Patent Application
20110075300
Embodiments of the invention generally relate to reducing the propagation of vibrations to a hard-disk drive (HDD) head.
A hard-disk drive (HDD) is a non-volatile storage device that is housed in a protective enclosure and stores digitally encoded data on one or more circular disks having magnetic surfaces (a disk may also be referred to as a platter). When an HDD is in operation, each magnetic-recording disk is rapidly rotated by a spindle system. Data is read from and written to a magnetic-recording disk using a read/write head which is positioned over a specific location of a disk by an actuator.
A read/write head uses a magnetic field to read data from and write data to the surface of a magnetic-recording disk. As a magnetic dipole field decreases rapidly with distance from a magnetic pole, the distance between a read/write head and the surface of a magnetic-recording disk must be tightly controlled. To provide a uniform distance between a read/write head and the surface of a magnetic-recording disk, an actuator relies on air pressure inside the hard drive enclosure to support the read/write heads at the proper distance away from the surface of the magnetic-recording disk while the magnetic-recording disk rotates. A read/write head therefore is said to “fly” over the surface of the magnetic-recording disk. That is, the air pulled along by a spinning magnetic-recording disk forces the head away from the surface of the magnetic-recording disk. When the magnetic-recording disk stops spinning, a read/write head must either “land” or be pulled away.
A write-head of a HDD records data onto the surface of a magnetic-recording disk in a series of concentric tracks. When a write-head writes data to a desired track of a magnetic-recording disk, it is important for the write-head to be located close to the desired track; failure to do so may result in a squeeze event, which may compromise data integrity and throughput, and in extreme cases, may result in hard errors and data loss. A squeeze event occurs when a write-head writes data too close to or overlapping with an adjacent track such that there is not enough of the adjacent track left for the adjacent track to be read properly by a read-head.
References markers may be recorded in each track of a magnetic-recording disk. These reference markers are referred to as servo information. To help properly position a read/write head, a HDD employs a servo mechanical control loop to maintain the read/write head in the correct position using the servo information stored on the magnetic-recording disk. When a read/write head reads the servo information (servo information being read may be referred to as a position-error signal, or PES), a relative position of the read/write head may be determined by a servo processor to enable the position of the read/write head, relative to the desired track, to be adjusted if necessary.
It is desirable, for a variety of reasons, to maintain a constant or approximately constant distance between the read/write head and the surface of the magnetic-recording disk to ensure proper operation of the read/write head. If the distance between a read/write head and the surface of a magnetic-recording disk fluctuates, then the strength of the magnetic dipole field between the read/write head and the surface of the magnetic-recording disk will also fluctuate, which may cause problems in reading data from or writing data to the magnetic-recording disk. Also, if the read/write head touches the surface of the magnetic-recording medium, then read/write head may scrape across the surface of a platter, which could grind away the thin magnetic film on the surface magnetic-recording medium and therefore cause data loss and potentially render the HDD inoperable.
It is observed that vibrations experienced by a lead suspension of a hard-disk drive (HDD) may be propagated to a head. The lead suspension may start to vibrate for different reasons, such as the HDD experiencing a mechanical shock, the circulating air flow within the HDD, and resonance vibrations.
Approaches are discussed herein for reducing the propagation of vibrations to a head of a persistent storage medium, such as a HDD. An HDD may compromise a lead suspension that includes a magnetic read/write head. The magnetic read/write head may be connected to the lead suspension by a plurality of leads. A portion of each of the plurality of leads, such as the solder ball joints, may be covered by a dampening material that is designed to absorb vibrations occurring in the lead suspension to prevent transmission of the vibrations to the magnetic read/write head. Alternately, the dampening material may be applied to other locations which can transmit vibrations to the magnetic read/write head, such as the limiter engagements. In this way, the dampening material reduces or eliminates the propagation of vibrations from the lead suspension to the read/write head.
Embodiments discussed in the Summary of the Invention section are not meant to suggest, describe, or teach all the embodiments discussed herein. Thus, embodiments of the invention may contain additional or different features than those discussed in this section.
Embodiments of the invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:
Approaches for reducing the propagation of vibrations to a hard-disk drive (HDD) head are described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the invention described herein. It will be apparent, however, that the embodiments of the invention described herein may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the embodiments of the invention described herein.
Embodiments of the invention may be implemented using a variety of different storage mediums. For example, embodiments of the invention may be implemented using a magnetic-recording storage medium, such as a hard-disk drive (HDD). With reference to
With further reference to
With further reference to
Embodiments of the invention also encompass HDD 100 that includes the HGA 110, the disk 120 rotatably mounted on the spindle 124, the arm 132 attached to the HGA 110 including the slider 110b including the head 110a.
With reference now to
Note that embodiments of the invention are not limited to storage devices that use a rigid magnetic disk or a magnetic recording medium, as embodiments of the invention may be implemented using a flexible disk substrate or to a recording medium that includes a ferroelectric or phase change, for example.
Having described the physical description of an illustrative embodiment of the invention, discussion will now be presented describing how vibrations may originate as well as propagate to a read/write head.
If lead suspension 100c is undergoing vibrations, then these vibrations may be transmitted to head 110a, as head 110a is physically connected to lead suspension 110c. Vibrations may occur in lead suspension 110c for a variety of reasons. For example, lead suspension 110c may experience resonance vibrations. Resonance refers to the tendency of a system to oscillate at a larger amplitude at some frequencies than other frequencies. To illustrate,
Additionally, if HDD 100 is bumped, lead suspension 110c may oscillate or vibration due to the mechanical shock. The circulating air flow within the enclosure of HDD 100, caused by the rotation of the platters, may also induce vibrations in lead suspension 110c.
Vibrations may propagate from lead suspension 110c to head 110a at any point of physical contact between lead suspension 110c and head 110a. In an embodiment, a main transmission area for the propagation of vibrations from lead suspension 110c to head 110a is at the solder lead connection of the lead suspension 110c to the thin-film connectors at the trailing edge of head 110a. Another potential transmission area for the propagation of vibrations from lead suspension 110c to head 110a is the limiter engagements. A limiter, shown in
It is undesirable for vibrations to propagate from lead suspension 110c to head 110a. If head 110a is vibrating, then errors in operations (some of which may be catastrophic and unrecoverable) may occur. If head 110a is experiencing vibrations, then the strength of the magnetic dipole field between head 110a and the surface of the magnetic-recording disk will fluctuate, which may cause problems with reading data from or writing data to the magnetic-recording disk. Also, if head 110a touches the surface of the magnetic-recording medium, then head 110a may scrape across the surface of the magnetic-recording disk, which could grind away the thin magnetic film on the surface magnetic-recording disk, causing scratches, dings and burnish marks and therefore cause data loss and potentially render the HDD inoperable.
Additionally, if head 110a is vibrating, it may be difficult for head 110a to read data from or write data to the appropriate track on the magnetic-recording disk. Head 110a may be particularly susceptible to vibrations during high stress conditions, such as loading head 110a on a ramp, unloading head 110a off a ramp, and track seeking. If head 110a picks up a resonance vibration that causes head 110a to vibrate before an air-bearing is established for head 110a, then head 110a can crash into the magnetic-recording disk, and consequently, destroy the magnetic-recording disk and any information that the magnetic-recording disk has previously recorded.
Head 110a may also vibrate during normal operation of HDD 100, such as when head 110a is seeking a single track or moving from track to track. When head 110a is seeking a single track in normal operation, lateral vibrations may prevent head 110a from being positioned correctly over the desired track, thereby preventing head 110a from being able to read from the desired track or write to the desired track causing track to track misalignment and position error. Also, vibrations during the normal operation of HDD 100 when head 110a is moving from track to track may cause fly height instability.
Consequently, embodiments of the invention provide an advantage over prior approaches by providing mechanisms for reducing or eliminating the propagation of vibrations, such as but not limited to resonance vibrations, from a lead suspension to a head.
In step 410, an appropriate dampening material is selected. The dampening material selected in step 410 will be applied to an appropriate location to reduce or eliminate the propagation of vibrations from lead suspension 110c to head 110a. The dampening material selected in step 410 may be any material that can absorb vibrations occurring in the lead suspension 110c to prevent their transmission to head 110a. Non-limiting, illustrative examples of a dampening material which may be employed in step 410 include a viscoelastic polymer, a viscous liquid, an epoxy, and glue.
In an embodiment, the particular dampening material selected in step 410 may be selected based on an outgassing property possessed by the dampening material. The outgassing property of a material refers to the type and amount of contaminants that are released or produced by the material. When building a new hard-disk drive (HDD), it is desirable to select a combination of materials which have low outgassing properties to minimize or avoid any contaminants introduced into the interior of HDD 100.
After a particular dampening material is selected for use, in step 420, the dampening material is applied to an appropriate location to prevent the propagation of vibrations to head 110a. In step 420, in an embodiment, the appropriate location (referred to as a transmission area) to which the dampening material is applied in step 420 is a location which is capable of propagating vibrations, such as resonance vibrations, from a source structure to head 110a by virtue of head 110a being physically connected to the source structure at the transmission area.
For example, lead suspension 110c may be a source of vibrations that are propagated to head 110a. Embodiments of the invention may be employed to prevent the propagation of vibrations from a variety of different types of lead suspensions. To illustrate, in an embodiment, lead suspension 110c may be an electrical lead suspension, or more particularly, an integrated lead suspension (ILS), a circuit integrated suspension (CIS), or a flex-on suspension. A flex-on suspension (FOS) is a general term of art that refers to a technology for embedding wires into a polymer on a stiff and flexible substrate for the purpose of getting electronic connections to the magnetic head from the arm-electronics (AE) module 160.
In an embodiment, the location on which the dampening material applied is the solder ball joint of each lead of the lead suspension. The leads may be built into the thin-film element of head 110a and may be coupled to electrical components of head 110a, such as components responsible for reading data, writing data, and a heater element. Note that embodiments of the invention may have different numbers of leads. For example, while 8 leads are common now, 6 leads have been used previously and 10 leads may be used in the future. Thus, in an embodiment, dampening material may be applied to the solder ball joint of any number of leads in steps 420.
To illustrate how the effect of applying the dampening material to the solder ball joints, consider
The dampening material may be applied to any location which physically connects lead suspension 110c with head 110a. To illustrate,
Advantageously, embodiments of the invention are able to eliminate or reduce the propagation of vibrations to head 110a. Desirably, the mass or the head and the flying characteristics of the head have not been modified, as would be the case if the dampening material would be applied to the slider. Also, by applying the dampening material to the location that physically connects lead suspension 110a and head 110c, it is more certain that vibrations will not propagate to head 110a than if the dampening material were applied to the slider.
In the foregoing specification, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. Thus, the sole and exclusive indicator of what is the invention, and is intended by the applicants to be the invention, is the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. Hence, no limitation, element, property, feature, advantage or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.
