Patent Publication Number: US-9412420-B2

Title: Hermetically sealing a disk drive assembly

Description:
RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 11/732,683, now U.S. Pat. No. 8,335,050, filed on Apr. 3, 2007 entitled “A DISK DRIVE WITH A SOLDER PREFORM HERMETIC SEAL,” by Kavosh et al., and assigned to the assignee of the present application. 
    
    
     TECHNICAL FIELD 
     The field of the present invention relates to disk drive data storage devices. More particularly, embodiments of the present invention are related to sealing a disk drive assembly. 
     BACKGROUND ART 
     Disk drives are used in many electronic devices such as laptops, MP3 players, GPS, PDA devices and other devices. Controlling the environment inside the disk drive assembly is a key component of these drives. One of the requirements of these drives includes sealing the drive from outside environment conditions. 
     For example, sealing the disk drive from the outside environment prevents contaminates such as dust and moisture from entering the disk drive. Furthermore, some disk drives are filled with a media such as argon to prevent oxidation and improve performance of the disk drive assembly. 
     One downside of sealing the disk drive assembly is that re-work becomes more difficult because the drive must be un-sealed prior to being able to service the drive. 
     SUMMARY OF THE INVENTION 
     A method for forming a seal for hermetically sealing a hard disk drive assembly is disclosed. The method includes forming a solder channel within a top cover of a disk drive enclosure and disposing a solder preform on a base of the disk drive enclosure such that the solder preform aligns with the solder channel when the top cover is positioned on the base. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention: 
         FIG. 1  is a schematic, top plan view of a hard disk drive in accordance with one embodiment of the present invention. 
         FIG. 2  is an illustration of a disk drive assembly including a top cover and a base in accordance with embodiments of the present invention. 
         FIG. 3  is a cross sectional view of an exemplary disk drive assembly including a solder preform in accordance with embodiments of the present invention. 
         FIG. 4A  is a cross sectional view of an exemplary disk drive assembly with solder preform on a top cover and a solder gasket on the base in accordance with embodiments of the present invention. 
         FIG. 4B  is a cross sectional view of an exemplary disk drive assembly with solder preform on a top cover and a solder channel in the base in accordance with embodiments of the present invention. 
         FIG. 5  is a flow diagram of an exemplary method for forming a seal for hermetically sealing a disk drive assembly in accordance with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiment(s) of the present invention. While the invention will be described in conjunction with the embodiment(s), it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. 
     Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, and components have not been described in detail as not to unnecessarily obscure aspects of the present invention. 
     The discussion will begin with an overview of a hard disk drive and components connected within. The discussion will then focus on embodiments of the invention that provide a system and method for sealing components of a hard disk drive. Specifically, the discussion will then focus on embodiments of this invention that provide a system and method for hermetically sealing a hard disk drive using a soldering process. In one embodiment, a solder seal is disposed between the top cover and base casting of the hard disk drive enclosure. In one embodiment, the solder seal hermetically seals the hard disk drive assembly without requiring welding or melting of the top cover or the base. 
     Although embodiments of the present invention will be described in conjunction with a hard disk drive solder seal and sealing process, it is understood that the embodiments described herein are useful outside of the art of disk drive assemblies, such as devices requiring hermetic sealing. 
     The utilization of a solder seal is only one embodiment and is provided herein merely for purposes of brevity and clarity. It is appreciated that the present invention uses a material for sealing the disk drive assembly that melts at a lower temperature than the top portion or the base portion of the disk drive enclosure. In one embodiment, the solder is applied to the disk drive enclosure as a solder preform. A solder preform is a segment of solder that can be aligned around the perimeter of the top cover and/or the base of a hard disk drive prior to assembly. The solder seal (solder preform) is melted and re-flowed to (solder) seal the disk drive assembly without melting and/or welding the top cover or the base material. By using a solder preform, the disk drive assembly can be more easily re-opened after sealing to allow re-work. Furthermore, the utilization of a laser to re-flow the solder seal is provided herein merely for purposes of brevity and clarity. It is appreciated that the present invention uses a laser for heating the solder seal, however, it is appreciated that many other methods for heating the solder seal could be used. 
     Overview 
     With reference now to  FIG. 1 , a schematic drawing of one embodiment of an information storage system comprising a magnetic hard disk file or drive  111  for a computer system is shown. Drive  111  has an outer housing or base  113  containing a disk pack having at least one media or magnetic disk  115 . A spindle motor assembly having a central drive hub  117  rotates the disk or disks  115 . An actuator  121  comprises a plurality of parallel actuator arms  125  (one shown) in the form of a comb that is movably or pivotally mounted to base  113  about a pivot assembly  123 . A controller  119  is also mounted to base  113  for selectively moving the comb of arms  125  relative to disk  115 . 
     In the embodiment shown, each arm  125  has extending from it at least one cantilevered electrical lead suspension (ELS)  127  (load beam removed). It should be understood that ELS  127  may be, in one embodiment, an integrated lead suspension (ILS) that is formed by a subtractive process. In another embodiment, ELS  127  may be formed by an additive process, such as a Circuit Integrated Suspension (CIS). In yet another embodiment, ELS  127  may be a Flex-On Suspension (FOS) attached to base metal or it may be a Flex Gimbal Suspension Assembly (FGSA) that is attached to a base metal layer. 
     The ELS may be any form of lead suspension that can be used in a Data Access Storage Device, such as a HDD. A magnetic read/write transducer or head is mounted on a slider  129  and secured to a flexure that is flexibly mounted to each ELS  127 . The read/write heads magnetically read data from and/or magnetically write data to disk  115 . The level of integration called the head gimbal assembly is the head and the slider  129 , which are mounted on suspension  127 . The slider  129  is usually bonded to the end of ELS  127   
     ELS  127  has a spring-like quality, which biases or presses the air-bearing surface of the slider  129  against the disk  115  to cause the slider  129  to fly at a precise distance from the disk. The ELS  127  has a hinge area that provides for the spring-like quality, and a flexing interconnect (or flexing interconnect) that supports read and write traces through the hinge area. A voice coil  133 , free to move within a conventional voice coil motor magnet assembly  134  (top pole not shown), is also mounted to arms  125  opposite the head gimbal assemblies. 
     Movement of the actuator  121  (indicated by arrow  135 ) by controller  119  causes the head gimbal assemblies to move along radial arcs across tracks on the disk  115  until the heads settle on their set target tracks. The head gimbal assemblies operate in a conventional manner and move in unison with one another, unless drive  111  uses multiple independent actuators (not shown) wherein the arms can move independently of one another. 
     Embodiments of the present invention include a solder seal and solder process for joining a base portion of a disk drive enclosure to a top cover of a disk drive enclosure. In one embodiment, the solder seal hermetically seals the disk drive assembly, meaning the environment inside the disk drive assembly is controllable and separate from the environment outside the disk drive assembly. 
     Embodiments of the present invention include depositing a solder seal (preform) to one or more components of a hard disk drive assembly, containing the solder seal within a solder channel, achieving a uniform solder joint around the perimeter of the disk drive assembly and maintaining localized, low temperature heating of the solder seal. It is appreciated that embodiments of the present invention hermetically seal a hard disk drive assembly without melting and/or welding the disk drive assembly. By not welding the components of the hard disk drive, the components can be later disassembled. In addition, by not melting and/or welding the disk drive components, heat related damage to the disk drive components is reduced. 
       FIG. 2  is an illustration of a disk drive assembly including a top cover  210  and a base  260  in accordance with embodiments of the present invention. In one embodiment of the invention, a solder preform seal  220  is positioned on the base  260  and is then subsequently re-flowed once the top cover  210  is positioned on the base  260  to seal (solder) the top cover  210  to the base  260 . In one embodiment, a laser  299  is used to heat a portion of the top cover  210  which heats the under lying solder preform seal to a temperature that re-flows the solder preform seal  220 , soldering the top  210  to the base  260 . In one embodiment, the solder seal is contained within a solder channel formed between the top cover  210  and the base  260 . A description of the solder channel is provided below. 
     It is appreciated that the solder preform seal could also be deposited on the base  260 . However, depositing the solder preform to the top cover reduces the heat required to melt the solder preform seal because thermal conductivity from the top cover to the solder preform is greater when the solder preform is in direct contact with the cover. 
     In one embodiment, a plurality of lasers  299  are used to heat portions of the top cover  210 . For example, a plurality of lasers  299  can be directed at a single point on the cover  210  and travel around the perimeter of the cover  210 . In another embodiment, multiple lasers  299  are used to heat more than one portion of the top cover  210  simultaneously such that multiple portions of the solder seal  220  are re-flowed simultaneously. For example, two lasers can start at opposing sides and work around the perimeter of the top  210  in opposite directions until the entire perimeter is heated. 
       FIG. 3  is a cross sectional view of an exemplary disk drive assembly including a solder preform seal  220  in accordance with embodiments of the present invention. As stated above, in one embodiment, a solder channel  340  is used to contain the solder seal  220 . In one embodiment, the solder channel  340  is formed in the top cover  210 . For example, the solder channel is stamped or machined into the top cover  210 . However, it is appreciated that the solder channel could be also formed in the base  260  or partially in the base  260  and partially in the cover  210 . 
     In one embodiment, the cross-sectional area of the solder preform seal  220  is similar to the cross sectional area of the solder channel  340 . As stated above, the solder channel can be stamped and/or machined in either the base  260  or the cover  210 . For purposes of clarity and brevity, the solder channel  340  is shown in the cover  210 . Having similar cross sectional areas ensures the solder can be completely contained within the solder channel  240 . Having similar cross sectional areas also ensures the solder seal  220  completely fills the solder channel  340  when heated and re-flowed. 
     In one embodiment, the solder preform seal  220  is a similar shape of the solder channel  340 . In this embodiment, the solder channel  340  comes in contact with the solder seal  220  on the base  260  when the cover  210  is positioned on the base  260 . Since the solder seal  220  is in direct contact with the top cover  210 , heating the top cover  210  also heats the solder seal  220 . In this embodiment, heat is thermally conducted from the top cover  210  to the solder seal  220 . 
     In one embodiment, a solder barrier (solder gasket)  310  is used to further control the flow of the solder seal  220 . In one embodiment, the solder barrier  310  is positioned on both sides of the solder seal  220  to serve as a solder gasket which prevents solder from flowing out of the solder channel  340 . It is appreciated that the solder barrier  310  could be located on the top cover  210 , on the base  260  or a combination of both. In one embodiment the solder barrier  310  comprises copper, however other materials such as high-temperature polyamide could be used in accordance with embodiments of the present invention. It is also appreciated that a “gasket” can be formed by forming a channel that contains the solder when heated. 
     In one embodiment, the solder barrier  310  provides a double seal for the disk drive assembly. For example, when the solder preform seal  220  is heated and reflowed within the solder channel  340 , a solder seal is formed at each of the solder barriers (gaskets), one of which is an inner seal and the other is an outer seal with respect to the hard disk drive enclosure. 
       FIG. 4A  is a cross sectional view of an exemplary disk drive assembly with a solder preform seal  220  on the top cover  210  and a solder gasket  310  on the base  260  in accordance with embodiments of the present invention. As stated above, the solder preform seal  220  can be formed on the disk drive components in any number of ways and configurations. As stated above, in one embodiment, the solder preform seal  220  can be formed on the base  260  while the solder channel is formed in the cover  210 . However, it is also appreciated that the solder preform seal  220  could be formed on both the cover  210  and the base  260 . The solder gasket  310  contains the solder when solder preform  220  is heated and reflowed. In one embodiment, the solder gaskets  310  form a solder channel  340 . 
       FIG. 4B  is a cross sectional view of an exemplary disk drive assembly with solder preform  220  on a top cover and a solder channel  340  in the base  260  in accordance with embodiments of the present invention. As stated above, the solder channel  340  may be formed as a groove machined or stamped in the disk drive components.  FIG. 4B  shows the solder channel  340  on the base and the solder preform  220  on the cover, however, it is appreciated that the solder preform seal could be formed within the solder channel in the base  260  or the cover  210 . For example, the solder channel  340  could be formed and then filled with the solder preform  220 . Once the cover and base are joined, the solder preform  220  is re-flowed to solder the base  260  to the top  210 . 
       FIG. 5  is a flow diagram of an exemplary method  500  for forming a seal for hermetically sealing a disk drive assembly in accordance with embodiments of the present invention. 
     At  510 , method  500  includes forming a solder channel within a top cover of a disk drive enclosure. As stated above, the solder channel could also be formed in the base portion of the disk drive enclosure. 
     At  520 , method  500  includes disposing a solder preform seal on a base portion of the disk drive enclosure such that the solder preform seal aligns with the solder channel when the top cover is positioned on the base. As stated above, in the case the solder channel is formed in the top cover, the solder seal is disposed on the base portion of the enclosure such that the top cover contacts the solder seal such that heat can be conducted through the top cover to the solder seal. 
     It is appreciated that a portion of the solder seal could be disposed on the top cover as well as a portion on the base of the enclosure. It is also appreciated that the solder channel and the solder preform may be formed on the same side. For example, the solder channel and the solder preform can be both formed on the top cover or both formed on the base. 
     In one embodiment of the invention, the shape of the solder preform seal is similar to the shape of the solder channel so that the solder seal completely fills the solder channel when heated and re-flowed. In one embodiment, a solder barrier (gasket) is disposed on both sides of the solder seal to prevent solder from flowing outside of the solder channel. 
     At  530 , method  500  includes heating a portion of the top cover such that the solder preform seal melts and flows within the solder channel forming a solder seal between the top cover and the base. As stated above, in one embodiment of the invention, a laser is used to provide localized heat to the cover portion of the disk drive enclosure to solder the top cover to the base. However, it is appreciated that any number of devices could be used to heat the solder preform seal to a temperature that enables the solder seal to re-flow (e.g. melt) and solder the cover to the base. 
     Using a solder seal allows the top to be subsequently removed from the base without damaging either the top or the base. Furthermore, the solder seal of the present invention requires much less heat to seal than conventional welding techniques used to seal hard drive enclosures. The lower temperature required for soldering results in less damage to components of the hard disk drive assembly, as opposed to conventional welding where higher temperatures are needed. 
     The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and it&#39;s practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the Claims appended hereto and their equivalents.