Preparation method of ultralow-profile metal foil with low permeation holes

Abstract

The invention discloses a preparation method of an ultra-low profile metal foil with low permeation holes. The preparation method comprises the following steps: S10, forming a stripping layer on the surface of a carrier foil; s20, electroplating a first metal foil on one surface, far away from the carrier foil, of the stripping layer; s30, sputtering a second metal foil on the surface, far away from the carrier foil, of the first metal foil; s40, electroplating a third metal foil on the surface, far away from the carrier foil, of the second metal foil; and S50, stripping the first metal foil, the second metal foil and the third metal foil from the carrier foil to obtain the ultralow-profile metal foil. Wherein the first metal foil, the second metal foil and the third metal foil form an ultra-low profile metal foil; the thickness of the first metal foil is 1 / 4-3 / 4 of the thickness of the ultra-low profile metal foil, and the second metal foil at least comprises Ni element. A compact metal foil is formed by combining an electroplating-sputtering-electroplating sandwich structure with a controllable stripping technology, permeation of chemical liquid medicine is blocked, the problem of permeation holes of traditional electrolytic copper foil is solved, and the yield of fine lines is increased.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal foil, in particular to a preparation method of ultra-low profile metal foil with low penetration hole. BACKGROUND

[0002] With the rapid development of global information technology towards digitization and networking, there is currently a need to meet the demand for super large capacity information transmission, high speed and ultra high density information processing, which undoubtedly puts forward more stringent requirements on the performance of electrolytic metal foil. As a key material, high-frequency transmission copper foil significantly affects the stability and reliability of signal transmission in high-frequency signal transmission scenarios.

[0003] In order to ensure that the metal foil has high-frequency transmission performance, the metal foil has an ultra-low profile surface. However, the high-frequency low-profile metal foil in the prior art often has a penetration hole, which in turn causes the circuit prepared thereby to have an open circuit or short circuit phenomenon.

[0004] In view of the above, in order to solve the problem of penetration hole, it is urgent to develop a preparation method of low-profile and low-penetration hole metal foil. SUMMARY

[0005] Therefore, the main purpose of the present application is to provide a preparation method of ultra-low profile metal foil with low penetration hole, which can solve the problem of penetration hole of high-frequency low-profile metal foil, avoid the open circuit or short circuit phenomenon of the circuit, and in turn improve the quality reliability of the circuit.

[0006] To achieve the above purpose, the present application provides a preparation method of ultra-low profile metal foil with low penetration hole, comprising the following steps:

[0007] (1) forming a stripping layer on the surface of a carrier foil;

[0008] (2) electroplating a first metal foil on the surface of the stripping layer away from the carrier foil;

[0009] (3) sputtering a second metal foil on the surface of the first metal foil away from the carrier foil;

[0010] (4) electroplating a third metal foil on the surface of the second metal foil away from the carrier foil;

[0011] (5) stripping the first metal foil, the second metal foil and the third metal foil from the carrier foil as a whole, i.e. obtaining an ultra-low profile metal foil;

[0012] Wherein, the first metal foil, the second metal foil and the third metal foil constitute an ultra-low profile metal foil; the thickness of the first metal foil is 1 / 4~3 / 4 of the thickness of the ultra-low profile metal foil, and the second metal foil at least comprises Ni element.

[0013] Optionally, the thickness of the peeling layer is 10 nm-1 micron, and the thickness of the second metal foil is 10 nm-1 micron.

[0014] Optionally, the second metal foil further comprises at least one of Co, P, Cr, and W.

[0015] Optionally, the second metal foil further comprises Al2O3.

[0016] Optionally, the second metal foil is formed by high-power pulse magnetron sputtering, and the peak power density is ≥1000 W / cm2.

[0017] Optionally, the carrier foil is subjected to degreasing treatment on the surface of the carrier foil before sputtering and / or electroplating of the peeling layer, and is dried and subjected to plasma treatment.

[0018] Optionally, the first metal foil is subjected to distilled water cleaning, vacuum drying, and plasma treatment before the second metal foil is formed.

[0019] Optionally, a transition layer is arranged between the second metal foil and the third metal foil.

[0020] Optionally, the transition layer comprises elements of the second metal foil and elements of the third metal foil.

[0021] Optionally, the third metal foil is made by a segmented process.

[0022] Compared with the prior art, the present application has the beneficial effect that: the ultra-low profile metal foil adopts a combination of a "sandwich structure design" of electroplating-sputtering-electroplating and a controllable peeling technology to achieve ultra-low surface roughness and chemical permeability. The second metal foil contains a nickel component, which can effectively inhibit grain boundary migration, eliminate pores, or block the penetration path using a grain boundary-free structure, thereby inhibiting the further generation of penetration holes; the second metal foil is formed by sputtering to form a dense metal foil, which blocks the penetration of etching liquid / chemical liquid, solves the "penetration hole problem" of traditional electrolytic copper foil, and improves the yield of fine lines. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a flowchart of a preparation method of a low-penetration-hole ultra-low profile metal foil provided by an embodiment of the present application. DETAILED DESCRIPTION

[0024] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0025] In the description and claims of the specification, it is to be understood that the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", and the like refer to the orientation or position shown in the drawings, and are used only for convenience in describing the embodiments of the present application, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be construed as limiting the embodiments of the present application.

[0026] In addition, the terms first, second, etc. in the specification and claims are only used for the purpose of distinguishing the description of the same technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated, nor necessarily describing the order or time sequence. The terms are interchangeable under appropriate circumstances. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features.

[0027] Please refer to Figure 1 , Figure 1 is a flow chart of a preparation method of a low-permeability hole ultra-low profile metal foil according to an embodiment of the present application. The preparation method of the ultra-low profile metal foil comprises the following steps:

[0028] S10: forming a stripping layer on the surface of the carrier foil;

[0029] S20: electroplating a first metal foil on the surface of the stripping layer away from the carrier foil;

[0030] S30: sputtering a second metal foil on the surface of the first metal foil away from the carrier foil;

[0031] S40: electroplating a third metal foil on the surface of the second metal foil away from the carrier foil;

[0032] S50: stripping the first metal foil, the second metal foil and the third metal foil from the carrier foil as a whole, i.e. obtaining an ultra-low profile metal foil.

[0033] The first metal foil, the second metal foil and the third metal foil form an ultra-low profile metal foil. The ultra-low profile metal foil is designed in a sandwich structure of electroplating-sputtering-electroplating and combined with a controllable peeling technology to achieve ultra-low surface roughness and chemical permeability resistance. In addition, the thickness of the first metal foil is 1 / 4-3 / 4 of the thickness of the ultra-low profile metal foil, so that the thickness of the first metal foil is in a proper range, and the penetration hole in the subsequent process cannot be covered, and the problem of the penetration hole cannot be solved, and the thickness of the third metal foil is relatively thick, and the penetration hole is more likely to occur. Therefore, the thickness of the first metal foil is 1 / 4-3 / 4 of the thickness of the ultra-low profile metal foil, and the problem of the penetration hole can be effectively solved. Further, the second metal foil at least comprises Ni element. The second metal foil adopts a nickel-containing component, which can effectively inhibit grain boundary migration, eliminate pores, or block the penetration path by using a grain boundary structure, thereby inhibiting the further generation of the penetration hole; the second metal foil is formed by a sputtering method to form a dense metal foil, which blocks the penetration of the etching liquid / chemical liquid, solves the problem of the penetration hole of the traditional electrolytic copper foil, and improves the yield of the fine line.

[0034] In one embodiment, step S10 of forming a peeling layer on the surface of the carrier foil specifically comprises:

[0035] S11: degreasing treatment is performed on the surface of the carrier foil, and drying is performed;

[0036] S12: after drying, the surface of the carrier foil is treated by plasma;

[0037] S13: a peeling layer is formed on the surface of the carrier foil.

[0038] In the embodiment of the present application, the surface of the carrier foil is subjected to degreasing treatment and drying and plasma treatment before sputtering and / or electroplating of the peeling layer. The degreasing agent is used to remove dirt, fingerprints and other contaminants on the surface of the carrier foil. The degreasing agent is composed of an alkaline degreasing solution and a non-ionic surfactant. Specifically, the alkaline degreasing solution is composed of 30 g / L NaOH and 20 g / L Na3PO4. The degreasing treatment process is assisted by ultrasonic treatment, the ultrasonic frequency is 40 kHz, the ultrasonic power is 300 W, the ultrasonic temperature is 60±5℃, the treatment time is 3-5 min, the particle contaminants can be peeled off, the residual amount of grease is ≤0.1 mg / m², and vacuum infrared radiation heating drying is performed, the vacuum pressure is 10 Pa negative pressure, the heating temperature is 100℃, and the heating time is 120 s. Then the surface of the carrier foil is bombarded by plasma, and the linear speed of the plasma treatment is 1-4 m / min. The surface of the carrier foil is activated to improve the adhesion. Finally, the peeling layer is formed on the surface of the carrier foil. -2

[0039] ​Optionally, the release layer is processed on the carrier foil by at least one of physical vapor deposition, electrolytic method or coating. Illustratively, the electrolytic method is to electroplate the release layer on the surface of the carrier foil close to the release layer. The physical vapor deposition is to use a vacuum device, adjust the composition of the target material, and deposit the release layer. The coating method is to coat the release layer on the surface of the carrier foil close to the release layer.

[0040] Preferably, in the embodiments of the present application, the physical vapor deposition is to use a magnetron sputtering to prepare a release layer with high purity and good uniformity, so that an impurity-free, high-quality and uniform-thickness release layer can be obtained, which is suitable for the demand of nanoscale thickness release layer. At the same time, the physical vapor deposition method can form a firm release layer on the carrier foil, which is conducive to stabilizing the peeling strength between the carrier foil and the release layer, and is not easy to fall off or peel off. The physical vapor deposition method for preparing the release layer has high purity, good uniformity, excellent adhesion, no pollution, moderate operating temperature, high efficiency, and high controllability of the composition, structure and thickness of the release layer, which is convenient for adjusting and optimizing the performance of the release layer. Illustratively, the sputtering temperature is 80-120℃, the sputtering power is DC 3-5 kW, the argon pressure is 0.3-0.6 Pa, the deposition rate is 0.5-1.2 nm / s, and the thickness control is 50-200 nm.

[0041] In the embodiments of the present application, the release layer plays a role of peeling, further improving the peeling stability of the carrier metal foil. After high-temperature pressing, peeling is performed, and the release layer can be left on the carrier layer, or left on the first metal foil, or part of the release layer is left on the carrier layer and part of the release layer is left on the first metal foil.

[0042] It is worth noting that the release layer includes at least one layer, and the material of the release layer can be an organic release layer, an inorganic release layer or a combination of the two.

[0043] Further, the material of the release layer is an organic release layer, which includes at least one of a nitrogen-containing compound, a sulfur-containing compound, and a carboxylic acid. Specifically, the release layer includes at least one of benzotriazole (BTA), carboxybenzotriazole (CBTA), N,N,(benzotriazolylmethyl)urea (BTD-U), 3-amino-1H-1,2,4-triazole (ATA), mercaptobenzothiazole (MBT), thiocyanuric acid (TCA), and 2-benzimidazole mercaptan (BIT), monobasic acid, oleic acid, linoleic acid, and linolenic acid. Preferably, multiple organic release layers are used in combination. This further improves the peeling stability of the carrier metal foil.

[0044] Further, the material of the peeling layer is an inorganic peeling layer, preferably including a metal base layer and / or an alloy layer, specifically including at least one of Ni-Mo, Ni-Co, Cr-Co, Ni-Cr, Mo-Co, W-Ni. Compared with the organic peeling layer, the peeling layer formed by the metal base layer and / or the alloy layer can meet the stable peeling performance after high-temperature pressing.

[0045] Further, the material of the peeling layer includes a mixed and / or stacked inorganic layer peeling layer and an organic layer peeling layer.

[0046] In one embodiment, step S20: electroplating a first metal foil on the surface of the peeling layer away from the carrier foil. The first metal foil includes at least one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold. Exemplarily, the first metal foil is a copper foil. The specific electroplating process includes: using a copper pyrophosphate system, including an electrolyte prepared from 20-30 g / L of Cu 2+ , 250-300 g / L of K4P2O7, 50-60 g / L of H2SO4, 3-5 ppm of sodium mercaptopropane sulfonate (MPS), 80-120 ppm of polyethylene glycol (PEG-6000), 0.5-1 ppm of tetrahydrothiazole thione (H1) and 50-70 ppm of chloride ion (Cl - ), heating to 35-45℃, and electroplating to form the first metal foil.

[0047] Preferably, the thickness of the first metal foil is controlled to be 1 / 4-3 / 4 of the thickness of the ultra-low profile metal foil, so that the thickness of the first metal foil is in a suitable range, and the penetration hole cannot be covered in the later process due to the thickness being too thick, and the problem of the penetration hole cannot be solved; and the third metal foil is relatively thick, and the penetration hole is more likely to occur due to the thickness being too thin. Therefore, the thickness of the first metal foil is 1 / 4-3 / 4 of the thickness of the ultra-low profile metal foil, which can effectively solve the problem of the penetration hole.

[0048] In one embodiment, step S30: sputtering a second metal foil on the surface of the first metal foil away from the carrier foil, specifically including:

[0049] S31: cleaning the first metal foil and drying;

[0050] S32: after drying, treating the surface of the first metal foil with plasma;

[0051] S33: sputtering a second metal foil on the surface of the first metal foil away from the carrier foil.

[0052] In the embodiments of the present application, the first metal foil is vacuum dried and plasma treated before forming the second metal foil. The first metal foil is cleaned before forming the second metal foil to clean the electroplating residual ions / organic matter, avoid the second metal foil from having pinholes, and prevent oxidation by vacuum drying. The surface of the carrier foil is then bombarded by plasma at a linear speed of 1-4 m / min. The surface of the carrier foil is activated to improve adhesion.

[0053] In the embodiments of the present application, the second metal foil is formed by high-power pulsed magnetron sputtering at a peak power density of ≥1000 W / cm². By means of ultra-high power pulses, electrons are accelerated and collide violently to generate high-density plasma, and high-energy ions bombard the target surface under a strong electric field. The sputtered metal atoms (M) are ionized by high-density electron collision, and a high-ionization-rate plasma is formed at an ionization rate of >70%. A negative bias voltage is applied to attract positive ions to collide with the substrate at high speed. Thus, a dense, uniform, high-performance thin film, a nanoscale dense, zero-pore thin film, and a reduced number of permeable holes on the surface of the metal foil are prepared. Exemplarily, the high-power pulse has a peak power density of 1000-1500 W / cm², a pulse frequency of 100-500 Hz, a pulse width of 50-100 μs, a working pressure of 0.5-1.0 Pa, and a bias voltage of -50V to -150V. Further, the second metal foil formed by magnetron sputtering has columnar crystal inhibition capability to generate a continuous thin film without grain boundary pores, thereby eliminating the permeable channels from the root.

[0054] Further, the second metal foil further comprises at least one of Co, P, Cr, and W. The second metal foil is formed of a Ni alloy, which can inhibit grain boundary migration or form a grain boundary-free layer to change the growth direction of the third metal foil, thereby facilitating the formation of a dense third metal foil and further reducing the permeable holes of the ultra-low profile copper foil. Exemplarily, a Ni-W alloy can inhibit the grain boundary migration of the first metal foil and eliminate pores. A Ni-P alloy is grain boundary-free, which inhibits the third metal foil from continuing to grow according to the pores of the first metal foil, thereby eliminating pores and forming a dense metal foil.

[0055] It is worth noting that the second metal foil further comprises Al2O3. The Al2O3 blocks the metal grain boundaries to form a “labyrinth effect” to block the path and inhibit the pores of the first metal foil from continuing to grow and extend to the third metal foil. The particle size distribution of the Al2O3 is D50=8±2 nm.

[0056] In one embodiment, step S40: electroplating a third metal foil on the surface of the second metal foil away from the carrier foil, the third metal foil comprising at least one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold. Exemplarily, the first metal foil is a copper foil. The specific electroplating process comprises: using a copper pyrophosphate system, including 40-60 g / L of Cu 2+ , 250-300 g / L of K4P2O7, 1-3 ppm of 2-mercaptobenzimidazole (MBI), preparing an electrolyte with a pH value of 8.2-8.8, heating to 45°C, electroplating at a current density of 5-10 A to form the third metal foil.

[0057] Preferably, the third metal foil is made by a segmented process. By "gradient electroplating + microstructure regulation", a dense metal foil is formed to meet the needs of fine lines. A large current is used to form a high overpotential, which in turn rapidly nucleates to form columnar crystals, increasing the density of the metal foil. Then, the reverse current is used to dissolve the dendrites to suppress the protrusions, forming a surface with extremely low roughness, which in turn facilitates the continuous control of the adverse development of metal foil pores, making the metal foil non-permeable, and meeting the needs of fine lines.

[0058] In one embodiment, step S50: the first metal foil, the second metal foil and the third metal foil are peeled off from the carrier foil as a whole, i.e. to obtain the ultra-low profile metal foil. The peeling can be physical peeling or non-physical peeling. The physical peeling can be manual peeling or equipment peeling. The non-physical peeling can be etching, etc. Mechanical peeling is performed by using professional peeling equipment. According to the thickness, material and carrier type of the metal foil, the peeling speed, peeling force and tool pressure of the equipment are adjusted to ensure that the metal foil is not damaged during the peeling process. It should be noted that the thickness of the peeling layer is 10 nanometers to 1 micrometer. The peeling layer plays a peeling role, further improving the peeling stability of the metal foil with carrier. When the peeling layer is too thin, it is difficult to form a film, which leads to unstable peeling and affects the quality and processing efficiency of the metal foil. When the peeling layer is too thick, the first metal foil cannot be smoothly spread on the surface of the peeling layer during the formation of the first metal foil. The proportion of penetration holes in the initial stage of the formation of the first metal foil is greatly increased, which eventually leads to a large number of penetration holes in the metal foil, and further leads to the phenomenon of open circuit or short circuit of the circuit prepared by the metal foil. Therefore, the thickness of the peeling layer is 10 nanometers to 1 micrometer, which can ensure stable peeling and reduce the penetration holes of the first metal foil, thereby greatly reducing the number of penetration holes of the metal foil and improving the processing capacity of the fine circuit. The role of the second metal foil is to inhibit the migration of grain boundaries, or to form a grain boundary-free layer, and to change the growth direction of the third metal foil, which is beneficial to the formation of a dense third metal foil, thereby reducing the penetration holes of the ultra-low profile metal foil. When the second metal foil is too thin, island growth may occur, which makes the second metal foil uneven, leading to the continuous growth and extension of the penetration holes of the first metal foil to the third metal foil, and further leading to the phenomenon of open circuit or short circuit of the circuit prepared by the metal foil; when the second metal foil is too thick, it will affect the overall conductivity of the metal foil, and further affect the transmission of high-frequency and high-speed signals of the metal foil, leading to large loss and unable to meet the high-frequency demand. Therefore, the thickness of the second metal foil is controlled to be 10 nanometers to 1 micrometer, which can reduce the penetration holes of the metal foil and meet the demand of high-frequency and high-speed signal transmission, and improve the quality and reliability of the circuit.

[0059] In one embodiment, a transition layer is arranged between the second metal foil and the third metal foil. The second metal foil functions to inhibit grain boundary migration, or to form a grain boundary-free layer, to change the growth direction of the third metal foil, to facilitate the formation of a dense third metal foil, and to reduce the penetration holes of the ultra-low profile metal foil. The third metal foil functions as a circuit conductor. The second metal foil and the third metal foil are different in material and have different coefficients of thermal expansion, and the mismatch of the coefficients of thermal expansion will generate thermal stress, leading to interlayer cracking. At the same time, the second metal foil and the third metal foil are different in material, which will cause the problem of insufficient bonding force. The transition layer arranged between the second metal foil and the third metal foil, on the one hand, causes the gradient change of the coefficient of thermal expansion, and is not easy to generate thermal stress when heated, avoiding interlayer cracking. On the other hand, the material gradient design optimizes the bonding force between the second metal foil and the third metal foil, avoiding interlayer separation.

[0060] Further, the transition layer includes elements of the second metal foil and elements of the third metal foil. By designing the transition layer to include elements of the second metal foil and elements of the third metal foil, because the transition layer has both the same elements as the second metal foil and the same elements as the third metal foil, the transition layer has a higher bonding force with the second metal foil and a higher bonding force with the third metal foil, and does not appear interlayer separation of the metal foil itself, affecting the processing quality and reliability of the circuit.

[0061] In summary, compared with the prior art, the beneficial effects of the present application are that the ultra-low profile metal foil adopts the combination of the "electroplating-sputtering-electroplating" sandwich structure design and controllable peeling technology to achieve ultra-low surface roughness and chemical penetration resistance. The second metal foil contains nickel components, which can effectively inhibit grain boundary migration, eliminate pores, or use a grain boundary-free structure to block the penetration path, thereby inhibiting the further generation of penetration holes. The second metal foil adopts a sputtering method to form a dense metal foil, which blocks the penetration of etching liquid / chemical liquid, solves the "penetration hole problem" of traditional electrolytic copper foil, and improves the yield of fine circuits.

[0062] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not exist contradictions, they should be considered as the scope of the present disclosure.

[0063] The above-described embodiments only express several implementation manners of the present application, facilitate specific and detailed understanding of the technical solutions of the present application, but cannot be understood as a limitation on the patent protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. It should be understood that, on the basis of the technical solutions provided by the present application, the technical solutions obtained by logical analysis, reasoning or limited experiments by the skilled person in the art all belong to the protection scope of the appended claims of the present application. Therefore, the patent protection scope of the present application should be subject to the content of the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A method for preparing an ultra-low profile metal foil with low permeability pores, characterized in that: The method for preparing the ultra-low profile metal foil comprises the following steps: (1) forming a release layer on the surface of the carrier foil; (2) electroplating a first metal foil on a surface of the release layer away from the carrier foil; (3) sputtering a second metal foil on a surface of the first metal foil away from the carrier foil; (4) electroplating a third metal foil on a surface of the second metal foil away from the carrier foil; (5) peeling the first metal foil, the second metal foil, and the third metal foil from the carrier foil as a whole, thereby obtaining an ultra-low profile metal foil; The first metal foil, the second metal foil and the third metal foil form an ultra-low profile metal foil; the thickness of the first metal foil is 1 / 4 to 3 / 4 of the thickness of the ultra-low profile metal foil, and the second metal foil includes at least Ni element.

2. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: The thickness of the peeling layer is 10 nanometers to 1 micrometer, and the thickness of the second metal foil is 10 nanometers to 1 micrometer.

3. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: The second metal foil further includes at least one element selected from the group consisting of Co, P, Cr, and W.

4. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: The second metal foil further includes Al2O3.

5. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: The second metal foil is formed by high-power pulsed magnetron sputtering, and the peak power density is ≥1000 W / cm².

6. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: The carrier foil is subjected to a degreasing treatment on its surface before the release layer is sputtered and / or electroplated, and is dried and plasma treated.

7. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: Before forming the second metal foil, the first metal foil is cleaned with distilled water, vacuum-dried, and plasma-treated.

8. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: A transition layer is provided between the second metal foil and the third metal foil.

9. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 8, wherein: The transition layer includes elements of the second metal foil and elements of the third metal foil.

10. The method for preparing an ultra-low profile metal foil with low permeability pores according to claim 1, wherein: The third metal foil is composited by adopting a segmented process.

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