Abstract:
A disk drive unit of the invention comprises a motor base; a disk stack comprising at least one disks; a spindle motor being attached to the motor base for rotating the disk stack; and a HSA comprising at least one HGA, which having first terminal pads; and a controlling circuit for controlling the at least one HGA, which having second terminal pads to connect with the first terminal pads; wherein both the first and second terminal pads are axially tightened face-to-face to have an electrical touch contact. The invention also discloses a method of manufacturing the disk drive unit and the HSA, and also a method of electrically connecting a terminal of head gimbal assembly with a terminal of controlling circuit thereof.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to head stack assemblies, disk drive units and manufacturing methods thereof, and more particularly to a method of connecting the head stack assemblies with its control circuit.  
       BACKGROUND OF THE INVENTION  
       [0002]     Disk drives are information storage devices that use thin film magnetic media to store data. Referring to  FIG. 1 , a typical disk drive in prior art comprises a head stack assembly (HSA)  104  with slider(s)  203  thereon, a magnetic disk  101  mounted on a spindle motor  102  which causes the magnetic disk  101  to spin, and a motor base  109  to enclose the above-mentioned components. The slider(s)  203  flies over the surface of the magnetic disk  101  at a high velocity to read data from or write data to concentric data tracks on the magnetic disk  101 , which is positioned radially by a voice coil  106  embedded (e.g. by epoxy potting or overmolding) in a fantail spacer  108  of the HSA  104 . Generally, a voice coil motor (VCM)  107  is used to drive the voice coil  106 .  
         [0003]     Referring to FIGS.  3 ( a ) and  3 ( b ), a traditional HSA  100  comprises two head gimbal assemblies (HGAs)  201  and  208 , a fantail spacer  205  interposed between the head gimbal assembly (HGA)  201  and the HGA  208 , and a plurality of securing means to couple the two HGAs  201  and  208  with the fantail spacer  205  together. A flexible printed circuit (FPC)  207  aligns with the fantail spacer  205  by a FPC assembly  217  to electrically connect with the two HGAs  201  and  208 . Also, the FPC assembly  217  is provided a plurality of FPC pads  98  thereon. In the related art, the plurality of securing means comprises a bearing  211 , a washer  213  and a nut  215 . In addition, two mounting holes  221 ,  228  are formed in the two HGAs  201  and  208 , respectively. In the fantail spacer  205  a mounting hole  225  forms corresponding to the mounting holes  221  and  228 . These mounting holes  221 ,  228  and  225  are provided to permit the bearing  211  extend therethrough so as to combine the above-mentioned components together with the help of the washer  213  and the nut  215 .  
         [0004]     In the prior art, also referring to FIGS.  3 ( a ) and  3 ( b ), the HGA  201  has a suspension flexure cable  231  running from the slider (not labeled) to a trace terminal  241  of the suspension flexure cable  231 ; similarly, the HGA  208  comprises a suspension flexure cable  238  which terminates with a trace terminal  248 . Each of the traces terminals  241  and  248  forms a plurality of terminal pads  99  thereon and each of the terminal pads  99  is shaped as a through-hole.  
         [0005]     Referring to FIGS.  3 ( a )- 3 ( b ), when the HSA  100  is assembled, the trace terminals  241  and  248  are positioned on the FPC assembly  217 . Then, the HGAs  201  and  208  are electrically connected with the FPC  207  by solder bonding the terminal pads  99  of the trace terminals  241  and  248  with the FPC pads  98  of the FPC assembly  217 . After that, with reference to  FIG. 2 , the HSA  100  is mounted in a motor base  900 , and later other essential parts are also assembled in the motor base  900  to form a disk drive unit.  
         [0006]     However, the traditional method to connect HGA with FPC by solder bonding can result in component contamination. To avoid component contamination, it is necessary to clean the HSA after solder bonding and yet such cleaning is rather difficult and costly because the bearing has some lubricant thereon and can not clean by water. More seriously, the solder bonding can cause damage to the surrounding electrical components and/or disk media during soldering. In addition, because the HSA must be cleaned before it is mounted in the base plate of the disk drive, so the HSA assembly line and the HDD assembly line cannot be integrated together. That is to say, it must assemble a HSA in HSA assembly line, and then install the HSA into the motor base in HDA assembly line. Furthermore, when there is something wrong with the HGA or the FPC, it must separate the HGA with the FPC for rework, such as repairing or replacing. However, separating the HGA with the FPC is also troublesome because the solders therebetween must be deleted and accordingly reworking the HSA is rather time-consuming and costly. Finally, when there is something wrong with some parts of the HSA, such as HGA, it is required to disassemble the whole HSA from the disk drive unit at first for repairing, accordingly, the cost for reworking the disk drive unit is rather high.  
         [0007]     It is therefore desirable to provide a head stack assembly, disk drive unit, and manufacturing method thereof to solve the above-mentioned problems.  
       SUMMARY OF THE INVENTION  
       [0008]     A main feature of the present invention is to provide a disk drive unit which is easily assembled and can rework its HGA in disk drive level, and a manufacturing method thereof.  
         [0009]     Another feature of the present invention is to provide a HSA which is easily assembled and reworked, and a manufacturing method thereof.  
         [0010]     A further feature of the present invention is to provide a method of connecting a terminal of HGA with a terminal of its control circuit.  
         [0011]     To achieve the above-mentioned features, a disk drive unit of the invention comprises a motor base; a disk stack comprising at least one disks; a spindle motor being attached to the motor base for rotating the disk stack; and a HSA comprising at least one HGA, which having first terminal pads; and a controlling circuit for controlling the at least one HGA, which having second terminal pads to connect with the first terminal pads; wherein both the first and second terminal pads are axially tightened face-to-face to have an electrical touch contact.  
         [0012]     In the present invention, each of the first and second terminal pads has a conductive layer thereon. In an embodiment, the disk drive unit further comprises conductive supporter disposed between the first and second terminal pads.  
         [0013]     A manufacturing method of disk drive unit comprises the steps of: providing at least one HGA, which having first terminal pads; providing a controlling circuit for controlling the at least one HGA, which having second terminal pads to connect with the first terminal pads; disposing the at least one HGA into a motor base; disposing the controlling circuit into the motor base; tightening the at least one HGA and the controlling circuit to the motor base so as to tighten both the first and second terminal pads face-to-face to have an electrical touch contact therebetween.  
         [0014]     In the present invention, the method comprises a step of plating each of the first and second terminal pads with a conductive layer thereon. In an embodiment, the method further comprises a step of disposing conductive supporter between the first and second terminal pads before they are tightened.  
         [0015]     A HSA of the present invention comprises at least one HGA, which having first terminal pads; and a controlling circuit for controlling the at least one HGA, wherein said controlling circuit having second terminal pads; wherein both the first and second terminal pads are axially tightened face-to-face to have an electrical touch contact.  
         [0016]     In the present invention, each of the first and second terminal pads has a conductive layer thereon. In an embodiment, the conductive layer is metal layer, such as gold layer. In another embodiment, the method further comprises conductive supporter disposed between the first and second terminal pads.  
         [0017]     In the invention, the conductive supporter is a soft metal solid and/or an oxidation resistance metal solid. In an embodiment, the conductive supporter is gold solid or gold ball.  
         [0018]     A method of electrically connecting a terminal of HGA with a terminal of controlling circuit thereof comprises the steps of: facing first terminal pads of at least one HGA and connecting second terminal pads of its controlling circuit to contact with each other; and both the first and second terminal pads are axially tightened face-to-face to have an electrical touch contact.  
         [0019]     In the present invention, the method comprises a step of plating each of the first and second terminal pads with a conductive layer thereon. In an embodiment, the method further comprises a step of disposing conductive supporter between the first and second terminal pads to support their electrical touch contact. The conductive supporter may be a metal ball, such as gold ball.  
         [0020]     Comparing with the prior art, 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 head stack assembly of the present invention do not need being cleaned before it is mounted in the motor base 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 drives. Finally, because the first terminal pads and the second terminal pads are axially secured with each other by secure means, so when there is something wrong with the HGA or the FPC, it can rework the HGA etc. in disk drive level.  
         [0021]     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  
       [0022]      FIG. 1  is a perspective view of a traditional disk drive unit;  
         [0023]      FIG. 2  is a perspective view of another traditional unassembled disk drive unit;  
         [0024]      FIG. 3 ( a ) is an exploded, perspective view of a head stack assembly (HSA) of the disk drive in  FIG. 2 ;  
         [0025]      FIG. 3 ( b ) is a perspective view of the assembled HSA in  FIG. 3 ( a );  
         [0026]      FIG. 4 ( a ) is a perspective view of an assembled HSA according to an embodiment of the present invention;  
         [0027]      FIG. 4 ( b ) is an exploded, perspective view of the HSA in  FIG. 4 ( a );  
         [0028]      FIG. 5  is an enlarged, perspective view of an fantail spacer of the HSA in  FIG. 4 ( b );  
         [0029]      FIG. 6  is a perspective view of a HGA of the HSA in  FIG. 4 ( b );  
         [0030]      FIG. 7  shows a process of putting a plurality of gold balls on FPC pads of FPC assemblies of the HSA in  FIG. 4 ( b );  
         [0031]      FIG. 8  shows a process of fastening the FPC assemblies with trace terminals of the HGAs of the HSA in  FIG. 4 ( b );  
         [0032]      FIG. 9  is a partial, cross-sectional view of the HSA in  FIG. 4 ( a ) taken along line A-A;  
         [0033]      FIG. 9A  is a cross-sectional view of the HSA of  FIG. 9  without gold balls;  
         [0034]      FIG. 10  is a perspective view of an assembled disk drive unit in accordance with an embodiment of the present invention;  
         [0035]      FIG. 11  is an exploded, perspective view of the disk drive unit in  FIG. 10 ;  
         [0036]      FIG. 12  is a perspective view of an assembled HSA according to a second embodiment of the present invention;  
         [0037]      FIG. 13  is an exploded, perspective view of the HSA in  FIG. 12 ;  
         [0038]      FIG. 14  is a perspective view of a HGA of the HSA in  FIG. 12 ;  
         [0039]      FIG. 15  is a perspective view of a fantail spacer with a FPC of the HSA in FIG  12 ;  
         [0040]      FIG. 16  is an enlarged, perspective view of an fantail spacer of the HSA in  FIG. 12 ;  
         [0041]      FIG. 17  is a cross-sectional view of the HSA in  FIG. 12  taken along line A-A;  
         [0042]      FIG. 17A  is a cross-sectional view of the HSA of  FIG. 17  without gold balls; and  
         [0043]      FIG. 18  is an exploded, perspective view of an disk drive unit in accordance with the second embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0044]     Referring now to the drawings in detail, FIGS.  4 ( a ) and  4 ( b ) show a head stack assembly (HSA) of a disk drive unit according to a first embodiment of the present invention. The HSA  100 ′ comprises two HGAs  201 ′,  208 ′ and a fantail spacer  205 ′ interposed between the HGA  201 ′ and the HGA  208 ′. In the present invention, a plurality of securing means are provided to couple the two HGAs  201 ′,  208 ′ with the fantail spacer  205 ′ together. In an embodiment of the present invention, the plurality of securing means comprises a bearing  211 ′, a screw  303 , two washers  213 ′,  301 , and a nut  215 ′. The HGA  201 ′ has a support plate  601  with a screw hole  611  formed therein, and the HGA  208 ′ also has a support plate  602  with a screw hole (not shown) formed therein. In addition, the fantail spacer  205 ′ forms a protrusion  413  with a screw hole (not shown) corresponding to the support plates  601  and  602 . Referring to  FIG. 4 ( b ), the washer  301  is also provided with a support protrusion  477  having a screw hole  478  therein.  
         [0045]     Referring to FIGS.  4 ( b ) and  6 , each of the two HGAs  201 ′ and  208 ′ has a suspension flexure cable which terminates with a trace terminal, i.e. the HGA  201 ′ has a trace terminal  311 , the HGA  208 ′ has a trace terminal  321 . The trace terminal  311  is positioned on the support plate  601  and provided with a plurality of terminal pads  361  and a screw hole  371  therein. Similarly, the trace terminal  321  is positioned on the support plate  602  and provided with a plurality of terminal pads  381  and a screw hole  391  therein.  
         [0046]     Referring to FIGS.  4 ( b ) and  6 , a flexible printed circuit (FPC)  207 ′ is aligned with the fantail spacer  205 ′ at an end thereof to electrically connect with the two HGAs  201 ′ and  208 ′. As an embodiment of the present invention, the FPC  207 ′ is aligned with the fantail spacer  205 ′ by two FPC assemblies  411  and  412  secured to an end of the FPC  207 ′. The two FPC assemblies  411  and  412  are positioned two sides of the protrusion  413  of the fantail spacer  205 ′. Additionally, the FPC assembly  411  is provided with a plurality of FPC pads  481  and a screw hole  482  corresponding to the terminal pads  361  and the screw hole  371  of the trace terminal  311 , respectively. Similarly, referring to  FIG. 5 , a plurality of FPC pads  491  and a screw hole  492  are formed on the FPC assembly  412  corresponding to the terminal pads  381  and the screw hole  391  of the trace terminal  321 .  
         [0047]     During assembly of the HSA  100 ′, firstly, the fantail spacer  205 ′ is aligned with the FPC  207 ′. Then, referring to  FIG. 7 , a plurality of gold balls  511  are provisionally disposed on the FPC pads  481  of the FPC assembly  411  and the FPC pads  491  of the FPC assembly  412 . After that, referring to  FIGS. 8 and 9 , the two HGAs  201 ′,  208 ′, the fantail spacer  205 ′ with the FPC  207 ′, and the washer  301  are assembled together by a screw  303 . Thus, the trace terminal  311  of the HGA  201  ′ is pressed to the FPC assembly  411  and simultaneously the trace terminal  321  of the HGA  208 ′ is pressed to the FPC assembly  412 . Accordingly, the gold balls  511  are sandwiched between the FPC pads  481  and the terminal pads  361 , and between the FPC pads  491  and the terminal pads  381  as well. Thus superior electrical connections between the two HGAs  201 ′,  208 ′ and the FPC  207 ′ is attained, see  FIG. 4 ( a ). Finally, with reference to  FIG. 4 ( b ), a plurality of locking members, i.e. the bearing  211 ′, the washers  213 ′ and the nut  215 ′, are used to secure the two HGAs  201 ′,  208 ′ with the fantail spacer  205 ′ together to form a HSA  100 ′, as shown in  FIG. 4 ( a ). In the present invention, the support plates  601 ,  602 , the protrusion  413  and the support protrusion  478  are superposed together with the screw holes thereon corresponding with each other, and a screw  303  is used to extend through the screw holes so as to sandwich the gold balls  511  firmly. In the present invention, the gold balls  511  are used for supporting an electrical touch contact of the FPC pads  481 ,  491  with the terminal pads  361 ,  381 . When reworking the HSA  100 ′, it only needs to uninstall the screw  303 , and the FPC pads  481 ,  491  will be separated with the terminal pads  361 ,  381  automatically because the gold balls are just provisionally disposed therebetween, while the related art must have a cleaning process because it uses solder bonding to connect the FPC pads with the terminal pads. Understandably, the gold balls  511  can be omitted herefrom, and the FPC pads  481 ,  491  touch contact with the terminal pads  361 ,  381  in a pad-to-pad way, as shown in  FIG. 9A . In this embodiment, each of the FPC pads  481 ,  491  and the terminal pads  361 ,  381  has a conductive layer formed thereon, the conductive layer can be formed by plating. In an embodiment, the conductive layer is metal layer, such as gold layer.  
         [0048]     Referring to  FIG. 11 , a disk drive unit  200  using the HSA  100 ′ may assembled as follows: firstly, mounting essential parts, such as disk, ramp load, spindle motor and VCM into the motor base  900 ′, and then the bearing  211 ′ can be mounted into the motor base  900 ′ by the screw  711 . Consequently, the washer  301 , the HGA  208 ′, the fantail spacer  205 ′ with the FPC  207 ′, the HGA  201 ′, the washer  213 ′ and the nut  215 ′ are installed into the motor base  900 ′ in sequence. Here, the nut  215 ′ and the screw  303  are used to tighten the HGAs  201 ′,  208 ′, and the fantail spacer  205 ′ with the FPC  207 ′. Thus electrical connection between the terminal pads of the HGAs  201 ′,  208 ′ and the FPC pads of the FPC  207 ′ is established and a disk drive unit is formed, as shown in  FIG. 10 . For rework, it only needs to uninstall the nut  215 ′ and the screw  303  to replace wrong/damage part in HDA level, such as replace the HGA  201  or  208 .) From the assembly process, it shows that the embodiment integrates the HSA process into the HDA process so as to greatly simply the assembly process and the rework process.  
         [0049]     Referring to  FIGS. 12 and 13 , according to a second embodiment of the present invention, a HSA  800  comprises two HGAs  801 ,  808  and a fantail spacer  805  interposed between the two HGAs  801 ,  808 . In the embodiment, each of the HGAs  801 ,  808  and the fantail spacer  805  has a mounting hole (that is, the mounting hole  851  in the HGA  801 , the mounting hole  858  in the HGA  808 , the mounting hole  855  in the fantail spacer  805 ). A bearing  811  extends through the mounting holes  858 ,  855 ,  851  in sequence and couples the two HGAs  801 ,  808  with the fantail spacer  805  together with the help of a washer  813  and a nut  815 .  
         [0050]     Referring to  FIGS. 12-14  and  17 , each of the two HGAs  801  and  808  has a HGA arm and a suspension flexure cable which terminates with a trace terminal. In the embodiment, the HGA  808  has a HGA arm  898  and a trace terminal  868 , the HGA  801  has a HGA arm  891  and a trace terminal  861 . The trace terminal  868  is disposed on the HGA arm  891 , one side of which is arc-shaped along the periphery of the mounting hole  858 . A plurality of terminal pads  878  is distributed on the trace terminal  868  along the arc-shaped side of the trace terminal  868 . Similarly, the trace terminal  861  is disposed on the HGA arm  891  and a plurality of terminal pads  871  are formed thereon.  
         [0051]     Referring to FIGS.  12 ,  15 - 17 , a flexible printed circuit (FPC)  807  is aligned with the fantail spacer  805  at an end thereof to electrically connect with the two HGAs  801  and  808 . In the embodiment, the fantail spacer  805  is cut a step (not labeled) on each side thereof for mounting the FPC  807  and thus forming a thick portion  51  and a thin portion  52 . In the embodiment, the FPC  807  is aligned with the fantail spacer  805  by two FPC assemblies  61  and  62  which are both secured to an end of the FPC  807 . Referring to  FIG. 16 , in the embodiment, the two FPC assemblies  61  and  62  are disposed on two sides of the thin portion  52  of the fantail spacer  805 ; while the two HGA arms  891 ,  898  are disposed on two sides of the thick portion  51  of the fantail spacer  805 . Referring to  FIG. 16 , each of the FPC assemblies  61  and  62  has an arc-shaped side along the periphery of the mounting hole  855  corresponding to the trace terminals  861 ,  868  of the HGAs  801  and  808 . A plurality of FPC pads  65  are provided on the FPC assembly  61  corresponding to the terminal pads  871  of the trace terminal  861 . Similarly, a plurality of FPC pads  66  are formed on the FPC assembly  62  corresponding to the terminal pads  878  of the trace terminal  868 .  
         [0052]     During assembly of the HSA  800 , referring to  FIG. 13 , firstly, the fantail spacer  805  is aligned with the FPC  807 , and then a plurality of gold balls  511  are provisionally disposed on the FPC pads  65 ,  66  of the FPC assemblies  61 ,  62 , respectively. After that, the bearing  811  extends through the mounting holes  858 ,  855 ,  851  in sequence so as to superpose the HGAs  801 ,  808 , the fantail spacer  805  with the FPC  807  together, accordingly, the trace terminals  861 ,  868  of the HGAs  801 ,  808  are disposed on the FPC assemblies  61 ,  62 , respectively. Then, with the help of the washer  813  and the nut  815 , the two HGAs  801 ,  808  and the fantail spacer  805  with the FPC  807  are assembled together to forming a HSA  800  so that the gold balls  511  are sandwiched firmly between the FPC pads  66  and the terminal pads  878 , and also between the FPC pads  65  and the terminal pads  871  under the press exerted by the bearing  811 , the washer  813  and the nut  815 . Thus superior electrical connections between the two HGAs  801 ,  808  and the FPC  807  is attained, see  FIGS. 12 and 17 . In the present invention, the gold balls  511  act as a conductive supporter to support an electrical touch contact of the FPC pads  65 ,  66  with the terminal pads  871 ,  878 . When reworking the HSA  800 , it only needs to uninstall the securing means (such as the bearing  811 , the washer  813 , the nut  815 ), and the FPC pads  65 ,  66  will be separated with the terminal pads  871 ,  878  automatically because the gold balls are just provisionally disposed therebetween, while the related art must have a cleaning process because it uses solder bonding to connect the FPC pads with the terminal pads. Understandably, the gold balls  511  can be omitted herefrom, and the FPC pads  65 ,  66  touch contact with the terminal pads  871 ,  878  in a pad-to-pad way, as shown in  FIG. 17A . In this embodiment, each of the FPC pads  65 ,  66  and the terminal pads  871 ,  878  has a conductive layer formed thereon, the conductive layer can be formed by plating. In an embodiment, the conductive layer is metal layer, such as gold layer.  
         [0053]     In the embodiment, because the trace terminals  861 ,  868  protrudes from the HGAs  801  and  808 , it is necessary to cut the steps on the fantail spacer  805  to ensure the terminal pads  871 ,  878  of the trace terminal  861 ,  868  and the FPC pads  65 ,  66  contacting with the gold balls  511 . In addition, the HSA  800  may further provide a screw hole on each of the HGAs  801 ,  808 , the fantail spacer  855 , the trace terminals  861 ,  868  and the FPC assemblies  61 ,  62 . These screw holes are all formed adjacent to the area of terminal pads  861  or  868 , or the area of the FPC pads  65  or  66 , which can be drilled through by a screw (not shown) so that the gold balls  511  can be sandwiched more firmly between the terminal pads  861  with the FPC pads  65 , and between the terminal pads  868  with the FPC pads  66 . Accordingly, a more superior electrical connection between the HGAs  801 ,  808  and the FPC  807  can be attained.  
         [0054]     In the present invention, referring to  FIG. 18 , a disk drive unit  300  using the HSA  800  may be assembled as follows: firstly, mounting essential parts, such as disk, ramp load, spindle motor and VCM into the motor base  900 ′, and then the bearing  811  can be mounted into the motor base  900 ′ by a screw  711 . After that, the HGA  808 , the fantail spacer  805  with the FPC  807 , the HGA  801  and the washer  813  are installed into the motor base  900 ′ in sequence. At last, the nut  815  is used to tighten the HGAs  801 ,  808 , and the fantail spacer  805  with the FPC  807  to establish electrical connection between the terminal pads of the HGAs  801 ,  808  and the FPC pads of the FPC  807 . For rework, it only needs to uninstall the nut  815  to replace wrong/damage part in HDA level. So the embodiment can also integrate the HSA process into the HDA process.  
         [0055]     In the present invention, because the trace terminals and the FPC assemblies are axially secured with each other by secure means to sandwich the gold balls therebetween, so the HSA of the present invention do not need being cleaned before it is mounted in the motor base of the disk drive, that is to say, the HSA assembly line and the disk drive assembly line can be integrated together.  
         [0056]     Obviously, conductive supporter between the terminal pads and the FPC pads is not limited to gold ball or gold solid. Other metal ball or metal solid, such as solder ball, can also act as a conductive supporter in the invention. Conductive supporter may be other conductive material which have a softness and an oxidation resistance. In addition, the HSA  100 ′ or  800  of the present invention is not limited to comprise two HGAs, for example, the amount of the HGAs may be one, four, or more than four. Accordingly, the structure of the HSA  100 ′ or  800  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.