Patent Publication Number: US-2005117255-A1

Title: FPC design and HGA assembly process

Description:
TECHNICAL FIELD OF THE INVENTION  
      The present invention generally relates to a new type of FPC (flex print cable) design and its process used in the magnetic head assembly process of HGA production for hard disk drives, and more specifically, to a reverse type of HGA using the new type of FPC design and a process for manufacturing this reverse type of HGA.  
     BACKGROUND OF THE INVENTION  
      In a conventional head gimbal assembly, a thin film magnetic head (slider) is mechanically attached to a suspension flexure by epoxy bonding. A thin film magnetic head transducer is electrically connected to read/write electronic by printed traces which run the length of the suspension. One end of these traces is ultrasonically bonded to gold plated transducer termination pads on the slider.  
      U.S. Pat. No. 4,996,623 discloses an integrated suspension fabricated by etching a copper alloy/polyimide/stainless steel laminate, the twisted pairs of wires have been replaced by a copper alloy lead structure. The electrical conductors that deliver information to and from the magnetic head are incorporated into a layer of the suspension. A method for producing had gimbal assemblies using integrated suspensions id disclosed, for example in U.S. Pat. No. 4,761,699.  
      U.S. Pat. No. 5,828,031 entitled “Head Transducer to Suspension Lead Termination by Solder Ball Place/Reflow”, issued to Pattanaik Surya on Oct. 27, 1998 discloses a method for forming electrical solder connections between a thin film magnetic head transducer and the conductors in an integrated suspension after the head has been mechanically attached to a suspension. A solder ball is placed between the head and conductor termination pads. A focused laser beam is used to produce solder reflow. The resulting solder connection has a fine grain structure and includes a pair of thin layers of intermetallic compounds in the regions where the solder connection abuts the head and conductor termination pads. However, the process is more complicated, and the process cost is higher.  
      Use of a flex cable on a suspension type of HGA  100  (called FSA (flex cable suspension assembly) design) is one of the conventional HGA designs, as shown in  FIG. 1 . 0 , which HGA comprises a suspension  10 , a flexure  20 , a FPC  30  (or flex cable) and a slider  40 .  
      Some traces  31  used as signal lines with corresponding bound pads  32  are provided on FPC  30 , and some bump pads  41  used as slider MR element terminals are provided on the slider  40 , as shown in  FIG. 1 . 1  and  FIG. 1 . 2 .  
      The conventional FSA process usually comprising steps: 
          a) cutting an FPC  30  from an FPC sheet;     b) mounting the FPC  30  to a suspension  10  by epoxy;     c) mounting a slider  40  to the FPC  30  on the suspension  10 ; and     d) connecting slider pads  41  to corresponding FPC pads  32 , respectively, by a GBB (gold ball bounding) or SBB (solder ball bounding) process.        

      As shown in  FIG. 3 . 1 , there is an SBB machine comprising a laser head with a focus system, a monitor with a camera positioning system and a flex cable sheet station with a conveyer system. The laser head can be controlled from the monitor to move vertically and horizontally by the camera positioning system, and the conveyer belt of the transport system can be controlled to move step by step.  
      An SBB bonding method for an HGA by means of an SBB machine comprises steps: 
          a) making a flex cable trace pattern onto a flex cable sheet by etching or the like;     b) mounting sliders onto the flex cable sheet by epoxy, with precise alignment to trace pads one by one;     c) connecting a slider&#39;s pad to the corresponding pads of the flex cable trace by SBB or the like;     d) cutting the flex cable provided with the sliders from the flex cable sheet;     e) mounting the flex cable provided with the sliders onto a suspension by epoxy or the like, and finishing an HGA.        

      The present invention intends to achieve developments in use of the SBB machine and method  
     SUMMARY OF THE INVENTION  
      As far as dynamics and functions of an HGA are concerned, some customers hope to get a reverse type of HGA structure, as shown in  FIGS. 2 . 1  and  2 . 2 , where the slider bounding area is provided on the opposite side of the flexure to that of the conventional flexure.  
      However, it is very difficult for the conventional assembly process to manufacture this reverse type of HGA.  
      Therefore, an object of the invention is to provide a reverse type of HGA by means of a new type FPC design.  
      A further object of the invention is to provide a process for manufacturing this reverse type of HGA.  
      In an aspect of the present invention, a reverse type of HGA comprises a suspension, a flexure, a modified FPC (or flex cable) and a slider, some traces with related bound pads on an FPC used as signal lines, and some bump pads on said slider used as slider MR element terminals;  
      wherein the bonding area of the slider of the reverse type of HGA is provided on the opposite side of the flexure to that of the conventional HGA.  
      In a further aspect of the present invention, an HGA assembling process for producing a reverse type of HGA comprising steps: 
          1) forming a reverse type of FPC;     2) mounting a slider to a FPC sheet by epoxy, bound pads being in alignment with bump pads;     3) finishing slider bounding by an SBB machine;     4) cutting the FPC with the slider from the FPC sheet; and     5) mounting the FPC with the slider to suspension by epoxy        

      Since the process of the present invention is performed by changing slider bounding from the suspension level to the FPC level, the problem of damage of a suspension by clamps and that of suspension pitch/roll change by heating are eliminated automatically.  
      It is very easy for an SBB process to design a fixture and machine to manufacture such a kind of slider bounding on an FPC and easy for mass production, with no damage to the suspension. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The objects and features of the present invention will become more apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals designate like elements, and in which:  
       FIG. 1 . 0  shows a conventional FSA type of HGA configuration;  
       FIG. 1 . 1  shows the detail drawing for slider area of  FIG. 1 . 0 ;  
       FIG. 1 . 2  shows the side view of the HGA in  FIG. 1 . 0 ;  
       FIG. 2 . 1  shows the details of the slider area of a reverse type of HGA;  
       FIG. 2 . 2  shows the side view of the reverse type HGA;  
       FIG. 3 . 1  shows the perspective diagram an SBB machine used by the present invention;  
       FIG. 3 . 2  shows the process drawing of the slider mounting on FPC sheet;  
       FIG. 3 . 3  shows the process drawing of FPC cutting; and  
       FIG. 3 . 4  shows the process drawing of an FSA type of HGA assembly. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION  
      Firstly, refer to  FIG. 2 . 1  which shows the details of the slider area of a reverse type of HGA in accordance with the present invention. The HGA comprises a suspension  10 , a flexure  20 , a modified FPC  30  (or flex cable) and a slider  40 . Some traces  31  with associated bound pads  32  on the FPC  30  are used as signal lines, and some bump pads  41  on the slider  40  used as slider MR element terminals, as shown in  FIGS. 2 . 1  and  2 . 2 .  
      In comparison of the reverse type of HGA shown in  FIGS. 2 . 1  and  2 . 2  to the conventional HGA shown in  FIGS. 1 . 1  and  1 . 2 , the bonding area of the slider  40  of the reverse type of HGA is provided on the opposite side of the flexure to that of the conventional HGA. With the exception of this, other details of the reverse type of HGA are identical to those of the conventional HGA, and further description of the reverse type of HGA of the present invention is omitted. Nevertheless, bonding a head of the reverse type of HGA by a conventional method is so difficult that it will touch, or even damage the suspension.  
       FIG. 3 . 1  shows the perspective diagram an SBB machine used by the present invention.  
      Now turn to  FIGS. 3 . 2 - 3 . 4 , an HGA assembling process in accordance with the present invention comprises steps: 
          1) forming a reverse type of FPC  30  as shown in  FIG. 2 . 1 ;     2) mounting a slider  40  to a FPC sheet  300  by epoxy, bound pads  32  being in alignment with bump pads  41 , as shown in  FIG. 3 . 2 ;     3) finishing slider bounding by an SBB machine, as shown in  FIG. 3 . 1 ;     4) cutting the FPC  30  with the slider  40  from the FPC sheet  300 , as shown in  FIG. 3 . 3 ; and     5) mounting the FPC  30  with slider  40  to suspension  10  by epoxy, as shown in  FIG. 3 . 4 .        

      While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.