Reducing oxygen consumption in sealed enclosure heat assisted magnetic recording disk drives

Abstract

Disclosed herein are sealed enclosure HAMR hard disk drives and methods for use therewith that reduce the rate of gaseous oxygen consumption within the sealed HAMR drive enclosure, thereby leaving an amount of oxygen that can be used to mitigate the effects of carbonaceous residue formation, thereby extending the service life of the HAMR drive. In a sealed enclosure HAMR hard disk drive comprising a component having an NdFeB alloy magnet, the sealed enclosure is filled with a gas mixture, the gas mixture includes predominantly helium and oxygen in an amount sufficient to mitigate carbonaceous residue formation during the life of the driver and nitrogen in an amount sufficient to reduce the rate of oxygen consumption due to oxidation of the NdFeB magnet.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of 63 / 605,789, filed December 4, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to a heat-assisted magnetic recording hard disk drive having a sealed enclosure. Background Art

[0004] Storage density in hard disk drives (HDDs) continues to increase. Areal density in shipping products exceeds one terabit per square inch (Tb / in 2 ), in the near future, the density will approach 5Tb / in 2 It is possible. Therefore, there is a constant need to develop disk and recording head related technologies that can maintain recording bit sizes close to 10 to 20 nanometers. Heat-assisted magnetic recording (HAMR) technology can improve bit stability in the nanoscale domain, but integrating HAMR technology into hard disk drives can be challenging. Summary of the invention

[0005] The present disclosure relates to methods for use with a sealed enclosure HAMR hard disk drive comprising a NdFeB alloy magnet. In certain aspects, such methods comprise filling the sealed enclosure with a gas mixture comprising helium and oxygen, the helium being present in the gas mixture in an amount of at least 90% by volume. Such methods may also comprise exposing the magnet to nitrogen in an amount sufficient to reduce the rate of oxygen consumption within the sealed enclosure.

[0006] In certain aspects, exposing the magnet to nitrogen includes exposing the magnet material to nitrogen during annealing of the magnet material and prior to placing the magnet within the sealed enclosure.

[0007] In some aspects, exposing the magnet to nitrogen comprises adding nitrogen to a gas mixture used to fill the sealed enclosure. For example, the gas mixture used to fill the sealed enclosure consists of helium in an amount of (100-xy) volume %, oxygen in an amount of x volume %, and nitrogen in an amount of y volume %, wherein x is greater than 0 and less than 10, wherein y is greater than 0, and wherein x+y is less than 10.

[0008] In certain aspects of the methods disclosed herein, the oxygen consumption rate is reduced so that the sealed enclosure maintains a sufficient amount of gaseous oxygen to react with organic residues within the sealed enclosure over a span of more than 4 years, preferably 5 years or more, of normal operation of the HAMR hard disk drive and at an average operating temperature of 62°C or less.

[0009] The present disclosure also relates to a sealed enclosure HAMR hard disk drive comprising at least one component, the at least one component comprising a NdFeB magnet. For example, such a component may be a voice coil motor or a spindle motor. The sealed enclosure is filled with a gas mixture comprising helium, oxygen, and nitrogen, the helium being present in an amount of at least 90 volume percent. The sealed enclosure of the HAMR hard disk drive maintains a sufficient amount of oxygen to react with organic residues within the sealed enclosure over a span of more than 4 years, preferably 5 years or more, of normal operation of the HAMR hard disk drive and at an average operating temperature of 62C or less.

[0010] In certain aspects, the NdFeB magnets are preconditioned by exposure to nitrogen before being placed in a sealed enclosure. In certain aspects, the NdFeB magnets are nickel plated or epoxy coated.

[0011] Preferably, when the sealed enclosure is sealed, the initial gas mixture consists of (100-xy) volume % helium, x volume % oxygen and y volume % nitrogen, wherein x is greater than 0 and less than 10, wherein y is greater than 0, and wherein x+y is less than 10.

[0012] These and other features and aspects of the various embodiments will be understood in view of the following detailed discussion and accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a graph depicting initial oxygen consumption rate versus initial oxygen fill level for a range of different average operating temperatures as observed in a tested HAMR drive.

[0014] Figure 2 is a graph depicting expected gaseous oxygen consumption over time in a test HAMR driver operating under normal conditions and at an average operating temperature of 62C.

[0015] Figure 3 A diagram of a sealed enclosure HAMR hard drive with the top cover cut away to indicate the internal components. DETAILED DESCRIPTION

[0016] The present disclosure relates to sealed enclosure HAMR drives and methods for use therewith that reduce the rate of gaseous oxygen consumption within the sealed drive enclosure, thereby leaving an amount of oxygen available to mitigate the effects of carbonaceous residue formation, thereby extending the useful life of the HAMR drive.

[0017] In heat-assisted magnetic recording (HAMR) disk drives, the surface of the recording medium is elevated to 500C or higher during writing. Without wishing to be bound by any theory, it has been observed that organic residues present at the HAMR head-disk interface can act as optical absorbers of near-field infrared light and thereby interfere with optimal HAMR drive operation. These organic residues, also known as carbonaceous residues or "stains," are believed to originate from thermal decomposition of volatile organic compounds within the drive housing. It has been found that the deleterious effects of these organic residues are effectively mitigated when oxygen is allowed to react with the organic residues.

[0018] HAMR actuators are typically implemented in sealed enclosures filled primarily with an inert gas such as helium. To help reduce the effects of contamination, a small amount of oxygen can be introduced into the sealed helium actuator environment. However, other components within the actuator may be susceptible to reacting with oxygen, thereby consuming the amount of oxygen that would otherwise be available to mitigate carbonaceous residues. For example, Figure 1 As seen in Figure 1, the initial oxygen consumption rate measured during testing of a similarly constructed sealed HAMR drive is plotted as a function of the initial oxygen content and three different average operating temperatures. A fit to the data using a surface reaction model is also plotted. Based on these test observations, it is estimated that under normal operating conditions and at a typical HAMR hard drive average operating temperature of 62C, nearly all of the gaseous oxygen will be depleted from the sealed drive in less than 3 years, as shown in Figure 1. Figure 2 as shown in .

[0019] Reducing the oxygen consumption rate allows more gaseous oxygen to be available for a longer period of time to mitigate carbonaceous residues, and may also allow a lower initial amount of oxygen to be used in the helium mixture or other inert gas mixture used to fill a sealed HAMR hard drive.

[0020] One hard drive component that may contribute to oxygen consumption includes magnets, such as neodymium iron boron (NdFeB) magnets, that are commonly used in voice coil motors (VCMs) that control the movement of recording head actuators and in spindle motors that control the rotation of magnetic recording disks. The NdFeB alloys used in such magnets are susceptible to corrosion and are therefore typically coated with a layer of electroplated nickel or a thin layer of copper sandwiched in a nickel film covering the magnet. NdFeB magnets may also be coated with or encapsulated in epoxy to reduce corrosion. However, such coated magnets may still be susceptible to corrosion and, therefore, result in an increased rate of oxygen consumption.

[0021] Using even small amounts of nitrogen to treat NdFeB alloys can significantly reduce corrosion rates. For example, nitrogen can be used to passivate substoichiometric neodymium oxide residing at grain boundaries in NdFeB magnet materials by producing neodymium nitride. Thus, oxygen consumption can be mitigated by introducing effective amounts of gaseous nitrogen to treat NdFeB magnet materials during annealing processes or other metallurgical processes when forming magnets or during the process of filling a sealed HAMR drive.

[0022] Figure 3 A sealed housing HAMR hard drive 300 is schematically shown. The housing 310 includes a top cover 320, which is cut away to indicate various internal components. The sealed housing 310 contains a magnetic recording medium 302 in the form of one or more disks, a recording head (or a slider with a recording head mounted thereon) 304 that includes components for writing data to and reading data from the medium 302, and an actuator arm 308 with the recording head 304 on the end. Movement of the actuator arm 308 is controlled by a voice coil motor (VCM), a component of which is a VCM magnet 306. The VCM magnet 306 can be composed of an NdFeB alloy. Other components in the hard drive may also include NdFeB magnets, such as a spindle motor ( Figure 3 not indicated in the table).

[0023] When filling a sealed enclosure of a HAMR drive according to aspects of the present disclosure, a mixture may be used that includes gaseous nitrogen added to an inert gas such as helium, as well as oxygen. Since nitrogen is available to react with the NdFeB magnet material, the addition of nitrogen is expected to reduce the rate of oxygen consumption. Thus, even though less oxygen is used in the initial fill mixture than would be required without the addition of nitrogen, the gaseous oxygen may remain available for a longer period of time over the life of the HAMR drive. While the presence of more oxygen in the fill mixture may ensure that the oxygen is available to mitigate the formation of carbonaceous residues, the presence of less oxygen may benefit drive operation, including reducing disk flutter.

[0024] In some embodiments, the gaseous mixture used to fill the sealed enclosure is composed of helium in an amount of (100-xy) volume %, oxygen in an amount of x volume %, and nitrogen in an amount of y volume %, wherein x is greater than 0, y is greater than 0, and x+y does not exceed about 10. Preferably, x is in the range of about 1 to 10, and x+y is less than 10. In some embodiments, y is not greater than x. As non-limiting examples, possible specific embodiments of x,y pairs include: (x,y)=(5,3); (x,y)=(3,2); and (x,y)=(2,1).

[0025] As an alternative or in addition to including nitrogen in the gaseous mixture filling the sealed enclosure of the HAMR drive, the NdFeB alloy used to make the magnet can be exposed to nitrogen before being assembled into the HAMR drive. For example, in the manufacture of NdFeB magnets, the alloy is first cast, ground into a powder, and finally pressed and sintered in argon or in a vacuum. The introduction of small amounts of nitrogen into the metallurgy can be beneficial to corrosion robustness and, therefore, help prevent oxygen depletion in the HAMR drive when using NdFeB magnets manufactured in this manner. Additionally, during magnet manufacturing and processing, it may be beneficial to incorporate small amounts of nitrogen in the chamber during annealing of the NdFeB magnet, for example, including nitrogen in an amount of about 1 to 10 volume % in the annealing chamber.

[0026] It should be understood that the various aspects disclosed herein may be combined in a manner different from the combinations specifically presented in the specification and drawings. It should also be understood that, depending on the instance, certain actions or events of any process or method described herein may be performed in a different order, may be added, merged, or omitted entirely. In addition, although for clarity, certain aspects of the present disclosure are described as being performed by a single module or unit, it should be understood that the technology of the present disclosure may be performed by a combination of units or modules.

[0027] As used herein, the term "or" refers to the inclusive definition, for example, meaning "and / or", unless its usage context clearly indicates otherwise. The term "and / or" means one or all of the listed elements or a combination of at least two of the listed elements.

[0028] As used herein, a list of elements followed by the phrases "at least one of" and "one or more of" means one or more of any of the listed elements or any combination of one or more of the listed elements.

[0029] As used herein, the term "coupled" or "connected" refers to at least two elements being attached to each other directly or indirectly. An indirect coupling may include one or more other elements between the at least two elements that are attached. In addition, in one or more embodiments, an element "on another element" may be directly or indirectly on another element, and may include intermediate components or layers therebetween. Both of these terms may be modified by "operationally" and "operably," which are used interchangeably to describe that a coupling or connection is configured to allow components to interact to perform a described or otherwise known function. For example, a controller may be operably coupled to a resistive heating element to allow the controller to provide current to the heating element.

[0030] As used herein, any terms related to position or orientation, such as "proximal," "distal," "terminal," "outer," "inner," etc., refer to relative positions and do not limit the absolute orientation of the embodiments, unless the context of their use clearly indicates otherwise.

[0031] Unless otherwise specified, all scientific and technical terms used herein have the meanings commonly used in the art. The definitions provided herein are for ease of understanding certain terms frequently used herein and are not intended to limit the scope of the present disclosure.

[0032] The words "preferred" and "preferably" refer to embodiments of the present disclosure that may provide certain benefits in certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. In addition, the description of one or more preferred embodiments does not mean that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the present disclosure.

[0033] Further examples

[0034] Example 1. A method for use with a heat-assisted magnetic recording (HAMR) hard drive comprising a sealed enclosure, the sealed enclosure containing a magnet, the magnet comprising a NdFeB alloy, the method comprising: filling the sealed enclosure with a gas mixture comprising helium and oxygen, the helium being present in the gas mixture in an amount of at least 90 volume percent; and exposing the magnet to an amount of nitrogen sufficient to reduce the rate of oxygen consumption within the sealed enclosure.

[0035] Example 2. The method of Example 1, wherein the step of exposing the magnet to nitrogen includes exposing the NdFeB alloy to nitrogen during annealing of the NdFeB alloy prior to placing the magnet within the sealed enclosure.

[0036] Example 3. The method of Example 1, wherein the step of exposing the magnet to nitrogen includes adding nitrogen to the gas mixture used to fill the sealed enclosure.

[0037] Example 4. A method according to Example 3, wherein the gas mixture is essentially composed of helium in an amount of (100-xy) volume %, oxygen in an amount of x volume %, and nitrogen in an amount of y volume %, wherein x is greater than 0 and less than 10, wherein y is greater than 0, and wherein x+y is less than 10.

[0038] Example 5. The method of Example 4, wherein x is about 1 or greater.

[0039] Example 6. The method of Example 4, wherein x is in the range of about 3 to about 5, and y is in the range of about 1 to about 3.

[0040] Example 7. The method of Example 4, wherein y is not greater than x.

[0041] Example 8. A method according to Example 1, wherein the oxygen consumption rate causes the sealed enclosure to maintain a sufficient amount of gaseous oxygen to react with organic residues within the sealed enclosure over a span of more than 4 years of normal operation of the HAMR hard drive and at an average operating temperature of 62C or less.

[0042] Example 9. The method of Example 1, wherein the magnet is nickel-plated or epoxy-coated.

[0043] Example 10. The method of Example 1, wherein the magnet is a voice coil motor magnet.

[0044] Example 11. The method of Example 1, wherein the magnet is a spindle motor magnet.

[0045] Example 12. A heat-assisted magnetic recording (HAMR) hard drive comprising: a sealed enclosure containing operating components of the HAMR hard drive, the operating components comprising NdFeB magnets; and a gas mixture filling the sealed enclosure, the gas mixture comprising helium, oxygen and nitrogen, the helium being present in an amount of at least 90 volume %, wherein the sealed enclosure maintains a sufficient amount of oxygen to react with organic residues within the sealed enclosure over a span of more than 4 years of normal operation of the HAMR hard drive and at an average operating temperature of 62°C or less.

[0046] Example 13. The HAMR hard disk drive of Example 12, wherein the NdFeB magnet is pre-conditioned by exposure to nitrogen prior to placement in the sealed enclosure.

[0047] Example 14. The HAMR hard disk drive of Example 12, wherein the NdFeB magnets are nickel plated or epoxy coated.

[0048] Example 15. The HAMR hard disk drive of Example 12, wherein the NdFeB magnet is a voice coil motor magnet.

[0049] Example 16. The HAMR hard disk drive of Example 12, wherein the NdFeB magnet is a spindle motor magnet.

[0050] Example 17. A HAMR hard drive according to Example 12, wherein when the sealed housing is sealed, the gas mixture consists of (100-xy) volume % helium, x volume % oxygen, and y volume % nitrogen, wherein x is greater than 0 and less than 10, wherein y is greater than 0, and wherein x+y is less than 10.

[0051] Example 18. The HAMR hard drive of Example 17, wherein x is approximately 1 or greater.

[0052] Example 19. The HAMR hard disk drive of Example 17, wherein x is in a range from about 3 to about 5, and y is in a range from about 1 to about 3.

[0053] Example 20. The HAMR hard disk drive of Example 17, wherein y is not greater than x.

Claims

1. A method for use with a heat-assisted magnetic recording (HAMR) hard disk drive comprising a sealed enclosure, the sealed enclosure containing a magnet, the magnet comprising a NdFeB alloy, the method comprising: filling the sealed enclosure with a gas mixture comprising helium and oxygen, the helium being present in the gas mixture in an amount of at least 90% by volume; as well as The magnet is exposed to nitrogen in an amount sufficient to reduce the rate of oxygen consumption within the sealed enclosure.

2. The method of claim 1, wherein the step of exposing the magnet to nitrogen comprises exposing the NdFeB alloy to nitrogen during annealing of the NdFeB alloy prior to placing the magnet within the sealed enclosure.

3. The method of claim 1, wherein the step of exposing the magnet to nitrogen comprises adding nitrogen to the gas mixture used to fill the sealed enclosure.

4. The method of claim 3, wherein the gas mixture consists essentially of helium in an amount of (100-xy) volume %, oxygen in an amount of x volume %, and nitrogen in an amount of y volume %, wherein x is greater than 0 and less than 10, wherein y is greater than 0, and wherein x+y is less than 10.

5. The method of claim 4, wherein x is about 1 or greater. 6 . The method of claim 4 , wherein x is in the range of about 3 to about 5, and y is in the range of about 1 to about 3. The method of claim 4 , wherein y is not greater than x.

8. The method of claim 1 , wherein the oxygen consumption rate is such that the sealed enclosure maintains a sufficient amount of gaseous oxygen to react with organic residues within the sealed enclosure over a span of more than 4 years of normal operation of the HAMR hard disk drive and at an average operating temperature of 62° C. or less.

9. A heat-assisted magnetic recording (HAMR) hard disk drive comprising: a sealed housing containing operating components of the HAMR hard disk drive, the operating components containing NdFeB magnets; and a gas mixture filling the sealed enclosure, the gas mixture comprising helium, oxygen and nitrogen, the helium being present in an amount of at least 90% by volume, wherein the sealed enclosure maintains a sufficient amount of oxygen to react with organic residues within the sealed enclosure over a span of more than 4 years of normal operation of the HAMR hard disk drive and at an average operating temperature of 62°C or less.

10. The HAMR hard disk drive of claim 9, wherein the NdFeB magnets are pre-conditioned by exposure to nitrogen prior to placement in the sealed enclosure.

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