HK1172993B - Electroless coated disks for high temperature applications and methods of making the same - Google Patents

Description

Electroless coated magnetic disks for high temperature applications and methods of making same

Technical Field

The present invention relates generally to hard disk drives and, more particularly, to an electroless coated magnetic disk for high temperature applications and a method of making the same.

Background

Magnetic disks used in hard disk drive media typically include an aluminum-magnesium (AlMg) substrate that is plated with a material such as nickel-phosphorus (NiP) to provide a smooth surface on which a magnetic recording layer is deposited on which data may be stored. To accommodate the growing demand for increased data storage space, future hard disk drives may utilize technologies such as EAMR (energy assisted magnetic recording) that require high magnetic anisotropy (K)_u) The magnetic recording layer of (1). Such a magnetic recording layer may comprise an alloy requiring a deposition temperature in excess of 300 deg.c. However, the current Ni — P coatings used to provide a smooth surface on which to deposit the magnetic recording layer cannot withstand such hot temperatures without significantly increasing the surface roughness.

Disclosure of Invention

Various embodiments of the present invention solve the above-described problems by providing aluminum magnetic disks with a coating that has increased thermal stability for use in high Ku magnetic recording layers.

According to one aspect of the subject disclosure, a disk for a hard disk drive includes a substrate comprising aluminum anda coating disposed on the substrate. The coating comprises Ni and X₁And X₂Of (2), wherein X₁Comprising one or more elements selected from the group consisting of Ag, Au, B, Cr, Cu, Ga, In, Mn, Mo, Nb, Pb, Sb, Se, Sn, Te, W, Zn and Zr, and wherein X₂Comprises B or P, and wherein X₁And X₂Not including the same elements.

In accordance with another aspect of the subject disclosure, a method of forming a disk for a hard disk drive comprises the steps of: providing a substrate comprising aluminum; providing a zincate layer on the substrate; and electroless plating a coating (electroless plating coating) on the zincate layer. The coating comprises Ni and X₁And X₂Of (2), wherein X₁Comprising one or more elements selected from the group consisting of Ag, Au, B, Cr, Cu, Ga, In, Mn, Mo, Nb, Pb, Sb, Se, Sn, Te, W, Zn and Zr, and wherein X₂Comprises B or P, and wherein X₁And X₂Not including the same elements.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:

FIG. 1 illustrates a disk for use in a hard disk drive in accordance with an aspect of the subject disclosure.

FIG. 2 is a flow chart illustrating a method of forming a disk for a hard disk drive in accordance with an aspect of the subject disclosure.

Detailed Description

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the invention.

FIG. 1 illustrates a magnetic disk 100 for use in a hard disk drive according to one aspect of the subject disclosure that includes a substrate 101 comprising aluminum and a coating 103 disposed on the substrate. The substrate 101 may include, for example, an alloy of aluminum (Al) and magnesium (Mg). The coating 103 comprises Ni, X₁And X₂Of (2), wherein X₁Including one or more elements selected from the group consisting of silver (Ag), gold (Au), boron (B), chromium (Cr), copper (Cu), gallium (Ga), indium (In), manganese (Mn), molybdenum (Mo), niobium (Nb), lead (Pb), antimony (Sb), selenium (Se), tin (Sn), tellurium (Te), tungsten (W), zinc (Zn), and zirconium (Zr), and wherein X₂Comprising boron (B) or phosphorus (P), and wherein X₁And X₂Not including the same elements. According to one aspect of the subject disclosure, the thickness of the coating may be between about 1 to 20 μm (micrometers).

According to one aspect of the subject disclosure, magnetic disk 100 can further include a zincate layer 102 disposed between substrate 101 and coating 103. The zincate layer 102 provides a barrier that can help prevent the aluminum substrate 101 from oxidizing. In accordance with another aspect of the subject disclosure, the magnetic disk 100 may further include a magnetic recording layer 104 disposed on the overcoat 103. The magnetic recording layer 104 may comprise a material that may require a high temperature (e.g., above 300 ℃) deposition process, including, for example, one or more of Fe, Pt, Sm, and Co.

In accordance with certain aspects of the subject disclosure, polished AlMg/Ni-X₁-X₂The disks are more susceptible to increased thermal stability than conventional NiP coated AlMg disks. For example, Cu is added toThe NiP coating alloy helps to suppress the magnetic properties of Ni that form in conventional NiP coatings at high temperatures (e.g., above 340 ℃) due to crystallization and crystal growth of Ni. In this regard, according to one aspect of the subject disclosure, X₁Cu and another element such as an element selected from the group consisting of B, In, Mo, Sn, and W may be included. Accordingly, In accordance with certain aspects of the subject disclosure, for example, the alloy may be a quaternary alloy such as Ni-Cu-In-P (i.e., where X is₁Including Cu and In and X₂Including P), Ni-Cu-Mo-P (i.e. where X is₁Including Cu and Mo and X₂Including P) or Ni-Cu-B-P (i.e. where X is₁Comprising Cu and B and X₂Including P).

In accordance with one aspect of the subject disclosure, the alloy may include between about 30% and about 70% Ni by weight and between about 3% and about 11% X by weight₂。X₁May represent between about 1.5% and about 42% by weight of the alloy.

According to one aspect of the subject disclosure, the coating, after polishing, can have a roughness R of less than about 0.5nm (nanometers) as measured with an atomic force microscope_a. In accordance with one aspect of the subject disclosure, because of the improved thermal stability of the coating, it maintains a roughness R of less than about 1.0nm as measured with an atomic force microscope after being heated to about 450 ℃_a。

FIG. 2 is a flow chart illustrating a method of forming a disk for a hard disk drive in accordance with an aspect of the subject disclosure. The method begins at step 201, wherein a substrate comprising aluminum is provided. In step 202, a zincate layer is disposed on a substrate. According to one aspect of the subject disclosure, the zincate layer may be deposited in an alkaline water bath under high ph conditions. Alternatively, the zincate layer may be deposited by an acidic zinc immersion process.

In step 203, a coating is provided on the zincate layer by electroless/electroless plating. The coating comprises Ni and X₁And X₂Of (2), wherein X₁Comprising one or more elements selected from the group consisting of Ag, Au, B, Cr, Cu, Ga, In, Mn, Mo, Nb, Pb, Sb, Se, Sn, Te, W, Zn and Zr, and wherein X₂Comprises B or P, and wherein X₁And X₂Not including the same elements. The step of electroless plating the coating may comprise placing the substrate in a plating solution comprising: ni and X₁One or more than one metal source for each of; a reducing agent for reducing the one or more than one metal sources, the reducing agent comprising X₂(ii) a One or more complexing agents (complexor) to reduce metal precipitation; one or more than one stabilizer; and one or more than one pH adjusting additive.

According to one aspect of the subject disclosure, the plating solution can have a pH between about 5 and about 9. This pH range may allow X to be achieved₁Between about 1.5% and about 42% by weight of each component. In accordance with another aspect of the subject disclosure, the plating solution may be maintained at a temperature between about 160 ° F and about 195 ° F when the substrate is placed in the plating solution.

According to one aspect of the subject disclosure, the plating solution can have a metal cycle (MTO) of less than 6 (metal open over). For example, according to one aspect of the subject disclosure, the MTO of the plating solution may be maintained between about 2.0 and 4.5. Maintaining the MTO at these levels may allow for economical plating performance and consistently reproducible plating results. The isolation of the phosphite in the bath may be used to maintain a stable phosphite concentration over the life of the bath.

According to one aspect of the subject disclosure, the one or more metal sources of Ni can include one or more of nickel sulfate, nickel sulfamate, nickel acetate, nickel chloride, nickel hypophosphite, and nickel fluoroborate. According to another aspect of the subject disclosure, X₁The one or more than one metal source of (a) may include copper sulfate, copper iodate, copper iodide, copper chloride, indium citrate, indium sulfate, indium acetate, molybdic acid, ammonium molybdate, sodium molybdate, tungstenOne or more than one of ammonium sulfate, sodium tungstate and indium chloride.

According to one aspect of the subject disclosure, the reducing agent may include one or more of hypophosphites, nickel hypophosphite, dimethylamine borane (DMAB), diethylamine borane (DEAB), borane amine (aminoborane), and sodium borohydride. According to another aspect of the subject disclosure, the one or more complexing agents may include one or more of citric acid, malic acid, lactic acid, an amino acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), a carboxylic acid, and any salt thereof.

According to one aspect of the subject disclosure, the one or more stabilizers can include one or more cations of Bi, Cd, Cu, Hg, In, Mo, Pb, Sb, and Sn, AsO^-2、MoO^-4、IO₃ ^-、NO₃ ^-Maleic acid, itaconic acid, methylbutynol, N-diethyl-2-propyn-1-amine and 2-butyn-1, 4-diol. In accordance with another aspect of the subject disclosure, the one or more than one stabilizing agent can include iodine or a compound thereof. The stabilizer may help prevent decomposition of the plating solution (e.g., by preventing nucleation of nickel particles in the plating solution).

In accordance with one aspect of the subject disclosure, the one or more pH adjusting additives can include K₂CO₃、Na₂CO₃、KHCO₃、NaHCO₃、NaOH、KOH、NH₄OH and N (CH)₂CH₃)₃One or more than one. According to another aspect of the subject disclosure, the one or more pH adjusting additives may include a buffer selected from the group consisting of boric acid, borax, triethanolamine, triethylenepentamine (triethylenepentamine), diethylenetriamine, acetate, propionate, succinate, and adipate.

According to one aspect of the subject disclosure, the plating solution may further include one or more than one dispersant, anionic surfactant, nonionic surfactant, and organic sulfur compound(s).

In step 204, the coating may be polished with a slurry comprising an abrasive in an aqueous solution, according to one aspect of the subject disclosure. For example, the abrasive may comprise one or more of nanodiamond, alumina, titania, zirconia, germania, silica, ceria and mixtures thereof. The pH of the slurry may be maintained between 3 and 9 during polishing.

According to one aspect of the subject disclosure, the slurry may further include an oxidizing agent, a complexing agent, and one or more than one organic amino compound. For example, the oxidizing agent may include one or more peroxy compounds (e.g., hydrogen peroxide), urea, permanganate, nitrate, and iodate. For example, the complexing agent may include one or more than one of citric acid, lactic acid, tartaric acid, succinic acid, malonic acid, oxalic acid, amino acids, or salts thereof. For example, the organic amino compound may include triethanolamine or the like.

According to one aspect of the subject disclosure, the slurry may further include a corrosion inhibitor comprising benzotriazole or benzoylphenylhydroxylamine. In accordance with another aspect of the subject disclosure, the slurry may further include a stabilizer including one or more of ammonium lauryl sulfate (ammonium lauryl sulfate), sodium lauryl sulfate (sodium dodecyl sulfate), and sodium lauryl sulfate (sodium lauryl sulfate).

According to one experimental embodiment of the subject disclosure, an exemplary polishing process was used to polish Ni-X coated with a thickness of about 10 μm₁P-coated AlMg disk, the exemplary polishing process comprising an acidic polishing step at a pH of about 2 and a second polishing step at a pH of about 9. Colloidal silica and/or nanodiamonds are used as abrasives in the second polishing step. To avoid chemical attack, the polishing slurry of the second step does not contain an active oxidizing agent such as H₂O₂. The second polishing step is carried out at a very low removal rate of less than 0.02 μm/min and leaves behind Ni-X₁-P tableA surface which is smooth and defect free (e.g. R measured by AFM on a 10 μm by 10 μm area) after a cleaning step with a conventional surfactant_a0.2 nm). No observation of P-Ni-X₁Erosion of the P coating.

Polished AlMg/Ni-X according to various experimental examples of the subject disclosure₁-P (e.g. wherein X₁Cu, CuMo, or CuIn) disks tend to exhibit increased thermal stability compared to conventional NiP coated AlMg disks. Temperature-dependent magnetic measurements on exemplary AlMg disks coated with Ni-Cu-P showed that the addition of Cu to the coating alloy helped to suppress the magnetic properties of Ni that form in conventional NiP layers at high temperatures (e.g., above 340 ℃) due to crystallization and crystal growth of Ni. This is done while the disk is cycled through a multi-module manufacturing type sputter and under vacuum (10)^-7To 10^-8Torr) to a temperature of about 450 c. The disk was supported at the OD by spring-loaded stainless steel pins. The pins hold the disk securely on a flat plate that is driven by the sputter to a subsequent deposition, heating and cooling module. The heater block is equipped with two resistive heater coils that heat each side of the disk by radiation. For the measurement, no additional coating was applied to the disk. The surface temperature of each disk is measured by a pyrometer that probes the temperature of the disk surface immediately after the disk is removed from the heater chamber. Approximately 1300W of heater power was applied for approximately 10 seconds to raise the disk temperature to approximately 450 deg.C. After heating, the disk is removed from the sputter without passing through a cooling station. No disk was bent or showed OD jingles or other damage caused by heating. The coating on the conventional AlMg/Ni-P disks had a hazy appearance after testing, indicating a significant increase in surface roughness (subsequently confirmed by AFM). Having Ni-X₁The surface of the P-coated disk remains shiny like a mirror. AFMRa measurements on these disks confirmed that the coating did not degrade at temperatures around 450 ℃.

The description of the present invention is provided to enable any person skilled in the art to practice the various embodiments described herein. While the present invention has been particularly described with reference to various figures and embodiments, it should be understood that these are for illustration purposes only and are not to be taken as limitations of the present invention.

There may be many other ways of implementing the invention. The various functions and elements described herein may be divided other than as shown without departing from the spirit and scope of the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments. Accordingly, many changes and modifications may be made by one having ordinary skill in the art without departing from the spirit and scope of the invention.

Reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more than one. The terms "a" or "an" refer to one or more than one. Underlined and/or italicized headings and subheadings are used for convenience only, do not limit the invention, and are not involved in the explanation of the description of the invention. Some elements of the various embodiments of the present invention described throughout this disclosure may be known or later come to be known to those skilled in the art, and all structural and functional equivalents thereof are expressly incorporated herein by reference and are intended to be encompassed by the present invention. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the foregoing specification.

Claims (11)

1. A disk for a hard disk drive, comprising:

a substrate comprising aluminum; and

a coating disposed on the substrate, the coating comprising Ni, X₁And X₂The alloy of (a) is preferably a metal alloy,

wherein X₁Including Cu and an element selected from the group consisting of B, In, Mo and W,

wherein X₂Including the group consisting of B or P,

wherein X₁And X₂Does not include the same elements; and is

Wherein the alloy comprises between 1.5 and 42 weight percent X₁And X in a weight percentage of between 3% and 11%₂。

2. The magnetic disk of claim 1 wherein said alloy is one of Ni-Cu-In-P, Ni-Cu-Mo-P and Ni-Cu-B-P.

3. The disk of claim 1 wherein said alloy is a quaternary alloy.

4. The magnetic disk of claim 1 wherein said alloy includes between 30 and 70 weight percent Ni.

5. The disk of claim 1 wherein the coating has a thickness of between 1 μm and 20 μm.

6. The magnetic disk of claim 1 wherein the coating has a roughness R of less than 0.5nm as measured with an atomic force microscope_a。

7. The magnetic disk of claim 1 wherein the coating maintains a roughness R of less than 1.0nm as measured by atomic force microscopy after being heated to 450 ℃_a。

8. The magnetic disk of claim 1 further comprising a zincate layer disposed between the substrate and the coating.

9. The magnetic disk of claim 1 wherein said substrate comprises Al-Mg.

10. The magnetic disk of claim 1 further comprising a magnetic recording layer disposed on the overcoat, the magnetic recording layer comprising one or more of Fe, Pt, Sm, and Co.

11. A hard disk drive comprising the magnetic disk of claim 1.