Abstract:
A semi-finished suspension ( 55 ) is used for manufacturing a head suspension ( 11 ) for a disk drive. The semi-finished suspension includes a base plate ( 37 ), a rigid part ( 27 ) solidly joined with the base plate through a bridge ( 57 ), and a protrusion being the bridge protruding from one of a base plate and rigid part and having a positioning hole ( 63 ) formed through the protrusion of the bridge. This positioning hole is aligned with a positioning hole ( 51 ) formed through part of a flexure ( 41 ).

Description:
RELATED APPLICATIONS 
   This application is a divisional of U.S. application Ser. No. 09/811,077, entitled “Method of Manufacturing Head Suspension For Disk Drive and Semi-Finished Suspension,” filed Mar. 16, 2001, issued as U.S. Pat. No. 6,571,455, which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a method of manufacturing a head suspension for a disk drive incorporated in an information processing unit such as a personal computer. 
   2. Description of the Related Art 
   A hard disk drive (HDD) used for an information processing unit has magnetic or magneto-optical disks to write and read data and a carriage. The carriage is turned around a spindle by a positioning motor. The carriage is disclosed in, for example, U.S. Pat. No. 4,167,765. This carriage has arms, a head suspension attached to each arm, and a head attached to the suspension and having a slider. 
   When each disk in the HDD is rotated at high speed, the slider slightly floats above the disk and air bearings are formed between the disk and the slider. 
     FIG. 1  shows a typical suspension  101  of an HDD. The suspension  101  has a load beam  103 . The load beam  103  is fixed to a base plate  105  by, for example, laser welding. The base plate  105  is fitted to a carriage arm of the HDD. 
   The load beam  103  consists of a rigid part  107  of L 1  in length and a resilient part  109  of L 2  in length. A flexure  111  is fixed to the rigid part  107  by, for example, laser welding. An end of the flexure  111  has a tongue  113  to which a slider  115  is attached. The tongue  113  is pushed by a dimple  117 , which is formed at an end of the rigid part  107 . Although the dimple  117  is depicted with a solid line in  FIG. 1 , it is actually on the back of the tongue  113 . 
   The rigid part  107  is provided with positioning holes  121  and  125 , and the flexure  111  is provided with positioning holes  123  and  127 . 
   The holes  121 ,  123 ,  125 , and  127  are set on positioning pins of a jig to align the rigid part  107  and flexure  111  with each other, and the rigid part  107  and flexure  111  are fixed to each other by, for example, laser welding. The positioning and fixing of the flexure  111  to the rigid part  107  determine the vibration characteristics of the suspension  101 . 
   Disks of recent HDDs are designed to densely record data and revolve at high speed. It is required, therefore, to provide a suspension of improved vibration characteristics to carry out precision positioning of a head on an HDD disk surface. 
   To meet the requirement, the suspension  101  must be compact. Namely, the distance A between the dimple  117  and a fitting center of the base plate  105  must be short. The distance A, however, must sufficiently be long to secure a proper distance between the holes  121  and  125  for correct positioning of the flexure  111  with respect to the rigid part  107 . 
   If the distance A is excessively shortened to improve vibration characteristics, the holes  121  and  125  will be too close to each other, thereby deteriorating positioning accuracy. 
   To solve this problem,  FIGS. 2A  to  2 C show a head suspension  101 A for a disk drive according to a prior art. This prior art forms a positioning hole  125  on the side of a base plate  105 . Even if the distance A ( FIG. 1 ) between a dimple  117  and a fitting center of the base plate  105  is short, a sufficient distance is secured between positioning holes  121  ( 123 ) and  125  ( 127 ) for correct positioning of a flexure  111  to a rigid part  107 . 
   Formation of the suspension  101 A will be explained.  FIG. 2A  is a plan view showing parts of the suspension  101 A before assembly, and  FIG. 2B  is a plan view showing the parts after assembly. In  FIG. 2A , the flexure  111  is provided with the positioning holes  123  and  127 . The base plate  105  is fitted to a reinforcing plate  129 . The reinforcing plate  129  is solidly joined with the rigid part  107  of a load beam  103  through a bridge  131 , to form a semi-finished suspension  133 . The rigid part  107  is provided with the positioning hole  121 , and the reinforcing plate  129  with the positioning hole  125 . 
   A resilient material  135  is used to form a resilient part  109  of the load beam  103 . The resilient material  135  is placed over the rigid part  107  and reinforcing plate  129  and is fixed thereto by, for example, laser welding. Thereafter, the base plate  105  is fitted to the reinforcing plate  129  and is fixed thereto by, for example, laser welding. 
   The semi-finished suspension  133  with the resilient material  135  and base plate  105  is set on a jig by passing pins of the jig through the holes  121  and  125 , and the flexure  111  is laid thereon by passing the jig pins passed through the holes  121  and  125  through the holes  123  and  127 , respectively. This precisely positions the flexure  111  with respect to the rigid part  107  as shown in FIG.  2 B. 
   The distance between the holes  121  ( 123 ) and  125  ( 127 ) is appropriate for precision positioning between the rigid part  107  and the flexure  111 . Under this state, the flexure  111  is fixed to the rigid part  107  by, for example, laser welding. 
   Thereafter, the bridge  131  is cut off by, for example, a press, to complete the suspension  101 A of FIG.  2 C. 
   One problem of this prior art is to leave the peripheries of the holes  125  and  127  on the base plate  105 , to cause a horizontal imbalance on the base plate  105 . This imbalance deteriorates the vibration characteristics of the suspension  101 A. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a method of manufacturing a head suspension or a semi-finished suspension that is compact, secures a sufficient distance between positioning holes, and involves no base-plate imbalance. 
   In order to accomplish the object, a first aspect of the present invention provides a method of manufacturing a head suspension for a disk drive. The head suspension has a base plate to be supported by a carriage, a load beam including a rigid part resiliently supported by the base plate, to apply load onto a slider, and a flexure positioned and fitted to the load beam and having a read-write head. The method includes a first step of forming a semi-finished suspension having the base plate, the rigid part solidly joined with the base plate through a bridge, and a protrusion protruding from one of the base plate and rigid part and having a positioning hole to be aligned with a positioning hole formed through part of the flexure, a second step of fixing a resilient material to the base plate and rigid part of the semi-finished suspension so that the base plate may resiliently support the rigid part through the resilient material, a third step of aligning the positioning hole of the flexure with the positioning hole of the protrusion and fixing the flexure to the rigid part, and a fourth step of cutting off the positioning-hole-formed part of the flexure, the bridge, and the protrusion including the positioning hole. 
   The first aspect may form the positioning hole of the protrusion in the vicinity of the base plate, to secure a proper distance between the positioning hole and a positioning hole formed through the rigid part. This results in precisely positioning the flexure with respect to the rigid part and correctly fixing the flexure thereto. The first aspect cuts off the bridge, the protrusion having the positioning hole, and the positioning-hole-formed part of the flexure. As a result, the suspension manufactured from the semi-finished suspension has no positioning holes including their peripheries, to cause no horizontal imbalance and improve the vibration characteristics of the suspension. In addition, the suspension of the first aspect is compact to further improve the vibration characteristics thereof. 
   A second aspect of the present invention makes the bridge serve as the protrusion. 
   The second aspect forms the positioning hole to be aligned with the positioning hole of the flexure on the bridge that solidly joins the rigid part to the base plate. The second aspect provides the same effect as the first aspect. 
   A third aspect of the present invention forms, in the first step, the positioning hole through one of the protrusion and bridge in the vicinity of the base plate. 
   The third aspect secures a proper distance between the positioning hole on one of the protrusion and bridge and a positioning hole on the load beam, to correctly position the flexure with respect to the load beam. 
   A fourth aspect of the present invention provides, in the first step, one of the protrusion and bridge with a corner in the vicinity of the base plate and forms the positioning hole at the corner. 
   The fourth aspect secures a long distance between the positioning hole on one of the protrusion and bridge and a positioning hole on the load beam, to make the suspension compact and correctly position the flexure with respect to the load beam. 
   A fifth aspect of the present invention provides a semi-finished suspension used for manufacturing a head suspension for a disk drive. The head suspension has a base plate to be supported by a carriage, a load beam including a rigid part resiliently supported by the base plate, to apply load onto a slider, and a flexure positioned and fitted to the load beam and having a read-write head. The semi-finished suspension has the base plate, the rigid part solidly joined with the base plate through a bridge, and a protrusion protruding from one of the base plate and rigid part and having a positioning hole to be aligned with a positioning hole formed through part of the flexure. 
   The fifth aspect cuts off the bridge and protrusion so that the base plate may have no positioning holes and their peripheries. As a result, a suspension manufactured from the semi-finished suspension of the fifth aspect involves no horizontal imbalance and shows improved vibration characteristics. 
   A sixth aspect of the present invention makes the bridge serve as the protrusion. 
   The sixth aspect forms the positioning hole to be aligned with the positioning hole of the flexure on the bridge that solidly joins the rigid part to the base plate. The bridge is cut off in the last stage so that the base plate may have no positioning holes including the peripheries of the holes. As a result, a suspension manufactured from the semi-finished suspension of the sixth aspect involves no horizontal imbalance and shows improved vibration characteristics. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view showing a head suspension for a disk drive according to a prior art; 
       FIG. 2A  is a plan view showing parts of a head suspension for a disk drive before assembly according to a prior art; 
       FIG. 2B  is a plan view showing an assembled state of the parts of  FIG. 2A , 
       FIG. 2C  is a plan view showing a finished suspension formed from the assembled parts of  FIG. 2B ; 
       FIG. 3  is a sectional view partly showing an HDD having head suspensions according to an embodiment of the present invention; 
       FIG. 4A  is a plan view showing parts of the suspension of the first embodiment before assembly; 
       FIG. 4B  is a plan view showing an assembled state of the parts of  FIG. 4A ; and 
       FIG. 4C  is a plan view showing a finished suspension formed from the assembled parts of FIG.  4 B. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3  is a sectional view partly showing an HDD having head suspensions according to an embodiment of the present invention. The HDD  1  has a carriage  5  that is turned around a spindle  3  by a positioning motor  7  such as a voice coil motor. 
   The carriage  5  has a plurality of (four in  FIG. 3 ) arms  9  each having the suspension  11  of the present invention. The suspension  11  has a write-read head  13 . 
   The carriage  5  is driven around the spindle  3  by the motor  7 , to move the head  13  onto a required track on a disk  15 . 
   The head  13  has a slider  17  to face a track on the disk  15 , and the slider  17  has a transducer (not shown). When the disk  15  is revolved at high speed, air enters between the slider  17  and the disk  15  to form air bearings between them to slightly float the slider  17  above the disk  15 . 
   The present invention is characterized by removing positioning holes from the suspension  11  before completing the manufacturing of the suspension  11 . First, the structure of the suspension  11  will be explained, and then, a method of manufacturing the same will be explained. 
     FIGS. 4A  to  4 C show the details of the suspension  11 , in which  FIG. 4A  is a plan view showing parts of the suspension  11  before assembly,  FIG. 4B  is a plan view showing an assembled state of the parts, and  FIG. 4C  is a plan view showing a finished state of the suspension  11 . 
   The suspension  11  shown in  FIG. 4C  is compact and has a base plate  19  and a load beam  21 . The base plate  19  is fitted to the carriage arm  9  (FIG.  3 ). Referring also to  FIG. 4A , the base plate  19  is made of, for example, stainless steel and has a flange  23  and a boss  25 . The flange  23  is circular in plan view. The boss  25  protrudes in the thickness direction of the flange  23 . The boss  25  is fitted to a hole  9   a  of the arm  9 . 
   The load beam  21  applies load onto the slider  17  and consists of a rigid part  27  and a resilient part  29 . The resilient part  29  is made of a resilient material  31  that is independent of the rigid part  27 . The rigid part  27  is made of, for example, stainless steel. The rigid part  27  may be made of an alloy of light metal (lighter than Fe) such as aluminum (Al) and titanium (Ti), or synthetic resin to reduce weight and increase rigidity. Alternatively, the rigid part  27  may be made of layers of two or more materials including light metal such as aluminum and titanium, alloys of light metal, and other metals such as stainless steel. 
   The resilient material  31  has a rectangular shape and extends over the base plate  19  (reinforcing plate  37 ) and rigid part  27 . The resilient material  31  is, for example, a thin stainless steel plate and has an accurate spring constant lower than that of the rigid part  27 . The resilient material  31  has a hole  33  fitted to the boss  25  of the base plate  19 . The diameter of the hole  33  is equal to or slightly larger than the diameter of the boss  25 . 
   When the resilient material  31  is laid on the reinforcing plate  37 , a side  31   a  of the resilient material  31  protrudes from the reinforcing plate  37 . A rectangular opening  35  is formed through the side  31   a  by etching, precision press, etc. The opening  35  partially reduces the bending rigidity (spring constant) of the resilient material  31  and forms the resilient part  29  between the sides  31   a  and  31   b . The side  31   a  overlaps a base end  27   b  of the rigid part  27  and is fixed thereto by laser welding, adhesives, etc. At this time, a front edge of the opening  35  is substantially on a rear edge  27   c  of the rigid part  27 . 
   The hole  33  of the resilient material  31  is fitted to the boss  25  of the base plate  19 , so that the side  31   b  overlaps the flange  23 . Namely, the side  31   b  is sandwiched between the flange  23  and the reinforcing plate  37 . The reinforcing plate  37  and the base plate  19  commonly serve as a base plate to be attached to the carriage arm  9  (FIG.  3 ). 
   The reinforcing plate  37  is made of, for example, stainless steel and has a positioning hole  39 . The hole  39  is made by, for example, etching to be precisely fitted to the boss  25  for correct horizontal positioning. 
   When the boss  25  is inserted into the hole  39 , the side  31   b  of the resilient material  31  is sandwiched between the flange  23  and the reinforcing plate  37  and is fixed there by, for example, laser welding. In this state, a front edge of the reinforcing plate  37  is substantially on a rear edge of the opening  35  of the resilient material  31 . 
   A flexure  41  is attached to the rigid part  27 . The flexure  41  has a metal base  43  made of, for example, a thin resilient stainless steel rolled plate. An insulating layer is formed on the metal base  43 , and a conductor  45  is formed on the insulating layer. An end of the conductor  45  is connected to a terminal of the head  13  and the other end thereof is connected to an external terminal (not shown). The flexure  41  is fixed to the rigid part  27  by laser welding, adhesives, etc. The flexure  41  has a tongue  47  to which the slider  17  of the head  13  is attached. 
   The suspension  11  of the structure mentioned above is fixed to the carriage dim  9  of FIG.  3 . More precisely, the boss  25  is inserted into the hole  9   a  of the arm  9  and is plastically widened by a jig, to fix the suspension  11  to the arm  9 . 
   The flange  23  of the base plate  19  is opposite to the arm  9  with the resilient material  31  interposing between them, to secure a gap between the load beam  21  and the disk  15 . Namely, the suspension  11  is compact, and at the same time, is capable of securing a sufficient inclination angle for the load beam  21  with respect to the disk  15 . 
   Since the rigid part  27  and resilient part  29  (i.e., the resilient material  31 ) that form the load beam  21  are discrete, they can be made of different materials with different thicknesses. As a result, requirements such as high rigidity for the rigid part  27  and a low spring constant for the resilient material  31  can simultaneously be met. 
   The resilient material  31  may be made of precision rolled material to provide a stable low spring constant. The resilient material  31  is sandwiched between the flange  23  and the reinforcing plate  37  both being thicker than the resilient material  31 . As a result, the resilient material  31  is stably supported by the base plate  19 , and the rigid part  27  is stably and resiliently supported by the base plate  19  through the resilient material  31 . 
   A method of manufacturing the suspension  11  of the present invention will be explained. 
   The flexure  41  is provide with positioning holes  49  and  51  in advance. The hole  49  is formed close to the tongue  47 , and the hole  51  is formed through a protrusion  53  protruding from the metal base  43 . The protrusion  53  has a hooked shape so that is may stably be set on a bridge  57  of a semi-finished suspension  55 . 
   A first step of the method forms the semi-finished suspension  55  by, for example, etching. The semi-finished suspension  55  consists of the rigid part  27  and reinforcing plate  37  that are connected to each other through the bridge  57 . The bridge  57  has a rectangular shape in plan view and has a corner  57   a  on the reinforcing plate  37  side and a corner  57   b  on the rigid part  27  side. The reinforcing plate  37  is connected to a scrap area (not shown) through legs  59 . Namely, many rigid parts  27  and reinforcing plates  37  are chained in rows and connected to the scrap area. 
   A front end  27   a  of the rigid part  27  has a positioning hole  61 , and the corner  57   a  of the bridge  57  has a positioning hole  63 . In this embodiment, the bridge  57  serves as a protrusion provided for the reinforcing plate  37  (serving as part of the base plate) or the rigid part  27 . The front end  27   a  has a dimple  60 . 
   The scrap area connected to many rigid parts  27  and reinforcing plates  37  has positioning holes, which are set on positioning pins of a jig. At this time, other positioning pins of the jig are inserted into the positioning holes  61  and  63  of each semi-finished suspension  55 . 
   A second step of the method sets chained resilient materials  31  over the chained semi-finished suspensions  55  by passing the positioning pins of the jig through positioning holes of a scrap area of the chained resilient materials  31 . 
   Each base plate  19  is set on each resilient material  31 , and the boss  25  is passed through the hole  33  and fitted to the hole  39 . In  FIGS. 4A  to  4 C, the base plate  19  resilient material  31 , and reinforcing plate  37  are laid in this order from the bottom, and are fixed together by, for example, laser welding. 
   A third step of the method passes the jig pins through the positioning holes  49  and  51  of the flexure  41  and the positioning holes  61  and  63  of the semi-finished suspension  55 , to align the positioning holes with each other. As a result, the flexure  41  is correctly positioned with respect to the rigid part  27 . At this time, the positioning hole  63  on the corner  57   a  of the bridge  57  is sufficiently distanced from the positioning hole  61  on the rigid part  27  even if the distance between the dimple  60  and a fitting center of the base plate  19  is short to improve the vibration characteristics of the suspension  11 . Due to the sufficient distance between the holes  61  and  63 , the flexure  41  is correctly positioned and fitted to the rigid part  27 . 
   Due to the correct positioning of the flexure  41 , the finished suspension  11  shows improved vibration characteristics. The correctly positioned flexure  41  and rigid part  27  are fixed to each other by, for example, laser welding in the third step as shown in FIG.  4 B. 
   A fourth step of the method cuts off the bridge  57  from the rigid part  27  and reinforcing plate  37 , as well as the legs  59 , to complete the suspension  11  of FIG.  4 C. 
   The completed suspension  11  has no positioning hole  63  and the periphery thereof around the base plate  19 , nor the positioning hole  51  and protrusion  53  around the flexure  41 . As a result, the base plate  19  is horizontally balanced to greatly improve the vibration characteristics of the suspension  11 . 
   In this way, the present invention secures a proper distance between the holes  61  and  63  for correct positioning of the flexure  41  to the rigid part  27  horizontally balances the base plate  19 , and miniaturizes the suspension  11  as a whole. These effects synergistically work to improve the total vibration characteristics of the suspension  11 . 
   The embodiment forms the positioning hole  63  on the corner  57   a  of the bridge  57 . The hole  63  may be shifted from the corner. The bridge  57  may have any configuration if it can solidly connect the rigid part  27  and reinforcing plate  37  to each other. The bridge  57  is not always required to have the corners  57   a  and  57   b . For example, the bridge  57  may have only the corner  57   a  and may be curved toward the rigid part  27  without a corner on the rigid part  27  side. 
   The embodiment forms the positioning hole  63  on the bridge  57 . Instead, the hole  63  may be formed through a protrusion, which is separately formed from the bridge  57 , to protrude from the reinforcing plate  37  or rigid part  27 . In this case, the protrusion may have a corner in the vicinity of the reinforcing plate  37 , and the positioning hole  63  may be formed through the corner to secure the distance between the hole  63  and the hole  61  on the rigid part  27 . This protrusion is prepared with the semi-finished suspension  55 . 
   The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.