Ferrite film manufacturing method

Abstract

A method for producing a ferrite film according to the present invention is characterized by comprising at least: a step (A) in which an iron plating film or an iron alloy plating film is formed on the surface of a base material; a step (B) in which the base material after the step (A) is brought into contact with an oxidation treatment agent, thereby subjecting the iron plating film or the iron alloy plating film to an oxidation treatment; and a step (C) in which the base material after the step (B) is subjected to a cooling treatment. This method for producing a ferrite film is also characterized in that: the oxidation treatment agent is a mixed solution that contains at least one basic compound and at least one nitric acid compound; and the cooling treatment is carried out by means of slow cooling at an average cooling rate of 1.5°C / minute or less.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a ferrite film. More specifically, the present invention relates to a method for easily producing a ferrite film having a sufficient thickness and being prevented from peeling off from a substrate by a wet process at low temperature and without applying pressure, without destroying the substrate. [Background technology]

[0002] Conventionally, the production of ferrite has required processing at high temperatures from the viewpoint of metal diffusion and oxidation.

[0003] For example, as shown in Patent Document 1, a method for producing MnZn-based ferrite powder has been proposed, in which a mixed powder of raw materials, metal oxides and metal hydroxides, is calcined at 800°C to 1000°C, the resulting calcined powder is granulated, the resulting granulated powder is sintered at a temperature higher than 1050°C and lower than 1150°C, and the granulated ferrite powder obtained by cooling to less than 150°C is further heat-treated at a temperature of at least 200°C or higher.

[0004] Furthermore, as shown in Patent Document 2, a method for producing a ferritic stainless steel sheet has been proposed, in which an Al-deposited layer-coated stainless steel sheet, which has an Al-deposited layer formed on the surface of a ferritic stainless steel sheet having a predetermined composition, is subjected to a heat treatment in which the stainless steel sheet is held at a temperature range of 600°C to 1300°C for one minute or more.

[0005] In addition to these, studies are also being conducted on the production of ferrite films by wet processes.

[0006] For example, Non-Patent Document 1 describes the Fe 3-x M xThere is a description of research into ferrite plating of O4 (M is Ni or Ni and Zn) films. In this research, an alternating current of 8.4 V and a frequency of 10 to 1000 Hz was applied between a gold-film-deposited substrate and a platinum electrode in a specified plating solution, and plating was carried out at 90°C for 1 hour, forming a Ni ferrite film or Ni-Zn ferrite film with a thickness of 0.3 to 1 μm on the surface of the substrate. This research revealed that the amount of metal contained in the ferrite film can be adjusted by appropriately changing the composition of the plating solution.

[0007] Here, when forming a ferrite film on the surface of a substrate with a complex shape, such as a tube, fiber, or printed circuit board, it is preferable to employ a plating method, which is a wet process using a plating solution, in that it can improve the uniformity of the ferrite film. However, the methods proposed in Patent Documents 1 and 2, for example, require heat treatment at an extremely high temperature of around 1000°C, which can cause damage to substrates with low heat resistance, making the methods proposed in Patent Documents 1 and 2 inapplicable.

[0008] On the other hand, in the study described in Non-Patent Document 1, plating is performed at a low temperature of 90°C, which is different from the above-mentioned method that requires heat treatment at a high temperature and is therefore applicable to substrates with low heat resistance. However, in the plating method in which alternating current adjusted to a predetermined voltage and frequency is applied, as in the study described in Non-Patent Document 1, the thickness of the plating film formed in one hour of plating treatment is limited to 1 μm, and plating films of this thickness are not practical. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2020-202348 [Patent Document 2] Patent No. 6791458 [Non-patent literature]

[0010] [Non-Patent Document 1] Tomoyuki ITOH, Qun ZHANG, Naoki SUGITANI and Masanori ABE; Ferrite Plating of Fe3-xMxO4 (M = Ni and Zn) Films Utilizing Alternate Electric Current; Journal of The Magnetics Society of Japan, Vol.18, Supplement, No.S1 (1994) Summary of the Invention [Problem to be solved by the invention]

[0011] An object of the present invention is to provide a method for easily producing a ferrite film having a sufficient thickness without breaking even a substrate having low heat resistance. [Means for solving the problem]

[0012] The present invention provides A step (A) of forming an iron plating film or an iron alloy plating film on a surface of a substrate; a step (B) of contacting the substrate that has been subjected to the step (A) with an oxidation treatment agent to subject the iron plating film or iron alloy plating film to an oxidation treatment; a step (C) of subjecting the substrate that has undergone the step (B) to a cooling treatment; At least the oxidation treatment agent is a mixed solution containing at least one basic compound and at least one nitric acid compound, The cooling treatment is carried out slowly at an average cooling rate of 1.5°C / min or less. The present invention relates to a method for producing a ferrite film.

[0013] In the production method of the present invention, the treatment temperature for the oxidation treatment is preferably 60°C to 250°C.

[0014] In the production method of the present invention, the nitric acid compound is preferably at least one selected from nitrous acid and nitrite salts.

[0015] In the manufacturing method of the present invention, it is preferable that the iron plating film is a pure iron plating film, and the iron alloy plating film is selected from an iron-nickel plating film, an iron-cobalt plating film, an iron-manganese plating film, an iron-copper plating film, an iron-manganese-zinc plating film, an iron-nickel-zinc plating film, and an iron-cobalt-zinc plating film. [Effects of the Invention]

[0016] According to the manufacturing method of the present invention, a ferrite film that is uniform and crack-free and has good adhesion to the substrate and is prevented from peeling, even when the substrate has low heat resistance, can be easily manufactured at low temperature and without pressure, without the need for conventional heat treatment at very high temperatures of around 1000°C or pressure treatment exceeding 100 MPa. DETAILED DESCRIPTION OF THE INVENTION

[0017] The method for producing a ferrite film of the present invention includes at least the following steps (A), (B), and (C). Step (A): A step of forming an iron plating film or an iron alloy plating film on the surface of a substrate. Step (B): A step of bringing the substrate that has been subjected to step (A) into contact with an oxidation treatment agent to subject the iron plating film or iron alloy plating film to oxidation treatment. Step (C): A step of subjecting the substrate that has undergone step (B) to a cooling treatment.

[0018] <Process (A)> First, in step (A), an iron plating film or an iron alloy plating film is formed on the surface of a substrate by electroplating.

[0019] The iron plating bath or iron alloy plating bath used in the electroplating treatment preferably contains, for example, one or more iron ion supplying compounds.

[0020] The iron ion supply compound is not particularly limited as long as it is one or more iron-soluble salts and their hydrates that generate iron ions in an aqueous solution, such as iron chloride, iron sulfate, iron nitrate, iron sulfamate, iron acetate, iron bromide, iron sulfide, iron citrate, ammonium iron citrate, ammonium iron sulfate, iron lactate, iron oxalate, iron phosphate, and iron pyrophosphate.

[0021] The content of the iron ion supply compound in the iron plating bath is not particularly limited, but is preferably about 1 g / L to 250 g / L, and more preferably about 5 g / L to 200 g / L.

[0022] The iron alloy plating bath may contain, together with the iron ion supply compound, one or more soluble salts of metals that form alloys with iron.

[0023] There are no particular limitations on the metal that forms an alloy with iron, and examples thereof include nickel, cobalt, manganese, copper, and zinc.

[0024] Examples of soluble salts of nickel include nickel chloride, nickel sulfate, nickel nitrate, nickel sulfamate, nickel acetate, nickel bromide, nickel sulfide, nickel citrate, ammonium nickel citrate, ammonium nickel sulfate, nickel lactate, nickel oxalate, nickel phosphate, and nickel pyrophosphate.

[0025] Examples of soluble salts of cobalt include cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt sulfamate, cobalt acetate, cobalt bromide, cobalt sulfide, cobalt citrate, ammonium cobalt citrate, ammonium cobalt sulfate, cobalt lactate, cobalt oxalate, cobalt phosphate, and cobalt pyrophosphate.

[0026] Examples of soluble salts of manganese include manganese chloride, manganese sulfate, manganese nitrate, manganese sulfamate, manganese acetate, manganese bromide, manganese sulfide, manganese citrate, ammonium manganese citrate, ammonium manganese sulfate, manganese lactate, manganese oxalate, manganese phosphate, and manganese pyrophosphate.

[0027] Examples of soluble copper salts include copper chloride, copper sulfate, copper nitrate, copper sulfamate, copper acetate, copper bromide, copper sulfide, copper citrate, ammonium copper citrate, ammonium copper sulfate, copper lactate, copper oxalate, copper phosphate, and copper pyrophosphate.

[0028] Examples of soluble zinc salts include zinc chloride, zinc sulfate, zinc nitrate, zinc sulfamate, zinc acetate, zinc bromide, zinc sulfide, zinc citrate, ammonium zinc citrate, ammonium zinc sulfate, zinc lactate, zinc oxalate, zinc phosphate, and zinc pyrophosphate.

[0029] The total content of the iron ion supply compound and the soluble salt of the metal that forms an alloy with iron in the iron alloy plating bath is not particularly limited, but is preferably about 1 g / L to 250 g / L, and more preferably about 5 g / L to 200 g / L.

[0030] There are no particular limitations on the combination and ratio of the iron ion supply compound and the soluble salt of the metal that forms an alloy with iron, and the combination and ratio of both compounds may be appropriately adjusted so that the iron alloy plating film formed from the iron alloy plating bath has a desired composition.

[0031] In the present invention, from the viewpoint of practicality, it is preferable that the iron plating film is a pure iron plating film, and the iron alloy plating film is selected from an iron-nickel plating film, an iron-cobalt plating film, an iron-manganese plating film, an iron-copper plating film, an iron-manganese-zinc plating film, an iron-nickel-zinc plating film, and an iron-cobalt-zinc plating film.

[0032] In the method for producing a ferrite film of the present invention, since no high-temperature treatment is performed as in the conventional method, the iron plating film or iron alloy plating film can be formed on a substrate without destroying the substrate, even if the substrate has low heat resistance. Therefore, the substrate used in the present invention is not particularly limited, and examples thereof include resin substrates such as epoxy resin, polyimide resin, polycarbonate resin, ABS resin, and PET resin, metal substrates, glass substrates, silicon substrates, sapphire substrates, wafers, and printed wiring boards.

[0033] In addition to the one or more iron ion supply compounds, or the one or more iron ion supply compounds and the one or more soluble salts of metals that form alloys with iron, the iron plating bath or iron alloy plating bath may contain various additives such as electrolytes, accelerators, polymeric surfactants, levelers, pH buffers, and chelating agents.

[0034] Examples of the electrolyte include acids and salts thereof.

[0035] Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid, sulfamic acid, acetic acid, citric acid, lactic acid, oxalic acid, phosphoric acid, and pyrophosphoric acid, and these can be used alone or in combination of two or more.

[0036] Examples of the accelerator include bis(3-sulfopropyl)disulfide (also known as 3,3'-dithiobis(1-propanesulfonic acid)), bis(2-sulfopropyl)disulfide, bis(3-sulfo-2-hydroxypropyl)disulfide, bis(4-sulfopropyl)disulfide, bis(p-sulfophenyl)disulfide, 3-benzothiazolyl-2-thio)propanesulfonic acid, N,N-dimethyl-dithiocarbamylpropanesulfonic acid, N,N-dimethyl-dithiocarbamylpropanesulfonic acid, N,N-dimethyl-dithiocarbamic acid-(3-sulfopropyl)-ester, 3-[(aminoiminomethyl)thio]-1-propanesulfonic acid, o-ethyl-diethylcarbonate-S-(3-sulfopropyl)ester, mercaptomethanesulfonic acid, mercaptoethanesulfonic acid, mercaptopropanesulfonic acid, and salts thereof. These may be used alone or in combination of two or more.

[0037] Examples of the polymer surfactant include polyethylene glycol, polypropylene glycol, Pluronic (registered trademark) type surfactants, Tetronic type surfactants, polyethylene glycol glyceryl ether, sulfonic acid group-containing polyalkylene oxide adduct amines, polyoxyethylene alkyl ether, bisphenol A polyethoxylate, sodium alkylnaphthalene sulfonate, and other nonionic polyether polymer surfactants, which may be used alone or in combination of two or more.

[0038] Examples of the leveler (smoothing agent) include amines, dyes, imidazolines, imidazoles, benzimidazoles, indoles, pyridines, quinolines, isoquinolines, anilines, and aminocarboxylic acids, which can be used alone or in combination of two or more.

[0039] Examples of the pH buffering agent include, but are not limited to, monocarboxylic acids such as formic acid, acetic acid, and propionic acid; dicarboxylic acids such as boric acids, phosphoric acids, oxalic acid, and succinic acid; oxycarboxylic acids such as lactic acid, tartaric acid, citric acid, malic acid, and isocitric acid; and oxo acids such as boric acid, metaboric acid, and tetraboric acid. These may be used alone or in combination of two or more.

[0040] Examples of the chelating agent include, but are not limited to, gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptolactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, succinic acid, glycolic acid, malic acid, tartaric acid, diglycolic acid, and salts thereof, some of which may be used alone or in combination of two or more. Further examples include ethylenediamine, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), iminodipropionic acid (IDP), hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraminehexaacetic acid (TTHA), ethylenedioxybis(ethylamine)-N,N,N',N'-tetraacetic acid, glycines, nitrilotrimethylphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, and salts thereof, which can be used alone or in combination of two or more.

[0041] The contents of the various additives in the iron plating bath or iron alloy plating bath are not particularly limited, and may be appropriately adjusted so that the desired iron plating film or iron alloy plating film is formed from the plating bath.

[0042] The iron plating bath or iron alloy plating bath can be prepared by appropriately blending, for example, one or more iron ion supplying compounds, or one or more iron ion supplying compounds and one or more soluble salts of metals that form alloys with iron, with various additives such as electrolytes, accelerators, polymeric surfactants, levelers, pH buffers, and chelating agents.

[0043] There are no particular limitations on the conditions for electroplating, and they may be adjusted as appropriate so that the desired iron plating film or iron alloy plating film is formed. For example, the bath temperature is about 20°C to 70°C, and the current density is 1 A / dm 2 ~30A / dm 2 The plating time is preferably about 45 to 8160 seconds.

[0044] There are no particular limitations on the thickness of the iron plating film or iron alloy plating film formed on the surface of the substrate, and it is preferable that it be, for example, about 5 μm to 30 μm.

[0045] <Process (B)> Next, in step (B), the substrate that has been subjected to step (A) is brought into contact with an oxidation treatment agent to subject the iron plating film or iron alloy plating film to oxidation treatment.

[0046] One of the major features of the manufacturing method of the present invention is that the step (B) is performed. This step (B) makes it possible to form a ferrite film without the need for high-temperature treatment or pressure treatment as in the conventional method.

[0047] The oxidation treatment agent with which the substrate that has been subjected to step (A), i.e., the substrate having an iron plating film or an iron alloy plating film formed on its surface, is brought into contact is a mixed solution containing at least one basic compound and at least one nitric acid compound. By subjecting the iron plating film or the iron alloy plating film to oxidation treatment using such a specific oxidation treatment agent, a ferrite film is formed.

[0048] Examples of the basic compound include sodium hydroxide, potassium hydroxide, calcium hydroxide, etc., and these can be used alone or in combination of two or more.

[0049] The content of the basic compound in the mixed solution is preferably 100 g / L to 850 g / L, and more preferably 150 g / L to 800 g / L. If the content of the basic compound is below the lower limit, the basicity may be insufficient and ferritization of the plating film may not proceed sufficiently, whereas if the content of the basic compound is above the upper limit, the solubility of the nitric acid compound in the mixed solution may decrease, and ferritization of the plating film may not proceed sufficiently, as in the case where the content is below the lower limit.

[0050] Examples of the nitric acid compound include nitric acid, nitrates such as sodium nitrate, potassium nitrate, calcium nitrate, magnesium nitrate, and ammonium nitrate, nitrous acid, and nitrites such as sodium nitrite, potassium nitrite, calcium nitrite, magnesium nitrite, and ammonium nitrite, which can be used alone or in combination of two or more. Among these, at least one selected from nitrous acid and nitrites is preferred because they can suppress the occurrence of cracks and easily form a more uniform ferrite film.

[0051] The content of the nitrate compound in the mixed solution is preferably 15 g / L to 300 g / L, more preferably 20 g / L to 250 g / L. If the content of the nitrate compound is below the lower limit, the oxidation reaction may not proceed sufficiently, and a ferrite film may not be formed. If the content of the nitrate compound is above the upper limit, the solubility limit may be exceeded, and the resulting solid substance may damage the surface of the formed film.

[0052] As a combination of a basic compound and a nitric acid compound, a combination of sodium hydroxide and / or potassium hydroxide with at least one selected from nitrous acid, sodium nitrite, and potassium nitrite is preferred, as this can suppress the occurrence of cracks and facilitate the formation of a more uniform ferrite film.

[0053] The ratio of the basic compound to the nitric acid compound contained in the mixed solution (basic compound / nitric acid compound (weight ratio)) is preferably 0.3 to 60, more preferably 0.6 to 35. If the ratio (weight ratio) is below the lower limit, the reaction may not proceed sufficiently and a ferrite film may not be formed, whereas if the ratio (weight ratio) is above the upper limit, the thickness of the resulting ferrite film may be insufficient.

[0054] In addition to the basic compound and the nitric acid compound, the mixed solution serving as the oxidation treatment agent may contain, for example, organic acids such as silicates, phosphates, amine hydroxy acids, carboxylic acids, and amino acids as corrosion inhibitors, within a range that does not impair the purpose.

[0055] The treatment temperature (temperature of the mixed solution) for the oxidation treatment is preferably 60°C to 250°C, more preferably 80°C to 230°C, and even more preferably 100°C to 220°C. If the treatment temperature is below the lower limit, the oxidation reaction may not proceed sufficiently, and a ferrite film may not be formed. If the treatment temperature is above the upper limit, the mixed solution may boil and become agitated, causing the film to peel off. Furthermore, the treatment time for the oxidation treatment is preferably about 100 to 400 minutes, and even more preferably about 150 to 350 minutes, in order to obtain a ferrite film having the desired sufficient thickness.

[0056] When a substrate having an iron plating film or an iron alloy plating film formed on its surface is brought into contact with an oxidation treatment agent, the substrate is usually immersed in the oxidation treatment agent, but the oxidation treatment agent may also be sprayed onto the substrate or applied with a brush. When immersing, the substrate may be left stationary in the oxidation treatment agent, but stirring or shaking may also be performed.

[0057] <Process (C)> Furthermore, in step (C), the substrate that has been subjected to step (B) is subjected to a cooling treatment, and this cooling treatment is carried out by slow cooling.

[0058] One of the major features of the manufacturing method of the present invention is that step (C) is performed, which can prevent the formed ferrite film from peeling off from the substrate and the occurrence of cracks in the ferrite film.

[0059] In the production method of the present invention, the slow cooling is carried out by adjusting the average cooling rate to 1.5°C / min or less, preferably 1.2°C / min or less, and more preferably 0.8°C / min or less. If the average cooling rate exceeds the upper limit, peeling of the ferrite film from the substrate and the occurrence of cracks in the ferrite film cannot be sufficiently suppressed. Furthermore, in consideration of workability and productivity, it is preferable to adjust the average cooling rate to 0.2°C / min or more, and more preferably 0.3°C / min or more.

[0060] There are no particular limitations on the means for subjecting the substrate to cooling treatment, but it is preferable to perform air cooling, such as natural air cooling or ventilated air cooling, so that the treatment temperature of the oxidation treatment is gradually reduced at or below the average cooling rate. There are also no particular limitations on the treatment time for the cooling treatment, and it is preferable to appropriately adjust the treatment time taking into account the treatment temperature of the oxidation treatment so that the final temperature of the substrate is, for example, about 20°C to 50°C after the cooling treatment.

[0061] There is no particular limitation on the thickness of the ferrite film thus obtained, but according to the manufacturing method of the present invention, it is possible to manufacture a uniform ferrite film having a sufficient thickness of, for example, about 2 μm to 10 μm and free from cracks. [Example]

[0062] Examples and comparative examples relating to the method for producing a ferrite film of the present invention will be described below in order. However, the present invention is not limited to these examples, and any modifications can be made within the scope of the technical concept of the present invention.

[0063] (1) Example 1 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form an iron-nickel-zinc plating film (thickness: 30 μm) on the surface of the substrate (copper plate). [composition] Iron sulfate hexahydrate 200g / L Nickel sulfate hexahydrate 35g / L Zinc sulfate heptahydrate 20g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0064] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L NaNO2: 200g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0065] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled under the following cooling treatment conditions to obtain a ferrite film (thickness 7.2 μm). The obtained ferrite film was approximately uniform, with almost no cracks observed. No damage to the substrate was observed. [Cooling treatment conditions] Method: Natural cooling to 40°C for 90 minutes Average cooling rate: approx. 1.33°C / min

[0066] (2) Example 2 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0067] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0068] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled under the following cooling treatment conditions to obtain a ferrite film (thickness 6.5 μm). The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was also observed. [Cooling treatment conditions] Method: Natural cooling to 40°C for 180 minutes Average cooling rate: approx. 0.67°C / min

[0069] (3) Example 3 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0070] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L KNO2: 200g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0071] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 5.5 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0072] (4) Example 4 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0073] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L HNO2: 200g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0074] <Process (C)> In the same manner as in Example 2, the oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness 6.1 μm). The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0075] (5) Example 5 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0076] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L NaNO2: 200g / L [Oxidation treatment conditions] Processing temperature: 200℃ Processing time: 240 minutes

[0077] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled under the following cooling treatment conditions to obtain a ferrite film (thickness 9.8 μm). The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was also observed. [Cooling treatment conditions] Method: Natural cooling to 40°C for 240 minutes Average cooling rate: approx. 0.67°C / min

[0078] (6) Example 6 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0079] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L NaNO2: 200g / L [Oxidation treatment conditions] Processing temperature: 80℃ Processing time: 60 minutes

[0080] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled under the following cooling treatment conditions to obtain a ferrite film (thickness: 2.0 μm). The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed. [Cooling treatment conditions] Method: Cool naturally to 40°C for 60 minutes Average cooling rate: approx. 0.67°C / min

[0081] (7) Example 7 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0082] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L NaNO2: 100g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0083] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 2.5 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0084] (8) Example 8 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0085] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L NaNO2: 25g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0086] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness 1.9 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0087] (9) Example 9 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0088] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] KOH: 750g / L NaNO2: 200g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0089] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (7.5 μm thick) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0090] (10) Example 10 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form a pure iron plating film (thickness: 30 μm) on the surface of the same substrate as in Example 1. [composition] Iron sulfate hexahydrate 200g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0091] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0092] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 5.8 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0093] (11) Example 11 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form an iron-nickel plating film (thickness: 30 μm) on the surface of the same substrate as in Example 1. [composition] Iron sulfate hexahydrate 200g / L Nickel sulfate hexahydrate 35g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0094] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0095] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 5.8 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0096] (12) Example 12 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form an iron-cobalt plating film (thickness: 30 μm) on the surface of the same substrate as in Example 1. [composition] Iron sulfate hexahydrate 200g / L Cobalt sulfate heptahydrate 40g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0097] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0098] <Process (C)> In the same manner as in Example 2, the oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness 6.2 μm). The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0099] (13) Example 13 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form an iron-manganese plating film (thickness: 30 μm) on the surface of the same substrate as in Example 1. [composition] Iron sulfate hexahydrate 200g / L Manganese sulfate pentahydrate 35g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0100] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0101] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 6.7 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0102] (14) Example 14 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form an iron-copper plating film (thickness: 30 μm) on the surface of the same substrate as in Example 1. [composition] Iron sulfate hexahydrate 200g / L Copper sulfate pentahydrate 35g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0103] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0104] <Process (C)> In the same manner as in Example 2, the oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness 6.1 μm). The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0105] (15) Example 15 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form an iron-manganese-zinc plating film (thickness: 30 μm) on the surface of the same substrate as in Example 1. [composition] Iron sulfate hexahydrate 200g / L Manganese sulfate pentahydrate 35g / L Zinc sulfate heptahydrate 20g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0106] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0107] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 6.3 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0108] (16) Example 16 <Process (A)> A plating bath was prepared with the following composition, and electroplating was carried out under the following plating conditions to form an iron-cobalt-zinc plating film (thickness: 30 μm) on the surface of the same substrate as in Example 1. [composition] Iron sulfate hexahydrate 200g / L Cobalt sulfate heptahydrate 35g / L Zinc sulfate heptahydrate 20g / L Trisodium citrate 30g / L [Plating conditions] Bath temperature: 50℃ Current density: 5A / dm 2 Plating time: Approximately 1080 seconds

[0109] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0110] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 6.8 μm) in the same manner as in Example 2. The obtained ferrite film was uniform and no cracks were observed. No damage to the substrate was observed.

[0111] (17) Comparative Example 1 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0112] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0113] <Process (C)> The oxidation treatment agent in which the substrate was immersed in the step (B) was cooled in the same manner as in Example 2, but a ferrite film could not be obtained, and no damage to the substrate was observed.

[0114] (18) Comparative Example 2 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0115] <Process (B)> In the same manner as in Comparative Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0116] <Process (C)> The oxidation treatment agent in which the substrate was immersed in step (B) was cooled under the following cooling treatment conditions, but a ferrite film could not be obtained and no damage to the substrate was observed. [Cooling treatment conditions] Method: Rapid cooling to 40°C over 10 minutes Average cooling rate: approx. 12°C / min

[0117] (19) Comparative Example 3 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0118] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L K2CrO4: 200g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0119] <Process (C)> The oxidation treatment agent in which the substrate was immersed in the step (B) was cooled in the same manner as in Example 2, but a ferrite film could not be obtained, and no damage to the substrate was observed.

[0120] (20) Comparative Example 4 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0121] <Process (B)> In the same manner as in Comparative Example 3, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0122] <Process (C)> The oxidation treatment agent in which the substrate was immersed in the step (B) was cooled in the same manner as in Comparative Example 2, but a ferrite film could not be obtained, and no damage to the substrate was observed.

[0123] (21) Comparative Example 5 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0124] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L K2S2O4: 200g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0125] <Process (C)> The oxidation treatment agent in which the substrate was immersed in the step (B) was cooled in the same manner as in Comparative Example 2, but a ferrite film could not be obtained, and no damage to the substrate was observed.

[0126] (22) Comparative Example 6 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0127] <Process (B)> An oxidation treatment agent was prepared with the following composition, and the substrate on whose surface a plating film had been formed in step (A) above was immersed in the oxidation treatment agent, and the plating film was subjected to oxidation treatment under the following oxidation treatment conditions. [composition] NaOH: 750g / L CuSO4: 200g / L [Oxidation treatment conditions] Processing temperature: 160℃ Processing time: 180 minutes

[0128] <Process (C)> The oxidation treatment agent in which the substrate was immersed in the step (B) was cooled in the same manner as in Comparative Example 2, but a ferrite film could not be obtained, and no damage to the substrate was observed.

[0129] (23) Comparative Example 7 <Process (A)> In the same manner as in Example 1, an iron-nickel-zinc plating film (thickness: 30 μm) was formed.

[0130] <Process (B)> In the same manner as in Example 1, the plating film formed in the step (A) was subjected to an oxidation treatment.

[0131] <Process (C)> In the same manner as in Comparative Example 2, the oxidation treatment agent in which the substrate was immersed in step (B) was cooled to obtain a ferrite film (thickness: 6.3 μm). The obtained ferrite film had significant cracks. No damage to the substrate was observed.

[0132] In Examples 1 to 16 and Comparative Examples 1 to 7, the substrates that had undergone step (C) were embedded in a cross-section observation resin (epoxy resin), polished, and then a field emission scanning electron microscope (FE-SEM, model number: S-4800, manufactured by Hitachi, Ltd.) was used to confirm whether a ferrite film had been formed and to measure its thickness.

[0133] In addition, the surfaces of the ferrite films obtained in Examples 1 to 16 and Comparative Example 7 were observed using a microscope (model number: VK-X1100, manufactured by Keyence Corporation, magnification: 1200x) to check for the occurrence of cracks and for the presence of peeling from the substrate, and the peeling rate was calculated based on the following formula. Ferrite film peeling rate (%) = (area where ferrite film peeled off / area of ​​substrate) x 100

[0134] The types of plating films, the compositions of the oxidation treatment agents, the oxidation treatment conditions, the cooling treatment conditions, and the thicknesses and peeling rates of the ferrite films in Examples 1 to 16 and Comparative Examples 1 to 7 are summarized in Tables 1 to 3 below.

[0135] [Table 1]

[0136] [Table 2]

[0137] [Table 3]

[0138] The following can be seen from Tables 1 to 3 above.

[0139] In Examples 1 to 16, a mixed solution containing a basic compound and a nitric acid compound was used as the oxidation treatment agent, and therefore a uniform ferrite film having a sufficient thickness of approximately 2 μm to 10 μm and free from cracks was produced. In contrast, in Comparative Examples 1 to 6, a solution containing only a basic compound (Comparative Example 1) or a mixed solution containing a basic compound and an acid compound other than a nitric acid compound (Comparative Examples 2 to 6) was used as the oxidation treatment agent, and therefore a ferrite film could not be produced regardless of the cooling treatment conditions.

[0140] In addition, in Examples 1 to 16, the cooling treatment was performed by slow cooling at an average cooling rate of 1.5°C / min or less, so the peeling rate of the ferrite film was low at 10% or less, and peeling of the ferrite film from the base was suppressed to a level that does not cause practical problems.In contrast, in Comparative Example 7, unlike Comparative Examples 1 to 6 as described above, a ferrite film having a sufficient thickness could be produced, but the cooling treatment was performed by rapid cooling at an average cooling rate of 12°C / min, so the peeling rate of the ferrite film exceeded 50%, and peeling of the ferrite film from the base could not be suppressed.

[0141] Furthermore, when the same iron-nickel-zinc plating film was used, a ferrite film with a sufficient thickness could be produced by setting the treatment temperature of the oxidation treatment at 100°C or higher as in Examples 2 and 5, compared to Example 6. Furthermore, a ferrite film with a sufficient thickness could be produced by using an oxidation treatment agent in which the amount of nitric acid compound relative to the amount of basic compound was sufficient as in Example 2, compared to Example 7 and Example 8.

[0142] Furthermore, when the same oxidation treatment was carried out using the same iron-nickel-zinc plating film, the peeling rate of the ferrite film was extremely low at less than 5% by carrying out the cooling treatment by lowering the treatment temperature of the oxidation treatment more gradually at a lower average cooling rate as in Example 2 compared to Example 1, and peeling of the ferrite film from the base was more sufficiently suppressed.

[0143] Furthermore, even when the type of plating film was changed as in Examples 10 to 16, a ferrite film having a sufficient thickness similar to that of Example 2, in which an iron-nickel-zinc plating film was used and oxidation treatment and cooling treatment were carried out in the same manner, was produced, and the peeling rate of the ferrite film was also very low at less than 5%, and peeling of the ferrite film from the base was more sufficiently suppressed. [Industrial Applicability]

[0144] The ferrite film produced by the production method of the present invention can be used in a wide range of fields, such as magnetic heads, magnetic cards, magnetic shields, optical devices, and disks.

Claims

1. A step (A) of forming an iron plating film or an iron alloy plating film on a surface of a substrate; a step (B) of contacting the substrate that has been subjected to the step (A) with an oxidation treatment agent to subject the iron plating film or iron alloy plating film to an oxidation treatment; A step (C) of subjecting the substrate that has undergone the step (B) to a cooling treatment; At least the oxidation treatment agent is a mixed solution containing at least one basic compound and at least one nitric acid compound, The cooling treatment is carried out by slow cooling at an average cooling rate of 1.5°C / min or less, The treatment temperature of the oxidation treatment is 80°C to 250°C, The ratio of the weight of the basic compound to the weight of the nitric acid compound contained in the mixed solution is 0.3 to 3.

75. A method for producing a ferrite film, comprising:

2. 2. The method for producing a ferrite film according to claim 1, wherein the nitric acid compound is at least one selected from the group consisting of nitrous acid and nitrite salts.

3. 3. The method for producing a ferrite film according to claim 1, wherein the iron plating film is a pure iron plating film, and the iron alloy plating film is selected from an iron-nickel plating film, an iron-cobalt plating film, an iron-manganese plating film, an iron-copper plating film, an iron-manganese-zinc plating film, an iron-nickel-zinc plating film, and an iron-cobalt-zinc plating film.

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