Patent Publication Number: US-11664049-B2

Title: Disk device with improved impact resistance

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 17/007,012 filed on Aug. 31, 2020 and is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-044975, filed on Mar. 16, 2020; the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a disk device. 
     BACKGROUND 
     Disk devices are known, which read and write information from and to a magnetic disk by heat assisted magnetic recording (HAMR). Such a HAMR disk device includes a magnetic head to which a laser diode is attached, for example. 
     The magnetic head increases in mass due to the attached laser diode. This may cause the magnetic head to easily vibrate, for example, when the disk device receives an impact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a plan view schematically illustrating a hard disk drive (HDD) according to a first embodiment; 
         FIG.  2    is a perspective view schematically illustrating a head gimbal assembly (HGA) of the first embodiment; 
         FIG.  3    is a perspective view schematically illustrating a part of the HGA of the first embodiment; 
         FIG.  4    is a perspective view schematically illustrating a part of the HGA of the first embodiment from a direction different from the direction in  FIG.  3   ; 
         FIG.  5    is a cross-sectional view illustrating a part of the HGA of the first embodiment; 
         FIG.  6    is a perspective view schematically illustrating a head unit of the first embodiment; 
         FIG.  7    is a cross-sectional view schematically illustrating an example of a method of mounting the head unit of the first embodiment; 
         FIG.  8    is a perspective view schematically illustrating a head unit according to a modification of the first embodiment; 
         FIG.  9    is a cross-sectional view illustrating a part of a HGA according to a second embodiment; 
         FIG.  10    is a perspective view schematically illustrating a head unit according to a first modification of the second embodiment; 
         FIG.  11    is a perspective view schematically illustrating a head unit according to a second modification of the second embodiment; 
         FIG.  12    is a cross-sectional view schematically illustrating a part of a HGA according to a third embodiment; 
         FIG.  13    is a plan view schematically illustrating a part of a HGA  22  according to a fourth embodiment; and 
         FIG.  14    is a cross-sectional view schematically illustrating a part of the HGA of the fourth embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a disk device includes a magnetic disk, a load beam, a flexure, a head unit, and a first restrictor. The load beam has a first face facing the magnetic disk. The flexure is attached to the first face. The head unit includes: a magnetic head attached to the flexure, configured to read and write information from and to the magnetic disk; and a heat-assister attached to the magnetic head, configured to heat the magnetic disk. The first restrictor is included in the head unit, configured to come in contact with at least one of the load beam and the flexure along with movement of the magnetic head away from the first face by a first distance. 
     First Embodiment 
     Hereinafter, a first embodiment will be described with reference to  FIGS.  1  to  7   . In the present specification, constituent elements of an embodiment may be represented by different expressions and be given different explanations. Such constituent elements and their descriptions are presented for illustrative purpose only and are not intended to limit the scope of the present invention. Constituent elements can also be identified by different names from those used in the present specification. Moreover, constituent elements can be described in different terms from the terms used in the present specification. 
       FIG.  1    is a plan view schematically illustrating a hard disk drive (HDD)  10  according to the first embodiment. The HDD  10  is an example of a disk device. The disk device may be another device such as a hybrid HDD. 
     As illustrated in  FIG.  1   , the HDD  10  includes a housing  11 , a plurality of magnetic disks  12 , a spindle motor  13 , a plurality of actuator assemblies  14 , a voice coil motor (VCM)  15 , a ramp load mechanism  16 , and a flexible printed wiring board (FPC)  17 .  FIG.  1    illustrates one magnetic disk  12  and one actuator assembly  14 . The magnetic disk  12  may also be referred to as a recording medium. 
     The housing  11  is formed of a metal such as an aluminum alloy, for example. The housing  11  is sealed by a lid, for example, and is filled with a gas such as helium. For the sake of explanation,  FIG.  1    illustrates the housing  11  in an opened state. The housing  11  houses the magnetic disk  12 , the spindle motor  13 , the actuator assembly  14 , the VCM  15 , the ramp load mechanism  16 , and the FPC  17 . 
     The magnetic disk  12  magnetically records information, applied with a magnetic field carrying the information. The magnetic disks  12  are placed on the top of each other with spacing, and rotated by the spindle motor  13  about a rotational shaft  13   a.    
     The actuator assembly  14  includes a carriage  21  and a plurality of head gimbal assemblies (HGA)  22 . The HGA  22  may also be referred to as a head suspension assembly. 
     The carriage  21  includes an actuator block  21   a  and a plurality of carriage arms  21   b . The actuator block  21   a  is driven by the VCM  15  and pivots about an arm shaft  21   c  that is substantially parallel to the rotational shaft  13   a . The plurality of carriage arms  21   b  is arranged with spacing and extends from the actuator block  21   a  in substantially the same direction. The carriage arms  21   b  have a plate shape that can enter in-between the adjacent magnetic disks  12 . 
     Along with the rotation of the actuator block  21   a , the carriage arms  21   b  move along the surface of the magnetic disk  12 . In this manner, the carriage  21  is movable relative to the magnetic disk  12 . 
     The HGAs  22  are attached to the tip ends of the corresponding carriage arms  21   b  and protrude from the carriage arms  21   b . The HGAs  22  are thus disposed with spacing in the arrangement direction of the magnetic disks  12 . 
       FIG.  2    is a perspective view schematically illustrating the HGA  22  of the first embodiment. As illustrated in  FIG.  2   , each of the HGAs  22  includes a base plate  25 , a hinge  26 , a load beam  27 , a flexure  28 , and a head unit  29 . 
     The base plate  25 , the hinge  26 , and the load beam  27  are formed of stainless steel, for example. The materials of the base plate  25 , the hinge  26 , and the load beam  27  are not limited to this example. 
     The base plate  25  is attached to a tip end of the carriage arm  21   b . The load beam  27  is of a plate shape thinner in thickness than the base plate  25 . The load beam  27  is attached to a tip end of the base plate  25  via the hinge  26  having elasticity. 
     The flexure  28  has an elongated strip shape. The shape of the flexure  28  is not limited to this example. The flexure  28  is a laminated plate including a metal plate (lining layer) such as stainless steel, an insulating layer formed on the metal plate, a conductive layer forming a plurality of wiring arrangements (wiring patterns) on the insulating layer, and a protective layer (insulating layer) covering the conductive layer, for example. 
     The head unit  29  is mounted on one end of the flexure  28 . The other end of the flexure  28  is connected to the FPC  17 . The FPC  17  serves to electrically connect the head unit  29  and a controller located outside the housing  11 , via the wiring of the flexure  28 , for example. 
       FIG.  3    is a perspective view schematically illustrating a part of the HGA  22  of the first embodiment.  FIG.  4    is a perspective view schematically illustrating a part of the HGA  22  of the first embodiment from a direction different from the direction in  FIG.  3   . The head unit  29  reads and writes, i.e., reproduces and records, information from and to the magnetic disk  12  by heat assisted magnetic recording (HAMR). 
     The head unit  29  includes a magnetic head  31  illustrated in  FIG.  3    and a laser unit  32  illustrated in  FIG.  4   . The laser unit  32  is an exemplary heat-assister. The laser unit  32  can be referred as, for example, a heating device, heater, assister, irradiator, unit, or device or part. The laser unit  32  is attached to the magnetic head  31 . 
     To read or write information from or to the magnetic disk  12  by the head unit  29 , the carriage  21  is driven by the VCM  15  to place the head unit  29  on a desired track of the rotating magnetic disk  12 . The head unit  29  reads and writes information from and to a desired track of the magnetic disk  12  as the magnetic disk  12  rotates. 
     To access the magnetic disk  12 , the VCM  15  rotates or loads the head unit  29  on the magnetic disk  12 . At the time of unloading which requires no access to the magnetic disk  12 , the VCM  15  rotates the head unit  29  to the position of the ramp load mechanism  16  and stops the head unit  29  there (unloading). 
     Hereinafter, the HGA  22  will be described in detail. The load beam  27  extends substantially in the same direction as the carriage arm  21   b . The extending direction of the load beam  27  may be inclined with respect to the extending direction of the carriage arm  21   b.    
     In the present specification, an X-axis, a Y-axis, and a Z-axis are defined for the sake of convenience, as illustrated in the drawings. The X-axis, the Y-axis, and the Z-axis are orthogonal to one another. The X axis is along the length of the load beam  27 . In other words, the X axis is parallel to the extending direction of the carriage arm  21   b  and the load beam  27 . The Y axis is along the width of the load beam  27 . The Z axis is along the thickness of the load beam  27 . 
     X direction, Y direction and Z direction are defined in the present specification. The X direction is along the X axis, and includes a +X direction indicated by an arrow X and a −X direction opposite to the arrow X. The Y direction is along the Y axis and includes a +Y direction indicated by an arrow Y and a −Y direction opposite to the arrow Y. The Z direction is along the Z axis and includes a +Z direction indicated by an arrow Z and a −Z direction opposite to the arrow Z. 
     The load beam  27  extends from the hinge  26  in the +X direction. The load beam  27  includes a tip end  27   a  and a base end  27   b . The tip end  27   a  is an end of the load beam  27  in the +X direction. The base end  27   b  is an end of the load beam  27  in the −X direction. The −X direction is an exemplary second direction. The tip end  27   a  and the base end  27   b  include not only the end or edge of the load beam  27  but also the portion in the vicinity of the end or edge. The base end  27   b  is connected to the carriage arm  21   b  of the carriage  21  via the hinge  26  and the base plate  25 . 
     The load beam  27  has a substantially triangular plate shape. In the Y direction the length or width of the load beam  27  shortens from the base end  27   b  toward the tip end  27   a . In other words, the load beam  27  is tapered in the +X direction. The shape of the load beam  27  is not limited to this example. 
       FIG.  5    is a cross-sectional view illustrating a part of the HGA  22  of the first embodiment. As illustrated in  FIG.  5   , the load beam  27  further includes a lower face  41 , an upper face  42 , and a dimple  43 . In this disclosure, the terms “upper” and “lower” are used for illustrative purpose only with reference to  FIG.  5   , and are not intended to limit the position, location, and direction of each element. The lower face  41  is an exemplary first surface. The upper surface  42  is an exemplary second surface. 
     The lower face  41  is substantially flat and faces the −Z direction. At the time of loading, the lower face  41  faces the corresponding magnetic disk  12  with spacing. At the time of unloading, the lower face  41  faces the lower face  41  of another load beam  27  with spacing, for example. The upper face  42  is opposite the lower face  41 . The upper face  42  is substantially flat and faces the +Z direction. The X direction and the Y direction are along the lower face  41  and the upper face  42 . The Z direction is orthogonal to the lower face  41  and the upper face  42 . The dimple  43  is a substantially hemispherical protrusion protruding from the lower face  41 . 
     The load beam  27  is provided with a first through-hole  45  and a second through-hole  46 . The first through-hole  45  is an exemplary hole. The first through-hole  45  and the second through-hole  46  penetrate the load beam  27  and opens to the lower face  41  and the upper face  42 , respectively. The first through-hole  45  and the second through-hole  46  may be provided as cutouts. 
     The first through-hole  45  is separated from the dimple  43  in the +X direction. The second through-hole  46  is separated from the dimple  43  in the −X direction. That is, the dimple  43  is located between the first through-hole  45  and the second through-hole  46 . 
     The first through-hole  45  is a substantially rectangular (quadrangular) hole extending in the X direction, for example. As illustrated in  FIG.  4   , the second through-hole  46  has a substantially T-shape and includes a wider part  46   a  and a narrower part  46   b.    
     The wider part  46   a  is a substantially rectangular or quadrangular part extending in the Y direction. The narrower part  46   b  is a substantially rectangular or quadrangular part, extending in the +X direction from a Y-directional center of the wider part  46   a . In the Y direction, the length of the narrower part  46   b  is shorter than the length of the wider part  46   a.    
     As illustrated in  FIG.  5   , the flexure  28  has a lower face  51  and an upper face  52 . The upper face  52  is an exemplary third face. The lower face  51  faces substantially the −Z direction. The upper face  52  faces substantially the +Z direction. At least a part of the upper face  52  of the flexure  28  faces the lower face  41  of the load beam  27 . 
     As illustrated in  FIG.  3   , the flexure  28  further includes at least one stationary part  55 , a gimbal (elastic support)  56 , and a tab  57 . The gimbal  56  is an exemplary elastic part. The tab  57  is an exemplary second restrictor. The stationary part  55 , the gimbal  56 , and the tab  57  are part of the flexure  28 . The stationary part  55  and the gimbal  56  each partially have the lower face  51  and the upper face  52 . 
     The upper face  52  of the stationary part  55  contacts with the lower face  41  of the load beam  27 . The stationary part  55  is fixed to the lower face  41  of the load beam  27  by spot welding, for example. As a result, the flexure  28  is attached to the lower face  41  of the load beam  27 . 
     The gimbal  56  is located in the vicinity of the tip end  27   a  of the load beam  27 . The gimbal  56  is connected to the stationary part  55  and is elastically movable with respect to the load beam  27  and the stationary part  55 . 
     For example, the gimbal  56  includes a tongue  56   a  and two arms  56   b . The magnetic head  31  of the head unit  29  is attached to the lower face  51  of the tongue  56   a . The upper face  52  of the tongue  56   a  is swingably supported by the dimple  43 . The two arms  56   b  extend from the +Z-directional end of the tongue  56   a  so as to surround the tongue  56   a , and are connected to the stationary part  55  that is apart from the tongue  56   a  in the −X direction. 
     Elastic deformation of the two arms  56   b  enables the tongue  56   a  and the head unit  29  to swing around the dimple  43  or move away from the lower face  41  of the load beam  27 . The tongue  56   a  is generally maintained in contact with the dimple  43  by the elastic force of the arm  56   b.    
     As illustrated in  FIG.  4   , the tab  57  includes an insertion  57   a  and two extensions  57   b . The insertion  57   a  extends from the −X directional end of the tongue  56   a  through the narrower part  46   b  of the second through-hole  46 . The extension  57   b  extends from the tip end of the insertion  57   a  in the Y direction. The extension  57   b  partially covers the upper face  42  of the load beam  27  in the Z direction. Thus, the load beam  27  is located between the extension  57   b  and the tongue  56   a  in the Z direction. 
     The extension  57   b  is generally separated from the upper face  42  of the load beam  27  in the +Z direction. For example, due to an impact applied to the HDD  10 , the tongue  56   a  and the head unit  29  may move away from the lower face  41  of the load beam  27  and the dimple  43 . 
     Along with the movement of the magnetic head  31  of the head unit  29  away from the lower face  41  by a given distance, the extension  57   b  of the tab  57  comes in contact with the upper face  42  of the load beam  27 . Thereby, the tab  57  works to restrict the magnetic head  31  from moving further from the lower face  41  beyond the given distance. The given distance is an exemplary second distance. The extension  57   b  may come in contact with the upper face  52  of the stationary part  55  of the flexure  28 . 
     The tab  57  is formed by bending a part of the flexure  28 , for example. At the time of bending the tab  57 , the insertion  57   a  passes through the narrower part  46   b  of the second through-hole  46  while the extension  57   b  passes through the wider part  46   a  of the second through-hole  46 . The tab  57  is not limited to this example, and may be another component attached to the flexure  28 . 
     As illustrated in  FIG.  3   , the magnetic head  31  has a substantially rectangular parallelepiped shape. The magnetic head  31  includes a first end  31   a  and a second end  31   b . The first end  31   a  is an end of the magnetic head  31  in the −X direction. The second end  31   b  is an end of the magnetic head  31  in the +X direction. The +X direction is an exemplary third direction. The second end  31   b  is opposite the first end  31   a.    
     As illustrated in  FIG.  5   , the magnetic head  31  further includes an opposing face  61  and a mounting face  62 . At the time of loading, the opposing face  61  faces the corresponding magnetic disk  12 . The mounting face  62  is opposite the opposing face  61 , and is attached to the lower face  51  of the tongue  56   a  with an adhesive, for example. 
     At the time of loading, each magnetic head  31  reads or writes information from or to the magnetic disk  12  while maintained in a slightly lifted state from the surface of the magnetic disk  12  by the lift occurring from the rotation of the magnetic disk  12 . That is, during loading, the opposing face  61  is slightly away from the magnetic disk  12 . Airflow is caused by the rotation of the magnetic disk  12 , flows in-between the magnetic disk  12  and the magnetic head  31  from the vicinity of the first end  31   a , and exits from the vicinity of the second end  31   b  to the outside. 
     The magnetic head  31  further includes a write element  65  and a read element  66 . The write element  65  may also be referred to as a magnetic-field generating element. The read element  66  may also be referred to as a reproducing element. The write element  65  is located closer to the second end  31   b  than the read element  66 . 
     The magnetic field generated by the write element  65  works to magnetize a magnetic recording layer of the magnetic disk  12  in a given direction, allowing information to be recorded thereon. The read element  66  reads the recorded information from the magnetic disk  12 . In this manner, the read element  66  and the write element  65  of the magnetic head  31  reads and writes from and to the magnetic disk  12 . 
     The laser unit  32  is attached to the mounting face  62  of the magnetic head  31 . The laser unit  32  emits laser light L to a micro area, containing the information, on the magnetic recording layer of the magnetic disk  12  to heat the micro area. The heated micro area lowers in coercive force and becomes easier to have information recorded thereon. The laser unit  32  includes an outer shell  71  and an optical device  72 . The outer shell  71  can also be referred to as a housing, a container, a case, or a cover, for example. 
       FIG.  6    is a perspective view schematically illustrating the head unit  29  of the first embodiment. The outer shell  71  is formed of metal and has a substantially rectangular parallelepiped box shape, for example. The outer shell  71  includes a lower face  71   a , an upper face  71   b , a first end face  71   c , a second end face  71   d  illustrated in  FIG.  5   , and two side faces  71   e  illustrated in  FIG.  6   . 
     As illustrated in  FIG.  5   , the lower face  71   a  faces the −Z direction. The lower face  71   a  is fixed to the mounting face  62  of the magnetic head  31  with an adhesive, for example. The upper face  71   b  is opposite the lower face  71   a , facing the +Z direction. 
     The first end face  71   c  is an end face of the outer shell  71  in the −X direction. The second end face  71   d  is opposite the first end face  71   c . The second end face  71   d  is an end face of the outer shell  71  in the +X direction. The side faces  71   e  are both end faces of the outer shell  71  in the Y direction. 
     The laser unit  32  includes a base  32   a . The base  32   a  includes the outer shell  71  and the optical device  72 . The base  32   a  is attached to the magnetic head  31  in the vicinity of the second end  31   b . In other words, the base  32   a  is attached to the magnetic head  31  at a position closer to the second end  31   b  than to the first end  31   a.    
     The base  32   a  protrudes from the second end  31   b  of the magnetic head  31  in the X direction. Thus, the second end  31   b  of the magnetic head  31  is located between the first end face  71   c  and the second end face  71   d  of the outer shell  71  in the X direction. That is, part of the lower face  71   a  is not fixed to the magnetic head  31  but exposed. A part of the exposed lower face  71   a  faces the corresponding magnetic disk  12  during loading. 
     The base  32   a  is attached to the mounting face  62  of the magnetic head  31  such that the base  32   a  extends from the mounting face  62  in substantially the Z direction. Substantially the Z direction intersects the lower face  41 , and is an exemplary extending direction. The base  32   a  extends from the mounting face  62  in substantially the Z direction so as to pass through the first through-hole  45 . In other words, the base  32   a  is attached to the mounting face  62  of the magnetic head  31  such that the base  32   a  can pass through the first through-hole  45 . Substantially the Z direction is not limited to the longitudinal direction of the base  32   a.    
     A part of the base  32   a  protrudes from the lower face  41  of the load beam  27  in the −Z direction through the first through-hole  45 . Another part of the base  32   a  protrudes from the upper face  42  of the load beam  27  in the +Z direction through the first through-hole  45 . The base  32   a  is separated from the edge of the load beam  27  defining the first through-hole  45  and the rest of the load beam  27 . 
     The optical device  72  is housed in the outer shell  71 . The optical device  72  includes a laser oscillation element and a lens, for example. The optical device  72  is not limited to this example. The optical device  72  is configured to emit laser light L from the exposed lower face  71   a  of the outer shell  71  to the magnetic disk  12 . The laser light L is an example of light. 
     The optical device  72  is not limited to this example. For example, the optical device  72  may include a near-field light generating member that converts the laser light L into near-field light. In this case, near-field light is an example of light. The optical device  72  can irradiate and heat the magnetic disk  12  with near-field light. 
     As described above, the heat-assister exemplified by the laser unit  32  irradiates the magnetic disk  12  with the laser light L or the near-field light to thereby heat a micro area of the magnetic disk  12  and lower the coercive force of the micro area. The heat-assister is not limited to this example, and the magnetic disk  12  may be heated by other means. For example, the heat-assister may irradiate the magnetic disk  12  with an energy ray or infrared light. The heat-assister may heat the magnetic disk  12  by thermal conduction or thermal radiation. 
     The laser unit  32  is provided with a protrusion  75 . The protrusion  75  is an exemplary first restrictor. In the first embodiment, the protrusion  75  is located away from the upper face  42  of the load beam  27  in the +Z direction, protruding in the +X direction from the second end face  71   d  of the outer shell  71 . In other words, the protrusion  75  protrudes from the base  32   a  in the +Z direction. The +X direction intersects substantially the Z direction, and is an example of first direction and protruding direction. 
     The protrusion  75  partially covers the upper face  42  of the load beam  27  in the Z direction (substantially Z direction). In other words, the protrusion  75  and a part of the load beam  27  are at the same position in the X direction. The load beam  27  is located between the protrusion  75  and the tongue  56   a  in the Z direction. 
     In the +X direction (X direction), the total length of the laser unit  32  and the protrusion  75  is shorter than the length of the first through-hole  45 . In other words, in the X direction, the sum of the distance between the first end face  71   c  and the second end face  71   d  of the outer shell  71  and the length of the protrusion  75  is shorter than the length of the first through-hole  45 . 
     In the Y direction, the length of the laser unit  32  is shorter than the length of the first through-hole  45 . In the Y direction, the length of the protrusion  75  is shorter than the length of the first through-hole  45 . In the Y direction, the protrusion  75  may be the same as or different in length from the laser unit  32 . 
     The part of the laser unit  32  including the protrusion  75  is larger in cross-sectional area orthogonal to substantially the Z direction than the part of the laser unit  32  passing through the first through-hole  45 . In other words, the cross-sectional area of the base  32   a  and the protrusion  75  orthogonal to substantially the Z direction is larger than the cross-sectional area of the base  32   a  orthogonal to substantially the Z direction. In the present embodiment, the area of the upper face  71   b  of the outer shell  71  including the protrusion  75  is larger than the area of the lower face  71   a  of the outer shell  71 . 
     The protrusion  75  is generally separated from the upper face  42  of the load beam  27  in the +Z direction. Due to an impact applied to the HDD  10 , for example, the tongue  56   a  and the head unit  29  may move away from the lower face  41  of the load beam  27  and the dimple  43 . 
     Along with the movement of the magnetic head  31  of the head unit  29  away from the lower face  41  by a given distance, the protrusion  75  comes in contact with the upper face  42  of the load beam  27 . Thereby, the protrusion  75  serves to restrict the magnetic head  31  from moving further from the lower face  41  beyond the given distance. The given distance is an exemplary first distance. The protrusion  75  may come in contact with the upper face  52  of the stationary part  55  of the flexure  28 . 
     As described above, at two separate positions in the X direction, the protrusion  75  and the tab  57  restrict the magnetic head  31  from moving away from the lower face  41  beyond the given distance. The tab  57  is apart from the protrusion  75  in the −X direction. The dimple  43  is located between the tab  57  and the protrusion  75  in the X direction. The first distance and the second distance may be the same or different from each other. 
     Hereinafter, an assembly method of the HGA  22  as a part of a manufacturing method of the HDD  10  will be described by way of example. The manufacturing method of the HDD  10  is not limited to the following method, and other methods may be used. First, the stationary part  55  of the flexure  28  is fixed to the lower face  41  of the load beam  27  by spot welding. 
       FIG.  7    is a cross-sectional view schematically illustrating an exemplary mounting method of the head unit  29  of the first embodiment. As illustrated in  FIG.  7   , the laser unit  32  is mounted in advance to the magnetic head  31 . For example, the magnetic head  31  and the laser unit  32  are individually inspected to determine if they meet the quality standard. The magnetic head  31  and the laser unit  32  having passed the inspection are joined together. The inspection is not limited to this example. 
     The magnetic head  31  is then placed close to the lower face  51  of the flexure  28 , so that the laser unit  32  passes through the first through-hole  45 . The laser unit  32  including the protrusion  75  is smaller in size than the first through-hole  45  in the X direction and the Y direction. Thus, the laser unit  32  can pass through the first through-hole  45 . 
       FIG.  7    illustrates a virtual head unit  29  before the laser unit  32  passes through the first through-hole  45 , by the chain double-dashed line, and the head unit  29  after the laser unit  32  has passed through the first through-hole  45 , by the solid line. As illustrated in  FIG.  7   , at the time when the laser unit  32  has passed through the first through-hole  45 , the protrusion  75  partially covers the first through-hole  45  but does not cover the upper face  42  of the load beam  27 . 
     Next, the head unit  29  is moved in the +X direction coinciding with the protruding direction of the protrusion  75  from the outer shell  71 . By this movement, the protrusion  75  partially covers the upper face  42  of the load beam  27 , as illustrated in  FIG.  5   . The mounting face  62  of the magnetic head  31  is attached to the flexure  28  while the protrusion  75  partially covers the upper face  42 . The HGA  22  is assembled in the manner as described above. 
     In the HDD  10  according to the first embodiment described above, the laser unit  32  is attached to the magnetic head  31  to heat the magnetic disk  12 . This increases the weight of the head unit  29  including the magnetic head  31 . Because of the weight increase, the head unit  29  may easily vibrate and move away from the lower face  41  if the HDD  10  receives an impact. In the present embodiment, however, the head unit  29  is provided with the protrusion  75 . The protrusion  75  serves to restrict further movement of the magnetic head  31  from the lower face  41  beyond the given distance by coming in contact with at least one of the load beam  27  and the flexure  28 , if the magnetic head  31  moves away from the lower face  41  by the given distance. That is, the head unit  29 , which is likely to vibrate due to the added mass of the laser unit  32 , is provided with the protrusion  75  serving to restrict the vibration beyond the given distance. This makes it possible to restrict the magnetic head  31  from moving away from the lower face  41  beyond a given distance in the heat assisted recording HDD  10  incorporating the laser unit  32 . Thus, the magnetic head  31  can be prevented from colliding with the opposing magnetic head  31 , for example. Furthermore, the magnetic head  31  can be less hindered from being lifted by the plastic deformation of a vibrating gimbal  56  caused by an impact. Consequently, the HDD  10  can be improved in impact resistance. 
     The protrusion  75  can also be described as follows. That is, the protrusion  75  protrudes from the base  32   a  of the laser unit  32  in the +X direction to partially cover at least one of the load beam  27  and the flexure  28  in substantially the Z direction. Because of this, the protrusion  75  can restrict the magnetic head  31  having moved at the given distance in the −Z direction from moving further from the lower face  41  beyond the given distance by coming in contact with the at least one of the load beam  27  and the flexure  28 . It is thus possible to prevent the magnetic head  31  from colliding with the opposing magnetic head  31 , for example, leading to improving impact resistance of the HDD  10 . 
     The load beam  27  has an upper face  42  opposite to the lower face  41  and is provided with the first through-hole  45 . The flexure  28  has the upper face  52  facing the lower face  41 . The laser unit  32  is attached to the magnetic head  31  such that the laser unit  32  can pass through the first through-hole  45 . The laser unit  32  includes the protrusion  75  that partially covers at least one of the upper face  42  of the load beam  27  and the upper face  52  of the flexure  28 . Thereby, the protrusion  75  comes in contact with and is supported by at least one of the upper faces  42  and  52  along with the movement of the magnetic head  31  away from the lower face  41  by a given distance. That is, as compared with using other means such as friction, the protrusion  75 , which restricts the movement of the magnetic head  31  by supporting, can ensure that the magnetic head  31  is prevented from moving apart from the lower face  41  beyond a given distance. Furthermore, the protrusion  75  of the laser unit  32  serves to restrict the magnetic head  31  to which the laser unit  32  is attached, from moving away from the load beam  27 . This can further ensure that the magnetic head  31  is prevented from moving apart from the lower face  41  beyond a given distance, as compared with restricting the movement of the magnetic head  31  at a position far from the laser unit  32 . 
     The protrusion  75  protrudes from the outer shell  71  of the laser unit  32 . This facilitates the design of the protrusion  75  serving as the first restrictor that restricts the movement of the magnetic head  31  beyond a given distance. 
     The protrusion  75  protrudes from the outer shell  71  in the +X direction along the lower face  41 . In the +X direction, the total length of the laser unit  32  and the protrusion  75  is shorter than the length of the first through-hole  45 . This allows the laser unit  32  to pass through the first through-hole  45  in attaching the magnetic head  31  to which the laser unit  32  is attached in advance to the flexure  28 . This facilitates the manufacturing of the HDD  10 . 
     The Y-directional width of the load beam  27  tapers in the +X direction. The protrusion  75  protrudes from the outer shell  71  in the +X direction. This makes it easier to form the first through-hole  45  long in the X direction in the load beam  27 . 
     The protrusion  75  partially covers the upper face  42  of the load beam  27  and comes in contact with the upper face  42  to restrict the magnetic head  31 , having moved away from the lower face  41  by the given distance, from moving further from the lower face  41  beyond the given distance. That is, the protrusion  75  is in contact with and supported by the load beam  27 . With this configuration, the protrusion  75  can further ensure that the magnetic head  31  is prevented from moving apart from the lower face  41  beyond the given distance, as compared with the protrusion  75  supported by an elastically deformable portion of the flexure  28 . 
     A base end  27   b  is an end of the load beam  27  in the −X direction and is directly or indirectly connected to the carriage  21 . The magnetic head  31  includes the first end  31   a  in the −X direction and the second end  31   b  in the +X direction opposite to the −X direction. The laser unit  32  is attached to the magnetic head  31  at a position closer to the second end  31   b  than to the first end  31   a . That is, the laser unit  32  is attached to the magnetic head  31  in the vicinity of the tip of the HGA  22 . Because of this, an impact applied to the HDD  10  may cause the head unit  29  to easily vibrate and move away from the lower face  41 . In the present embodiment, however, the head unit  29  is provided with the protrusion  75 , as described above, which makes it possible to restrict the magnetic head  31  from moving away from the lower face  41  beyond a given distance. 
     The tab  57  is included in the flexure  28  apart from the protrusion  75  in the −X direction. Along with the movement of the magnetic head  31  away from the lower face  41  by a given distance, the tab  57  comes in contact with at least one of the load beam  27  and the flexure  28  and thereby restricts the magnetic head  31  from moving further from the lower face  41  beyond the given distance. That is, at two separate positions in the X direction, the protrusion  75  and the tab  57  function to restrict the movement of the magnetic head  31 . This can ensure that the magnetic head  31  is prevented from moving apart from the lower face  41  beyond a given distance. 
       FIG.  8    is a perspective view schematically illustrating the head unit  29  according to a modification of the first embodiment. As illustrated in  FIG.  8   , the protrusion  75  may protrude from the side face  71   e  of the outer shell  71  in the +Y direction or the −Y direction. In other words, the protrusion  75  may protrude from the base  32   a  of the laser unit  32  in the +Y direction or the −Y direction. In this case, in the Y direction, the total length of the laser unit  32  and the protrusion  75  is set at least partially shorter than the length of the first through-hole  45 . 
     Second Embodiment 
     Hereinafter, a second embodiment will be described with reference to  FIG.  9   . In the following embodiments, constituent elements with functions similar to the functions of the already-described elements, are denoted by the same reference numerals and description thereof may be omitted. Constituent elements denoted by the same reference numeral may not have the same function or property but may have different functions and properties according to the respective embodiments. 
       FIG.  9    is a sectional view illustrating a part of the HGA  22  according to the second embodiment. As illustrated in  FIG.  9   , in the second embodiment, the protrusion  75  protrudes in the +X direction from the second end face  71   d  of the outer shell  71 . In the +X direction (X direction), the total length of the laser unit  32  and the protrusion  75  is longer than the length of the first through-hole  45 . In other words, in the X direction, the sum of the distance between the first end face  71   c  and the second end face  71   d  of the outer shell  71  and the length of the protrusion  75  is longer than the length of the first through-hole  45 . 
     Meanwhile, in the +X direction (X direction) the length of the laser unit  32  is shorter than the length of the first through-hole  45 . In other words, in the X direction, the distance between the first end face  71   c  and the second end face  71   d  of the outer shell  71  is shorter than the length of the first through-hole  45 . The laser unit  32  is separated from the edge of the load beam  27  defining the first through-hole  45  and the rest of the load beam  27 . 
     The following will describe an assembly method of the HGA  22  as a part of the manufacturing method of the HDD  10  according to the second embodiment by way of example. First, the stationary part  55  of the flexure  28  is fixed to the lower face  41  of the load beam  27  by spot welding. 
     Next, before attachment of the laser unit  32 , the mounting face  62  of the magnetic head  31  having passed the inspection is attached to the flexure  28 . Next, the laser unit  32  having passed the inspection is placed close to the mounting face  62  of the magnetic head  31  through the first through-hole  45 .  FIG.  9    illustrates a virtual laser unit  32  before passing through the first through-hole  45 , by the chained double-dashed line, and the laser unit  32  after passing through the first through-hole  45 , by the solid line. 
     The laser unit  32  excluding the protrusion  75  is smaller in size than the first through-hole  45  in the X direction and the Y direction. Thus, the laser unit  32  can pass through the first through-hole  45 . 
     Next, the laser unit  32  is attached to the mounting face  62  of the magnetic head  31  with the protrusion  75  partially covering the upper face  42  of the load beam  27 . The HGA  22  is assembled in the manner as described above. 
     In the HDD  10  of the second embodiment described above, the protrusion  75  protrudes from the outer shell  71  in the +X direction along the lower face  41 . In the +X direction, the total length of the laser unit  32  and the protrusion  75  is longer than the length of the first through-hole  45 . In the +X direction, the length of the laser unit  32  is shorter than the length of the first through-hole  45 . That is, the protrusion  75  can reliably contact with at least one of the load beam  27  and the flexure  28  along with the movement of the magnetic head  31  away from the lower face  41  by a given distance. Moreover, the size of the first through-hole  45  can be reduced. In manufacturing the HDD  10  of the present embodiment, the magnetic head  31  is attached to the flexure  28  in advance, and the laser unit  32  is then attached to the magnetic head  31  such that the laser unit  32  passes through the first through-hole  45 . This makes it possible to avoid complication of the manufacturing of the HDD  10 . 
       FIG.  10    is a perspective view schematically illustrating the head unit  29  according to a first modification of the second embodiment.  FIG.  11    is a perspective view schematically illustrating the head unit  29  according to a second modification of the second embodiment. As illustrated in  FIGS.  10  and  11   , the head unit  29  may include a plurality of protrusions  75 . In the examples of  FIGS.  10  and  11   , two protrusions  75  protrude from the outer shell  71  of the base  32   a.    
     In the example of  FIG.  10   , one of the protrusions  75  protrudes in the +X direction from the first end face  71   c  of the outer shell  71  of the base  32   a . The other protrusion  75  protrudes in the −X direction from the second end face  71   d  of the outer shell  71  of the base  32   a . In the X direction, the total length of the laser unit  32  and the two protrusions  75  is set shorter than the length of the first through-hole  45 . 
     In the example of  FIG.  11   , the two protrusions  75  protrude in the Y direction from the two side faces  71   e  of the outer shell  71  of the base  32   a . In this case, the total length of the laser unit  32  and the two protrusions  75  is set shorter than the length of the first through-hole  45  in the Y direction. 
     Third Embodiment 
     Hereinafter, a third embodiment will be described with reference to  FIG.  12   .  FIG.  12    is a cross-sectional view schematically illustrating a part of the HGA  22  according to the third embodiment. As illustrated in  FIG.  12   , in the third embodiment, the HDD  10  further includes a restricting member  81  instead of the protrusion  75 . The restricting member  81  is an exemplary first restrictor. The HDD  10  may include both the protrusion  75  and the restricting member  81 . 
     The restricting member  81  is formed of metal and has a plate shape, for example. The material and shape of the restricting member  81  are not limited to this example. The restricting member  81  is attached to the upper face  71   b  of the outer shell  71  with an adhesive, for example. 
     A part of the restricting member  81  protrudes in the +X direction from the second end face  71   d  of the outer shell  71 , for example. The restricting member  81  partially covers the upper face  42  of the load beam  27  in the Z direction. 
     In the X direction, the distance between the first end face  71   c  of the outer shell  71  and an end face  81   a  of the restricting member  81  in the +X direction is longer than the length of the first through-hole  45 . Meanwhile, in the +X direction (X direction), the length of the laser unit  32  is shorter than the length of the first through-hole  45 . In other words, in the X direction, the distance between the first end face  71   c  and the second end face  71   d  of the outer shell  71  is shorter than the length of the first through-hole  45 . The laser unit  32  and the restricting member  81  are separated from the edge of the load beam  27  defining the first through-hole  45  and the rest of the load beam  27 . 
     For example, an impact applied to the HDD  10  may cause the tongue  56   a  and the head unit  29  to move away from the lower face  41  of the load beam  27  and the dimple  43 . Along with the movement of the magnetic head  31  of the head unit  29  away from the lower face  41  by a given distance, the restricting member  81  comes in contact with the upper face  42  of the load beam  27 . Thereby, the restricting member  81  can restrict the magnetic head  31  from moving away from the lower face  41  beyond the given distance. The given distance is an exemplary first distance. The restricting member  81  may come in contact with the upper face  52  of the stationary part  55  of the flexure  28 . 
     Hereinafter, an assembly method of the HGA  22  as a part of the manufacturing method of the HDD  10  according to the third embodiment will be described by way of example. First, the stationary part  55  of the flexure  28  is fixed to the lower face  41  of the load beam  27  by spot welding. Next, the mounting face  62  of the magnetic head  31  is attached to the flexure  28 . 
     The laser unit  32  may be attached in advance to the magnetic head  31 , or may be attached to the magnetic head  31  attached to the flexure  28 . The laser unit  32  passes through the first through-hole  45  when the magnetic head  31  is placed closer to the flexure  28  or when the laser unit  32  is placed closer to the mounting face  62  of the magnetic head  31 . 
     Next, the restricting member  81 , while partially covering the upper face  42  of the load beam  27 , is attached to the upper face  71   b  of the outer shell  71 .  FIG.  12    illustrates a virtual restricting member  81  before being attached to the laser unit  32 , by the chained double-dashed, and the restricting member  81  after being attached to the laser unit  32 , by the solid line. The HGA  22  is assembled in the manner as described above. 
     In the HDD  10  of the third embodiment described above, the restricting member  81  is attached to the outer shell  71  of the laser unit  32 . This can facilitate the manufacturing of the laser unit  32  including the first restrictor without forming the first restrictor such as the restricting member  81  and the laser unit  32  in a unified manner. 
     Fourth Embodiment 
     Hereinafter, a fourth embodiment will be described with reference to  FIGS.  13  and  14   .  FIG.  13    is a plan view schematically illustrating a part of the HGA  22  according to the fourth embodiment.  FIG.  14    is a sectional view schematically illustrating a part of the HGA  22  of the fourth embodiment. 
     As illustrated in  FIG.  13   , the load beam  27  of the fourth embodiment is provided with a first through-hole  91  instead of the first through-hole  45 . The first through-hole  91  penetrates the load beam  27  and opens to the lower face  41  and the upper face  42 . 
     The flexure  28  of the fourth embodiment further includes a stationary part  95  in addition to the stationary part  55  of the first embodiment. As with the stationary part  55 , the stationary part  95  is a part of the flexure  28 . The stationary part  95  partially has a lower face  51  and an upper face  52 . 
     The upper face  52  of the stationary part  95  comes in contact with the lower face  41  of the load beam  27 . The stationary part  95  is fixed to the lower face  41  of the load beam  27  at a welding spot S by spot welding, for example. 
     The stationary parts  55  and  95  include, for example, a metal plate such as stainless steel. The stationary parts  55  and  95  have higher rigidity than the arm  56   b . One of the stationary parts  55  is separated from the tongue  56   a  in the −X direction, as in the first embodiment. The other stationary part  95  is separated from the tongue  56   a  in the +X direction. That is, the tongue  56   a  is located between the two stationary parts  55 . 
     In the fourth embodiment, the arm  56   b  serves to connect the tongue  56   a  and the two stationary parts  55  and  95 . The elastic deformation of the arm  56   b  allows the tongue  56   a  and the head unit  29  to move with respect to the dimple  43 , the load beam  27 , and the two stationary parts  55  and  95 . 
     As illustrated in  FIG.  14   , the laser unit  32  is attached to the mounting face  62  of the magnetic head  31  such that the laser unit  32  can pass through the first through-hole  91 . The laser unit  32  is separated from the edge of the load beam  27  defining the first through-hole  91  and from the rest of the load beam  27 . The first through-hole  91  exposes at least a part of the upper face  52  of the stationary part  95 . The laser unit  32  is also separated from the stationary part  95 . 
     The protrusion  75  partially covers the first through-hole  91  but does not cover the upper face  42  of the load beam  27 . Furthermore, the protrusion  75  partially covers the upper face  52  of the stationary part  55  of the flexure  28  in the Z direction (substantially Z direction). The protrusion  75  may partially cover both the upper face  42  of the load beam  27  and the upper face  52  of the stationary part  55  of the flexure  28  in the Z direction. 
     In the +X direction (X direction), the total length of the laser unit  32  and the protrusion  75  is shorter than the distance between the stationary part  95  and an edge  91   a  of the first through-hole  91 . The edge  91   a  is located at the end of the first through-hole  91  in the −X direction and extends in substantially the Y direction. The protruding direction of the protrusion  75  and the size of the first through-hole  91  are not limited to this example, and may be designed in various manners such as in the second to third embodiments. Furthermore, the HDD  10  of the fourth embodiment may include the restricting member  81  of the third embodiment instead of the protrusion  75 . 
     In the fourth embodiment, an impact applied to the HDD  10 , for example, may cause the tongue  56   a  and the head unit  29  to move away from the lower face  41  of the load beam  27  and the dimple  43 . Along with the movement of the magnetic head  31  of the head unit  29  away from the lower face  41  by a given distance, the protrusion  75  comes in contact with the upper face  52  of the stationary part  95  of the flexure  28 . Thereby, the protrusion  75  can restrict the magnetic head  31  from moving away from the lower face  41  beyond the given distance. The given distance is an exemplary first distance. 
     In the HDD  10  of the fourth embodiment described above, the flexure  28  includes the stationary part  95  fixed to the load beam  27 ; and the gimbal  56  that is connected to the stationary part  95  and is elastically movable with respect to the stationary part  95 . The protrusion  75  partially covers the upper face  52  on the stationary part  95  and comes in contact with the upper face  52  of the stationary part  95  along with the movement of the magnetic head  31  away from the lower face  41  by a given distance, thereby restricting the magnetic head  31  from moving further from the lower face  41  beyond the given distance. That is, the protrusion  75  comes in contact with and is supported by the fixed portion of the flexure  28  to the load beam  27 . With this configuration, the protrusion  75  can more reliably restrict the magnetic head  31  from moving away from the lower face  41  beyond a given distance, as compared with the protrusion  75  supported by the gimbal  56  of the flexure  28 . 
     The first to fourth embodiments have described the example that the laser unit  32  includes the protrusion  75  and the restricting member  81  serving as an exemplary first restrictor. However, the first restrictor may be included in another part of the head unit  29 , such as the magnetic head  31 . For example, the restricting member  81  may be attached to the magnetic head  31 . 
     The first to fourth embodiments additionally include the following technical ideas: 
     [1] A disk device manufacturing method including: 
     allowing a heat-assister attached to a magnetic head to pass through a hole opening to a first face and a second face of a load beam, the second face opposite to the first face; 
     moving the magnetic head in a direction in which a protrusion protrudes from the heat-assister along the first face; and 
     attaching the magnetic head to a flexure while the protrusion partially covers the second face. 
     [2] A disk device manufacturing method including: 
     allowing a heat-assister to pass through a hole opening to a first face and a second face of a load beam, the second face opposite to the first face; 
     attaching the heat-assister to a magnetic head while a protrusion that protrudes from the heat-assister along the first face partially covers the second face. 
     [3] A disk device manufacturing method including: 
     allowing a heat-assister to pass through a hole opening to a first face and a second face of a load beam, the second face opposite to the first face; and 
     attaching a restricting member to the heat-assister such that the restricting member partially covers the second face. 
     According to at least one of the first to fourth embodiments described above, the heat-assister is attached to the magnetic head for heating the magnetic disk. This increases the weight of the head unit including the magnetic head, and may make the head unit easily vibrate and move apart from the first face when the disk device receives an impact. In any of the embodiments, however, the head unit is provided with the first restrictor. If the magnetic head moves away from the first face by the first distance, the first restrictor comes in contact with at least one of the load beam and the flexure and thereby restricts the magnetic head from moving further from the first face beyond the first distance. That is, the head unit, which is likely to vibrate due to the added mass of the heat-assister, includes the first restrictor serving to restrict the head unit from vibrating beyond the first distance. This makes it possible to avoid the magnetic head from moving away from the first face beyond the given first distance in the heat assisted magnetic recording (HAMR) disk device including the heat-assister. That is, the magnetic head can be prevented from colliding with the opposing magnetic head, for example, leading to improving the impact resistance of the disk device. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.