Abstract:
Hermetic seals that maintain a data storage device atmosphere enable the use to alternate atmospheres to reduce the aerodynamic drag and turbulent excitation within the head disk assembly (HDA). A metallic seal having a base layer and a plating layer is compressed between the data storage device cover and base such that the plating layer fills surface asperities of the cover and base to create a hermetic seal therein between. Alternatively, the data storage device is encased inside a metallic can formed by seam sealing two housings together. Alternatively, an epoxy seam is dispensed around the periphery of the data storage device base to seal the cover thereon. An O-ring acts as a barrier to isolate the epoxy from the HDA atmosphere.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to devices for storing data. More specifically, the present invention relates to disk drives that are hermetically sealed and the methods for providing such seals.  
         BACKGROUND  
         [0002]    Disk drives are widely used in computers and data processing systems for storing information. These disk drives commonly use magnetic storage disks to store data in digital form. In order to obtain higher storage capacities, disk drives have evolved from utilizing a single rotating, storage disk, to utilizing a plurality of spaced apart, rotating, storage disks.  
           [0003]    Each storage disk typically includes a data storage surface on each side of the storage disk. These storage surfaces are divided into a plurality of narrow, annular, concentric regions of different radii, commonly referred to as “tracks.” Typically, an actuator assembly is used for precisely positioning a data transducer proximate the appropriate track on the storage disk to transfer information to and from the storage disk.  
           [0004]    The need for increased storage capacity and compact construction of the disk drive has led to the use of smaller disks having increased track density, i.e., more tracks per inch. With these systems, the accurate and stable positioning of the data transducer proximate the appropriate track is critical to the accurate transfer and/or retrieval of information from the rotating storage disks.  
           [0005]    As is well known in the art, the rotating storage disks are excited by internal and external vibration of the disk drive. This vibration causes axial motion in the rotating disks. Unfortunately, some of this axial motion is transferred to the data transducers. This can lead to errors in the transfer of data caused by the inaccurate positioning of the data transducer relative to the tracks on the rotating disks. This is commonly referred to as “track mis-registration (TMR).” 
           [0006]    Moreover, the need to rapidly access information has led to disk drives having storage disks which are rotated at ever increasing speeds. Presently, disk drives having disks that rotate at about 7,200 RPM are currently available. However, high speed disk drives that rotate at 10,000 RPM or more RPM are presently being designed. At these high speeds, a significant portion of the internal vibration is caused by turbulent excitation of the head/disk assembly. Thus, the increased rotational speed of the storage disks often results in increased levels of vibration of the rotating disks and increased occurrences of TMR. Additionally, the higher RPMs generate more aerodynamic drag on the disks and increase drive power consumption.  
           [0007]    It is known that alternate atmospheres surrounding the head/disk assembly (HDA) can reduce the magnitude of the aforementioned aerodynamic drag and turbulent excitation. For example, the use of helium is disclosed in U.S. Pat. No. 5,454,157. However, conventional disk drives use relatively permeable gaskets and seals in combination with a controlled diffusion filtered path to replenish the HDA as it gradually leaks outward. This type of conventional design prevents the use of alternate HDA atmospheres such as helium. In addition, known methods for hermetically sealing the HDA have yet to be successfully implemented.  
           [0008]    Therefore, there exists a need for a hermetically sealed disk drive assembly that overcomes the drawbacks of the prior art.  
         SUMMARY  
         [0009]    The present invention is directed to a hermetically sealed data storage device and the methods for hermetically sealing a data storage device e.g. a disk drive. According to a first embodiment of the present invention, a disk drive assembly is hermetically encased within a metallic can. The metallic can comprises a top housing and a bottom housing. Each housing includes a sealing flange extending around its periphery. After the disk drive assembly is securely placed into the bottom housing, the top and bottom housings are mated together and sealed together by forming a seam seal with the seal flanges.  
           [0010]    According to a second embodiment, a metallic gasket having a C-shaped cross-sectional area is implemented to hermetically seal a disk drive assembly. The C-seal includes a base layer and a plating layer, with the length of the seal extending the periphery of the disk drive base, similar to conventional elastomer gaskets. After the disk drive cover is placed over the disk drive base and C-seal, the cover is clamped, thus compressing the C-seal. The resulting compression forces the plating layer to fill surface asperities in the area of disk drive cover and base that contact the C-seal.  
           [0011]    In a third embodiment, an epoxy seam is provided between the disk drive cover and base to hermetically seal the head disk assembly (HDA). An O-ring type gasket is utilized to isolate the epoxy from the HDA. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0013]    [0013]FIG. 1 is a perspective view of a conventional disk drive;  
         [0014]    [0014]FIG. 2 a  is a cross-sectional view of a disk drive assembly sealed in accordance with one embodiment of the present invention.  
         [0015]    [0015]FIG. 2 b  is a simplified cross sectional view of the bottom housing shown in FIG. 2 a.    
         [0016]    [0016]FIG. 2 c  is a simplified cross sectional view of the top housing shown in FIG. 2 a.    
         [0017]    [0017]FIG. 3 a  is a magnified cross-sectional view of the seam seal area highlighted in FIG. 2.  
         [0018]    [0018]FIG. 3 b  is a simplified view of the stages of forming a seam seal shown in FIG. 2 a.    
         [0019]    [0019]FIG. 4 is a top view of a C-seal in accordance with another embodiment of the present invention;  
         [0020]    [0020]FIG. 5 is a cross-sectional view of the C-seal of FIG. 4.  
         [0021]    [0021]FIG. 6 is a cross-sectional view of the C-seal of FIG. 4 showing a compressed and uncompressed state.  
         [0022]    [0022]FIG. 7 is a cross-sectional view of a disk drive assembly sealed with the C-seal of FIG. 4.  
         [0023]    [0023]FIG. 8 is a magnified view of the C-seal area highlighted in FIG. 7.  
         [0024]    [0024]FIG. 9 is a magnified view of the seal-cover interface highlighted in FIG. 8.  
         [0025]    [0025]FIG. 10 is a cross-sectional view of a disk drive assembly sealed in accordance with another embodiment of the present invention.  
         [0026]    [0026]FIG. 11 a  is an isometric view of a connector pin assembly for providing electrical connections with the present invention.  
         [0027]    [0027]FIG. 11 b  is a cross sectional view of the connector pin assembly of FIG. 11 a.   
     
    
     DESCRIPTION  
       [0028]    A detailed description of the various components of a disk drive is provided in U.S. Pat. No. 5,208,712, issued to Hatch et al. and assigned to Quantum Corporation, the assignee of the present invention. The contents of U.S. Pat. No. 5,208,712 are incorporated herein by reference. Accordingly, only the structural aspects of a disk drive which are particularly significant to the present invention are provided herein.  
         [0029]    Initially, a conventional disk drive assembly  1  is shown in FIG. 1. The disk drive assembly  1  includes a baseplate  2  which houses the various components of a disk drive, including a disk assembly  15 , actuator assembly  7 , and electrical components  8 . The baseplate  2  is enclosed by a cover  3  to create an enclosure therein between. A sealing gasket  9  is provided between the cover  3  and baseplate  2  as set screws  6  are typically used to secure the cover  3  to the baseplate  2 . As previously mentioned, the sealing gasket  9  is typically permeable, and in conjunction with a filtered inlet (not shown) enable the replenishing of the disk drive internal environment.  
         [0030]    [0030]FIG. 2 a  shows one embodiment of the present invention, for hermetically sealing a disk drive assembly  1 . The disk drive  1 , including a baseplate  2  and a disk assembly  15  are enclosed within a metallic “can” including a bottom housing  40  and a top housing  30 . When assembled, the metallic can is slightly larger, dimensionally, than the overall dimensions of the disk drive  1 . Bottom housing  40 , shown in FIG. 2 b,  includes a base  43 , four side walls  42  and a sealing flange  41  extending somewhat perpendicularly from the end of the side walls  42 . Each side wall may be formed somewhat tapered away from the opposing side wall so that the disk drive assembly  1  may be securely press fit therein. Alternatively, the disk drive assembly  1  may be secured to the bottom housing with spot welds or with a gasket. The sealing flange  41  has a width w of approximately 0.15 inches and extends around the periphery of the bottom housing  40 .  
         [0031]    [0031]FIG. 2 c  shows top housing  30 , including a cover  33 , four side walls  32  extending from the cover  33  and sealing flange  31 . Sealing flange  31  has a width W of approximately 0.20 inches, extending around the periphery of the top housing  30  and includes a curved end  35  formed at the end of the flange  31 , which is necessary for forming a double seam seal.  
         [0032]    Top and bottom housing,  30  and  40 , are preferably formed from a thin metallic (e.g. aluminum) sheet and into the configurations shown in FIG. 2 b  and  2   c.  After the disk drive assembly  1  is secured to the bottom housing  40 , the top housing  30  is mated over the bottom hosing  40 , enclosing the disk drive assembly  1  and forming an enclosure therein. To seal the top housing  30  to the bottom housing  40 , a double seam sealing process, similar to that used in the beverage can industry, is utilized to form the resulting seal shown in FIG. 3 a.  Details of the seam sealing process are known to those skilled in the beverage can industry and are not and thus are not included so as not to obscure the present invention. As shown, a sealing material  38  is placed and compressed therein between to hermetically seal the enclosure. The sealing material may be an elastomer gasket characterized by minimal outgassing. FIG. 3 b  shows the different stages of forming the double seam seal shown in FIG. 3 a.    
         [0033]    The actual dimensions of the top housing  30  and bottom housing  40  will vary depending on the overall dimensions of the specific data storage device. The foregoing dimensions are given for descriptive purposes only.  
         [0034]    [0034]FIG. 11 a  shows an electrical connector pin assembly  100  that may be used in conjunction with the metallic can shown in FIG. 2 a  to provide electrical connections to the disk drive without effecting the integrity of the hermetic seal of the can. As shown, the connector pin assembly  100  includes a body  101  and a plurality of pins  102 . The body  101  includes a flange area  103  which extends around the periphery of the body  101  and provides a positive stop to abut against the bottom housing  40  when the assembly  100  is inserted therein. The body  101  is preferably made of the same material as the bottom housing  40 . The connector pin assembly  100  is inserted into an opening (not shown), dimensioned to snuggly receive the body  101 , defined in the bottom housing  40  and may be secured therein with a suitable epoxy (not shown) to ensure a hermetic seal. The epoxy preferably has a coefficient of thermal expansion that is equivalent to that of the housing  40  and the body  101 . Connector pins  102  extend from both sides of the body  101  to provide male connectors for the disk drive and a PC controller board. The location of the female connectors in the disk drive coincide with the opening in the bottom housing  40 . As shown in FIG. 11 b,  each pin  102  is secured within openings in the body  101  by a suitable epoxy  105 . The epoxy  105  provides hermetic integrity and preferably has a coefficient of thermal expansion equivalent to the that of the body  101  material. As the body  101  is inserted into and secured to bottom housing  40 , the connector pins  102  are inserted into female connectors in the disk drive assembly. The remaining externally exposed portions of pins  102 , may then be connected to a PC controller board.  
         [0035]    According to a second embodiment of the present invention, a metallic gasket is compressed between a disk drive cover  55  and base  50  to form a hermetic seal therein between. FIG. 4 shows a metallic seal  70  having a C-shaped cross sectional area. The C-seal  70  is preferably formed in a shape to resemble known disk drive gaskets, i.e. one that follows the periphery of a disk drive base housing. The C-seal  70  is formed with a C-shaped cross sectional area, as illustrated in FIG. 5. The C-seal  70  includes a base layer  72  and a plating layer  75 . The base layer  72  is preferably made of an alloy, e.g. monel alloy or aluminum alloy, while the plating layer  75  is a thin layer of a soft metal e.g. lead, tin, gold that enables the C-seal  70  to be compressed into a compressed state  70 ′, as shown in FIG. 6 without plastic deformation. As shown in FIGS. 7 and 8, the C-seal  70  is compressed between a disk drive cover  55  and base  50  to provide a hermetic seal. The C-seal  70  is placed within a channel  76  defined around the periphery of the base  50 . As the cover  55  is placed over and secured to the base  50 , using set screws (not shown), the compression force provided by the screws compresses the cover  55  and base  50  against C-seal  70  such that a meshing between the plating layer  75  and the base  50  and the cover  55  creates a hermetic seal within the enclosure inside the disk drive assembly. As further illustrated in the magnified view of FIG. 9, surface asperities in the cover  55  and base  50  are filled in by the plating layer  75  material to create the hermetic seal. Typically, a clamping force provided by a clamping apparatus is required to compress the C-seal, prior to securing the set screws to the disk drive cover  55 . The necessary clamping force will depend on the thickness and compressibility of the C-seal  70 . The base layer  72  is approximately 0.007 inches in thickness while the plating layer is approximately 0.002 inches thick. To ensure hermetic integrity over various operating conditions and ranges of temperature, the coefficient of thermal expansion of the plating layer  75  and base layer  72  are preferably compatible with that of the disk drive base  50  and cover  55 .  
         [0036]    A third embodiment of the present invention involves using a combination of a sealing gasket and an epoxy seam around the periphery of the disk drive cover-base interface. As shown in FIG. 10, a barrier  53 , e.g. an O-ring, separates the epoxy  52  from the disk drive enclosure  54 , preventing any possible outgassing from the epoxy  52  from entering the disk enclosure  54 . Preferably, the epoxy will have a coefficient of thermal expansion that is compatible with that of the cover  55  and base  51   
         [0037]    The above described embodiments have been shown to maintain the HDA atmosphere leak rate at less than 1 cc per 10 8  seconds or 5% of the volume of HDA atmosphere over 10 years. As such the present invention is ideally suited to accommodate alternative disk drive atmospheres such as helium, which can reduce aerodynamic drag and turbulent excitation of the disks, thereby reducing the occurrence of TMR and also reducing disk drive power consumption.  
         [0038]    Additionally, while the present invention has been described with respect to a disk drive, it should be understood that the present invention also finds utility in hermetically sealing other data storage devices e.g. optical, magneto-optical storage devices having various form factors e.g. 2.5″, 3.5″, 5.25″, etc.  
         [0039]    While the particular disk drive as herein shown and disclosed in detail are fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.