at a predetermined angle oblique to the horizontal direction of the film by electric field induction.

6. The multi-layer, spirally oriented, high thermally conductive, metal-based, shield and absorbent foil of claim 1 wherein, The metal foil base layer is one of a copper foil, an aluminum foil, a nickel foil, and a silver foil, and has a thickness of 10-200 um. One side or both sides of the metal foil base layer have at least one heat-conducting and wave-absorbing layer. The number of heat-conducting and wave-absorbing layers on one side of the metal foil base layer is 0-10. Each layer has a thickness of 10-400 um.

7. A method for preparing the multilayer spiral-oriented high-heat-conducting metal-based shielding and wave-absorbing sheet according to any one of claims 1-6, comprising the following steps: The sheet-shaped heat-conducting fillers with negative charges and the spherical magnetic fillers with positive charges are prepared by a ball milling method, and the anisotropic hybrid heat-conducting and wave-absorbing fillers are prepared by electrostatic self-assembly. The bonding polymer material, the anisotropic hybrid heat-conducting and wave-absorbing filler, the polar solvent, and the additive are mixed and ball milled for 2-5 hours to prepare a heat-conducting and wave-absorbing coating slurry after defoaming. The prepared heat-conducting and wave-absorbing coating slurry is coated on the metal foil base layer, and the coated sheet is placed horizontally, oriented in an alternating electric field with the orientation direction inclined to the horizontal direction of coating, and dried to be pre-solidified while being oriented, and the orientation direction is marked; the step is repeated to coat at least one layer of the heat-conducting and wave-absorbing coating slurry on the metal foil base layer, and the coated sheet is horizontally rotated by 90° compared with the orientation direction of the previous layer before each orientation and pre-solidification, so that the filler orientation direction is different from that of the previous heat-conducting and wave-absorbing layer, and the whole layer is completely solidified after all the layers are coated to obtain the multi-layer spiral oriented high-heat-conducting metal-based shielding and wave-absorbing sheet.

8. The method of claim 7, wherein the multilayer, spirally oriented, high thermal conductive metal-based, shield and absorbent foil is prepared by the steps of: The preparation of the sheet-shaped heat-conducting filler with negative charge comprises the following steps: 20-50 parts of the heat-conducting filler, 80-100 parts of deionized water, and 1-10 parts of sodium p-styrenesulfonate are mixed, the pH value is adjusted to be less than the isoelectric point of the heat-conducting filler, and the sheet-shaped heat-conducting filler with negative charge is obtained by drying after ball milling for 12-48 hours; The preparation of the magnetic filler with positive charge comprises the following steps: 20-50 parts of the magnetic filler, 80-100 parts of deionized water, and 1-10 parts of polydiallyldimethylammonium chloride are mixed, the pH value is adjusted to be greater than the isoelectric point, and the magnetic filler with positive charge is obtained by drying after ball milling for 12-48 hours; The electrostatic self-assembly comprises the following steps: 5-20 parts of the sheet-shaped heat-conducting filler with negative charge and the magnetic filler with positive charge in a mass ratio of 1:0.5-1.5 are dispersed in 60 parts of deionized water, stirred at 100-200 r / min for 15-60 min, and then left to stand for 15-30 min, and the deionized water is washed and the sodium chloride salt is extracted by suction filtration, and the anisotropic hybrid heat-conducting and wave-absorbing filler is obtained by drying; The method for coating the prepared heat-conducting and wave-absorbing coating slurry on the metal foil base layer is one of blade coating, spraying, slot coating, and dipping; The orientation and pre-solidification method comprises the following steps: the coated sheet is placed in a vacuum oven, two electrode plates are placed on the vacuum oven, the electrode plates are parallel to each other but inclined to the horizontal plane as a whole, the included angle between the electrode plates and the horizontal plane is 30°-60°, the electrode plates are connected to a voltage with an amplitude of 500-3000 v and a frequency of 1-10 Hz, and the sheet is pre-solidified in the electric field at a temperature lower than the solidification temperature for 10-30 min to lock the orientation of the filler and ensure that the filler does not collapse.

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