Slider having shock and particle resistance

A slider for a hard disk includes a leading structure having a first air bearing surface portion, a trailing structure having a second air bearing surface portion, and a cavity between the leading structure and the trailing structure. The leading structure has one or more interior walls defining a pit therein. A hard disk drive includes a rotatable magnetic recording disk and the slider.

BACKGROUND

Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A magnetic hard disk drive is an example of an information storage device that includes one or more heads that can both read and write.

In magnetic hard disk drives, each read head typically comprises a body called a “slider” that carries a magnetic transducer on its trailing end. The magnetic transducer typically comprises a writer and a read element. The magnetic transducer's writer may be of a longitudinal or perpendicular design, and the read element of the magnetic transducer may be inductive or magnetoresistive (e.g. so-called “giant” magneto-resistive read element, tunneling magneto-resistive read element, etc). In a magnetic hard disk drive, the transducer is typically supported in very close proximity to the magnetic disk by a hydrodynamic air bearing. As the motor rotates the magnetic disk, the hydrodynamic air bearing is formed between an air bearing surface of the slider of the read head, and a surface of the magnetic disk. The thickness of the air bearing at the location of the transducer is commonly referred to as “flying height.”

Magnetic hard disk drives are not the only type of information storage devices that have utilized air bearing sliders. For example, air bearing sliders have also been used in optical information storage devices to position a mirror and an objective lens for focusing laser light on the surface of disk media that is not necessarily magnetic.

The flying height is a parameter that affects the performance of an information storage device. If the flying height is too high, the ability of the transducer to write and/or read information to/from the disk surface may be substantially degraded. Therefore, reductions in flying height can facilitate desirable increases in the areal density of data stored on a disk surface. However, it is not beneficial to eliminate the air bearing between the slider and the disk surface entirely, because the air bearing serves to reduce friction and wear (between the slider and the disk surface) to an acceptable level. Excessive reduction in the nominal flying height may degrade the tribological performance of the disk drive to the point where the lifetime and reliability of the disk drive become unacceptable.

Another factor that can adversely affect the tribological performance of the read head, and therefore also adversely affect the disk drive's lifetime and reliability, is the extent to which particulate debris can enter the air bearing during operation. Because the thickness of the air bearing is just a few tens of nanometers or less (typically minimum at the trailing edge of the slider because of the slider's positive pitch angle), even small debris particles can be large enough to interfere with the desired spacing between the air bearing surface and the disk surface. Such particulate debris that enter into the air bearing can undesirably cause abrupt thermal disturbances to the read element and/or temporarily change the flying characteristics of the slider, potentially causing immediate reading or writing errors. Such debris that enter into the air bearing can also drag along the disk surface and possibly damage the disk surface, potentially destroying data and/or leading to future tribological failure (e.g. head crash).

Air bearing features that discourage the entry of particulate debris have been proposed before. However, past air bearing design features that discourage the entry of particulate debris have been detrimental to the flying characteristics of the slider, for example reducing super-ambient pressure in key regions of the air bearing and thereby unacceptably reducing the load carrying capacity of the air bearing. Certain such design features can also adversely affect the ability of the air bearing to maintain an acceptable roll angle in the face of expected changes to the skew angle of the slider (relative to the direction of disk surface motion). Such skew angle changes are expected as the actuator positions the read head to different disk radii. The shortcomings of contemporary air bearing design features to discourage entry of particles may be exacerbated in sliders having a smaller air bearing area, such as newer smaller-form factor sliders (e.g. the so-called “femto” form factor).

Accordingly, what is needed in the art is an air bearing design that can discourage the entry of particulate debris while maintaining acceptable air bearing performance characteristics even in small form factor sliders.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings is intended as a description of various exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring the concepts of the present invention. Acronyms and other descriptive terminology may be used merely for convenience and clarity and are not intended to limit the scope of the invention.

The various aspects of the present invention illustrated in the drawings may not be drawn to scale. Rather, the dimensions of the various features may be expanded or reduced for clarity. In addition, some of the drawings may be simplified for clarity. Thus, the drawings may not depict all of the components of a given apparatus or method.

The word “exemplary” is used herein to mean serving as an example, instance, or illustration. Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. Likewise, the term “embodiment” of an apparatus, method or article of manufacture does not require that all embodiments of the invention include the described components, structure, features, functionality, processes, advantages, benefits, or modes of operation.

Any reference to an element herein using a designation such as “first,” “second,” and so forth does not generally limit the quantity or order of those elements. Rather, these designations are used herein as a convenient method of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element.

As used herein, the term “about” followed by a numeric value means within engineering tolerance of the provided value.

In the following detailed description, various aspects of the present invention will be presented in the context a slider for a hard disk drive (HDD). However, those skilled in the art will realize that these aspects may be extended to any suitable application where air bearing sliders are implemented. Accordingly, any reference to a slider as part of an HDD is intended only to illustrate the various aspects of the present invention, with the understanding that such aspects may have a wide range of applications.

Aspects of a slider for a hard disk includes a leading structure having a first air bearing surface portion, a trailing structure having a second air bearing surface portion, and a cavity between the leading structure and the trailing structure. The leading structure has one or more interior walls defining a pit therein.

Aspects of a hard disk drive include a rotatable magnetic recording disk and a slider for use with the magnetic recording disk. The slider includes a leading structure having a first air bearing surface portion, a trailing structure having a second air bearing surface portion, and a cavity between the leading structure and the trailing structure. The leading structure has one or more interior walls defining a pit therein.

FIG. 1shows a hard disk drive100including a disk drive base102, at least one disk104(such as a magnetic disk, magneto-optical disk, or optical disk), a spindle motor106attached to the base102for rotating the disk104, and a head stack assembly (HSA)110. The spindle motor106typically includes a rotating hub on which disks are mounted and clamped, a magnet attached to the hub, and a stator. Various coils of the stator are selectively energized to form an electromagnetic field that pulls/pushes on the magnet, thereby rotating the hub. Rotation of the spindle motor hub results in rotation of the mounted disks. The HSA110typically includes at least one actuator arm114, and at least one head gimbal assembly (HGA)124that includes a read head.

During operation of the disk drive, the HSA110rotates to position the read head along an arc adjacent desired information tracks on the disk104. The HSA110includes a pivot bearing cartridge118to facilitate such rotational positioning. The HSA110typically includes a voice coil that interacts with one or more fixed magnets on a magnetic yoke112, to rotate the HSA110. For example, when the HSA110is rotated such that the HGA124leaves a ramp120, the read head is loaded onto a surface of the disk104. Other disk drive components shown inFIG. 1include a flex cable bracket116and a recirculation air filter108.

FIG. 2shows a head gimbal assembly (HGA)200that includes a load beam202, a laminated flexure204, and a swage mount206. The HGA200also includes a slider210in accordance with an embodiment of the present invention, which is bonded to a tongue of the laminated flexure204. The laminated flexure204provides structural support and compliance to the slider210, and also provides a plurality of electrically conductive traces218, preferably including traces for carrying electrical signals from/to a read/write transducer of head210.

FIG. 3is a perspective view of an exemplary embodiment of a slider300. The slider features are not to scale but rather are exaggerated so as to be easily discernible.FIG. 4is a plan view of the slider300. Referring toFIGS. 3 and 4, the slider300may include a transducer302for at least reading information from an adjacent disk surface. The slider300may also include a base304, which is typically fabricated from a ceramic material such as alumina titanium carbide. The slider300may have a leading edge306and a trailing edge308that is opposite the leading edge. The slider300may also have a first air bearing surface portion310and a second air bearing surface portion311, each of which is normal to the trailing edge308. Other devices and transducers (e.g. a slider based microactuator, a heater for protrusion control, etc) may also be disposed on or adjacent the trailing face, in addition to the read transducer. For example, the read transducer may be part of a merged transducer that also includes a write transducer.

The air bearing surface310defines an upstream direction (e.g.312) pointing from the trailing edge308to the leading edge306. The term “upstream” is used herein only to define a directional convention to facilitate description of relative positions on the air bearing surface, and does not require the presence or existence of any stream. For example, “upstream” can be understood to refer to a range of directions across the air bearing surface310that generally point away from the trailing edge308and towards the leading edge306. As such, in disk drive applications, upstream directions would ultimately be generally opposite the motion of an adjacent rotating disk surface. An upstream direction would be a direction within the aforementioned range. The term “downstream” is used herein as an antonym of “upstream.”

For each upstream direction, the air bearing surface310defines a lateral axis that is orthogonal to that upstream direction. For example, for a zero-skew upstream direction312that is parallel to the air bearing surface310, the air bearing surface310defines a corresponding lateral axis314that is parallel to the leading edge306or the trailing edge308(i.e. orthogonal to that upstream direction). The width of the slider can be measured along lateral axis. For example, so-called “femto” form factor sliders would then typically have a width of 0.70 mm and a length of 0.85 mm, while so-called “pico” form factor sliders would then typically have a width of 1.00 mm and a length of 1.25 mm. Non-zero skew upstream directions are also contemplated herein. As noted above, the features of air bearing surface are not to scale inFIG. 3, but rather are vertically exaggerated (i.e. exaggerated in a direction normal to both the upstream direction and the lateral axis) so as to be easily discernible.

In the exemplary embodiment ofFIGS. 3 and 4, the slider300may include a leading structure316and a trailing structure318, which may be separated by deep cavities320, also referred herein as sub-ambient pressure cavities320. The deep cavities320may be located between and separate the leading structure316from the trailing structure318. The deep cavities320may provide an area of sub-ambient pressure in operation. The trailing structure318may include a trailing pad322. The trailing pad322may include a surface324adjacent the read transducer302. As shown inFIG. 3, the surface324of the trailing pad322may lie in a plane, where the plane is the farthest plane from the slider body304relative to the other features of the slider300. The term “plane” used herein thus refers to the plane in which the surface324of the trailing pad322lies. For example, the plane in which the surface324lies may be the closest plane to the media relative in use, relative to the other slider features. The air bearing surface310is located along the surface324and thus lies in the plane. The sub-ambient pressure cavities320may be recessed relative to the plane/air bearing surface310by about 500 nm or more.

The transducer302may include an overcoat material (e.g. alumina) that is incidentally slightly recessed from the plane, because alumina may etch away more rapidly than does alumina titanium carbide during fabrication of the air bearing. During operation, the trailing pad322may develop a super-ambient pressure region between the air bearing surface and the surface of an adjacent disk that can help maintain a desired flying height at the location of transducer. For example, in the embodiment ofFIGS. 3 and 4, the trailing pad322may create a region of high pressure, including the highest pressure generated by the air bearing surface310during normal operation of the head.

In the exemplary embodiment ofFIGS. 3 and 4, a pressurizing step326may located upstream of the trailing pad322. The pressurizing step326preferably includes a surface that is recessed relative to the plane/air bearing surface by about 100 nm to about 250 nm. During operation, the pressurizing step326can enhance the super-ambient pressure between the trailing pad322and the surface of an adjacent disk. Such enhanced pressurization may reduce the surface area required for the trailing pad322.

In the exemplary embodiment ofFIGS. 3 and 4, in addition to the deep sub-ambient cavities320, the air bearing surface310may include stepped sub-ambient pressure cavities330. The stepped sub-ambient pressure cavities330may include two distinct portions of different depth: a deep portion334and a shallow portion336. The deep portion334of the stepped sub-ambient pressure cavities330may be recessed relative to the plane/air bearing surface by about 800 nm or more, for example from about 800 to about 2000 nm. The deep portion334may be less recessed as compared to a pit350, which is discussed in more detail below. The shallow portion336of the stepped sub-ambient pressure cavities330may be recessed relative to the plane/air bearing surface by about 300 nm or more, for example from about 300 nm to about 800 nm. The shallow portion336may be more recessed than the pressuring step326. As shown inFIGS. 3 and 4, the shallow portion336may be located downstream of the deep portion334and adjacent to the trailing pad322. During operation, one or more of these sub-ambient pressure cavities320,330can develop a sub-ambient pressure region between the air bearing surface310and the surface of an adjacent disk. The sub-ambient pressure may serve to reduce flying height sensitivities to changes in altitude and air bearing geometries. The stepped sub-ambient pressure cavities330have been found to provide an optimal balance between shock damage prevention and maintaining altitude performance.

In the exemplary embodiment ofFIGS. 3 and 4, the leading structure326of the air bearing surface310may include two leading pads342also having a surface344in the plane (i.e., the surface344is in the same plane as the surface324) and disposed upstream of the sub-ambient pressure cavities320. The two leading pads342together may span at least 60% of the width of the slider. Preferably but not necessarily, the two leading pads342may be shaped and adjoined together to form a shape like a letter W that is oriented so that the center peak346of the W points in the upstream direction, as shown inFIGS. 3 and 4. The center peak346of the W may have a substantially rectangular U shape (e.g., two vertical legs354joined by a horizontal base leg356) so as to define a pit350, which is described in more detail below. Furthermore, as shown inFIGS. 3 and 4, the center peak346of the W may terminate at the leading edge306. During operation, the leading pads342can develop a super-ambient pressure region between the air bearing surface310and the surface of an adjacent disk, causing the slider to assume a positive pitch attitude. In the exemplary embodiment ofFIGS. 3 and 4, the leading pads also include leading pressurizing steps348. The leading pressurizing steps348preferably include a surface that is recessed relative to plane/air bearing surface by about 100 nm or more, for example between about 100 nm to about 250 nm. During operation, the leading pressurizing steps348can help develop super-ambient pressure between the leading pads342and the surface of an adjacent disk.

In the exemplary embodiment ofFIGS. 3 and 4, the leading pads also include secondary leading pressurizing steps349and trailing pressurizing steps338. The secondary leading pressurizing steps349and the trailing pressuring steps338preferably include surfaces that are recessed relative to the plane/air bearing surface by about 100 nm or more, for example between about 100 nm to about 250 nm. During operation, the secondary leading pressurizing steps349can help develop super-ambient pressure between the leading pads342and the surface of an adjacent disk.

In the exemplary embodiment ofFIGS. 3 and 4, the slider300includes trenches360disposed upstream of the leading pads342. The trenches360may be recessed relative to the plane/air bearing surface by about 600 nm or more, preferably about 800 nm or more. For example the trenches may be recessed by about 600 nm to about 2000 nm, more preferably from about 800 nm to about 1500 nm. As shown inFIGS. 3 and 4, the trenches360may be disposed adjacent to the center peak346of the leading pads342. For example, the trenches360may be disposed adjacent the base leg356of the rectangular U shape (e.g., may extend parallel to the base leg356). Thus, in an exemplary embodiment, the trenches360are non-continuous (e.g., comprise two separate trenches). Each of the trenches360may extend about ⅓ the width of the slider base304. Thus, together, the trenches360may extend about ⅔ the width of the slider base304. The trenches360may help facilitate control of the so-called “roll profile.” The roll profile is the variation of slider roll angle, over a range of skew angles and velocities (relative to the motion of an adjacent disk) that correspond to variation in the position of the slider from the disk inner diameter to the disk outer diameter during operation of the disk drive. Typically, “flattening” of the roll profile (e.g. less variation of slider roll versus skew angle and/or velocity changes), is desirable. In the exemplary embodiment ofFIGS. 3 and 4, the trenches360may have an extent measured along the upstream direction that is at least 25 microns and no more than 8% of the total slider length measured along the upstream direction. These dimensional limits may avoid undesirable fabrication process consequences (e.g. due to tolerance stack-up), and/or to allow air flow having a lateral component through the trenches (sufficiently to adequately pressurize the air bearing surface).

In the exemplary embodiment ofFIGS. 3 and 4, the slider300may include a pit350recessed relative to the plane/air bearing surface and disposed adjacent the leading face306. In this context, “adjacent” means only that there is no air bearing feature in the plane that is closer than the “adjacent” feature. The pit350helps prevent particulate contamination from entering the air bearing and also increases shock resistance. The pit350may be recessed relative to the plane/air bearing surface by about 600 nm or more, more preferably about 1000 nm or more. For example, the pit may be recessed from about 600 nm to about 2500 nm, more preferably from about 1000 nm to about 2000 nm. The pit350may be recessed by the same amount or greater than the recess of the trenches360. The pit350may have a polygonal shape. In the exemplary embodiment shown inFIGS. 3 and 4, the pit350is formed as a six sided polygon, i.e., a hexagon. As shown inFIGS. 3 and 4, the pit350may be an irregular hexagon, i.e., not all of the sides have the same length. The pit350may continuously laterally span at least 25% of the width of the slider base304. This size may ensure adequate particle capture over a practical range of skew angles, while allowing sufficient airflow around the pit to adequately pressurize the air bearing surface over a practical range of skew angles. As shown inFIG. 3, the pit350may be at least partially defined the leading pad342of the leading structure316. For example, as shown inFIGS. 3 and 4, three of the side walls defining the pit are part of the leading pad342and lie in the plane/air bearing surface. As also shown inFIG. 3, the pit350may be at least partially defined by the steps349of the leading structure. For example, as shown inFIGS. 3 and 4, two of the side walls defining the pit350may be part of the steps349. Thus, the walls that define the pit350may be interior walls of the leading structure316. The pit350may be centered along the width of the slider base304.

In the exemplary embodiment ofFIGS. 3 and 4, the pit350preferably has an extent measured along the upstream direction that is about 50 to about 100 microns and about 10-20% of the total slider base304length measured along the upstream direction. These dimensional limits may avoid undesirable fabrication process consequences (e.g. due to tolerance stack-up), and/or to allow sufficient air flow having a lateral component immediately downstream of the pit, to adequately pressurize the air bearing surface.

It has been found that the combination of the pit350and trenches360adequately captures particles and increase shock resistance. The pit350in particular contributes to shock resistance. It has been found that the combination of trenches360and the pit350at the leading edge306increases the suction force and damping, thus increasing shock resistance.

In the embodiment ofFIGS. 3 and 4, the slider300optionally may include two leading outboard dots370in the primary plane. Each leading outboard dot370preferably defines a dot radius in the range 10 microns to 45 microns. Each leading outboard dot370is adjacent the leading face306, adjacent a corner of the air bearing surface310, and laterally adjacent a trench360. During operation, the leading outboard dots370may serve to prevent damage to the head disk interface under certain conditions that would otherwise lead to contact between a corner of the slider and an adjacent disk surface.

FIGS. 5 and 6are cross-sectional views of the slider300shown inFIG. 4, taken along the5-5and6-6inFIG. 4, respectively. For clarity, the step heights are not to scale but rather are exaggerated so as to be easily discernible. Now referring additionally toFIGS. 5 and 6, the trailing pad322and the leading pad342includes surfaces that are not recessed and instead establishes an air bearing surface datum plane (referred above as the “plane”)500, from which the recession of other surfaces of the slider300that are parallel to the plane500may be measured.

In the exemplary embodiment ofFIGS. 5 and 6, the pit350includes a surface in a plane510that is recessed relative to the plane500/air bearing surface by a recession depth560. The sub-ambient pressure cavities320each include a surface in the plane510by a deep cavity recession depth560. The pit350depth and the sub-ambient pressure cavities320depth are discussed above. The deep portions334of the stepped pressure cavities318include a surface in the plane510. The shallow portion336of the stepped pressure cavities318include a surface in an intermediate plane520that lies between the plane500and the plane510, and that is recessed from the plane500by a recession depth570. The depth of both the deep portion334and the shallow portion336are discussed above.

In the exemplary embodiment ofFIGS. 5 and 6, the leading pressurizing steps348and the secondary leading pressuring steps349may each include a surface in a plane530that may lie between the plane500and the intermediate plane520. The plane530may be recessed from the primary500by depth580. The depth of the leading pressuring steps348and the secondary leading pressuring steps349are described above.