Nickel-phosphorus alloy coated substrate, solution for electroless plating of nickel-phosphorus alloy film, and method for producing nickel-phosphorus alloy coated substrate

Abstract

To provide a solution for electroless plating, capable of reducing the thickness distribution of a NiP film in the outer-peripheral end of a substrate without spoiling the corrosion resistance of the NiP film; a method for manufacturing a NiP coated substrate using the same; and a NiP coated substrate manufactured thereby.SOLUTION: A solution for electroless plating a NiP film includes nickel ions, hypophosphite ions, a complexing agent and indium ions. The concentration of the indium ions is 0.18-1.8 ppm; a method for manufacturing a NiP coated substrate includes forming a NiP film with the solution; the NiP coated substrate includes a substrate and the NiP film formed on the substrate; and the NiP film includes indium at a concentration of 70-620 ppm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a nickel-phosphorus alloy coated substrate, a solution for electroless plating of a nickel-phosphorus alloy film, and a method for producing a nickel-phosphorus alloy coated substrate. [Background technology]

[0002] Magnetic recording media used in hard disk drives are generally manufactured by forming a nickel-phosphorus alloy (NiP) film on a substrate using electroless plating, polishing the NiP film, and then forming a magnetic layer on the NiP film.

[0003] Patent Document 1 describes a magnetic recording medium having a non-magnetic substrate, a nickel-phosphorus plating film, and a magnetic layer. The NiP plating film contains 0.05 to 1 wt % of at least one element selected from the group consisting of tin, manganese, indium, and antimony.

[0004] Patent Document 2 describes an aqueous plating bath composition for electroless deposition of nickel and nickel alloys. This composition contains a nickel ion source and a stabilizer, and the stabilizer contains at least one metal ion selected from indium ions and gallium ions, and at least one selected from elemental iodine, an iodide ion-containing compound, an iodate ion-containing compound, and a periodate ion-containing compound. The concentration of the at least one metal ion selected from indium ions and gallium ions is within the range of 0.01 to 0.5 mmol / L. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 01-269224 [Patent Document 2] Patent No. 6667525 Summary of the Invention [Problem to be solved by the invention]

[0006] When a NiP film is formed on a substrate by electroless plating, a relatively thick NiP film may be formed near the outer edge of the substrate. To equalize this film thickness distribution, the NiP film is polished. However, long polishing times can cause a deterioration in the quality of the NiP film (e.g., an increase in defects). Therefore, it is desirable to narrow the film thickness distribution of the NiP film formed by electroless plating and shorten the polishing time. Furthermore, the NiP film is required to have high corrosion resistance.

[0007] Therefore, the present invention provides a solution for electroless plating that can reduce the film thickness distribution of a NiP film at the outer peripheral edge of a substrate without impairing the corrosion resistance of the NiP film, a method for manufacturing a NiP-coated substrate using the solution, and a NiP-coated substrate that can be manufactured using the solution. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a nickel-phosphorus alloy coated substrate comprising a substrate and a nickel-phosphorus alloy film formed on the substrate, the nickel-phosphorus alloy film containing indium at a concentration of 70 to 620 ppm.

[0009] According to one aspect of the present invention, there is provided a solution for electroless plating of a nickel-phosphorus alloy film, comprising nickel ions, hypophosphite ions, a complexing agent, and indium ions, the concentration of the indium ions being 0.18 to 1.8 ppm.

[0010] According to one aspect of the present invention, there is provided a method for producing a nickel-phosphorus alloy coated substrate, which comprises forming a nickel-phosphorus alloy film by electroless plating using the solution of the above aspect.

[0011] According to one aspect of the present invention, there is provided a magnetic recording medium having the nickel-phosphorus alloy coated substrate of the above aspect.

[0012] According to the present invention, it is possible to reduce the film thickness distribution of the NiP film at the outer peripheral edge of the substrate without impairing the corrosion resistance of the NiP film. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes embodiments. The present invention is not limited to the following embodiments, and various design modifications can be made without departing from the spirit of the present invention as defined in the claims. In this application, a numerical range expressed using the symbol "to" includes the numerical values ​​before and after the symbol "to" as the lower and upper limits, respectively.

[0014] (1) Solution for electroless plating of NiP films A solution for electroless plating according to an embodiment contains nickel ions, hypophosphite ions, a complexing agent, and indium ions.

[0015] The concentration of indium ions in the solution is 0.18 to 1.8 ppm, 0.3 to 1.5 ppm, or 0.3 to 0.8 ppm. As a result, as shown in the examples described later, it is possible to form a NiP film that has high corrosion resistance and a small film thickness distribution at the outer peripheral edge of the substrate. As a source of indium ions, a water-soluble indium salt such as indium nitrate, indium sulfate, or indium chloride can be used. These indium salts may be used alone or in combination of two or more.

[0016] The other components contained in the solution according to the embodiment and their concentrations may be similar to those of solutions generally used for electroless plating of NiP films.

[0017] As a source of nickel ions, a water-soluble nickel salt, such as nickel sulfate, nickel chloride, nickel carbonate, nickel acetate, or nickel sulfamate, is used. These nickel salts may be used alone or in combination of two or more. The concentration of nickel ions in the solution may be, for example, 1 to 30 g / L.

[0018] As a source of hypophosphite ions, for example, hypophosphorous acid or a salt thereof, such as sodium hypophosphite or potassium hypophosphite, can be used. The concentration of hypophosphite ions in the solution may be 5 to 80 g / L. The hypophosphite ions act as a reducing agent.

[0019] The complexing agent may be a dicarboxylic acid or an alkali salt thereof, such as tartaric acid, malic acid, citric acid, succinic acid, malonic acid, glycolic acid, gluconic acid, oxalic acid, phthalic acid, fumaric acid, maleic acid, or lactic acid, or a sodium salt, potassium salt, or ammonium salt thereof. Two or more of these may be used in combination, and at least one of them may be an oxydicarboxylic acid. The concentration of the complexing agent in the solution may be 0.01 to 2.0 mol / L.

[0020] The solution according to the embodiment may further contain a stabilizer, a pH adjuster, a brightener, a mildew inhibitor, or a surfactant. The stabilizer may be a lead compound, such as lead (II) acetate, in which case the solution according to the embodiment contains lead ions. The pH adjuster may be an acid, an alkali, or a salt. The solution according to the embodiment may contain water as a solvent.

[0021] The solution according to the embodiment may not contain iodine. Here, "not containing" means that iodine is substantially not contained, specifically, that iodine is not detected by inductively coupled plasma atomic emission spectrometry (ICP-AES). The chemical species of iodine is not limited, and includes, for example, elemental iodine, iodide ions, iodate ions, and periodate ions. Therefore, the solution according to the embodiment may not contain elemental iodine, iodide ions, iodate ions, or periodate ions.

[0022] (2) NiP coated substrate The NiP-coated substrate is obtained by immersing the substrate in the above solution and performing electroless plating. The NiP-coated substrate has a substrate and a NiP film formed thereon.

[0023] The substrate may have a circular ring shape. The substrate may be non-conductive (insulating), conductive, or semi-conductive. Non-conductive substrates include substrates made of glass, ceramics, or plastic. Conductive substrates include substrates made of metals or conductive metal oxides. Semi-conductive substrates include substrates made of semi-metals or compound semiconductors. In particular, the substrate may be made of aluminum, an aluminum alloy, or glass.

[0024] The NiP film contains In at a concentration of 70 to 620 ppm, preferably 170 to 410 ppm, and more preferably 170 to 200 ppm. As shown in the examples below, such NiP films have high corrosion resistance and a small film thickness distribution at the outer peripheral edge of the substrate. The NiP film may also contain phosphorus (P) at a concentration of 10 to 13 wt %. The composition of the NiP film can be determined by dissolving the NiP film in nitric acid and quantifying the elements in the resulting solution using ICP-AES. The NiP film may be free of iodine. Here, "free" means substantially free of iodine, specifically meaning that iodine is not detected by ICP-AES. The chemical species of iodine is not limited and includes, for example, elemental iodine, iodide ions, iodate ions, and periodate ions. Therefore, the NiP film may not contain elemental iodine, iodide ions, iodate ions, or periodate ions.

[0025] The NiP film has a sufficiently small film thickness distribution at the outer peripheral edge of the NiP-coated substrate. Specifically, the maximum height of the NiP film surface from the reference plane in a region 0 to 2 mm away from the outer peripheral edge of the NiP-coated substrate can be 3% or less, 2.9% or less, 2.8% or less, 2.5% or less, or 2.4% or less of the NiP film thickness, and can be 0% or more, more than 0%, or 1.6% or more of the NiP film thickness. The maximum height of the NiP film surface from the reference plane in a region 0 to 2 mm away from the outer peripheral edge of the NiP-coated substrate is determined based on the surface profile of the NiP film measured using a stylus surface profilometer (e.g., a Dektak 150 manufactured by Bruker). The reference plane is defined as a plane containing a straight line passing through a first point on the surface of the NiP film 2 to 5 mm away from the outer peripheral edge toward the center of the NiP-coated substrate and a second point on the surface of the NiP film 1 to 5 mm away from the first point toward the center of the NiP-coated substrate.

[0026] Furthermore, the NiP film has good corrosion resistance. Specifically, when a NiP-coated substrate is immersed in 30% nitric acid heated to 45°C for 150 seconds, the area percentage of holes formed on the surface of the NiP film can be 0.75% or less. The area percentage of holes can be determined from images of the NiP film surface observed with an optical microscope after the NiP-coated substrate is immersed in nitric acid.

[0027] The NiP coated substrate can be used for any purpose, for example, to form a magnetic layer on the NiP coated substrate to produce a magnetic recording medium.

[0028] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention as defined in the claims. Further embodiments can also be provided by combining the above embodiments. [Example]

[0029] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0030] An aqueous solution containing 27 g / L of nickel sulfate, 30 g / L of sodium hypophosphite, 30 g / L of lactic acid, 30 g / L of malic acid, 6 g / L of succinic acid, 20.5 g / L of sodium hydroxide, and lead(II) acetate was prepared. Furthermore, indium nitrate was added to the solution in Examples 1 to 8 and Comparative Examples 2 to 4. Bismuth(III) sulfate was added to the solution in Comparative Example 5. Antimony(III) acetate was added to the solution in Comparative Example 6. Ammonium molybdate tetrahydrate was added to the solution in Comparative Example 7. The amounts of each additive were set so that the solution after the addition contained In, Bi, Sb, or Mo ions at the concentrations listed in Table 1. Thus, the plating solutions of each Example and Comparative Example were obtained.

[0031] An annular aluminum alloy plate (JIS A-5052, inner diameter 25 mm, outer diameter 95 mm) was subjected to alkali etching treatment and zinc substitution treatment. The aluminum alloy plate was immersed in a plating solution heated to 85°C. As a result, a NiP film having a thickness shown in Table 1 was formed on the aluminum alloy plate. In this way, test specimens for each example and comparative example were obtained.

[0032] (1)Elemental analysis The NiP film of each specimen was dissolved in nitric acid, and the elements in the resulting solution were quantified by ICP-AES. The In concentration (i.e., the In concentration in the NiP film) and the P concentration (i.e., the P concentration in the NiP film) were determined based on the total amount of Ni, P, Pb, and In. The results are shown in Table 1.

[0033] (2) Surface profile measurement The surface profile of the NiP film on each specimen was measured using a stylus surface profilometer (Bruker's "Dektak 150"). Based on the obtained surface profile, the maximum height (maximum height) of the NiP film surface from the reference plane was determined in the region 0 to 2 mm from the outer edge of the specimen. Similar measurements were performed seven times, and the average of the maximum heights was calculated. The results are shown in Table 1. The reference plane was defined as a plane containing a straight line passing through a first point on the NiP film surface 2 to 5 mm from the outer edge of the specimen toward the center of the specimen, and a second point on the NiP film surface 1 to 5 mm from the first point toward the center of the specimen.

[0034] (3) Corrosion resistance evaluation Each specimen was immersed in 30% nitric acid heated to 45°C for 150 seconds. Optical microscope images of the NiP film surface were processed to determine the area ratio of holes formed on the surface. The results are shown in Table 1.

[0035] (4) Polishing The specimens of Examples 1 to 8 were polished. The surface profiles of the polished specimens were measured, and the maximum value of the height of the NiP film surface from the reference plane (maximum height) was determined in an area 0 to 2 mm away from the outer peripheral edge of the specimen. All specimens had a sufficiently small maximum height suitable for use in the manufacture of magnetic recording media for hard disk drives.

[0036] [Table 1]

[0037] As shown in Table 1, the NiP films of Examples 1 to 8, which were formed using a plating solution containing indium at a concentration of 0.18 to 1.8 ppm and contained indium at a concentration of 79 to 620 ppm, had small maximum heights. The NiP films of Examples 1 to 8 also had small area ratios of corrosion pits. Furthermore, the NiP films of Examples 2 to 7, which were formed using a plating solution containing indium at a concentration of 0.36 to 1.44 ppm and contained indium at a concentration of 176 to 410 ppm, had even smaller maximum heights. The NiP films of Examples 2 to 4, which were formed using a plating solution containing indium at a concentration of 0.36 to 0.72 ppm and contained indium at a concentration of 176 to 194 ppm, had particularly small maximum heights.

[0038] The NiP films of Comparative Examples 1 to 4, which were formed using plating solutions with indium concentrations of less than 0.18 ppm or more than 1.8 ppm and less than 70 ppm or more than 620 ppm, had large maximum heights. The NiP films of Comparative Examples 3 and 4 also had large area proportions of corrosion pits. The NiP films of Comparative Example 5, which used a plating solution containing bismuth, and Comparative Example 6, which used a plating solution containing antimony, had large maximum heights and large area proportions of corrosion pits. The NiP film of Comparative Example 7, which used a plating solution containing molybdenum, had a small maximum height but a large area proportion of corrosion pits.

Claims

1. A substrate; a nickel-phosphorus alloy film formed on the substrate; and A nickel-phosphorus alloy coated substrate for a magnetic recording medium, wherein the nickel-phosphorus alloy film contains indium at a concentration of 70 to 620 ppm.

2. 2. The nickel-phosphorus alloy coated substrate according to claim 1, wherein the nickel-phosphorus alloy film contains phosphorus at a concentration of 10 to 13 wt %.

3. 3. The nickel-phosphorus alloy coated substrate according to claim 1, wherein the nickel-phosphorus alloy film contains the indium at a concentration of 170 to 410 ppm.

4. The nickel-phosphorus alloy coated substrate according to any one of claims 1 to 3, wherein the nickel-phosphorus alloy film does not contain iodine.

5. Contains nickel ions, hypophosphite ions, a complexing agent, and indium ions; The solution for electroless plating of a nickel-phosphorus alloy film for a magnetic recording medium has an indium ion concentration of 0.18 to 1.8 ppm.

6. 6. The solution of claim 5, wherein the indium ions are present in a concentration of 0.3 to 1.5 ppm.

7. 7. The solution according to claim 5 or 6, which is free of iodine.

8. The solution according to any one of claims 5 to 7, further comprising lead ions.

9. A method for producing a nickel-phosphorus alloy coated substrate, comprising forming a nickel-phosphorus alloy film by electroless plating using the solution according to any one of claims 5 to 8.

10. A magnetic recording medium having the nickel-phosphorus alloy coated substrate according to any one of claims 1 to 4.

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