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

Abstract

This invention provides an electroless plating solution that does not compromise the corrosion resistance of the NiP film and reduces the film thickness distribution of the NiP film at the outer edge of the substrate, a method for manufacturing a NiP-coated substrate using the solution, and a NiP-coated substrate that can be manufactured thereby. The electroless plating solution for the NiP film contains nickel ions, hypophosphite ions, a bonding agent, and indium ions, wherein the concentration of the indium ions is 0.18 to 1.8 ppm. The method for manufacturing the NiP-coated substrate includes forming a NiP film using the aforementioned solution. The NiP-coated substrate has a substrate and a NiP film formed on the substrate, wherein the NiP film contains indium at a concentration of 70 to 620 ppm.

Description

Technical Field

[0001] []

[0002] This invention relates to a nickel-phosphorus alloy coated substrate, a solution for electroless plating of nickel-phosphorus alloy films, and a method for manufacturing a nickel-phosphorus alloy coated substrate. Prior Technology

[0003] Magnetic recording media used in hard disk drives are generally manufactured by forming a nickel-phosphorus alloy (NiP) film on a substrate using an electroless plating method, grinding the NiP film, and forming a magnetic layer on the NiP film.

[0004] 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% by weight of at least one selected from the group consisting of tin, manganese, indium, and antimony.

[0005] Patent Document 2 describes an aqueous plating bath composition for electroless electrolytic deposition of nickel and nickel alloys. This composition includes a nickel ion source and a stabilizer. The stabilizer contains at least one metal ion selected from indium and gallium ions, and at least one ion selected from iodine monomers, compounds containing iodide ions, compounds containing iodate ions, and compounds containing periodate ions. The concentration of the at least one metal ion selected from indium and gallium ions is in the range of 0.01 to 0.5 mmol / L. [Previous Technical Documents] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 01-269224 [Patent Document 2] Japanese Patent No. 6667525 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] When NiP films are formed on a substrate using electroless plating, a relatively thick NiP film sometimes forms near the outer edge of the substrate. To uniformize this film thickness distribution, the NiP film is polished. However, prolonged polishing can sometimes lead to a decrease in NiP film quality (e.g., increased defects). Therefore, it is desirable to reduce the film thickness distribution of NiP films formed by electroless plating and shorten the polishing time. Furthermore, high corrosion resistance is required for the NiP film.

[0009] Therefore, an electroless plating solution is provided that does not impair the corrosion resistance of the NiP film and can reduce the film thickness distribution of the NiP film at the outer edge of the substrate, a method for manufacturing a NiP coated substrate using the solution, and a NiP coated substrate that can be manufactured therefrom. [Methods to solve the problem]

[0010] According to one aspect of the present invention, a nickel-phosphorus alloy coated substrate is provided, which has a substrate and a nickel-phosphorus alloy film formed on the substrate, wherein the nickel-phosphorus alloy film contains indium at a concentration of 70 to 620 ppm.

[0011] According to one aspect of the present invention, a solution for electroless plating of nickel-phosphorus alloy films can be provided, which contains nickel ions, hypophosphite ions, a bonding agent and indium ions, wherein the concentration of the aforementioned indium ions is 0.18~1.8ppm.

[0012] According to one aspect of the present invention, a method for manufacturing a nickel-phosphorus alloy coated substrate is provided, which includes forming a nickel-phosphorus alloy film by electroless plating using a solution of the above-described aspect.

[0013] According to one aspect of the present invention, a magnetic recording medium having a nickel-phosphorus alloy coated substrate as described above can be provided.

[0014] The present invention can reduce the thickness distribution of NiP film at the outer edge of the substrate without compromising the corrosion resistance of the NiP film. This specification contains the disclosure of Japanese Patent Application No. 2021-093867, which forms the basis of the priority claim in this application. Implementation

[0015] []

[0016] The following describes the embodiments. This invention is not limited to the following embodiments; various design changes can be made without departing from the spirit of the invention as described in the claims. In this application, the numerical range indicated by the symbol "~" includes the values ​​before and after the symbol "~" as the upper and lower limits, respectively.

[0017] (1) Solution for electroless plating of NiP films The solution used in the electroless plating process contains nickel ions, hypophosphite ions, a bonding agent, and indium ions.

[0018] The concentration of indium ions in the solution is 0.18~1.8 ppm, 0.3~1.5 ppm, or 0.3~0.8 ppm. Therefore, as shown in the examples described later, a NiP film with high corrosion resistance and a smaller film thickness distribution at the outer edge of the substrate can be formed. Water-soluble indium salts, such as indium nitrate, indium sulfate, and indium chloride, can be used as the indium ion supply source. These indium salts can be used alone or in combination of two or more.

[0019] The other components and their concentrations in the solution used in the implementation can be the same as those used in the electroless plating of NiP films.

[0020] Water-soluble nickel salts, such as nickel sulfate, nickel chloride, nickel carbonate, nickel acetate, and nickel ammonium sulfonate, can be used as the source of nickel ions. These nickel salts can be used alone or in combination of two or more. The concentration of nickel ions in the solution can be, for example, 1 to 30 g / L.

[0021] As a source of hypophosphite ions, such as hypophosphite or its salts, sodium hypophosphite or potassium hypophosphite can be used. The concentration of hypophosphite ions in the solution can be 5~80 g / L. Hypophosphite ions act as a reducing agent.

[0022] The ligating agent is a dicarboxylic acid or its basic salt, such as tartaric acid, malic acid, citric acid, succinic acid, malonic acid, glycolic acid, gluconic acid, oxalic acid, phthalic acid, fumaric acid, maleic acid, lactic acid, or their sodium, potassium, or ammonium salts. Two or more of these may be used together, with at least one being an oxodiacarboxylic acid. The concentration of the ligating agent in the solution can be 0.01–2.0 mol / L.

[0023] The solution in the embodiment may further contain stabilizers, pH adjusters, gloss agents, fungicides, or surfactants. Lead compounds such as lead(II) acetate can be used as stabilizers, in which case the solution in the embodiment contains lead ions. Acids, bases, or salts can be used as pH adjusters. The solution in the embodiment may contain water as a solvent.

[0024] The solution in the embodiment may be iodine-free. Here, "non-iodine-free" means substantially non-existent, specifically, undetectable by inductively coupled plasma luminescence analysis (ICP-AES). Furthermore, the chemical species of iodine are not limited, including, for example, monomeric iodine, iodide ions, iodate ions, and periodate ions. However, the solution in the embodiment may also be free of any of monomeric iodine, iodide ions, iodate ions, or periodate ions.

[0025] (2)NiP coated substrate A NiP-coated substrate is obtained by electroless plating of the substrate by immersing it in the above solution. The NiP-coated substrate has a substrate and a NiP film formed thereon.

[0026] The substrate may have a ring-shaped form. Furthermore, the substrate may be non-conductive (insulating), conductive, or semi-conductive. Examples of non-conductive substrates include those made of glass, ceramic, or plastic. Examples of conductive substrates include those made of metal or conductive metal oxides. Examples of semi-conductive substrates include those made of semi-metallic or compound semiconductor materials. In particular, the substrate may be made of aluminum, aluminum alloys, or glass.

[0027] The NiP film may contain In at a concentration of 70-620 ppm, preferably 170-410 ppm, and even more preferably 170-200 ppm. As shown in the examples described later, this NiP film exhibits high corrosion resistance while having a smaller film thickness distribution at the outer edge of the substrate. Furthermore, the NiP film may contain phosphorus (P) at a concentration of 10-13% by weight. The composition of the NiP film can be determined by dissolving the NiP film in nitric acid and quantifying the elements in the solution using ICP-AES. The NiP film may be iodine-free. Here, "iodine-free" means substantially absent, specifically meaning undetectable by ICP-AES. Furthermore, the chemical type of iodine is not limited, including, for example, monomeric iodine, iodide ions, iodate ions, and periodate ions. However, the NiP film may also be free of any of monomeric iodine, iodide ions, iodate ions, or periodate ions.

[0028] The NiP film has a very small thickness distribution at the outer edge of the NiP-coated substrate. Specifically, the maximum height of the NiP film from the surface reference plane in the region 0-2 mm from the outer edge of the NiP-coated substrate can be less than 3%, 2.9%, 2.8%, 2.5%, or 2.4% of the NiP film thickness, and can be more than 0%, more than 0%, or more than 1.6% of the NiP film thickness. The maximum height of the NiP film from the surface reference plane in the region 0-2 mm from the outer edge of the NiP-coated substrate is obtained based on the surface profile of the NiP film measured by a stylus-type surface shape measuring instrument (e.g., Bruker's "Dektak 150"). The reference plane system is defined as a plane containing a straight line passing through a first point on the surface of the NiP film at a distance of 2-5 mm from the outer edge of the NiP coated substrate toward the center of the NiP coated substrate, and a second point on the surface of the NiP film at a distance of 1-5 mm from the first point toward the center of the NiP coated substrate.

[0029] Furthermore, the NiP film exhibits excellent corrosion resistance. Specifically, when a NiP-coated substrate is immersed in 30% nitric acid heated to 45°C for 150 seconds, the area ratio of pores formed on the surface of the NiP film can be less than 0.75%. The area ratio of pores was obtained by observing an image of the NiP film surface after immersion in nitric acid using an optical microscope.

[0030] NiP-coated substrates can be used for any application. For example, a magnetic layer can be formed on a NiP-coated substrate to manufacture magnetic recording media.

[0031] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments. Various modifications can be made without departing from the spirit of the present invention as described in the claims. Embodiments combining the above embodiments can also be provided. [Example]

[0032] The present invention will now be described in detail with reference to the embodiments, but the present invention is not limited to these embodiments.

[0033] An aqueous solution containing 27 g / L nickel sulfate, 30 g / L sodium hypophosphite, 30 g / L lactic acid, 30 g / L malic acid, 6 g / L succinic acid, 20.5 g / L sodium hydroxide, and lead(II) acetate was prepared. Furthermore, in Examples 1-8 and Comparative Examples 2-4, indium nitrate was added to the solution. In Comparative Example 5, bismuth(III) sulfate was added to the solution. In Comparative Example 6, antimony(III) acetate was added to the solution. In Comparative Example 7, ammonium molybdate tetrahydrate was added to the solution. The amounts added were set such that the solution contained In, Bi, Sb, or Mo ions at the concentrations listed in Table 1 after addition. The plating solutions of each example and comparative example were thus obtained.

[0034] An annular aluminum alloy plate (JIS A-5052, inner diameter 25 mm, outer diameter 95 mm) was subjected to alkaline etching and zinc replacement treatment. The aluminum alloy plate was immersed in a plating solution heated to 85°C. This process formed a NiP film with the thicknesses shown in Table 1 on the aluminum alloy plate. The test specimens for each embodiment and comparative example were thus obtained.

[0035] (1) Elemental analysis The NiP films of each test specimen were dissolved in nitric acid, and the elements in the solution were quantified by ICP-AES. The In concentration (i.e., the In concentration in the NiP film) and 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.

[0036] (2) Surface profile measurement The surface profile of the NiP film of each test subject was measured using a stylus-type surface profile measuring instrument (Bruker Dektak 150). Based on the obtained surface profile, the maximum height (maximum height) of the reference plane of the NiP film surface in the region 0-2 mm from the outer edge of the test subject was determined. The same measurement was performed 7 times, and the average of the maximum height was calculated. The results are shown in Table 1. The reference plane is defined as the plane containing the straight line passing through the first point on the NiP film surface 2-5 mm from the outer edge of the test subject towards the center of the test subject, and the second point on the NiP film surface 1-5 mm from the first point towards the center of the test subject.

[0037] (3) Corrosion resistance evaluation Each test 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 pores formed on the surface. The results are shown in Table 1.

[0038] (4) Grinding The test specimens of Examples 1-8 were ground. The surface profile of the ground test specimens was measured, and the maximum height (maximum height) of the height from the reference plane of the NiP film surface in the region 0-2 mm from the outer edge of the test specimen was determined. Each test specimen has a sufficiently small maximum height suitable for use in the manufacture of magnetic recording media for hard disk drives.

[0039]

[0040] As shown in Table 1, the NiP films of Examples 1-8, which contain indium at a concentration of 79-620 ppm and are formed using a plating solution containing indium at a concentration of 0.18-1.8 ppm, have a smaller maximum height. Furthermore, the NiP films of Examples 1-8 also have a smaller area ratio of etched pores. Moreover, the NiP films of Examples 2-7, which contain indium at a concentration of 176-410 ppm and are formed using a plating solution containing indium at a concentration of 0.36-1.44 ppm, have an even smaller maximum height. The NiP films of Examples 2-4, which contain indium at a concentration of 176-194 ppm and are formed using a plating solution containing indium at a concentration of 0.36-0.72 ppm, have an exceptionally small maximum height.

[0041] The NiP films of Comparative Examples 1-4, formed using plating solutions with indium concentrations below 0.18 ppm or above 1.8 ppm and indium concentrations below 70 ppm or above 620 ppm, exhibited larger maximum heights. The NiP films of Comparative Examples 3 and 4 also showed larger areas of etched pits. The NiP films of Comparative Example 5, using a plating solution containing bismuth, and Comparative Example 6, using a plating solution containing antimony, showed larger maximum heights and larger areas of etched pits. The NiP film of Comparative Example 7, using a plating solution containing molybdenum, had a smaller maximum height but a larger area of ​​etched pits. All publications, patents and patent applications cited in this specification are directly cited and incorporated herein.

Claims

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

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

3. The nickel-phosphorus alloy coated substrate of claim 1 or 2, wherein the aforementioned nickel-phosphorus alloy film contains the aforementioned indium at a concentration of 170 to 410 ppm.

4. The nickel-phosphorus alloy coated substrate as claimed in claim 1 or 2, wherein the aforementioned nickel-phosphorus alloy film is free of iodine.

5. An electroless plating solution for nickel-phosphorus alloy films used in magnetic recording media, comprising nickel ions, hypophosphite ions, a bonding agent and indium ions, wherein the concentration of the aforementioned indium ions is 0.18 to 1.8 ppm.

6. The solution as claimed in item 5, wherein the aforementioned indium ions are contained at a concentration of 0.3 to 1.5 ppm.

7. The solution, as requested in item 5 or 6, does not contain iodine.

8. The solution as requested in item 5 or 6, which further contains lead ions.

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

10. A magnetic recording medium having a nickel-phosphorus alloy coated substrate as claimed in any one of claims 1 to 4.