Abstract:
According to an embodiment of the present invention, an improved method and system are provided. In one embodiment, gold balls are provided and a holder using a vacuum suction force is used to pick up each gold ball. The ball is then placed next to the desired bonding pad(s) and vibrated to achieve partial melting of the ball and bonding pad(s).

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention pertains to a method and apparatus for manufacturing components of a hard disk drive. More particularly, the present invention pertains to conductive ball bonding of components such as bonding pads on a head slider device and bonding pads on a suspension or the like.  
       BACKGROUND OF THE INVENTION  
       [0002]     Hard disk drives are common information storage devices essentially consisting of a series of rotatable disks that are accessed by magnetic reading and writing elements. These data transferring elements, commonly known as transducers, are typically carried by and embedded in a slider body that is held in a close relative position over discrete data tracks formed on a disk to permit a read or write operation to be carried out. In order to properly position the transducer with respect to the disk surface, an air bearing surface (ABS) formed on the slider body experiences a fluid air flow that provides sufficient lift force to “fly” the slider and transducer above the disk data tracks. The high-speed rotation of a magnetic disk generates a stream of airflow or wind along its surface in a direction substantially parallel to the tangential velocity of the disk. The airflow cooperates with the ABS of the slider body, which enables the slider to fly above the spinning disk. In effect, the suspended slider is physically separated from the disk surface through this self-actuating air bearing. The ABS of a slider is generally configured on the slider surface facing the rotating disk, and greatly influences its ability to fly over the disk under various conditions.  
         [0003]     As shown in  FIG. 1  an ABS design known for a common catamaran slider  5  may be formed with a pair of parallel rails  2  and  4  that extend along the outer edges of the slider surface facing the disk. Other ABS configurations including three or more additional rails, with various surface areas and geometries, have also been developed. The two rails  2  and  4  typically run along at least a portion of the slider body length from the leading edge  6  to the trailing edge  8 . The leading edge  6  is defined as the edge of the slider that the rotating disk passes before running the length of the slider  5  towards a trailing edge  8 . As shown, the leading edge  6  may be tapered despite the large undesirable tolerance typically associated with this machining process. The transducer or magnetic element  7  is typically mounted at some location along the trailing edge  8  of the slider as shown in  FIG. 1 . The rails  2  and  4  form an air bearing surface on which the slider flies, and provide the necessary lift upon contact with the air flow created by the spinning disk. As the disk rotates, the generated wind or air flow runs along underneath, and in between, the catamaran slider rails  2  and  4 . As the air flow passes beneath the rails  2  and  4 , the air pressure between the rails and the disk increases thereby providing positive pressurization and lift. Catamaran sliders generally create a sufficient amount of lift, or positive load force, to cause the slider to fly at appropriate heights above the rotating disk. In the absence of the rails  2  and  4 , the large surface area of the slider body  5  would produce an excessively large air bearing surface area. In general, as the air bearing surface area increases, the amount of lift created is also increased. Without rails, the slider would therefore fly too far from the rotating disk thereby foregoing all of the described benefits of having a low flying height.  
         [0004]     As illustrated in  FIG. 2 , a head gimbal assembly  40  often provides the slider with multiple degrees of freedom such as vertical spacing, or pitch angle and roll angle which describe the flying height of the slider. As shown in  FIG. 2 , a suspension  74  holds the HGA  40  over the moving disk  76  (having edge  70 ) and moving in the direction indicated by arrow  80 . In operation of the disk drive shown in  FIG. 2 , an actuator  72  moves the HGA over various diameters of the disk  76  (e.g., inner diameter (ID), middle diameter (MD) and outer diameter (OD)) over arc  78 .  
         [0005]     The magnetic read/write head of the slider is electrically coupled to circuitry in the disk drive. Typically, bonding pads are provided on the slider that are to be electrically coupled to bonding pads on the suspension. In many cases, the bonding pads of the slider will be orthogonal to the bonding pads of the flexure. The prevalent method for providing this electrical connection is through conductive ball bonding. Gold and solder are examples of the materials used for the conductive balls. In one example of gold ball bonding, the gold is provided as a solid wire through a capillary, which holds the end of the wire in place. The gold is properly grounded. The slider is appropriately positioned on the suspension and placed on a support. A separate electrode is provided that is coupled to a voltage source via a switch. In this example, the orthogonal bonding pads of the slider/suspension are positioned below the tip of the gold wire. The electrode is brought close to the tip of the gold wire. Once the switch is closed, voltage as high as several thousand volts is applied to the electrode. This causes a spark to jump from the electrode to the gold wire and a portion of the gold wire melts. This process for creating a liquid gold ball is referred to in the art as electronic flame off (EFO).  
         [0006]     The capillary holding the wire and molten gold ball and the support holding the suspension and slider are brought close to one another (e.g., the capillary is moved down towards the orthogonal bonding pads of the slider and the suspension). Force is applied to one of the components to push the gold ball and the bonding pads together. At the same time, vibration, such as ultrasonic vibration, is applied to one or both of the components. Friction between the gold ball and the bonding pads causes friction and the outer surfaces of the ball and pads heats up melting their outer layers, and resulting in an improved electrical connection between the pads via the gold ball. Finally the wire is pulled away from the slider/suspension and the ball breaks off from the wire.  
         [0007]     One problem with this system is that the volume of the gold ball varies from placement to placement. If the volume is too small, then an electrical connection may not be made or may be too fragile and easily dislodged during operation of the slider/suspension (e.g., during a “head slap”). If the volume is too large, then the electrical connection could extend to other pads on the slider or suspension resulting in inoperability. This system also includes large voltages and sparks that can damage read/write circuitry of the slider (especially MR sensors).  
         [0008]     In view of the above, there is a need for an improved method and apparatus for conductive ball bonding of electrical bonding pads.  
       SUMMARY OF THE INVENTION  
       [0009]     According to an embodiment of the present invention, an improved method and system are provided. In one embodiment, gold balls are provided and a holder using a vacuum suction force is used to pick up each gold ball. The ball is then placed next to the desired bonding pad(s) and vibrated to achieve partial melting of the ball and bonding pad(s). Doing so relieves the need for the EFO processes of generating a spark to create the gold ball at the end of a gold wire. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of a flying slider with a read and write element assembly having a tapered conventional catamaran air bearing slider configuration.  
         [0011]      FIG. 2  is a plan view of a mounted air bearing slider over a moving magnetic storage medium.  
         [0012]      FIG. 3  is a diagram of a system implementing a first operation according to an embodiment of the present invention.  
         [0013]      FIG. 4  is a diagram of the system of  FIG. 3  implementing a second operation according to an embodiment of the present invention.  
         [0014]      FIG. 5  is a diagram of the system of  FIG. 3  implementing a third operation according to an embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION  
       [0015]     Referring to  FIG. 3 , a diagram of a first operation according to an embodiment of the present invention is shown. In this embodiment, a plurality of conductive balls are provided initially. As shown in  FIG. 3 , the conductive balls  11  are provided in a tray  12 . In this example, the conductive balls are made of gold. Depending on the dimensions of the bonding pads, the conductive balls can have a variety of sizes. With a pad size of 140 micrometers, the conductive balls can have a diameter of 130 micrometers with a tolerance of 20 micrometers. With a pad of size of 90 micrometers, the conducive balls can have a diameter of 85 micrometers with a tolerance of 15. In this embodiment, the conductive balls are fabricated using an atomization process that produces balls have a wide range of diameters. Based on the sieving process, the balls can be sorted to meet the above qualifications. Conductive balls as described herein may be purchased from Technic, Inc. (Cranston, R.I.).  
         [0016]     A workpiece  15  that requires an electrical connection to be made includes at least one bonding pad. In this example, workpiece  15  is a read/write slider  16  with bonding pad  16   a  and a suspension  17  with bonding pad  17   a . A vacuum  21  is provided that provides a suction force for picking up one or more of the conductive balls. In this example, the vacuum is coupled to a cylinder  22 , which in turn is coupled to or part of a holder  23 . According to an embodiment of the present invention, holder  23  (with cylinder  22 ) is the same capillary that is used to hold conductive wire that is known in the art. Thus, the devices that are used to manipulate and/or hold the capillary and workpiece that are used in the EFO method described above may also be used to implement this embodiment of the present invention.  
         [0017]     Referring to  FIG. 4 , a second operation of this embodiment is shown. In  FIG. 4 , the holder  23  is moved over the gold balls  11  and tray  12 . With the vacuum  21  running, a suction force appears at the opening of holder  23 . Because of the size of the opening, the suction force is of a sufficient magnitude that one of the balls  11   a  will become lodged in the holder&#39;s opening.  
         [0018]     Referring to  FIG. 5 , a third operation of this embodiment is shown. In  FIG. 5 , the holder  23  is moved towards the workpiece  15  so that the ball  11   a  is in contact with at least one of the conductive pads. In this embodiment, a vibration source  30  provides ultrasonic vibration to the ball (e.g., through holder  23 ) causing the outer layer of the ball  11  to liquefy as well as the bonding pad(s) improving the electrical bond between them.  
         [0019]     While the present invention has been described with reference to the aforementioned applications, this description of the preferred embodiments is not meant to be construed in a limiting sense. It shall be understood that all aspects of the present invention are not limited to the specific depictions, configurations or dimensions set forth herein which depend upon a variety of principles and variables. Various modifications in form and detail of the disclosed apparatus, as well as other variations of the present invention, will be apparent to a person skilled in the art upon reference to the present disclosure. It is therefore contemplated that the appended claims shall cover any such modifications or variations of the described embodiments as falling within the true spirit and scope of the present invention.  
         [0020]     For example, though gold balls are described in the implementations of  FIGS. 3-5 , other conductive materials may be used, including solder, copper and silver (especially gold plated copper or silver balls, which are cheaper by volume than gold). Also, when stating above that one apparatus is moved towards another apparatus, one skilled in the art will appreciate either or both apparatus may be moved relative to each other to facilitate the method of creating an electrical connection as described above. Furthermore, though the embodiment of the present invention is directed to creating an electrical connection where there is an orthogonal relationship between the bonding pads (e.g., for a slider/suspension connection), the present invention can be expanded other types of relationships between the bonding pads including where the bonding pads are parallel to one another.