Abstract:
Connecting a head gimbal assembly with a controlling circuit, including the steps of facing connecting terminals of the head gimbal assembly and the connecting terminal of the controlling circuit to contact with each other and fastening the head gimbal assembly with the controlling circuit to maintain a touch connection of the terminals thereof.

Description:
FIELD OF THE INVENTION 
   The present invention relates to head stack assemblies and manufacturing methods thereof, and more particularly to a method of connecting HGA (head gimbal assembly) with controlling circuit thereof. 
   BACKGROUND OF THE INVENTION 
   Disk drives are information storage devices that use magnetic media to store data. Referring to  FIG. 1 , a typical disk drive in related art comprises a head stack assembly (HSA)  904  with slider(s)  903  thereon, a magnetic disk  901  mounted on a spindle motor  902  to spin the magnetic disk  901 , and a housing  907  to enclose the above-mentioned components. The slider(s)  903  is including in sensor to read data from or write data to the surface of the magnetic disk  901  by surfacing over it, which is positioned radially by a voice coil  906  embedded (e.g. by epoxy potting or overmolding) in a fantail spacer  908  of the HSA  904 . Generally, a voice coil motor (VCM)  914  is used to drive the voice coil  906 . 
   Referring to  FIGS. 2(   a ) and  2 ( b ), the HSA  904  comprises four head gimbal assemblies  971 ,  973 ,  975  and  977 . In the related art, the HSA  904  further comprises a spacer  81 ′ interposed between the head gimbal assembly (HGA)  971  and the HGA  973 , a fantail spacer  831 ′ sandwiched between the HGA  975  and the HGA  977 , and a plurality of securing means to couple the four HGAs  971 ,  973 ,  975 ,  977  with the spacer  81 ′ and the fantail spacer  831 ′ together. A flexible printed circuit (FPC)  9 ′ is aligned with the fantail spacer  831 ′ by a FPC assembly  835 ′ formed at an end of the FPC  9 ′ to electrically connect with the four head gimbal assemblies  971 ,  973 ,  975 ,  977 . The FPC assembly  835 ′ has a plurality of solder pads  999  thereon. Referring to  FIG. 2(   c ), the fantail spacer  831 ′ has a mounting block  839 ′ with an opening  838 ′ formed therein used for aligning with the FPC assembly  835 ′. In the related art, the plurality of securing means comprises a bearing  70 ′, a washer  76 ′ and a nut  78 ′. Each of the four head gimbal assemblies  971 ,  973 ,  975 ,  977  forms a big hole (not labeled) therein and so does the spacer  81 ′ and the fantail spacer  831 ′. These big holes are provided to permit the bearing  70 ′ extend therethrough so as to combine these parts together with the help of the washer  76 ′ and the nut  78 ′. 
   In the related art, also referring to  FIGS. 2(   a ) and  2 ( b ), each of the four head gimbal assemblies  971 ,  973 ,  975 ,  977  has a suspension flexure cable (not labeled) running from the slider  903  to a trace terminal of the suspension flexure cable (the trace terminals of the HGAs  971 ,  973 ,  975 ,  977  are labeled as “ 961 ”, “ 963 ”, “ 965 ”, “ 967 ”, respectively). Each of the trace terminals  961 ,  963 ,  965 ,  967  forms a plurality of terminal pads  99  corresponding to the solder pads  999  and each of the terminal pads  99  is shaped as a through-hole. The layout of the terminal pads  99  on each of the trace terminals  961 ,  963 ,  965 ,  967  is same as the other. 
   Referring to  FIG. 2(   a ), when the HSA  904  is assembled, the trace terminals  961 ,  963 ,  965 ,  967  are positioned on the FPC assembly  835 ′ and a slot  8  is defined between two adjacent trace terminals of the trace terminals  961 ,  963 ,  965 ,  967 . In the related art, the HGAs  971 ,  973 ,  975 ,  977  are electrically connected with the FPC  9 ′ by solder bonding the terminal pads  99  of the trace terminals  961 ,  963 ,  965 ,  967  with the solder pads  999  of the FPC assembly  835 ′. 
   However, the traditional method uses solder bonding process for connecting HGA with FPC. It results in occurrence of component contamination. To avoid component contamination, it is necessary to clean the HSA after solder bonding process. Such cleaning process is also rather difficult and costly. More seriously, the solder bonding process might cause a damage of the surrounding electrical components and/or disk media. In addition, the HSA assembly line and the hard disk drive (HDD) assembly line cannot be integrated together because the HSA must be cleaned before it is mounted in the housing of the disk drive. Furthermore, there is a case to separate the HGA with the FPC for rework (repairing or replacing) when there is something wrong with the HGA or the FPC. However, separating the HGA with the FPC is also troublesome because the solders bonded therebetween must be deleted. Accordingly, reworking the HSA is rather time-consuming and costly. Finally, because the terminal pads on each of the trace terminals has the same layout, it makes the electrical traces of the FPC, which connect with the terminal pads, rather jam-packed and accordingly the design and fabrication of the IC module of the FPC becomes difficult. 
   It is therefore desirable to provide a HSA and manufacturing method thereof, a disk drive unit using the HSA to solve the above-mentioned problems. 
   SUMMARY OF THE INVENTION 
   A main feature of the present invention is to provide a method of connecting head gimbal assemblies (HGAs) with its control circuit which is convenient for rework of HSA. 
   Another feature of the present invention is to provide a HSA which is easily assembled and reworked, a manufacturing method thereof and a disk drive unit using the HSA. 
   To achieve the above-mentioned features, a method of connecting head gimbal assembly with controlling circuit thereof, comprises the steps of: facing connecting terminals of at least one head gimbal assemblies and connecting terminal of their controlling circuit to contact with each other; and fastening said at least one head gimbal assembly with their controlling circuit to maintain a touch connection of said connecting terminals thereof. In the present invention, the method further comprises a step of disposing a conductive medium between said connecting terminals of said at least one head gimbal assemblies and said connecting terminal of their controlling circuit. 
   In an embodiment of the present invention, the method further comprises a step of forming a plurality of terminal pads on each of said connecting terminals of said at least one head gimbal assemblies and their controlling circuit. In the present invention, the conductive medium is disposed between the terminal pads on said connecting terminals of said at least one head gimbal assemblies and the terminal pads on said connecting terminal of their controlling circuit. 
   A head stack assembly of the present invention comprises at least one head gimbal assemblies and a controlling circuit for controlling the at least one head gimbal assemblies. Each of the at least one head gimbal assemblies has a connecting terminal and said controlling circuit has a connecting terminal as well. The connecting terminals of at least one head gimbal assemblies touch connects with the connecting terminal of said controlling circuit by fastening said at least one head gimbal assemblies with said controlling circuit. 
   In the present invention, a conductive medium is disposed between said connecting terminals of said at least one head gimbal assemblies and the connecting terminals of said controlling circuit. As an embodiment, said conductive medium is gold ball or solder ball. A plurality of terminal pads are formed on each of said connecting terminals of said at least one head gimbal assemblies and said controlling circuit. The conductive medium is disposed between the terminal pads on said connecting terminals of said at least one head gimbal assemblies and the terminal pads on said connecting terminal of said controlling circuit. In an embodiment of the present invention, the terminal pads on each pair of connecting terminals of said head gimbal assemblies are symmetrically distributed along a contacting surface of the pair of connecting terminals. 
   A method of forming a head stack assembly, comprises the steps of: forming at least one head gimbal assemblies; wherein forming each of the head gimbal assemblies comprises forming a connecting terminal thereon; forming a controlling circuit having a connecting terminal, which is used for controlling the at least one head gimbal assemblies; facing the connecting terminals of at least one head gimbal assemblies and the connecting terminal of said controlling circuit to contact with each other; and fastening said at least one head gimbal assembly with said controlling circuit to maintain a touch connection of said connecting terminals thereof. In the present invention, the method further comprises a step of disposing a conductive medium between said connecting terminals of said at least one head gimbal assemblies and said controlling circuit. 
   A disk drive unit comprises a housing; a disk stack comprising at least one disks; a spindle motor being attached to the housing for rotating the disk stack; and a HSA. The HSA comprises at least one head gimbal assemblies and a controlling circuit for controlling the at least one HGAs. Each of the at least one HGAs has a connecting terminal; said controlling circuit having a connecting terminal as well. The connecting terminals of at least one head gimbal assemblies and the connecting terminal of said controlling circuit touch connecting with each other by fastening said at least one head gimbal assembly with said controlling circuit. In the present invention, a conductive medium is disposed between said connecting terminals of said at least one head gimbal assemblies and said connecting terminal of said controlling circuit. 
   Comparing with the prior art, a method of connecting HGA with a FPC of a HSA of the present invention solves the problems of component contamination, component damage, and cleaning because solder is not used in connection process. In addition, because the HSA of the present invention do not need being cleaned before it is mounted in the base plate of the disk drive, so the HSA assembly line and the disk drive assembly line can be integrated together, accordingly it improves the efficiency of manufacturing the disk drive units. Furthermore, when there is something wrong with the HGA or the FPC, it does not need separate the HGA with the FPC for repairing or replacing (that is, making rework of the HSA more easily). Finally, because the terminal pads on each pair of trace terminals are formed symmetrically along the contacting surface thereof when they are positioned together, it makes the distribution of the electrical traces of the FPC more reasonable, and accordingly the design and fabrication of the IC module of the FPC becomes easy. 
   Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of a preferred embodiment thereof when taken in conjunction with the accompanying drawings, wherein: 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a traditional disk drive; 
       FIG. 2(   a ) is a perspective view of a traditional assembled head stack assembly (HSA); 
       FIG. 2(   b ) is an exploded, perspective view of the HSA in  FIG. 2(   a ); 
       FIG. 2(   c ) is a perspective view of a fantail spacer of the HSA in  FIG. 2(   b ); 
       FIG. 3  is a perspective view of an assembled HSA according to an embodiment of the present invention; 
       FIG. 4  is an exploded, perspective view of the HSA in  FIG. 3 ; 
       FIG. 5  is an exploded, perspective view of an fantail spacer assembly of the HSA in  FIG. 4 ; 
       FIG. 6  is a perspective view of the assembled fantail spacer assembly of  FIG. 5 ; 
       FIG. 7  shows a process of putting a plurality of metal balls onto corresponding FPC pads of a FPC assembly; 
       FIG. 8  is a perspective view to show trace terminals of HGAs being positioned on the FPC assembly of the HSA in  FIG. 3 ; 
       FIG. 9  shows a process of fastening the trace terminals of  FIG. 8  with the FPC assembly; 
       FIG. 10  is a perspective view to show the trace terminals of  FIG. 8  being fastened with the FPC assembly; 
       FIG. 11  is an enlarged, partial view of two assembled trace terminals of the HGAs; 
       FIG. 12  is a cross-sectional view of the HSA in  FIG. 10  taken along line A-A; and 
       FIG. 13  shows a disk drive unit with the HSA of  FIG. 3  mounted therein. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings in detail,  FIGS. 3 and 4  show a head stack assembly (HSA) of a disk drive unit according to an embodiment of the present invention. The HSA  904 ′ comprises four HGAs  22 ,  24 ,  26 ,  28  and a plurality of securing means to couple the four HGAs  22 ,  24 ,  26 ,  28  together. In the present invention, the HSA  904 ′ further comprises a spacer  81  interposed between the head gimbal assembly (HGA)  22  and the HGA  24 , a fantail spacer assembly  83  sandwiched between the HGA  26  and the HGA  28 , and a plurality of locking members to lock the four head gimbal assemblies  22 ,  24 ,  26 ,  28  with the fantail spacer assembly  83  on its lateral side. A flexible printed circuit (FPC)  9  is aligned with the fantail spacer assembly  83  at an end thereof to electrically connect with the four HGAs  22 ,  24 ,  26  and  28 . In an embodiment of the present invention, the plurality of securing means comprises a bearing  70 , two screws  72 ,  74 , a washer  76  and a nut  26 , each of the four HGAs  22 ,  24 ,  26 ,  28  forms three holes (not labeled) therein, the spacer  81  and the fantail spacer assembly  83  also form corresponding holes (not labeled) therein, these holes are provided to permit the bearing  70  and the corresponding screws  72 ,  74  extend therethrough so as to combine these parts together with the help of the washer  76  and the nut  78 . Additionally, the plurality of locking members comprise two screws  100 ,  200 , two washers  101 ,  102 , and a mount plate  300 . 
   With reference to  FIG. 4 , each of the four head gimbal assemblies  22 ,  24 ,  26 ,  28  comprises a suspension flexure cable which terminates with a trace terminal, i.e. the HGA  22  has a trace terminal  224 , the HGA  24  has a trace terminal  244 , the HGA  26  has a trace terminal  264 , and the HGA  28  has a trace terminal  284 . In the present invention, the trace terminals  224  and  244  are folded face to face from the HGAs  22  and  24 , respectively; similarly, the trace terminals  264  and  284  are folded face to face from the HGAs  26  and  28 , respectively. A detail view of the assembled trace terminals  224 ,  244  is shown on  FIG. 11 .  FIG. 11  shows the trace terminal  224  and the trace terminal  244  being positioned together. The trace terminal  224  is provided with a plurality of terminal pads  228  and a screw hole  227  formed on an end thereof. In addition, the trace terminal  224  also forms a fixing hole  225  in a lateral side thereof. Similarly, the trace terminal  244  is provided with a plurality of terminal pads  248 , a screw hole  247  and a fixing hole  245 . When the two trace terminals  224 ,  244  are positioned together, the terminal pads  228  and the terminal pads  248  are symmetrically distributed along the contacting surface of the two trace terminals  224 ,  244 , simultaneously, the two fixing holes  225  and  245  mutually define an assembly hole  290  to let the screw  100  extend therethrough (best see  FIG. 10 ). In the present invention, an assembly and structures of two trace terminals  264  and  284  are similar with the trace terminals  224  and  244 , and a detail description of such assembly and structures is omitted herefrom. 
   Referring to  FIGS. 5 and 6 , the fantail spacer assembly  83  comprises a fantail spacer  831 , a flexible printed circuit (FPC) assembly  835 , a FPC stiffener  833  positioned between the fantail spacer  831  and the FPC assembly  835 , and a screw  837  to secure the fantail spacer  831 , the FPC assembly  835  and the FPC stiffener  833  together. The fantail spacer  831  forms a protrusion  839  with two taped holes  836  and  838  therein to support the FPC assembly  835  and the FPC stiffener  833  on a lateral side thereof. In addition, the FPC stiffener  833  forms three mounting holes  832 ,  834  and  840  therein and four alignment pins  842  overmolded thereon. The FPC assembly  835  has three mounting holes  844 ,  846  and  848  corresponding to the three mounting holes  832 ,  834  and  840  and four alignment holes  847  to let the four alignment pins  842  extend therethrough. Additionally, a plurality of FPC pads  849  shaped as blind holes are also formed on the FPC assembly  835  corresponding to the terminal pads of the trace terminals  224 ,  244 ,  264 ,  284  (wherein the terminal pads on the trace terminals  224 ,  244  are labeled as “ 228 ”, “ 248 ”, see  FIG. 12 ). 
   Referring to  FIG. 4 , the spacer  81  has a protrusion  811  formed thereon to support the FPC assembly  835  and the FPC stiffener  833 . A taped hole  813  is formed on the protrusion  811  corresponding to the mounting hole  840  of the FPC stiffener  833  and the mounting hole  848  of the FPC assembly  835 . In an embodiment of the present invention, the spacer  81  also has an alignment aperture  815  therein for precisely assembly of the HSA  904 ′. 
   During assembly, referring to  FIGS. 5 and 6 , firstly, the FPC stiffener  833  is aligned with the FPC assembly  835 , accordingly, the four alignment pins  842  of the FPC stiffener  833  extend through the four alignment holes  847  of the FPC assembly  835  and simultaneously the three mounting holes  844 ,  846  and  848  of the FPC assembly  835  are aligned with the three mounting holes  832 ,  834  and  840  of the FPC stiffener  833 . Then, the FPC stiffener  833  and the FPC assembly  835  are put on the fantail spacer  831  with the taped hole  838 , the mounting hole  832  and the mounting hole  844  being aligned, and subsequently the screw  837  extends through the mounting hole  832  and the mounting hole  844  and engages with the taped hole  838 . Thus, a fantail spacer assembly  83  is formed, as shown in  FIG. 6 . 
   Subsequently, referring to  FIG. 7 , a plurality of metal balls  400 , such as gold balls, or solder balls, are bonded on the FPC pads  849  of the FPC assembly  835 . Then, referring to  FIG. 8 , the four head gimbal assemblies  22 ,  24 ,  26 ,  28 , the spacer  81  and the fantail spacer assembly  83  are assemblied together so as to put the trace terminals  224 ,  244 ,  264 , and  284  on the FPC assembly  835 , and accordingly the metal balls  400  are sandwiched between the FPC pads  849  and the terminal pads of the trace terminals  224 ,  244 ,  264 ,  284  (wherein the terminal pads on the trace terminals  224 ,  244  are labeled as “ 228 ”, “ 248 ”, see  FIG. 11 ). Finally, with reference to  FIGS. 9 and 10 , a plurality of locking members, i.e. two screws  100 ,  200 , two washers  101 ,  102  and a mount plate  300 , are used to secure the FPC pads  849  with the terminal pads firmly and thus a superior electrical connection between the HGAs  22 ,  24 ,  26 ,  28  and the FPC  9  is attained, see  FIG. 12 . 
   Referring to  FIG. 13 , After assembly of the HSA  904 ′, the HSA  904 ′ is put into and secured with a base plate  907 ′, and other essential parts, such as disk  901 ′, ramp  430 , spindle motor  902 ′ and VCM  914 ′, are also mounted into the base plate  907 ′. Thus a disk drive unit is formed. 
   In the present invention, the HSA  904 ′ is not limited to comprise four HGAs, for example, the amount of the HGAs may be one, two, or more than four. Accordingly, the structure of the HSA  904 ′ maybe change in accordance with the amount of HGAs. Such changes are well known to a person ordinarily skilled in the art, a detail description of such HSA is thus omitted. 
   It is understood that the invention may be embodied in other forms without departing from the spirit thereof. Thus, the present examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.