Iron-plated metal foil and method for producing iron-plated metal foil

Abstract

An iron-plated metal foil according to the present invention comprises: a metal foil that has a thickness of not more than 100 μm; and an iron-plated film that is provided on the metal foil and that has a thickness of not more than 10 μm, wherein when the thickness of the metal foil is 5 μm, the thickness of the iron-plated film is 1 μm, and the iron-plated metal foil is processed to have a longitudinal and transverse size of 50 mm×50 mm, the amount of warpage of the iron-plated metal foil is not more than 15 mm.

Description

Iron-plated metal foil and method for manufacturing iron-plated metal foil

[0001] The present invention relates to an iron-plated metal foil and a method for producing the iron-plated metal foil.

[0002] Iron-plated metal surfaces are used as electromagnetic shielding materials for electronic devices. In particular, electronic devices have become smaller in recent years, which has led to a demand for thinner metal foils, which are the base materials for plating.

[0003] Patent Document 1 describes a plating material containing 0.02 to 0.5 wt % of nitrogen in an iron plating film. Furthermore, Patent Document 2 describes a material obtained by iron plating a cold-rolled steel sheet as a technology related to continuous strip plating.

[0004] JP-A-9-228092 Patent No. 7205664

[0005] On the other hand, as the base material becomes thinner, the shape of the material after plating becomes more susceptible to the effects of internal plating stress. Specifically, if tensile stress occurs in the plating film, the material will warp toward the plated surface. Iron plating films are particularly susceptible to tensile stress, making them prone to warping (curling), and materials that have curled cannot be used as raw materials for electronic components.

[0006] However, the nitrogen-containing iron plating described in Patent Document 1 does not include any explanation regarding warping of the plating, and it is expected that the internal stress is high, probably because the plating has a hardness of 1000 to 1100 Hv.

[0007] Furthermore, Patent Document 2 describes a method of iron-plating a steel material and then subjecting the iron plating to a surface treatment such as chemical conversion treatment or painting, but does not mention an iron-plated metal foil in which warping is well suppressed.

[0008] For this reason, there is a demand for the development of a material that reduces internal stress even when iron is plated on a thin material such as a metal foil, thereby effectively suppressing warping.

[0009] In view of such problems, embodiments of the present invention provide an iron-plated metal foil in which warping is effectively suppressed and a method for manufacturing the iron-plated metal foil.

[0010] The embodiments of the present invention that solve the above problems are specified as follows: 1. An iron-plated metal foil comprising a metal foil having a thickness of 100 μm or less and an iron-plated film having a thickness of 10 μm or less provided on the metal foil, wherein the iron-plated metal foil has a warpage of 15 mm or less when the metal foil is 5 μm thick, the iron-plated film is 1 μm thick, and the iron-plated metal foil is processed to a size of 50 mm x 50 mm. 2. The iron-plated metal foil according to 1 above, wherein the iron-plated film has a thickness of 1 μm or less. 3. The iron-plated metal foil according to 1 or 2 above, wherein the iron-plated film has a surface roughness Ra of 0.4 μm or less. 4. The iron-plated metal foil according to any one of 1 to 3 above, wherein the metal foil is a nickel foil. 5. 5. A method for producing an iron-plated metal foil according to any one of paragraphs 1 to 4, in which an iron plating film is formed on the surface of a metal foil by electroplating, wherein the pH of the iron plating solution used in the electroplating is 3.5 to 5.5. 6. A current density of the electroplating is 0.1 to 20 A / dm 2 7. The method for producing an iron-plated metal foil according to 5 above, wherein the iron plating solution used in the electroplating has a trivalent iron ion concentration of 0.7 g / L or less. 8. The method for producing an iron-plated metal foil according to any one of 5 to 7 above, wherein the iron plating solution used in the electroplating contains a benzothiazole-based compound. 9. The method for producing an iron-plated metal foil according to any one of 5 to 8 above, wherein the electroplating is carried out so that a current flows through one surface of the metal foil.

[0011] According to the embodiments of the present invention, it is possible to provide an iron-plated metal foil in which warping is effectively suppressed and a method for manufacturing the iron-plated metal foil.

[0012] FIG. 2 is a schematic diagram for explaining a method for measuring the amount of warpage of an iron-plated metal foil.

[0013] Preferred embodiments of the present invention will be described in detail below, but the present invention should not be construed as being limited thereto. Various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the gist of the present invention. The multiple components disclosed in this embodiment can be appropriately combined to form various inventions. For example, some components may be omitted from all the components shown in this embodiment.

[0014] <Iron-Plated Metal Foil> The iron-plated metal foil according to the embodiment of the present invention includes a metal foil and an iron-plated film provided on the metal foil. Note that the iron-plated metal foil according to the embodiment of the present invention may have an intermediate layer, such as an iron strike plating layer or a nickel plating layer, provided between the metal foil and the iron-plated film, or may have an anti-corrosion layer, an iron compound layer, an iron alloy layer, or the like, provided on the surface of the iron-plated film, to the extent that the effects of the present invention are not impaired.

[0015] (Metal Foil) The iron-plated metal foil according to the embodiment of the present invention has a thickness of 100 μm or less. When the iron-plated metal foil according to the embodiment of the present invention is used in a small electronic device, a thickness of 100 μm or less has the effect of reducing the mass and volume. The iron-plated metal foil according to the embodiment of the present invention preferably has a thickness of 3 to 100 μm, more preferably 4 to 50 μm.

[0016] The metal foil of the iron-plated metal foil according to the embodiment of the present invention is not particularly limited, but examples thereof include nickel foil, nickel alloy foil, copper foil, copper alloy foil, titanium foil, titanium alloy foil, stainless steel foil, permalloy foil, 42 alloy foil, Kovar foil, Inconel foil, and Hastelloy foil.

[0017] (Iron Plating Film) The iron plating film of the iron-plated metal foil according to the embodiment of the present invention has a thickness of 10 μm or less. When the iron-plated metal foil according to the embodiment of the present invention is used in a small electronic device, an iron plating film having a thickness of 10 μm or less has the effect of reducing the mass and volume. The iron plating film of the iron-plated metal foil according to the embodiment of the present invention preferably has a thickness of 5 μm or less, more preferably 3 μm or less, and even more preferably 1 μm or less. The lower limit of the iron plating film of the iron-plated metal foil according to the embodiment of the present invention is not particularly limited, and may be, for example, 0.1 μm or more, 0.2 μm or more, or 0.4 μm or more. The thickness of the iron plating film of the iron-plated metal foil can be measured using a fluorescent X-ray film thickness meter (SFT9550X, manufactured by Hitachi High-Technologies Corporation) or the like.

[0018] The composition of the iron plating film of the iron-plated metal foil according to the embodiment of the present invention is not particularly limited, but it is desirable from the viewpoint of plating corrosion resistance that it contains as few impurities other than iron as possible, for example, 99.9% iron.

[0019] (Warpage) The iron-plated metal foil according to the embodiment of the present invention has a metal foil thickness of 5 μm, an iron plating film thickness of 1 μm, and a warpage of 15 mm or less when processed into a size of 50 mm x 50 mm. The iron-plated metal foil according to the embodiment of the present invention thus exhibits excellent suppression of warpage. The warpage is preferably 10 mm or less, more preferably 8 mm or less, even more preferably 6 mm or less, and even more preferably 4 mm or less.

[0020] The warpage of the iron-plated metal foil according to the embodiment of the present invention can be measured as follows. First, the iron-plated metal foil is processed to a thickness of 5 μm, a thickness of 1 μm, and a size of 50 mm x 50 mm. When the thickness of the iron-plated metal foil is greater than 5 μm or the thickness of the iron-plated film is greater than 1 μm, the thickness can be reduced to 5 μm or 1 μm, respectively, by etching or mechanical polishing. When the thickness of the iron-plated metal foil is less than 5 μm or the thickness of the iron-plated film is less than 1 μm, the thickness can be increased to 5 μm or 1 μm, respectively, by deposition using vapor deposition or sputtering. Although these methods require a long time for deposition, they generate almost no stress, allowing accurate measurement of the warpage of the iron-plated metal foil. The iron-plated metal foil can be processed to the desired size by cutting or other methods. When iron-plated metal foil warps, it always bends with the iron plating film facing inward. Therefore, when the iron-plated metal foil is placed on a horizontal table with the metal foil side facing downwards, as shown in Figure 1, both edges of the metal foil surface are slightly raised. The distance between the edge of the metal foil and the horizontal table is measured and used as the amount of warpage. If the edge of the metal foil is not linear (e.g., if the edge is wavy), the distance between the edge of the metal foil and the horizontal table varies depending on the measurement position. In this case, the "amount of warpage" of the iron-plated metal foil in this invention is defined as the distance at the maximum position between the edge of the metal foil and the horizontal table. The "distance between the edge of the metal foil and the horizontal table" refers to the distance between the starting point of a perpendicular line drawn from the horizontal table and the intersection point of the perpendicular line with the edge of the metal foil. The distance can be obtained, for example, by placing a scale (straight ruler) vertically on a horizontal table and measuring the distance between the edge of the metal foil and the horizontal table.

[0021] (Surface Roughness) The surface roughness Ra of the iron plating film of the iron-plated metal foil according to the embodiment of the present invention is preferably 0.4 μm or less. This configuration provides the effect of making the iron plating film of the iron-plated metal foil rust-resistant. The surface roughness Ra can be evaluated using an OPTELICS HYBRID MC2000 manufactured by Lasertec Corporation in accordance with JIS Standard B0601 (2013). The surface roughness Ra of the iron plating film of the iron-plated metal foil according to the embodiment of the present invention is preferably 0.3 μm or less, more preferably 0.2 μm or less, and even more preferably 0.1 μm or less. The lower limit of the surface roughness Ra of the iron plating film of the iron-plated metal foil according to the embodiment of the present invention is not particularly limited, and may be, for example, 0.005 μm or more, or 0.01 μm or more.

[0022] (Carbon Concentration) The carbon concentration in the iron plating film of the iron-plated metal foil according to the embodiment of the present invention is preferably 100 ppm or less. When the carbon concentration in the iron plating film is 100 ppm or less, corrosion resistance and bendability are improved. The relationship between carbon concentration and corrosion resistance is related to iron-carbon compounds formed in the iron plating film. That is, the presence of iron-carbon compounds forms local cells in the iron plating film, making it more likely that spot-like corrosion (pitting corrosion) will occur in the plating. On the other hand, with regard to the relationship between carbon concentration and bendability, as the carbon concentration in the iron plating film increases, the plating becomes harder and the bendability of the iron plating film deteriorates. The carbon concentration in the iron plating film of the iron-plated metal foil according to the embodiment of the present invention is more preferably 80 ppm or less, even more preferably 50 ppm or less, and even more preferably 20 ppm or less. The carbon concentration in the iron plating film of the iron-plated metal foil according to the embodiment of the present invention can be measured using a TOF-SIMS 4S manufactured by ION-TOF.

[0023] (Uses) As described above, the iron-plated metal foil according to the embodiment of the present invention is well suppressed in warpage, and therefore the iron-plated metal foil according to the embodiment of the present invention can be used in many industrial fields, such as electronic components and electromagnetic shielding materials.

[0024] <Method for Manufacturing Iron-Plated Metal Foil> In the method for manufacturing an iron-plated metal foil according to an embodiment of the present invention, first, a metal foil is prepared. The metal foil can be manufactured, for example, by rolling a metal ingot to obtain a metal foil (rolled foil), or by electroplating to obtain a metal foil (electrolytic foil). However, the method is not limited to these, and the metal foil may be manufactured by any method according to an embodiment of the present invention.

[0025] Next, an iron plating film is formed on the surface of the metal foil by electroplating. Internal stresses usually occur in plated films; for example, compressive stress occurs in zinc plating and cadmium plating, and tensile stress occurs in iron, nickel, and chromium plating. When plating a thin metal foil as in the present invention, internal stress in the plating easily causes warping (curling) of the metal foil. The method for producing an iron-plated metal foil according to an embodiment of the present invention effectively suppresses this curling.

[0026] Iron plating solutions can be used that contain inorganic chemicals such as iron(II) sulfate, iron sulfamate, iron(II) chloride, and ammonium chloride, as well as organic additives. For example, sulfur-containing compounds such as iron sulfate and iron sulfamate have the effect of reducing the internal stress of the plating film, so it is preferable to add them in a high proportion. Similarly, benzothiazole compounds such as saccharin sodium can also reduce the internal stress of the plating film, as described below, so they can be added in small amounts. However, if the amount added is too large, the corrosion resistance of the plating will decrease and rust will easily form, so the amount added must be adjusted. As for other additives, small amounts of nonionic surfactants can also be added as pitting inhibitors.

[0027] The concentrations of the chemicals constituting the iron plating solution can be, for example, 150 to 300 g / L of iron sulfate (II, heptahydrate), 10 to 100 g / L of iron chloride (II, tetrahydrate), and 4 to 50 g / L of ammonium chloride. The temperature of the iron plating solution is preferably 30 to 70°C, and more preferably 32 to 55°C.

[0028] If a large amount of hydrogen is generated during plating, it will be absorbed into the plating film. The hydrogen absorbed into the plating film will escape from the plating film over time, generating tensile stress within the plating. The tensile stress causes curling in the metal foil on which the iron plating film is formed, resulting in problems such as difficulty in handling after plating. In contrast, in the method for producing iron-plated metal foil according to an embodiment of the present invention, the pH of the iron plating solution is controlled to 3.5 to 5.5. By controlling the pH of the iron plating solution to 3.5 or higher, it is possible to suppress the generation of hydrogen during plating and reduce the amount of hydrogen absorbed into the plating film. Furthermore, by controlling the pH of the iron plating solution to 5.5 or lower, it is possible to suppress the generation of insoluble iron hydroxide in the plating solution and prevent the occurrence of poor plating appearance. The pH of the iron plating solution is preferably 4.25 to 4.75.

[0029] The current density of the electroplating is 0.1 to 20 A / dm 2 It is preferable that the current density of the electroplating is 0.1 A / dm 2 When the current density of the electroplating is 20 A / dm or more, it is possible to prevent the occurrence of unplated portions in a part of the plating. 2 If the current density is less than 1000 kJ / s, scorching of the plating can be suppressed, and the plating film can be prevented from having a poor appearance. If scorching of the plating occurs, the unevenness of the plating film increases at the location where scorching occurs, which increases the amount of moisture adhered, making drying after plating difficult and causing rust. The current density of electroplating is preferably 2 to 15 A / dm 2 and more preferably 3 to 10 A / dm 2 is.

[0030] The iron plating solution used in electroplating preferably has a trivalent iron ion concentration of 0.7 g / L or less. A trivalent iron ion concentration of 0.7 g / L or less effectively prevents scorching during plating in high current density regions, such as when the metal foil is a strip edge, and also prevents rust from forming during plating and increases in internal stress in the plating film. The iron plating solution used in electroplating preferably has a trivalent iron ion concentration of 0.05 to 0.6 g / L, more preferably 0.05 to 0.5 g / L.

[0031] In the method for producing iron-plated metal foil according to an embodiment of the present invention, the surface of the metal foil is plated with iron, and pure iron is preferably used as the anode for electroplating. An insoluble anode made of platinum-plated titanium can be used as the anode for electroplating. While using an insoluble anode has the advantage of avoiding the problem of anode-induced impurities being mixed into the plating film, it is prone to problems such as a decrease in the pH of the plating solution due to oxygen generation at the anode and the generation of trivalent iron ions. In contrast, a soluble anode such as iron can avoid these problems. Furthermore, using a high-purity iron anode can further reduce the amount of impurities precipitated in the iron plating film.

[0032] The iron plating solution used in electroplating preferably contains a benzothiazole-based compound. Examples of the benzothiazole-based compound include sodium benzothiazole, saccharin, and saccharin sodium. For example, the amount of saccharin sodium added is preferably 0 to 1.0 g / L, more preferably 0 to 0.4 g / L. The benzothiazole-based compound functions as a stress relaxation agent in the iron plating solution, and the addition of this compound can reduce internal plating stress and effectively suppress warpage of the iron-plated metal foil.

[0033] In the method for producing an iron-plated metal foil according to an embodiment of the present invention, iron plating is applied to the surface of the metal foil. However, both the front and back surfaces of the metal foil may be plated, or only one surface may be plated. For example, in conventional plating, a current is passed through a pair of anodes (placed outside the material to be plated) installed in a plating tank, and both surfaces of the metal foil are plated. On the other hand, by supplying a current to only one side of the anode and conducting electroplating so that the current flows through one surface of the metal foil in the plating solution, iron-plated metal foil with different compositions on the front and back surfaces, one side being iron and the other being the material of the metal foil, can be produced. As another example, it is also possible to produce a foil with an iron plating film formed on only one side of the unplated metal foil by contacting one side of the foil with a film or resin and then plating the foil.

[0034] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0035] <Preparation of Samples for Test Examples 1 to 6> (Metal Foil) Nickel foil with a thickness of 5 μm was prepared as the metal foil. The nickel foil was produced by rolling and had a glossy appearance. This nickel foil was cut into a size of 110 mm wide x 200 mm long to prepare metal foil for iron plating in a beaker.

[0036] (Iron plating solution, electroplating method) Two types of iron plating solution, iron plating solution A and iron plating solution B, were prepared. For electroplating, a 2-liter beaker containing the iron plating solution and an anode was used, and the solution was stirred with a stirrer. Next, the nickel foil was placed in the iron plating solution, and the nickel foil and the anode were connected to a DC power source. Next, the current was turned on, and the current density was set to 2 to 23 A / dm. 2 Electroplating was performed for 20 to 200 seconds, forming a 1 μm thick iron plating (iron plating film) on one side of the nickel foil. The temperature of each iron plating solution was 50°C, and the pH was 2.2 to 5.0, with dilute sulfuric acid and aqueous sodium hydroxide used to change the pH. A titanium / platinum-plated insoluble anode and an iron plate were used as the anode. The sample preparation conditions for Test Examples 1 to 6 are shown in Table 1.

[0037] Iron plating solution A: Iron (II) sulfate heptahydrate: 250 g / L, Iron (II) chloride tetrahydrate: 50 g / L, Ammonium chloride: 20 g / L

[0038] Iron plating solution B: Iron (II) sulfate heptahydrate: 250 g / L, Iron (II) chloride tetrahydrate: 50 g / L, Ammonium chloride: 20 g / L, Sodium saccharin dihydrate: 2 g / L

[0039]

[0040] <Composition of Iron Plating Film> The compositions of the iron plating films of the samples of Test Examples 1 to 6 were evaluated by the following method. The compositions were measured using a TOF-SIMS 4S manufactured by ION-TOF, and it was confirmed that all samples were pure iron with a purity of 99.9% or higher.

[0041] <Warpage of iron-plated metal foil> Samples of Test Examples 1 to 5 were cut to a size of 50 mm x 50 mm. Next, as shown in Figure 1, the processed samples were placed with the metal foil side facing downwards on a horizontal table. At this time, both ends (edges) of the surface of the metal foil of the sample were slightly raised. The distance between the edge of the metal foil and the horizontal table was measured, and this was taken as the amount of warpage. The evaluation results are shown in Table 2.

[0042]

[0043] As shown in Table 2, the warpage of the samples of Test Examples 1, 2, 4, and 5, in which the pH of the iron plating solution for electroplating was 4.8 to 5.0, was 15 mm or less, indicating that warpage was well suppressed. On the other hand, the warpage of the sample of Test Example 3, in which the pH of the iron plating solution for electroplating was 2.2, exceeded 15 mm.

[0044] <Surface Roughness Ra of Iron Plating Film> For the samples of Test Examples 1, 5, and 6, the surface roughness Ra of the iron plating film was measured in accordance with JIS Standard B0601 (2013) using an OPTELICS HYBRID MC2000 manufactured by Lasertec Corporation by scanning a field of view measuring 150 μm in length and 150 μm in width. Measurements were performed using a laser light source, a 50x objective lens, a brightness of 230, a light source intensity of 50%, automatic tilt correction, and quadratic curve flatness correction. Measurements were performed at five locations on each sample, and the average value was taken as the surface roughness Ra. The evaluation results are shown in Table 3.

[0045] <Corrosion Resistance> After the samples of Test Examples 1, 5, and 6 were left indoors for 7 days, the surfaces of the iron plating films of the samples were observed under a microscope. The evaluation results are shown in Table 3.

[0046]

[0047] As shown in Table 3, in Test Examples 1 and 5, in which the surface roughness Ra of the iron plating film was 0.4 μm or less, no rust was observed in the corrosion resistance test. On the other hand, in Test Example 6, in which the surface roughness Ra of the iron plating film exceeded 0.4 μm, rust was observed in the corrosion resistance test.

[0048] <Potential for Contribution to SDGs> According to the above-described embodiment, it is possible to provide an iron-plated metal foil with effectively suppressed warpage and a method for manufacturing the iron-plated metal foil, which may improve the yield and performance of products manufactured using the iron-plated metal foil. Therefore, this embodiment may contribute to Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and Goal 12 "Ensure sustainable consumption and production patterns" of the Sustainable Development Goals (SDGs) led by the United Nations.

Claims

1. An iron-plated metal foil comprising a metal foil having a thickness of 100 μm or less and an iron-plated film having a thickness of 10 μm or less provided on said metal foil, wherein the iron-plated metal foil has a thickness of 5 μm, a thickness of 1 μm, and a warpage of 15 mm or less when processed to a size of length x width = 50 mm x 50 mm.

2. The iron-plated metal foil according to claim 1, wherein the thickness of the iron-plated film is 1 μm or less.

3. The iron-plated metal foil according to claim 1, wherein the surface roughness Ra of the iron-plated film is 0.4 μm or less.

4. The iron-plated metal foil of claim 1, wherein said metal foil is a nickel foil.

5. A method for producing iron-plated metal foil, in which an iron plating film is formed on the surface of a metal foil by electroplating, according to any one of claims 1 to 4, wherein the pH of the iron plating solution used in the electroplating is 3.5 to 5.

5.

6. The current density of the electroplating is 0.1 to 20 A / dm 2 The method for producing an iron-plated metal foil according to claim 5, wherein 7. The method for producing iron-plated metal foil according to claim 5, wherein the iron plating solution used in the electroplating has a trivalent iron ion concentration of 0.7 g / L or less.

8. The method for producing iron-plated metal foil according to claim 5, wherein the iron plating solution used in the electroplating contains a benzothiazole-based compound.

9. The method for producing iron-plated metal foil according to claim 5, wherein the electroplating is carried out so that a current flows through one surface of the metal foil.

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