Abstract:
A method of making a magnetic head suspension assembly includes attaching a slider with a magnetic head to an intermediate flexible circuit. The attached combination is then inserted into a spin stand tester for the testing of electrical performance. If the attached combination fails the test, it is discarded, thereby avoiding the cost of discarding an entire head suspension assembly. On the other hand, if the attached combination passes the test, it is mounted to a load beam to form the head suspension assembly. Thereafter, a flex circuit can be attached to the load beam and intermediate flexible circuit to provide electrical connections to the magnetic head through the intermediate flexible circuit.

Description:
CROSS REFERENCE TO RELATED DOCUMENT 
     The present application is a division of application Ser. No. 09/250,894, now U.S. Pat. No. 6,151,196 which was filed on Feb. 16, 1999. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to fabrication and testing of magnetic head suspension assemblies. 
     BACKGROUND OF THE INVENTION 
     FIG. 1 shows a fragmentary view of a prior art disk drive having an actuator arm assembly  2  and a stack of spaced apart disks  4  rotatable about a common spindle  5  as represented by the arrow  20 . The actuator arm assembly  2  is also rotatable about an actuator arm axis  6 . The arm assembly  2  includes a plurality of actuator arms  8 A- 8 C which extend into the spaces between the disks  4 A and  4 B. Attached to each of the actuator arms  8 A- 8 C is a magnetic head suspension assembly  10 , which comprises a resilient load beam  12 , a flexure  14  and a slider  16 . Each load beam  12  is attached to one of the actuator arms  8 A- 8 C via a base plate  25  having a boss  40  snugly inserted into the actuator hole  42  as shown in FIG.  1 . 
     FIG. 2 shows the magnetic head suspension assembly  10  in further detail. The load beam  12  is made of resilient material which is slightly bent toward the disk surface  18  (FIG.  1 ). Underneath the distal end of the load beam  12  is the flexure  14 . An alignment hole  33  in the load beam  12  is provided for the alignment of the corresponding hole in the flexure  14 , thereby orienting the flexure  14  in a proper location. The flexure  14  is fixedly attached onto the load beam  12  in the area surrounding the alignment hole  33  via welding. 
     The flexure  14  has an integrally formed tongue portion  26 . Fixedly attached to the tongue portion  26  is the slider  16 . Stamped at the end of the load beam  12  is a dimple  28  which is urged against the tongue portion  26  of the flexure  14 . The dimple  28  acts as the fulcrum for the resilient flexure  14  to provide gimbaling action. At the edge of the slider  16  is a magnetic head transducer  24 . Electrical signals written in or read out of the transducer  24  are conducted by wires  30  disposed on the load beam  12  and guided by one of the load beam ribs  32 A. As an alternative, a flex circuit  34  is used in lieu of the wires  30 . Instead, electrical signals are sent or received through the traces  36  (shown partially as a representation in phantom) embedded on the flex substrate  38  of the flex circuit  34 . 
     The topology of the disk surface  18 , though highly polished, is not at all uniform at microscopic scale. Very often, the disks  4 A and  4 B are not rotating about the spindle at a perfectly perpendicular angle. A minute angular deviation would translate into varying disk-to-slider distances while the disks  4 A and  4 B are spinning. For reliable data writing and reading, the slider  16  thus has to faithfully follow the topology of the spinning disks  4 A and  4 B, without ever contacting the disk surfaces  18 . The head gimbal assembly  22  is employed to accommodate the disk surface topology. Basically, the gimbal assembly  22  is designed to dynamically adjust the position of the slider  16  to conform to the irregular disk surface  18  while the disk is spinning. To meet this end, the flexure inside the gimbal assembly  22  must be sufficiently flexible and agile on one hand, yet stiff enough to resist physical deformation on the other hand. 
     The magnetic suspension assembly  10 , which includes the slider  16 , the flexure  14 ,the load beam  12 , the baseplate  25 , and either the wires  30  or the flex circuit  34 , needs to be tested prior to installation to a disk drive. Heretofore, testing of the magnetic head suspension assembly  10  involved inserting the entire assembly  10  into the arm of a spin station which performs the tests. Of all the constituent parts of the suspension assembly  10 , the transducer  24  is the most delicately fabricated component. Often, the failure of the assembly  10  is the electrical malfunctioning of the transducer  24 . Since the magnetic head suspension assembly  10  is permanently attached, the entire assembly  10  has to be rejected as a consequence. 
     The technological trend in disk drive manufacturing is toward miniaturization. As a consequence, sliders are reduced in size. A fixed area of a wafer can now yield more sliders than in the past. Accordingly, costs for each slider fabricated with the transducer  24  decrease. Instead, a greater portion of the manufacturing cost shifts to the other components of the assembly  10 . Thus, rejecting the entire assembly  10  which includes the base plate  25 , the load beam  12 , the flexure  14  and the flex circuit  34  is wasteful and unnecessarily increases manufacturing costs. 
     There is also a trend toward new designs which include active integrated circuits (not shown) disposed near the transducer  24 . For example, integrated circuits may be placed on the flex circuit  34  or the load beam  12 . Weak signals picked up by the transducer are immediately amplified by the integrated circuits before the next stage of signal amplification during data reading, for instance. Placing the active circuits close to transducer  24  substantially improves the signal-to-noise ratio (SNR) of the magnetic head assembly  10 . Adopting the prior art approach of testing and manufacturing of the assembly  10  would further aggravate the situation and is even more wasteful because the active circuits also need to be discarded in the event of test failure. Accordingly, there has been a long-felt need for building magnetic head suspension assemblies without the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a method of prescreening defective components prior to final assembly in the manufacturing of magnetic head suspension assemblies, thereby improving production yield and reducing manufacturing costs. 
     In accordance with the invention, a slider is fabricated with a magnetic head transducer and then attached to an intermediate flexible circuit. The combination is thereafter inserted into a spin stand tester for the testing of various electrical parameters. If the attached combination fails the test, it is discarded. On the other hand, if the attached combination passes the test, it is mounted onto a load beam to form the magnetic head suspension assembly. In one embodiment, the intermediate flexible circuit affixed with the slider is attached to a load beam having a flexure. In another embodiment, the intermediate flexible circuit is attached to a load beam having no pre-disposed flexure, wherein the intermediate flexible circuit acts as the flexure in the final assembly. 
     Accordingly, the magnetic heads, which normally experience the highest failure rate, are isolated and rejected prior to final assembly, without affecting the associated components which are more expensive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1, as described above, is a fragmentary view of a disk drive having a known magnetic head suspension assembly interacting with a plurality of disks; 
     FIG. 2, as described above, is an enlarged perspective view of the known magnetic head suspension assembly attached to an actuator arm; 
     FIGS. 3A-3F are sequential views showing the steps of testing and fabricating the magnetic head suspension assembly in accordance with a first method of the invention; 
     FIG. 3G is an exploded view showing the relationship of the various components of the magnetic head suspension assembly fabricated in accordance with the method show in FIGS. 3A-3F; 
     FIGS. 4A-4F are sequential views showing the steps of testing and fabricating the magnetic head suspension assembly in accordance with a second method of the invention; 
     FIG. 4G is an exploded view showing the relationship of the various components of the magnetic head suspension assembly fabricated in accordance with the method shown in FIGS. 4A-4F; and 
     FIG. 4H is an enlarged view of the distal end of the flex circuit revealing the bonding tabs. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is now directed to FIGS. 3A-3F which shows the method of manufacturing and testing a magnetic suspension assembly in accordance with the invention. 
     The inventive process starts with providing a slider  50  having a magnetic head transducer  52  formed thereon. The magnetic head transducer  52  can be embedded within the slider  50 . For example, a relatively thick layer of alumina (Al 2 O 3 ) can be coated onto the trailing surface  54  of the slider  50 . The magnetic head transducer  52  can be an inductive head, an anistropic magnetoresistive head (AMR), a giant magnetoresistive head (GMR), or a combination thereof as a merged head. There is also a plurality of bonding pads  55  deposited on the trailing surface  54  of the slider  50 . 
     Next, a flexible interconnect flexible member  56  is provided as shown in FIG.  3 B. Preferably, the flexible member  56  is made of a flexible material such as polyimide. Formed on the flexible member  56  at the distal end  58  is an electrical footprint  60  for receiving the slider  50 . Formed on the flexible member  56  at the proximal end  62  is a plurality of signal pads  64 . The electrical footprint  60  and the signal pads  64  are electrically connected through electrical traces  66  formed on the sides of the flexible member  56 . Extended beyond the electrical footprint  60  is a tongue portion  59  for attaching the slider  50 . There is also an alignment hole  68  formed on the flexible member  56 . 
     The slider  50  is then mechanically attached to the tongue portion  59  of flexible member  56  as shown in FIG.  3 C. The attachment can be achieved by different methods such as ultrasonic bonding, soldering, or adhesive bonding, for example. The slider  50  is attached to the flexible member  56  such that the slider bonding pads  55  correspondingly aligned with the footprint  60  on the flexible member  56 . The bonding of the bonding pads  55  to the electrical footprint  60  can be accomplished through different methods such as ball bonding, tab bonding, stitch bonding or soldering. 
     Prior to final assembly, the electrical properties of the magnetic head  52  need to be tested. Reference is now directed to FIG.  3 D. The slider  50  which is attached to the member  56 , collectively called a combination  57 , is inserted into the jaws  70 A and  70 B of a spin tester  72 . Mechanical clamping and electrical connection (not shown) between the member  56  and the spin tester  72  are provided by the jaws  70 A and  70 B. A load mechanism  48  having a load tip  51  is then moved toward the combination  57 . The load tip  51  is then slightly landed onto the slider  50  in the combination  57 . The point of landing should be where the dimple  78  (see FIG. 3G) would eventually urge the slider  50  in the final assembly. The load mechanism  48  provides the simulated load force onto the slider  50  such that a predetermined flying height of the slider  50  above surface of the disk  73  (F The disk  73  of the spin tester  72  is then spun at an angular velocity T. At this juncture, various electrical tests are conducted. 
     It should be noted that the flexible member  56  in this method by itself is relatively flexible and does not have a high degree of rigidity. Thus, the member  56  does not have adequate yaw stiffness by itself to withstand any high acceleration commonly encountered during track seeking in actual applications. However, the member  56  is stiff enough, and with the help of the load mechanism  48 , to maintain the slider  50  at a predetermined flying height above the disk surface  73  to allow testing. 
     If the combination  57  fails the tests, the entire combination  57  is discarded. If the combination  57  passes the tests, the combination  57  is attached to a flexure  74 , which is pre-welded onto the load beam  82 , as shown in FIG.  3 E. Specifically, the attachment is between the flexure tongue  76  and the flexible member tongue  59  (FIG.  3 B). The attachment can be adhesive bonding or soldering, for instance. Mechanical attachment of the flexible member  56  to the flexure  74  at the proximal end  62  is optional. 
     To provide electrical connection to the suspension assembly  84 , a flex circuit  86  is attached onto the load beam  82 , as shown in FIG.  3 F. The electrical pads  64  on the flexible member is soldered onto the corresponding pads (not shown) of the flex circuit  86 . Instead of soldering, other attachment methods such as stitch bonding or tab bonding can also be employed. The flex circuit  86  can be securely attached to the proximal end portion  88  and the center portion  89  of the load beam  82 . 
     FIG. 3G shows an exploded view of the suspension assembly  84  illustrating the relative positions of the components in additional detail. 
     FIGS. 4A-4F show a second method of testing and manufacturing of a magnetic suspension assembly in accordance with the invention. 
     As with the previous method, it starts with providing a slider  50  having a magnetic head transducer  52  formed thereon as shown in FIG.  4 A. The magnetic head  52  can be embedded within the slider  50  and can be an inductive head, an anistropic magnetoresistive head (AMR), a giant magnetoresistive head (GMR), or a combination thereof as a merged head. A plurality of bonding pads  55  are deposited on the trailing surface  54  of the slider  50 . 
     A flexible interconnect flexible member  96  is then provided as shown in FIG.  4 B. For this method, the flexible member  96  has a base substrate  93  made of flexible material. Exemplary material can be polyimide or stainless steel. It should be noted that the rigidity of the flexible member  96  in this method is higher than the corresponding rigidity of the flexible member  56  shown in the previous method. The reason is that the flexible member  96  used in this method also assumes the role as a flexure in the final assembly. That is, the flexible member  96  serves the dual function of acting as an interconnect member for testing and also as a flexure in the final assembly. 
     The flexure member  96  has a pair of outriggers  95 . Disposed between the outriggers  95  are a first tongue  98  and a second tongue  99 . Formed on the flexible member  96  at the distal end  92  is an electrical footprint  60  for receiving the slider  50 . Formed on the flexible member  96  at the proximal end  62  (FIG. 3E) is a plurality of signal pads  64 . The slider footprint  60  and the signal pads  64  are electrically connected through electrical traces  66  formed on the sides of the flexible member  96 . Electrical traces  66  and signal pads  60  and  64  are etched from a copper sheet that is attached to substrate  93  of the flexible member  56 . If the substrate  93  is made of conductive material such as steel, an insulating layer is sandwiched between the electrical traces, the signal pads  6 ider  50  is then attached to the tongue  98  of the flexible member  96  as shown in FIG.  4 C. The attachment can be achieved by different methods as described previously. The attachment of the slider  50  corresponds to and is in alignment with the footprint  60  of the flexible member  96 . It should be noted that the slider  50  does not contact the outriggers  95  of the flexible member  96 , thereby allowing the slider  50  to gimbal about the dimple  100  (FIG. 4G) during flight. 
     What follows is the electrical testing of the magnetic head  52 . The slider  50  with the magnetic head  52  in conjunction with the flexible member  96  is collectively called a combination  97 . The combination  97  is first flipped over and inserted into the jaws  70 A and  70 B of a spin tester  72  as shown in FIG.  4 D. Mechanical clamping and electrical connection (not shown) between the flexible member  96  and the spin tester  72  are provided by the jaws  70 A and  70 B. A load mechanism  48  having a load tip  51  is then moved toward the combination  57 . The load tip  51  is then slightly landed onto the slider  50  in the combination  97 . The point of landing should be where the dimple  100  (see FIG. 4G) would eventually urge the slider  50  in the final assembly. The load mechanism  48  provides the simulated load force onto the slider  50  such that a predetermined flying height of the slider  50  above the disk surface  73  can be maintained. The disk  73  of the spin tester  72  is then spun at an angular velocity. Electrical and connectivity tests are performed on the magnetic head  52  and electrical traces  66 , respectively. 
     If the combination  97  fails the tests, the entire combination  97  is discarded. If the combination  97  passes the tests, in this method, the combination  97  is attached directly to a load beam  82 . If the flexible member  96  is made of polymeric material, attachment methods such as adhesive bonding or ultrasonic bonding can be used. If the flexible member  96  is made of metallic material, attachment methods such as adhesive bonding, soldering or welding can be employed. The areas of attachment are the second tongue  99  and the adjacent end  94  (FIG. 4E) of the flexible member  96 , which areas are fixedly bonded onto the load beam  82 . As mentioned before, in this method, the flexible member  96  also serves as a flexure in the final magnetic suspension assembly  104  (FIG.  4 F). 
     A flex circuit  86  is also attached to the load beam  82  as shown in FIG.  4 F. The flex circuit  86  provides electrical connections to the flexible member  96 . The flex circuit  86  can be securely attached to the proximal end  88  and the center portion  89  of the load beam  82 . The electrical connection between the flex circuit  86  and the flexible member  96  can be by tab bonding of the flex circuit tabs  108  (FIG. 4H) to the signal pads  64  of the flexible member  96 . Other bonding methods such as stitch bonding or reflow soldering can also be used. 
     FIG. 4G shows an exploded view of the suspension assembly  104  illustrating the relative positions of the components in additional detail. 
     Variations in shapes and materials are possible within the scope of the invention. For example, the flexible interconnect members described in the specification are made of polyimide or stainless steel. Other materials can be used as substitutes.