Environmental corrosion protection for hard disk drive elements by thermal activation

1. Technical Field

This invention relates in general to corrosion protection and in particular to protecting computer hard disk drive components from environmental corrosion during storage and shipment. Still more particularly, the invention relates to environmental corrosion protection for hard disk drive components, such as magnetic read/write heads, by electrothermally activating the heads to raise their temperature above the ambient temperature.

2. Description of the Prior Art

Generally, a digital data access and storage system for a computer system consists of one or more storage devices that store data on storage media such as magnetic or optical data storage disks. In magnetic disk storage systems, a storage device is called a hard disk drive (HDD), which includes one or more hard disks and an HDD controller to manage local operations concerning the disks. Hard disks are rigid platters, typically made of aluminum alloy or a mixture of glass and ceramic, covered with a magnetic coating. Typically, two or more platters are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).

The only other moving part within a typical HDD is the head assembly. Within most drives, one read/write head is associated with each side of each platter and flies just above or below the platter's surface. Each read/write head is connected to a semi-rigid arm apparatus which supports the entire head flying unit. More than one of such arms may be utilized together to form a single armature unit.

Each read/write head scans the hard disk platter surface during a “read” or “write” operation. The head/arm assembly is moved utilizing an actuator which is often a voice coil motor (VCM). The stator of a VCM is mounted to a base plate or casting on which is also mounted the spindle supporting the disks. The base casting is in turn mounted to a frame via a compliant suspension. When current is fed to the motor, the VCM develops force or torque which is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. As the read/write head nears the desired track, a reverse polarity signal is applied to the actuator, causing the signal to act as a brake, and ideally causing the read/write head to stop directly over the desired track.

During storage and shipment, some computer systems are exposed to extreme environmental conditions such as high temperatures and high humidity. Under such conditions, the exposed computer components tend to corrode at an accelerated rate compared to components that are stored under normal conditions where the environmental surroundings are substantially maintained at comfortable or ideal levels. Consequently, extended exposure to harsh atmospheres will ultimately hasten the failure of the components. The small magnetic read/write heads in hard disk drives are particularly susceptible to accelerated failure when stored in extreme conditions.

A computer system hard disk drive contains magnetic heads for reading data to and writing data from storage media disks. The heads are coupled to an electrical source that thermally excites the heads during non-operation of the disk drive in order to raise the temperature of the heads. The temperature increase induces a mechanism such as a local, low humidity barrier at each of the heads. When the disk drive is stored in harsh environmental atmospheres, such as high temperatures and high humidity, the mechanism or low humidity barrier is sufficient to overcome the ambient conditions and reduce environmental corrosion of the heads.

Thus, it is an object of the invention is to provide improved corrosion protection.

Another object of the invention is to protect computer hard disk drive components from environmental corrosion during storage and shipment.

Still another object of the invention is to provide environmental corrosion protection for hard disk drive components, such as magnetic read/write heads, by thermally activating the heads in order to raise their temperature above the ambient temperature.

Additional objects and advantages of the invention will become apparent in light of the description which follows.

So that the manner in which the features, advantages and objects of the invention, as well as others which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiment thereof which is illustrated in the appended drawings, which drawings form a part of this specification. It is to be noted, however, that the drawings illustrate only a preferred embodiment of the invention and is therefore not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.

FIG. 1 is a schematic drawing of a hard disk drive file.

FIG. 2 is a schematic drawing of a portion of the file of FIG. 1 .

FIG. 3 is a plot of the change in magnetic head resistance over time for various heads in the file of FIGS. 1 and 2.

Referring to FIG. 1, a schematic drawing of an information storage system comprising a magnetic hard disk file or drive 11 for a computer system is shown. Drive 11 has an outer housing or base 13 containing a plurality of stacked, parallel magnetic disks 15 (one shown) which are closely spaced apart. Disks 15 are rotated by a motor located therebelow about a central drive hub 17 . A plurality of stacked, parallel actuator arms 21 (one shown) are pivotally mounted to base 13 about a pivot assembly 23 . A controller 19 is mounted to the base for selectively moving arms 21 relative to disks 15 .

In the embodiment shown, each arm 21 comprises a mounting support 25 , a pair of parallel, cantilevered load beams or suspensions 27 extending from each mounting support 25 , and a head gimbal assembly 29 with an air bearing slider having at least one magnetic read/write head secured to each suspension 27 for magnetically reading data from or magnetically writing data to disks 15 . Suspensions 27 have a spring-like quality which biases or maintains them in parallel relationship relative to one another. A motor assembly 31 having a conventional voice coil motor is also mounted to pivot assembly 23 opposite head gimbal assemblies 29 . Movement of an actuator driver 33 (indicated by arrow 35 ) moves head gimbal assemblies 29 radially across tracks on the disks 15 until the heads on assemblies 29 settle on the target tracks. The head gimbal assemblies 29 operate in a conventional manner and always move in unison with one another, unless drive 11 uses a split actuator (not shown) wherein the arms move independently of one another.

Referring now to FIG. 2, a simplified schematic drawing of a circuit portion of drive 11 depicting head 37 on arm 21 . Head 37 is coupled to an electrical source or heating circuit 39 located within drive 11 . Like the other components of drive 11 , heating circuit 39 is controlled by controller 19 , and preferably located within the slider or assembly 29 . In addition, the temperature of head 37 may be elevated selectively by other means as well, such as a heating coil, magnetic induction, or still other means such as those commonly known in the art. During non-operation of the drive 11 , a current or voltage is suitably supplied to the heating circuit 39 by a battery to thermally heat the slider. In a preferred embodiment, the heating circuit 39 includes one or more write elements or read elements of the head. Alternatively, the heating circuit includes a heating coil or magnetically inductive element. The heating circuit is activated manually or automatically during non-operation of drive 11 to provide current or voltage bias to heat the slider. Suitable heating circuits will be known to those skilled in the art.

The bias across head 37 increases the temperature locally around the sensor. Note that the bias across head 37 may be applied on a continuous basis, or pulsed in an intermittent fashion. The temperature increase induces a corrosive-inhibiting mechanism that effectively reduces corrosion of head 37 . For example, the temperature increase may create a local, lower relative humidity barrier, envelope, or zone 41 at head 37 as compared to the ambient atmospheric conditions. The low humidity envelope 41 surrounding head 37 is sufficient to reduce corrosion under some environmental conditions. Other mechanisms also may be employed for accomplishing the same objective.

The following environmental corrosion experiment demonstrates the beneficial influence of thermally exciting heads 37 . In this experiment, a shut off disk drive 11 containing ten heads 37 was stored in a temperature/humidity chamber and exposed to a controlled atmosphere for 28 days. The heads 37 were prepared in a stressed condition and the atmosphere was maintained at a temperature of 50° C. and 90% relative humidity (RH). During the first 24 days of the experiment, the heads 37 were constantly thermally activated through resistive heating resulting from a continuous bias current therethrough. As illustrated in FIG. 3, the change in head resistance (MRR) of each of the heads 37 through the first 24 days is very small and no appreciable environmental corrosion took place. The elevated temperature and relatively lower humidity of the barrier 41 around heads 37 created by the thermal activation previously described, actively protected heads 37 from corroding under these harsh environmental conditions. Barrier 41 prevents the more humid ambient atmosphere from corrosively attacking the components.

However, during the following four days of the experiment the thermal activation of heads 37 was removed. Thus, during days 25-28, the heads 37 were completely exposed to the 50° C., 90% RH environment without their additional corrosion protection. After day 24, the MRR for heads 37 f , 37 h , 37 i , and 37 j increased significantly. These changes were consistent with expected corrosion effects. The heads 37 were subject to normal environmental corrosion when they were not actively protected by the thermal activation of the present invention.

The present invention has several advantages. Thermal activation of components protects the components from the corrosive effects of some harsh environmental conditions. By elevating the temperature of the components, the barrier prevents the more humid ambient atmosphere from corrosively attacking the components.

While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.